Superfund Research Program
This list features recent publications from SRP grantees highlighted in the monthly e-Posted Notes newsletter. For a database of grantee-authored publications from currently funded and previously funded centers and programs dating back to 1995, see the grantee publications page.
Environmentally Friendly Technology Treats Wastewater
Northeastern University SRP Center researchers developed a novel system to remove the contaminant p-nitrophenol (PNP) from wastewater. Center Director Akram Alshawabkeh and trainee Patrick Compton led the team.
PNP, a toxic organic compound commonly used in manufacturing and agriculture, can be found in industrial wastewater and is associated with adverse health outcomes, including harmful effects to the nervous system. The contaminant’s chemical characteristics make it hard to break down in the environment, so robust and effective water treatment technologies are needed.
The team designed an electrochemical reactor — a device that uses electricity to facilitate chemical reactions — composed of activated carbon encased in a stainless-steel mesh to remove and degrade PNP from water. When an electrical current flows through the reactor, electrons are transferred between reacting species, generating hydroxyl radicals, a chemical species known for its ability to destroy organic compounds. As wastewater flows through the reactor, activated carbon adsorbs PNP onto its surface, where it is decomposed by the formed hydroxyl radicals.
The system also allows for the carbon to be regenerated after it has been used, making the technology more environmentally friendly and cost effective than traditional remediation approaches, says the team.
The researchers conducted several tests under changing conditions, including water pH and flow rate, contaminant concentration, and the amount of activated carbon used, to fine tune their system and assess its performance. They found that their technology was more effective at removing PNP and could be used over longer periods of time compared to traditional methods, such as using activated carbon alone.
According to the authors, their technology holds great promise for removing organic contaminants, as well as contaminant mixtures, from wastewater efficiently and without the need for extensive maintenance of the system.To learn more about this research, please refer to the following sources:
- Compton P, Dehkordi NR, Sarrouf S, Ehsan MF, Alshawabkeh AN. 2023. In-situ electrochemical synthesis of H2O2 for p-nitrophenol degradation utilizing a flow-through three-dimensional activated carbon cathode with regeneration capabilities. Electrochim Acta 441:141798. doi:10.1016/j.electacta.2022.141798 PMID:36874445 PMCID:PMC9983606
Revealing Racial and Ethnic Inequalities in Drinking Water Contamination
A nationwide analysis by researchers at the Columbia University Northern Plains SRP Center found racial and ethnic inequalities associated with exposure to uranium and arsenic in public drinking water systems.
Arsenic and uranium are naturally occurring elements that can contaminate groundwater used by public water systems. Exposure to these toxic metals is associated with cancer and cardiovascular, respiratory, and neurological diseases, among a variety of other health problems. The U.S. Environmental Protection Agency (EPA) notes that there is no known safe level of exposure to either contaminant.
The team gathered nationwide estimates from over 2,000 counties of arsenic and uranium concentrations based on the most recent publicly available monitoring data compiled by the EPA. Using racial, ethnic, and sociodemographic data from the 2010 U.S. Census, they generated maps to visualize racial and ethnic compositions of communities and their level of exposure to arsenic and uranium in drinking water at the county level.
Researchers found higher concentrations of toxic metals in community water systems serving Hispanic, American Indian, Alaskan Native, and Black communities, compared to areas with higher proportions of non-Hispanic White residents.
According to the authors, these findings likely reflect the effect of structural environmental racism in the U.S. The team concluded that their research may advance environmental justice initiatives by informing regulatory action and financial and technical support to protect racial and ethnic minorities.To learn more about this research, please refer to the following sources:
- Martinez-Morata I, Bostick BC, Conroy-Ben O, Duncan DT, Jones MR, Spaur M, Patterson KP, Prins SJ, Navas-Acien A, Nigra AE. 2022. Nationwide geospatial analysis of county racial and ethnic composition and public drinking water arsenic and uranium. Nat Commun 13(1):7461. doi:10.1038/s41467-022-35185-6 PMID:36460659 PMCID:PMC9718774
Improving Liver Models for Cancer Risk Assessment
Researchers at the TAMU SRP Center showed that advancements in human liver cell-based experiments can reduce uncertainties when assessing the health risk of contaminants.
The team studied trichloroethylene (TCE) and tetrachloroethylene (PCE), chemicals used in dry cleaning and metal degreasing that are detected widely at Superfund sites, making them high priorities for risk assessment. Prior studies have shown that TCE and PCE can cause liver cancer, but the extent of their metabolism in the body remained unclear.
The researchers worked to resolve these uncertainties using human, rat, and mouse liver cells in special platforms called micropatterned cocultures (MPCCs), which surround the liver cells with connective tissue cells to form a structurally stable system that mimics conditions in the human body. They then exposed the cells to TCE and PCE and measured the formation of metabolites, or substances that form from the breakdown of chemicals in the body.
After comparing results from the MPCC liver models to conventional cell models, as well as to results of previous studies, the team found that their MPCC model was the closest match to metabolism estimates of living organisms. They explained that their data may be used to inform the U.S. Environmental Protection Agency’s toxicity assessments.
According to the authors, these findings suggest that that novel engineered liver platforms, like MPCCs, can provide relevant estimates of metabolic rates for toxic chemicals, improving efforts to quantify their health effects.To learn more about this research, please refer to the following sources:
- Valdiviezo A, Brown GE, Michell AR, Trinconi CM, Bodke VV, Khetani SR, Luo Y, Chiu WA, Rusyn I. 2022. Reanalysis of trichloroethylene and tetrachloroethylene metabolism to glutathione conjugates using human, rat, and mouse liver in vitro models to improve precision in risk characterization. Environ Health Perspect 130(11):117009. doi:10.1289/EHP12006 PMID:36445294 PMCID:PMC9707501
Measuring PFAS in Fish Tissue
Researchers from the University of Rhode Island (URI) SRP Center identified and quantified PFAS in fish. The team aimed to better understand the ability of the chemicals to build up, or bioaccumulate, in freshwater fish to inform fish consumption advisories and decrease human exposure.
PFAS are a large group of human-made chemicals associated with many adverse health effects. PFAS parent compounds, or precursors, can degrade into terminal PFAS, which do not break down further under normal environmental conditions. In this study, researchers investigated precursors of perfluoroalkyl acids (PFAA), which have been widely found in commercial products and environmental samples, such as fish.
The URI scientists used a toolbox of analytical and statistical methods to detect and measure 37 PFAS and their precursors in fish tissue samples from nine freshwater ecosystems in New Hampshire. They also screened for the presence of other precursors in fish muscle tissue.
The researchers found perfluorobutane sulfonamide (FBSA), a PFAA precursor, in all fish samples. They also found perfluorooctane sulfonate (PFOS) — a highly bioaccumulative PFAS that was phased out in 2002 — in most fish samples at high levels. Specifically, all but two fish samples analyzed PFOS levels exceeding the daily recommended consumption limit for adults and about a fifth of samples exceeded the weekly consumption limit.
The authors note that fish consumption advisories are primarily developed for PFOS, but their work indicates that regulatory efforts should consider additional bioaccumulative PFAS, including PFAA precursors like FBSA.To learn more about this research, please refer to the following sources:
- Pickard HM, Ruyle BJ, Thackray CP, Chovancova A, Dassuncao C, Becanova J, Vojta S, Lohmann R, Sunderland E. 2022. PFAS and precursor bioaccumulation in freshwater recreational fish: implications for fish advisories. Environ Sci Technol 56(22):15573-15583. doi:10.1021/acs.est.2c03734 PMID:36280234 PMCID:PMC9670858
Microorganisms Can Reduce PCB Emissions from Sediment
In a recent study, researchers at the University of Iowa found that polychlorinated biphenyl (PCB)-degrading microorganisms can reduce PCBs emitted from contaminated sediment into the air. PCBs are widespread environmental pollutants and evidence has shown that exposure to PCBs increases the risk of developing adverse health effects, such as poor birth outcomes, cardiovascular disease, hypertension, and diabetes.
In this study, researchers hypothesized that PCB emissions from contaminated sediment could be minimized by adding microorganisms that naturally degrade PCBs, a process called bioaugmentation. They tested this in lab-scale bioreactors — devices that support microbial growth in controlled microenvironments — using PCBs from contaminated sediments and Paraburkholderia xenovorans strain LB400, a type of bacteria which was isolated from PCB-contaminated landfill soil in 1985.
To test whether the microorganisms could minimize emissions from sediment to air, they measured the concentration of PCBs in the sediment and air in bioreactors with PCB-degrading microorganisms added and in those without over 35 days. The results showed that bioaugmented treatments decreased total PCB mass in the vapor phase by an average of 57% in comparison to non-bioaugmented controls. The microorganisms preferentially degraded PCBs with lower numbers of chlorine atoms, which are more likely to volatize from soil than other PCBs.
They also tested the effect of saponin, a compound found in plants that may make PCBs more bioavailable for microorganisms. They found that saponin allowed for a stable abundance of a gene responsible for PCB degradation. This suggests that saponin could aid in biodegradation, the authors noted.
According to the researchers, their results show that PCB-degrading microorganisms can lower PCB emissions from contaminated sediments, potentially reducing human exposure.To learn more about this research, please refer to the following sources:
- Bako CM, Martinez A, Ewald JM, Hua J, Ramotowski DJ, Dong Q, Schnoor JL, Mattes TE. 2022. Aerobic bioaugmentation to decrease polychlorinated biphenyl (PCB) emissions from contaminated sediments to air. Environ Sci Technol 56(20):14338-14349. doi:10.1021/acs.est.2c01043 PMID:36178372 PMCID:PMC9583607
Optimizing Materials to Remove Uranium from Water
Researchers from the University of New Mexico (UNM) SRP Center reported on a series of experiments to optimize specialized materials that can remove uranium from water and better understand the mechanisms behind how they work. The UNM SRP Center focuses on understanding and reducing exposures to members of the Navajo Nation living near abandoned uranium mines.
The team looked at polymer sorbent materials made with nanofibers, which give them a high surface area and porosity, and added phosphonate functionalized groups. These functional groups help to bind uranium over a wide range of pH in the environment.
First, they tested which materials removed the most uranium from the water and found that phosphonate groups with longer alkyl chains performed best. The researchers attributed this to the fact that longer chains are better integrated and retained within the material, which create sites for uranium to bind.
Next, they sought to understand how realistic environmental conditions in water — specifically the presence of minerals calcium and carbonate — affect uranium uptake. They found that both calcium and carbonate reduced the ability of the sorbent to take up uranium, which they suggested may be related to interactions with the minerals that change the oxidation state of uranium in water.
Finally, they explored the mechanism by which the functionalized materials bound uranium. The team reported that uranium largely bound to phosphonate with a negative surface charge, and that the presence of minerals may influence uranium uptake by shifting its charge from positive to negative, making it repel from the polymer rather than bind to it.
According to the researchers, these findings will help in designing materials that are even better suited for detecting and removing uranium from water.To learn more about this research, please refer to the following sources:
- Shaikh N, Qian J, Kim S, Phan H, Lezama-Pacheco JS, Ali AS, Cwiertny DM, Forbes T, Haes AJ, Cerrato JM. 2022. U(VI) binding onto electrospun polymers functionalized with phosphonate surfactants. J Environ Chem Eng 10(5):108448. doi:10.1016/j.jece.2022.108448 PMID:36060014 PMCID:PMC9435318
Passive Samplers Accurately Measure PFAS in Water
Researchers at the URI SRP Center demonstrated that passive samplers can better capture PFAS concentrations over time in diverse aquatic environments.
PFAS are a class of widely used and extremely persistent chemicals found globally in air, soil, and water. As PFAS are increasingly associated with negative health effects in humans, it is important to understand their distribution throughout the environment.
Typical water sampling methods for PFAS are discrete, meaning they provide a snapshot of PFAS concentrations at one point in time. Passive sampling — an environmental monitoring technique that allows pollutants to collect and accumulate on a sampler over time — may provide a more representative picture of average PFAS levels. It may also reduce costs by eliminating the need for frequent sampling trips.
In this study, the researchers tested the ability of a new passive sampler, consisting of a hollow plastic tube filled with adsorbent powder, to take up PFAS in a variety of surface water environments. They deployed the passive samplers for one month in water discharged from two wastewater treatment plants (WWTPs), as well as at nine sites throughout Rhode Island’s Narragansett Bay. The researchers also collected daily water samples from the WWTP locations to measure actual PFAS concentrations that could be compared to the samplers.
After extracting and analyzing the samples for 24 common PFAS, they found good agreement between the discrete samples and estimated passive sampler concentrations, mostly within 50% of the measured concentrations. The highest PFAS levels were detected in the northern part of the Bay, closest to the largest cities and industrial sites, but the team noted PFAS concentrations varied over time.
According to the authors, passive samplers may be useful for understanding contaminant concentrations in dynamic surface waters, and they may provide a suitable long-term monitoring tool for PFAS.To learn more about this research, please refer to the following sources:
- Gardiner C, Robuck AR, Becanova J, Cantwell MG, Kaserzon S, Katz D, Mueller JF, Lohmann R. 2022. Field validation of a novel passive sampler for dissolved PFAS in surface waters. Environ Toxicol Chem doi:10.1002/etc.5431 PMID:35833595
New Study Finds Associations Between Common Chemical Mixtures and Breast Cancer
Most environmental studies that assess health risks from chemical exposures have focused on evaluating relationships between individual, well-known chemicals and health effects. A new study from the University of North Carolina at Chapel Hill (UNC) SRP Center identified understudied chemicals that frequently occur in the same products as those linked to breast cancer, which could inform studies on how exposure to chemical mixtures influences disease risk.
Breast cancer — the leading cause of cancer-related death in women — has increasingly been linked to chemicals commonly found in the environment, from consumer products to food and water sources. The researchers used databases containing chemical inventories and cancer information to efficiently categorize chemicals based on their association with breast cancer. They sifted through data on thousands of chemicals to identify compounds that frequently occur in the environment and are understudied in their relation to breast cancer risk.
The team then used the data to determine which of the understudied chemicals most often occur alongside chemicals with known breast cancer associations. They compared the chemical and structural similarities between the understudied group and the breast cancer chemicals to identify those that should be prioritized in future toxicological studies.
The researchers selected 50 understudied chemicals and organized them based on their patterns of co-exposure and similarities to breast cancer chemicals. According to the authors, these chemicals — on their own and in mixtures — may warrant further investigation to understand how everyday exposures may influence breast cancer risk.To learn more about this research, please refer to the following sources:
- Koval L, Dionisio KL, Friedman KP, Isaacs KK, Rager JE. 2022. Environmental mixtures and breast cancer: identifying co-exposure patterns between understudied vs breast cancer-associated chemicals using chemical inventory informatics. J Expo Sci Environ Epidemiol doi:10.1038/s41370-022-00451-8 PMID:35710593
Combining Data Mining and Cell Studies to Better Evaluate Chemical Mixtures
Researchers at the UNC SRP Center have demonstrated an innovative method for identifying components of chemical mixtures and health outcomes associated with exposures. Combining a data-driven approach with cell-based studies allowed the team to determine chemical combinations that are potentially harmful.
Humans regularly encounter an enormous number of chemical combinations in consumer products, food, and water. Because it is not feasible to test the toxicity of all possible combinations through lab experiments, the authors employed computer-based data-mining techniques to characterize frequently co-occurring chemicals that could then be further evaluated in the lab.
Using chemical exposure information from a publicly available database, the research team analyzed and identified chemicals that frequently appear in the household environment. They homed in on chemical mixtures that affect PPAR?, a well-studied protein involved in liver metabolism. Increases in PPAR? activity can alter expression of genes critical to insulin regulation.
The researchers assessed the effects of five understudied chemicals on liver cells. They tested the chemicals in vitro for changes in the expression of insulin-related genes. Individual exposure to each chemical yielded little to no effect on cell health. When the chemicals were combined, however, insulin-related gene expression significantly increased.
According to the authors, these findings suggest that exposure to chemical mixtures may intensify biological changes in the liver, compared to single-chemical exposures.To learn more about this research, please refer to the following sources:
- Carberry C, Turla T, Koval L, Hartwell HJ, Fry RC, Rager JE. 2022. Chemical mixtures in household environments: In silico prediction and in vitro testing of potential join action on PPARy in human liver cells. Toxics 10(5):199. doi:10.3390/toxics10050199 PMID:35622613 PMCID:PMC9146550
Nanofiltration Membranes Can Sustainably Separate PFAS from Water
New membranes synthesized by researchers at the University of Kentucky SRP Center can improve the removal of PFAS in drinking water.
PFAS are a class of widely used and extremely persistent chemicals associated with a variety of negative health outcomes in humans. The removal of PFAS presents a challenge for drinking water providers.
Commonly used water filtering technologies, such as those that rely on carbon or resins to capture contaminants, cannot remove smaller PFAS molecules and can also potentially produce harmful byproducts. In addition, typical adsorption materials become saturated and need to be replaced frequently, impacting their sustainability.
In this study, the researchers synthesized microfiltration membranes that can hold materials within their pores. A synthetic polymeric nanofiltration membrane allows the pores to decrease in size and trap even small PFAS particles. This water purification method allows PFAS to get stuck in the membrane and separate from the water.
A disadvantage of nanofiltration membranes is that a percentage of the water does not pass through the membrane. When this remaining water is contaminated with PFAS, it needs to be treated before it can be discharged. To overcome this limitation, the team added a sponge-like thin film as a top layer, thereby creating a system that can more efficiently adsorb PFAS.
The researchers observed that their membranes successfully separated small and large PFAS molecules from water. According to the authors, this system shows promise as a sustainable water treatment process for PFAS.To learn more about this research, please refer to the following sources:
- Leniz-Pizarro F, Vogler RJ, Sandman P, Harris N, Ormsbee LE, Liu C, Bhattacharyya D. 2022. Dual-functional nanofiltration and adsorptive membranes for PFAS and organics separation from water. ACS ES&T Wat 2(5):863-872. doi:10.1021/acsestwater.2c00043
Sex-Specific Associations of Prenatal Phthalate Exposure and Adverse Birth Outcomes
Exposure during pregnancy to chemicals found in consumer products was associated with increased risk of preterm birth, according to a study by the PROTECT SRP Center and collaborators. Preterm birth, when babies are born before completion of 37 weeks of pregnancy, is considered a risk factor for future health complications, including neurological diseases and hearing loss.
Phthalates are a class of chemicals widely used in the manufacturing of household goods. They’re used in personal care products and to make plastic more flexible in items like toys, vinyl flooring, shower curtains, and food packaging. Human and animal studies indicate that exposure to phthalates can interfere with normal hormone function and development.
Using urine samples from over 1,000 pregnant women enrolled in the study, the researchers analyzed metabolites – molecules from metabolic breakdown – of common phthalates. Next, they used statistical methods to explore the association between metabolites and adverse health outcomes, such as preterm birth and low birth weight, and whether they differed between female and male babies.
The authors observed a correlation between more phthalate exposure and an increased risk of preterm birth, as well as greater odds of having small female babies and large male babies. The study also identified several metabolites as predictive of adverse birth outcomes. According to the team, this evidence underscores the importance of policy regulations that aim to provide safer personal care products to consumers.To learn more about this research, please refer to the following sources:
- Cathey A, Watkins DJ, Rosario Z, Velez-Vega C, Mukherjee B, Alshawabkeh AN, Cordero JF, Meeker JD. 2022. Biomarkers of exposure to phthalate mixtures and adverse birth outcomes in a Puerto Rico birth cohort. Environ Health Perspect 130(3):doi:10.1289/EHP8990 PMID:35333099 PMCID:PMC8953418
Link Between PFAS and Liver Disease Revealed
Human exposure to PFAS may affect biological pathways associated with non-alcoholic fatty liver disease (NAFLD), according to SRP-funded research at Boston University.
PFAS are chemicals used in firefighting foams and in everyday products designed to repel stains, grease, and water. Humans are exposed to these substances mainly through diet and contaminated water. Exposure to PFAS has been associated with many negative health outcomes, including a possible link to NAFLD.
Researchers explored whether a causal relationship existed between PFAS exposure and specific NAFLD-related metabolic processes. They measured PFAS in the liver and blood of 105 individuals with NAFLD and observed that PFAS concentrations were associated with disturbances in certain metabolic pathways in the liver, such as lipid and bile acid metabolism. According to the authors, previous research has also documented changes to those pathways in patients with NAFLD.
The team then compared the results to mice exposed to perfluorooctanoic acid (PFOA), one of the most widely detected PFAS in humans. They observed that PFOA caused changes in mice that were similar to those found in humans. The findings suggest that PFAS exposure may increase the likelihood and severity of NAFLD by altering important metabolic pathways, say the researchers.
According to the authors, females may be more sensitive to the effects of PFAS, as the association between liver metabolism and PFAS exposure was stronger in females than males, even at lower exposure levels.To learn more about this research, please refer to the following sources:
- Sen P, Qadri S, Luukkonen PK, Ragnarsdottir O, McGlinchey A, Jantti S, Juuti A, Arola J, Schlezinger JJ, Webster TF, Oresic M, Yki-Jarvinen H, Hyotylainen T. 2022. Exposure to environmental contaminants is associated with altered hepatic lipid metabolism in non-alcoholic fatty liver disease. J Hepatol 76(2):doi:10.1016/j.jhep.2021.09.039 PMID:34627976
New Approach Treats Stormwater, Increases Water Supplies
A new water-treatment system may be useful for removing trace organic contaminants from stormwater. The system was developed by UC Berkeley SRP Center project leader David Sedlak and SRP trainee Yanghua Duan. Their approach offers new conservation options for water-stressed cities, particularly in the context of climate change.
Most methods to clean up contaminated stormwater are costly and time-consuming to maintain. To overcome these challenges, the researchers developed a compact system that generates hydrogen peroxide from oxygen before exposing it to ultraviolet light. The ultraviolet light converts the hydrogen peroxide into highly reactive hydroxyl radicals, which react with and remove most organic contaminants in stormwater.
To reduce the energy required to produce hydrogen peroxide, the team used sodium sulfate, a compound that has an electric charge. Their improved approach requires less energy than traditional approaches, while also allowing the hydrogen peroxide solution to be stored for up to three days. According to the authors, this strategy also reduces the cost of treatment since sodium sulfate is relatively inexpensive compared to electricity from power plants.
The investigators tested the efficiency of the system and observed it was able to remove 90% of organic contaminants commonly found in urban runoff. However, the efficiency decreased as the concentration of organic matter in stormwater increased.
According to the researchers, this model can inform the design of full-scale treatment systems for contaminated stormwater, but more research is necessary to optimize the approach under site-specific conditions.To learn more about this research, please refer to the following sources:
- Duan Y, Sedlak DL. 2021. An electrochemical advanced oxidation process for the treatment of urban stormwater. Water Res. X 13(12):100127. doi:10.1016/j.wroa.2021.100127 PMID:34927040 PMCID:PMC8649961
New Sensor Targets Probable Carcinogen
A team from the Massachusetts Institute of Technology (MIT) SRP Center has developed a molecular sensor to detect a contaminant called N-nitrosodimethylamine (NDMA), part of a chemical family known as N-nitrosamines.
N-nitrosamines are probable human carcinogens found widely in air, water, and food. They can form as industrial byproducts—from rubber and pesticide manufacturing, for example—as well as through natural processes, like when stomach acid reacts with proteins in meat.
To address nitrosamine contamination, experts need efficient, inexpensive ways to detect these chemicals in the environment. However, sensors designed to target nitrosamines are rare, according to the MIT team.
Led by Timothy Swager, the researchers created polymers that specifically bind with NDMA. Using spectral analyses, the team confirmed that the polymers, which consist of a cone-shaped cavity containing tungsten, can bind to oxygen in the NDMA.
Next, the team combined the polymers with a quartz-based device used to measure tiny changes in mass. They found that the unit was highly sensitive to NDMA, estimating that it may be able to detect levels as low as 5 parts per billion in air. Even in humid air, the sensor retained relatively high sensitivity—a promising sign for real-world applications.
According to the researchers, their sensor could be a fast and cost-effective way to detect NDMA. In addition, the technology could inform the design of future sensors used to detect other types of nitrosamines.To learn more about this research, please refer to the following sources:
- Lu R, Yuan W, Croy RG, Essigmann JM, Swager TM. 2021. Metallocalixarene polymers for gravimetric detection of N-nitrosodialkylamines. J Am Chem Soc 143:doi:10.1021/jacs.1c08739 PMID:34793165 PMCID:PMC8811785
Linking Environmental Exposures and Gut Bacteria to Liver Disease
Changes to gut bacteria caused by a type of dioxin may contribute to the development of non-alcoholic fatty liver disease (NAFLD), according to a study by the Michigan State University SRP Center. The dioxin, known as TCDD, is a byproduct of burning organic materials.
In mice, TCDD exposure has been linked to fat buildup and cell damage in the liver, key characteristics of NAFLD development in humans. The team wanted to understand the underlying mechanisms and the role of the gut microbiome in NAFLD development and progression.
Researchers conducted metagenomic sequencing, which looks at all genes in an organism and their functions, to evaluate differences in bacterial diversity and abundance in mice exposed to TCDD.
They observed that the composition of gut bacteria was different in mice exposed to TCDD and resembled the microbiome of patients with NAFLD. For example, TCDD-exposed mice had more species of Lactobacillus bacteria often associated with NAFLD, diabetes, and liver fibrosis and fewer types of other bacteria, such as Lactobacillus murinus. Decreases in Lactobacillus murinus have been reported in human NAFLD.
The team also reported that in mice exposed to TCDD, increased Lactobacillus species were associated with higher expression of genes responsible for bile acid metabolism. Bile acids play a key role in glucose, lipid, and energy regulation and alterations to their metabolism contribute to liver disease, obesity, and diabetes.
The authors also linked higher abundance of some Lactobacillus bacteria with increased expression of a gene associated with the synthesis of vitamin K12, which is stored in fatty tissue and the liver. These findings were similar to those in publicly available microbiome data from patients with liver disease.
According to the team, these findings highlight similarities between liver damage in mice following TCDD exposure and human NAFLD and point to the gut microbiome as a potential factor affecting disease development.To learn more about this research, please refer to the following sources:
- Fling RR, Zacharewski TR. 2021. Aryl hydrocarbon receptor (AhR) activation by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) dose-dependently shifts the gut microbiome consistent with the progression of non-alcoholic fatty liver disease. Int J Mol Sci 22(22):12431. doi:10.3390/ijms222212431 PMID:34830313 PMCID:PMC8625315
Exposure to Some Workplace Chemicals May Speed Up Epigenetic Aging
Researchers at the UC Berkeley SRP Center found that regular workplace exposures to benzene and trichloroethylene may affect certain markers of biological aging, or bodily decline. Unlike chronological age, based on birth date, biological age can speed up or slow down based on epigenetic changes, which are environmental and behavioral factors that affect the way genes work.
Traditionally, studies looking at the effect of chemical exposures on biological aging have focused on telomeres, sections of DNA at the end of chromosomes. The team, which included UC Berkeley SRP Center Director Martyn Smith, wanted to see how regular exposure to chemicals commonly found in factories affect a type of epigenetic change called DNA methylation.
They recruited three groups of willing participants who worked in factories in China that reported the use of benzene, trichloroethylene, and formaldehyde. The team also included control groups, matched by age and sex, from nearby factories who had not been exposed to those chemicals.
After monitoring each group’s exposure over the course of three weeks, they analyzed blood samples for certain types of DNA methylation. They compared their findings to five different epigenetic clocks—collections of DNA methylation patterns that are highly accurate at predicting chronological age. Their goal was to find patterns that did not match established clocks, which would indicate that the rate of biological aging was faster or slower than chronological aging.
Compared to controls, the team found that workers exposed to benzene had increased biological aging. Some evidence suggested that certain levels of trichloroethylene had a similar effect. According to the authors, these results indicate that some chemicals may cause epigenetic changes that accelerate biological aging.To learn more about this research, please refer to the following sources:
- van der Laan L, Cardenas A, Vermeulen R, Fadadu RP, Hubbard AE, Phillips RV, Zhang L, Breeze C, Hu W, Wen C, Huang Y, Tang X, Smith MT, Rothman N, Lan Q. 2021. Epigenetic aging biomarkers and occupational exposure to benzene, trichloroethylene and formaldehyde. Environ Int 158:106871. doi:10.1016/j.envint.2021.106871 PMID:34560324
New Tool May Help Prioritize PFAS for Additional Testing
A new tool developed by researchers at the NCSU SRP Center can quickly characterize important information about how PFAS may be transported within the body.
The research team set out to develop a high-throughput approach to predict the physical and chemical properties of PFAS compounds, their biological activity, and potential to be toxic. Specifically, they used a protein called albumin, which binds to hormones, pharmaceuticals, and chemicals and transports them through blood, to characterize protein binding properties for PFAS. Protein binding plays a key role in how chemicals are absorbed, metabolized, or excreted, all critical factors in how much of the contaminant is able to cross biological membranes and potentially cause harm.
The team developed and optimized an approach, called differential scanning fluorimetry, to measure the binding interactions between albumin and 24 different PFAS chemicals. Their approach can also be used to determine the different characteristics of PFAS that influence binding.
For example, they found straight-chain PFAS compounds were more likely to bind to albumin than branched PFAS compounds. They also observed that PFAS compounds with a 6-9 carbon chain length could bind to albumin more easily compared to PFAS with shorter or longer carbon chains.
While the tool was developed using albumin, the team noted that their approach is flexible to use with other proteins as well. According to the authors, differential scanning fluorimetry may be useful as a rapid, high-throughput approach to determine the protein binding properties of different PFAS, identify their chemical structures, and allow researchers to prioritize PFAS for further toxicity studies.To learn more about this research, please refer to the following sources:
- Jackson TW, Scheibly CM, Polera ME, Belcher SM. 2021. Rapid characterization of human serum albumin binding for per- and polyfluoroalkyl substances using differential scanning fluorimetry. Environ Sci Technol 55(18):12291-12301. doi:10.1021/acs.est.1c01200 PMID:34495656 PMCID:PMC8651256
Airborne PM May Increase Risk for Heart Disease
Researchers at the Louisiana State University (LSU) SRP Center revealed new information about how exposure to particulate matter (PM)-containing environmentally persistent free radicals (EPFRs) can damage the heart and lungs in mice.
EPFRs, a relatively recently recognized class of contaminants that are generated when hazardous wastes are combusted or thermally treated, exist in significant concentrations in atmospheric PM. While exposure to PM is known to contribute to heart and lung disease, the specific health effects of EPFRs have not been thoroughly evaluated. Previous studies in animals and cells suggested that EPFRs may trigger changes that increase oxidative stress and inflammation first in the lungs, and then throughout the body, leading to strain on the circulatory system and ultimately the heart.
To better understand the mechanism by which EPFR exposure may cause this type of damage, the team exposed mice to PM containing EPFR and measured inflammation and oxidative stress in the lungs and cardiovascular system. They also analyzed gene expression and assessed lung and circulatory function.
Contrary to previous studies, the team did not find evidence of increased inflammation in the lungs or blood. Instead, they observed oxidative stress and other indicators of vascular dysfunction, as well as reduced circulatory and lung function, occurring simultaneously.
According to the authors, these findings demonstrate for the first time that cardiovascular dysfunction precedes lung inflammation following exposure to PM containing EPFRs, and that the circulatory system may be affected by EPFRs.To learn more about this research, please refer to the following sources:
- Harmon AC, Noel A, Subramanian B, Perveen Z, Jennings MH, Chen Y, Penn A, Legendre K, Paulsen DB, Varner KJ, Dugas TR. 2021. Inhalation of particulate matter containing free radicals leads to decreased vascular responsiveness associated with an altered pulmonary function. Am J Physiol Heart Circ Physiol 321(4):H667-H683. doi:10.1152/ajpheart.00725.2020 PMID:34415187
Early Life PFOS Exposure Alters Pathways Related to Alzheimer’s Disease
NIEHS-funded researchers at the University of Rhode Island SRP Center found evidence that exposure to perfluorooctanesulfonic acid (PFOS) early in life may be linked to pathways related to Alzheimer’s disease (AD).
PFOS doesn’t break down easily and can accumulate over time in the environment and in the body. Previous research demonstrated that some of these substances are linked to brain damage and behavioral disorders, but this is the first study to explore the link between early life exposure and AD later in life.
The team exposed female mice to PFOS during pregnancy and lactation. As adults, their pups had increased levels of GSK3B, a protein involved in inflammatory response, memory impairment, and other processes related to AD. They also found increased levels of ApoE, a protein involved in transporting fats through the bloodstream and injury repair in the brain, in mice exposed to PFOS. The accumulation of ApoE has been associated with insoluble twisted fibers inside brain cells, a common occurrence in AD patients.
In an open field maze test to evaluate rodent behavior, the researchers observed that mice exposed to PFOS traveled further distances and spent more time standing on their back legs compared to mice that were not exposed to the chemical. According to the authors, these behaviors have been previously linked to brain cell damage.
In human brain cells, the team observed that low concentrations of PFOS increased the levels of tau, a protein known to be involved in AD development and progression when dysregulated. They also found higer levels of amyloid proteins, which are known to accumulate and damage the brain in AD patients.
According to the authors, these findings suggest that PFOS exposure early in life may alter rodent behavior and several biological pathways associated with AD, but future research is needed to clarify these mechanisms.To learn more about this research, please refer to the following sources:
- Basaly V, Hill J, Bihaqi SW, Marques E, Slitt AL, Zawia NH. 2021. Developmental perfluorooctanesulfonic acid (PFOS) exposure as a potential risk factor for late-onset Alzheimer's disease in CD-1 mice and SH-SY5Y cells. Neurotoxicology 86:26-36. doi:10.1016/j.neuro.2021.06.008 PMID:34224775
SRP Researchers Use Plants to Understand Contaminant Metabolism
In a new NIEHS-funded study, researchers from the Iowa University SRP Center provided the first evidence that poplar trees can further degrade certain polychlorinated biphenyl (PCB) metabolites or transform back to their original forms. These findings provide insights into the transport and transformation of PCB metabolites, which could help researchers understand new sources of these compounds in the environment.
PCBs are a large and complex group of chemicals that often occur in mixtures and can contaminate soil, groundwater, and air. However, some PCB metabolites can be more toxic than the parent compounds, and their environmental occurrence and persistence is not well characterized. Poplar trees are widely used in environmental remediation studies to remove, contain, immobilize, or metabolize contaminants in soil or water.
The researchers exposed poplar trees to two PCB metabolites, a methoxy-PCB and a PCB sulfate, to study how they are they are taken up by the plant and transformed.
PCB metabolites were taken up by the roots and transported to the leaves. They found that the methoxy-PCB was transformed into both a hydroxyl-PCB and a sulfate PCB. Similarly, sulfate PCB was transformed into both a hydroxyl-PCB and a methoxy-PCB. Their study demonstrated interconversion of the three compounds for the first time in plants.
According to the authors, these findings shed light on how plants may act as new sources of these PCB metabolites, which may be more toxic than the parent compounds. They explained that more research should be done to demonstrate the environmental hazard of these transformations.To learn more about this research, please refer to the following sources:
- Li Y, Bako CM, Saktrakulkla P, Lehmler H, Hornbuckle KC, Schnoor JL. 2021. Interconversion between methoxylated, hydroxylated and sulfated metabolites of PCB 3 in whole poplar plants. Sci Total Environ 785:147341. doi:10.1016/j.scitotenv.2021.147341 PMID:33933776 PMCID:PMC8610232
Study Sheds Light on Hormone Disruptors in Sewage Sludge
Many compounds used in households persist past their period of intended use, with significant fractions reaching wastewater treatment plants. Researchers at University of California (UC) Davis SRP Center identified several contaminants in sewage sludge in California. Specifically, the researchers noted that these contaminants have the capability to disrupt the normal activity of estrogen. Sewage sludge is used in agricultural lands and gardens as a soil enrichment or to replace commercial fertilizers.
Many synthetic chemicals have been found to mimic, block, and interfere with hormones, such as estrogen, in humans and in wildlife. Exposure to these chemicals, called endocrine disruptors, has been linked to increased risk of diseases like diabetes, obesity, cancers, and reproductive disorders.
The researchers used an approach called nontargeted analysis, which allows identification of unknown chemicals in the environment. They used this approach to measure contaminants in samples from several wastewater treatment plants in California. They then used a bioassay with cells that respond to estrogenic activity in chemicals to determine which of the contaminants measured could be estrogen disruptors.
The team found 31 compounds from anthropogenic origin with estrogenic activity. These compounds consisted of fragrances, antibiotics, synthetic hormones, pain medication, and plasticizer metabolites. They identified diisobutyl phthalate, a chemical used in soft plastics such as shower curtains, and levorphanol, an opioid pain medication, to be the most abundant chemicals found in 75% of samples, signifying their widespread use and persistence in California.
The researchers were also interested in evaluating how wastewater treatment mechanisms affect the activity and abundance of these chemicals, so they analyzed samples before and after different treatment processes.
They observed that water treatment techniques decreased the abundance of chemicals that speed up estrogenic activity but increased the abundance of chemicals that block estrogen. According to the authors, little research has been done on estrogen blocking compounds in sludge, and these findings show that further work is needed to identify and characterize contaminants with these capabilities.To learn more about this research, please refer to the following sources:
- Black G, Ho G, Denison MS, Young TM. 2021. Using Estrogenic Activity and Nontargeted Chemical Analysis to Identify Contaminants in Sewage Sludge. Environ Sci Technol 55:6729-6739. doi:10.1021/acs.est.0c07846 PMID:33909413
First-of-its-Kind Model Simulates VOCs in Sewer Gas
Researchers from the UK SRP Center developed an innovative model to simulate the concentration of volatile organic compounds (VOCs) in sewer gas. The model can be used as a tool to support sewer assessment guidelines, risk assessment studies, and strategies that protect health.
Near hazardous waste sites, VOCs can be transported through sewer pipes and migrate into indoor spaces through a process called vapor intrusion where humans may then inhale the harmful chemicals. However, numerical models that provide guidance to characterize and predict VOC concentrations in sewer gas at vapor intrusion sites have not been available until now.
The team, led by Center Director Kelly Pennell, included various factors in the model, such as temperature, groundwater depth, and sewer construction characteristics to incorporate a range of conditions. They also accounted for processes, like mass transfer and vapor diffusion, that affect how VOCs move and change in the sewer system. The researchers verified the model’s predictions using field data from a sewer system constructed near a Superfund site. They analyzed how well the model worked under different conditions, and found it was flexible enough to account for variations in factors that influence VOC concentrations, such as temperature.
While additional refinements are needed to reflect complex sewer systems, the team's unique combination of field studies and modeling approaches revealed new insights into potential exposure risks from sewer gas inhalation resulting from vapor intrusion.To learn more about this research, please refer to the following sources:
- Roghani M, Li Y, Rezaei N, Robinson A, Shirazi E, Pennell KG. 2021. Modeling fate and transport of volatile organic compounds (VOCs) inside sewer systems. Ground Water Monit Remediat 41:doi:10.1111/gwmr.12449 PMID:35018089 PMCID:PMC8744132
Understanding the Health Risk from Organisms in Arsenic-contaminated Shallow Lakes
Consuming certain fish, crayfish, and snails from arsenic-contaminated shallow lakes may pose a greater risk to human health compared to deep lakes, according to a new University of Washington (UW) SRP Center study.
The team, led by UW SRP researchers Rebecca Neumann, James Gawel, and Julian Olden, measured arsenic concentrations in sediments in arsenic-contaminated lakes in the Puget Sound region of Washington. They observed arsenic concentrations at the bottom of lakes were similar in most study sites, but arsenic measured in sediments along the shore in the shallowest lake was six times higher than concentrations in the deepest lake.
To understand potential exposure to humans, the team measured total arsenic in the tissues of aquatic organisms commonly consumed by humans, including snails, crayfish, and sunfish. They observed that overall, each organism showed a trend of increasing arsenic accumulation with increasing proximity to shore sediments. According to the authors, arsenic contamination near the shore may affect organisms lower on the food chain more strongly. For example, snails contained the highest concentration of arsenic of the three organisms in the study.
Using a risk assessment model provided by the Washington State Department of Health, they determined the potential health risks from eating the contaminated organisms. Their model results, based on the average consumption rates for the U.S. population, showed the greatest cancer risk for consuming snails and crayfish from sediments in shallow lakes compared to deep lakes. Estimated cancer risk increased exponentially for people eating more than the average for these organisms.
According to the researchers, these results reinforce the need to include shallow lakes when assessing human exposure. In future research, the authors recommend surveying lake users to understand their consumption practices and developing strategies to communicate potential health risks of eating the species included in this study.To learn more about this research, please refer to the following sources:
- Hull EA, Barajas M, Burkart K, Fung SR, Jackson BP, Barrett PM, Olden J, Neumann RB, Gawel J. 2021. Human health risk from consumption of aquatic species in arsenic-contaminated shallow urban lakes. Sci Total Environ 770:145318. doi:10.1016/j.scitotenv.2021.145318 PMID:33736365 PMCID:PMC8032223
Controlling the Properties of Nanomaterials
Researchers at the Brown University SRP Center discovered a new way to control the properties of graphene-based nanomaterials. These materials, which have high elasticity, flexibility, and electrical and thermal conductivity, can be used for a variety of environmental applications, such as membranes that selectively bind to certain chemicals or pollutants or passive samplers to detect contaminants in the environment.
The team starts with graphene oxide (GO) nanosheets that are re-assembled or blended, a process that often leads to layer stacking and dramatic loss of surface area. Thermal exfoliation is a technique that involves rapid heating of graphene materials, which forces the nanosheets apart and increase volume and surface area. According to the researchers, this method has not been widely studied and can destroy the GO films if not performed correctly.
The researchers compared flat GO films with those engineered to have wrinkles and films of various thicknesses to explore how they behaved during thermal exfoliation at different temperatures and instrument heating rates. Their goal was to determine the optimal process to increase the surface area and electrical conductivity of the materials.
When instruments were heated quickly to high temperatures, GO films underwent explosive exfoliation, creating GO powders. When heated more slowly, there was no exfoliation at low temperatures and non-explosive exfoliation at higher temperatures. According to the authors, the resulting materials have different surface areas, textures, and conductivities that are useful for different applications. However, they wanted to create large, flexible GO films that had higher electrical conductivity and pore sizes.
The team developed a simple approach where they confined GO films between glass plates during thermal exfoliation process to try and preserve their macroscopic structure. With this technique, GO films remained intact and flexible, while having high porosity, surface area, and conductivity. Importantly, they scaled up their approach using stainless steel plates to produce large GO films with mechanical stability and high electrical conductivity.
According to the authors, these results may have implications for other researchers trying to optimize thermal treatment process to produce a variety of graphene-based materials for diverse applications, from solar cells to sensors. For example, in a recent publication, selected as NIEHS Paper of the Month, the team demonstrated that these types of nanomaterials can be used to clean-up contaminated water.To learn more about this research, please refer to the following sources:
- Kwon Y, Castilho CJ, Liu M, Saleeba Z, Hurt RH, Kulaots I. 2021. Controlling pore structure and conductivity in graphene nanosheet films through partial thermal exfoliation. Carbon N Y 174:227-239. doi:10.1016/j.carbon.2020.12.050 PMID:33633411 PMCID:PMC7901814
Understanding the Role of the Gut in Adaptations to Environmental Pollutants
In a recent publication, Duke SRP Center researchers found differences in the gut microbiomes of fish from a polluted river that have developed resistance to polycyclic aromatic hydrocarbons (PAHs) compared to fish from a cleaner section of the river that do not have PAH-resistance. These shifts were mirrored by metabolic differences in the two groups of fish.
The Atlantic Wood Superfund Site in the Elizabeth River is heavily contaminated with PAHs, highly toxic contaminants that can harm humans as well as fish. Remarkably, Atlantic killifish in the site have adapted over time to resist the effects of PAH exposure.
The research team collected PAH-adapted adult killifish from the Atlantic Wood Superfund Site and non-adapted fish from King’s Creek, another site in the river where PAH levels are much lower.
The researchers measured 163 biological molecules in fish gut that are important in metabolism and identified several differences between the two groups. For example, PAH-resistant fish had lower levels of tryptophan, amino acids that regulate energy and protein synthesis, and higher levels of spermidine, molecules that protect against oxidative stress. Fish in the contaminated site also had increased levels of sphingolipids, a class of lipids that provide structural function to the cell and protection from harmful environmental factors.
Additionally, the authors analyzed bacteria in fish gut samples to investigate how the microbiome might be linked to shifts in metabolism. They observed lower bacterial species richness and diversity in the gut of fish from the more contaminated site. Specifically, PAH-resistant fish had reduced levels of sphingolipid containing bacteria. The team suggests the potential relationship between bacteria and sphingolipids and the impact of the fish metabolism in regulating sphingolipids needs to be further investigated.
According to the authors, these findings indicate the gut may play an important role in how some animals adapt to contamination. In future work, the researchers suggest exploring the complex dynamics between metabolites and the gut microbiome.To learn more about this research, please refer to the following sources:
- Redfern L, Jayasundara N, Singleton D, Di Giulio RT, Carlson J, Sumner SJ, Gunsch C. 2021. The role of gut microbial community and metabolomic shifts in adaptive resistance of Atlantic killifish (Fundulus heteroclitus) to polycyclic aromatic hydrocarbons. Sci Total Environ 776:145955. doi:10.1016/j.scitotenv.2021.145955 PMID:33647645 PMCID:PMC8294123
Clarifying the Protective Effects of Antioxidants Against EPFRs
In a recent study, Oregon State University SRP Center researchers identified potential protective effects of antioxidants TEMPOL (4-Hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl) and PBN (N-tertbutyl-a-phenylnitrone) against environmentally persistent free radicals (EPFRs).
EPFRs are primarily emitted from combustion and thermal processing of organic materials and have been shown to trigger oxidative stress, but hazards are still largely unknown. Multiple studies have shown that PBN and TEMPOL have protective effects on oxidative stress and inflammation.
The team exposed zebrafish at various developmental stages to increasing concentrations of EPFRs, and to combinations of EPFRs with TEMPOL or PBN to investigate whether the antioxidants would prevent EPFR induced toxicity.
Results showed that exposure to particles containing EPFRs interfered with normal development in zebrafish. The researchers reported on a series of developmental abnormalities and adverse behavioral effects. However, the researchers found that TEMPOL ameliorated the toxicity of EPFRs and decreased mortality. PBN, on the other hand, was not protective against EPFRs in zebrafish. Compared to TEMPOL, PBN was not able to penetrate the cell wall, which may have dampened its effects.
According to the researchers, TEMPOL may suppress the toxicity of EPFRs by preventing oxidative stress and inflammation in intact zebrafish embryos. They propose further experiments to verify that TEMPOL can better penetrate cells than PBN in zebrafish. Although the mechanism by which TEMPOL reduces toxicity from EPFR exposure is still unclear, the team’s current findings pave the way for further studies of the protective effects of antioxidants.
- Guan X, Truong L, Lomnicki S, Tanguay RL, Cormier SA. 2021. Developmental hazard of environmentally persistent free radicals and protective effect of TEMPOL in zebrafish model. Toxics 9:doi:10.3390/toxics9010012 PMID:33467068 PMCID:PMC7829864
New Strategy to Predict Arsenic Contamination in Agricultural Fields
Columbia University SRP Center researchers demonstrated a process to more effectively measure concentrations of arsenic in soil. The procedure will allow rice farmers to identify where and to what extent their fields are affected by arsenic in soil and make informed decisions about interventions and best farming practices.
In Bangladesh, arsenic-contaminated groundwater is used extensively to irrigate rice fields. Arsenic from irrigation water accumulates in soil over time and can be taken up by plants, negatively impacting crop productivity and reducing yield.
The team collected soil samples from 21 rice fields in Bangladesh during rice growing seasons over the course of three years. They adapted a low-cost field kit used to measure arsenic concentration in well water to measure the fraction of arsenic in collected soil samples that is leachable in water. By comparing the field kit results against measurements performed using more expensive X-ray fluorescence spectrometry, the team confirmed the validity and accuracy of the approach.
According to the researchers, a set of measurements obtained for one rice growing season should remain valid for several seasons because the level of arsenic in soil reflects at least a decade of accumulation.
The researchers also developed mathematical models to calculate the probability the average soil arsenic concentration in a plot is above a certain threshold based on the results from field kits. According to the authors, this process will allow farmers to predict whether the extent of arsenic contamination within portions of their fields is above or below a certain threshold for intervention.
- Huhmann LB, Harvey CF, Gross J, Uddin A, Choudhury I, Ahmed KM, Duxbury JM, Bostick BC, van Geen AF. 2021. Evaluation of a field kit for testing arsenic in paddy soil contaminated by irrigation water. Geoderma 382:doi:10.1016/j.geoderma.2020.114755 PMID:33162565 PMCID:PMC7643838
Investigating the Endocrine Disrupting Potential of PAHs During Pregnancy
Northeastern University SRP Center researchers provided new insights into the endocrine disrupting potential of PAHs during pregnancy in a prospective human pregnancy cohort study. Biomarkers of PAH exposure are associated with various health endpoints including asthma, breast cancer, cardiovascular disease, and reduced sperm quantity. Although PAHs have been suggested as endocrine disrupting compounds in previous animal and in vitro studies, human studies are currently lacking.
Researchers utilized data on 659 pregnant women from the Puerto Rico Testsite for Exploring Contamination Threats (PROTECT) longitudinal birth cohort in Puerto Rico. They assessed associations between repeated measures of certain urinary hydroxylated PAH (OH-PAH) metabolites and serum hormones during gestation, as OH-PAHs have been shown to be reliable biomarkers of PAH exposure. Gestational age and fetal sex were analyzed as well.
The team found that PAH exposure resulted in decreased concentrations of male and female sex hormones. They also found that changes in hormone concentrations were dependent on fetal sex and gestational age. Because a balance of critical hormones is necessary for endocrine regulation of pregnancy and fetal development, these hormone changes may have pregnancy and labor consequences with potential implications for fetal and child health.
According to the researchers, these findings demonstrate the importance of studying PAH exposures during pregnancy and highlight the potential complexity of their impacts on human pregnancy. Future research will aim to assess relationships between PAH exposures and adverse birth outcomes within the PROTECT cohort, and to understand how PAH exposures may be related to and interact with other environmental exposures.
- Cathey A, Watkins DJ, Rosario Z, Velez-Vega C, Loch-Caruso R, Alshawabkeh AN, Cordero JF, Meeker JD. 2020. Polycyclic aromatic hydrocarbon exposure results in altered CRH, reproductive, and thyroid hormone concentrations during human pregnancy. Sci Total Environ 749:10. doi:10.1016/j.scitotenv.2020.141581 PMID:32829279
New Technique Predicts the Potential Effects of Chemical Mixtures
In a recent collaboration, University of California, Berkeley SRP and Boston University SRP researchers developed an approach to predict the potentially harmful effects chemicals mixtures have on a molecular pathway involved in the body’s stress response. This publication stems from an SRP K.C. Donelly Externship
The group tested a novel approach called Generalized Concentration Addition (GCA). GCA is a chemical analytical approach that uses mathematical functions to predict the joint effect of co-exposures.
The authors applied GCA to a mixture of synthetic glucocorticoids, a class of steroid hormones that respond to stress in the body and reduce inflammation, in an in vitro bioassay. Synthetic glucocorticoids are used as anti-inflammatory and immunosuppressive drugs. These hormones act as ligands by binding to the glucocorticoid receptor (GR), a steroid receptor present in almost every cell in the human body.
In a previous study, the group demonstrated that GCA successfully predicts the activity of a mixture of ligands that bind to receptors with one binding site. However, steroid receptors introduce complexity since they have two binding sites.
The researchers found that their modified GCA approach can successfully be applied to ligands that activate GR and can accommodate mixtures containing different types of ligands.
To evaluate the efficacy of GCA to predict the GR modifying behavior of mixtures, the researchers also generated experimental data. They found that GCA effectively quantified the activity of glucocorticoids mixtures and characterized their modifying effect on GR activation.
These findings are relevant for predicting the effects of exposures since several environmental compounds, such as heavy metals, are also capable of modifying GR signaling.
- de la Rosa R, Schlezinger JJ, Smith MT, Webster TF. 2020. Application of generalized concentration addition to predict mixture effects of glucocorticoid receptor ligands. Toxicol Vitro 69(7):104975. doi:10.1016/j.tiv.2020.104975 PMID:32858110 PMCID:PMC7594746
Mercury Filtration Process Yields Promising Industrial Applications
University of Kentucky SRP Center researchers demonstrated a process involving three different membranes to effectively remove trace amounts of mercury from wastewater. The procedure consists of a preliminary pre-filtration step followed by ultrafiltration and thiol adsorption.
Thiol groups are compounds that form strong bonds with heavy metals such as mercury, lead, or cadmium, making them practical for removing metals from wastewater.
In a previous study, the team established the efficacy of the third filtration step, thiol membrane adsorption. They confirmed that thiol membrane pores soak up contaminants like heavy metals as water flows through. The current study builds on this discovery by adding two additional filtration steps.
The pre-filtration membrane removes large particulates that could potentially foul or damage membranes in the second and third steps. The ultrafiltration step removes any particles that would interfere with the thiol membrane through additional size exclusion. The third step sends water through the thiol membrane to adsorb dissolved mercury.
The researchers found that three steps are necessary because carryover of particulates can cause significant flux reductions by fouling membrane surfaces and clogging membrane pores. They also found that the adsorption efficiency of the thiol membrane is around 97%, confirming these membranes are effective at removing dissolved mercury from wastewater.
The researchers also developed mathematical models to predict membrane performance over a wide range of conditions. According to the authors, these results show promising potential for industrial application and commercialization of thiol-functionalized membranes.
- Islam MS, Vogler RJ, Al Hasnine SM, Hernandez S, Malekzadeh N, Hoelen T, Hatakeyama E, Bhattacharyya D. 2020. Mercury removal from wastewater using cysteamine functionalized membranes. ACS Omega 5(35):22255-22267. doi:10.1021/acsomega.0c02526 PMID:32923783 PMCID:PMC7482228
Chronic Arsenic Exposure Linked to More Aggressive Cancers
Researchers from the UA SRP Center recently uncovered the mechanism by which exposure to low levels of arsenic may lead to cancer. The team found that exposure to small concentrations of arsenic through contaminated groundwater over a long period of time may trigger changes in cells that make cancer more aggressive and more likely to spread to other organs of the body.
The team treated specialized lung cells with low levels of arsenic for three months and analyzed changes to normal cell processes and functions. They found that arsenic exposure increased the malignant transformation of cells, the process by which healthy cells become cancer cells, and increased their ability to spread throughout the body. These changes involved the NFR2 signaling pathway, which regulates the expression of antioxidant proteins that protect against cell damage triggered by injury and inflammation. While NRF2 activation is thought to protect against short term chemical exposure, according to the researchers, long-term arsenic exposure may promote changes that lead to more aggressive cancers.
The group further explored molecular targets that could reduce NRF2 activation and protect cells against arsenic exposure. By using cells lacking an important gene involved in the NRF2 pathway, called SOX9, they observed a drastic decrease in the types of cellular changes that led to cancer in their earlier experiments.
According to the authors, understanding the NRF2 mechanism may be useful in designing better therapies, such as those targeting SOX9, to treat aggressive lung cancers.
- Schmidlin CJ, Zeng T, Liu P, Wei Y, Dodson M, Chapman E, Zhang DD. 2020. Chronic arsenic exposure enhances metastatic potential via NRF2-mediated upregulation of SOX9. Toxicol Appl Pharmacol 402:12. doi:10.1016/j.taap.2020.115138 PMID:32682831
Linking DNA Modifications with Childhood Leukemia
Researchers at the University of California, Berkeley SRP Center recently uncovered clues that may help predict childhood leukemia using bloodspots taken at birth. In the new study, researchers led by Stephen Rappaport used untargeted approaches to measure modifications to DNA that may be associated with childhood leukemia.
Untargeted approaches look for known and unknown modifications to DNA and proteins in biological samples such as blood and serum. In this study, the researchers used newborn blood spots to measure modifications that may be triggered by exposure to harmful chemicals in the womb.
The team measured a specific type of DNA modification, called adducts, in 782 newborn bloodspots to look for differences between children who later developed two different types of leukemia and children who did not. The abundance of some of the adducts measured in samples were different among the groups. For example, children who later developed a specific type of childhood acute lymphoblastic leukemia had more adducts involving reactive carbonyl species. Children who later developed acute myeloid leukemia, on the other hand, had lower levels of a different adduct compared to children without the disease.
According to the authors, the occurrence of certain adducts points to distinct molecular mechanisms involved in different types of childhood leukemia. While additional studies with more individuals are needed, they suggest certain alterations triggered during gestation and measurable in newborn bloodspots may be useful predictors of childhood leukemia.To learn more about this research, please refer to the following sources:
- Yano Y, Schiffman C, Grigoryan H, Hayes J, Edmands WM, Petrick L, Whitehead TP, Metayer C, Dudoit S, Rappaport SM. 2020. Untargeted adductomics of newborn dried blood spots identifies modifications to human serum albumin associated with childhood leukemia. Leuk Res 88:106268. doi:10.1016/j.leukres.2019.106268 PMID:31760269 PMCID:PMC6937378
Environmental Risk Maps Improve Estimates of Mine Contamination on Navajo Nation
University of New Mexico SRP Center researchers created the first environmental risk maps for the Navajo Nation that consider multiple factors related to metal exposure from abandoned uranium mines, such as air and water transport of contaminants from mine sites. The maps can help researchers and decision makers identify areas most vulnerable to contamination from mine waste and may prove useful in informing actions to reduce exposures and improve health.
The research team used the GIS-based multi-criteria decision analysis (GIS-MCDA) model to create the maps. This is the first time the model, which accounts for multiple exposure routes, has been used to estimate mine-related metal contamination on the Navajo Nation. Previous models only considered proximity to mine sites and a single exposure route, such as breathing windblown dust or drinking contaminated water, to estimate exposure risk.
The researchers created the model to account for factors that play a role in the movement of contaminants in the environment such as proximity to abandoned uranium mines, topography, meteorology, vegetation, and proximity to roads and surface drainages. By comparing the model results and uranium concentrations from soil and sediment samples collected across the Navajo Nation, the team confirmed the validity and accuracy of the approach.
Using the model, they estimated that 20% of the Navajo Nation is at high risk for metal contamination from abandoned mines, 66% at medium risk, and 14% at low risk. Proximity to mine sites was the most influential factor for elevated contamination risk, but proximity to roads, drainages, and certain landforms, like valleys and lower slopes, also increased contamination risk.
According to the authors, this research may be useful to tribal, state, and federal agencies working to clean up abandoned uranium mines and reduce human exposure to harmful contaminants found in mine wastes.To learn more about this research, please refer to the following sources:
- Lin Y, Hoover JH, Beene D, Erdei E, Liu Z. 2020. Environmental risk mapping of potential abandoned uranium mine contamination on the Navajo Nation, USA, using a GIS-based multi-criteria decision analysis approach. Environ Sci Pollut Res Int doi:10.1007/s11356-020-09257-3 PMID:32468361
Enzyme Protects Against PAH Exposure in Roundworms
Researchers from the Duke University SRP Center found that CYP1A, a member of the cytochrome P450 enzyme family, protected against the harmful effects of exposure to polycyclic aromatic hydrocarbons (PAHs). P450 enzymes can either safely metabolize and excrete PAHs or transform them into more toxic products that damage DNA and proteins. Study results suggest CYP1A safely excretes PAH, protecting against PAH toxicity.
The researchers inserted copies of the CYP1A gene from zebrafish into the roundworm, Caenorhabditis elegans (C. elegans), which does not naturally have the P450 enzymes that metabolize PAHs. By using a species naturally lacking these enzymes, they were able to link protective or damaging effects of PAH metabolism directly to CYP1A.
They exposed C. elegans to either the PAH benzo[a]pyrene (BaP) alone, or a real-world mixture of PAHs collected from the Elizabeth River Superfund site.
In worms without CYP1A, exposure to either BaP or the PAH mixture resulted in delayed growth, a lower number of offspring, and indicators of mitochondrial dysfunction. BaP exposed worms with CYP1A were protected against these adverse effects. In worm exposed to the PAH mixture, CYP1A only protected against indicators of mitochondrial dysfunction.
To test if CYP1A transformed PAHs into products that damage DNA, the researchers produced a strain of C. elegans lacking critical DNA repair pathways. They found that even without DNA repair pathways, CYP1A still had protective effects in BaP exposed worms. This suggests that CYP1A does not metabolize BaP into DNA damaging products.
The authors concluded that CYP1A aids in the safe metabolism and excretion of PAHs and did not transform PAHs into products that can damage DNA. They also highlighted the value of using genetically altered C. elegans in toxicology studies to better understand metabolic pathways in fish and mammals.To learn more about this research, please refer to the following sources:
- Harris JB, Hartman JH, Luz AL, Wilson JY, Dinyari A, Meyer JN. 2020. Zebrafish CYP1A expression in transgenic Caenorhabditis elegans protects from exposures to benzo[a]pyrene and a complex polycyclic aromatic hydrocarbon mixture. Toxicology 440 (11):doi:10.1016/j.tox.2020.152473 PMID:32360973 PMCID:PMC7313633
New Technique Improves PFAS Analysis in Complex Samples
In a recent study, SRP-funded researchers at the TAMU SRP Center provided a proof of concept for a new approach to rapidly characterize PFAS in wastewater. PFAS are a large and diverse class of chemicals found in consumer products and firefighting foam that are persistent in the environment.
The team combined a new step using a laboratory technique called ion mobility spectrometry (IMS) to the traditional liquid chromatography-mass spectrometry (LC-MS) approach to analyzing samples for PFAS.
Using analytical standards and complex wastewater samples, the team demonstrated that the IMS step improved LC-MS results by providing more descriptive information about the PFAS compounds present in the sample. For example, it helped to characterize structural properties of PFAS compounds, including identifying the positions where fluorine molecules branch off the main chemical structure.
According to the authors, including IMS in LC-MS analysis can help rapidly identify existing and emerging PFAS chemical species, and may be particularly useful to enhancing untargeted approaches that seek to characterize unknown contaminants in environmental samples.To learn more about this research, please refer to the following sources:
- Dodds J, Hopkins ZR, Knappe D, Baker ES. 2020. Rapid characterization of per- and polyfluoroalkyl substances (PFAS) by ion mobility spectrometry-mass spectrometry (IMS-MS). Anal Chem 92:4427-4435. doi:10.1021/acs.analchem.9b05364 PMID:32011866 PMCID:PMC7173758
Liver Injury Caused by Vinyl Chloride is Sex-Dependent in Mice
University of Louisville SRP Center grantees discovered that male mice are more susceptible than female mice to liver injury from exposure to vinyl chloride (VC). According to the authors, the findings emphasize the importance of assessing sex differences in animal and human epidemiology studies to better identify at-risk populations.
VC, a common industrial chemical, has been associated with toxicant-associated steatohepatitis (TASH), a severe form of fatty liver disease, in men working at rubber-production plants. Because previous VC studies on TASH have only been performed in male mouse models, the researchers examined VC inhalation in male and female mice and compared changes in body weight and the liver.
For 12 weeks, male and female mice were fed either a low-fat or high-fat diet and exposed to VC or room air using an inhalation chamber. Compared to males, females were less susceptible to effects on weight of combined exposure to VC and high-fat diet, as demonstrated by lower body weight and fat composition. VC also exacerbated fatty liver disease in males but not in females. Markers of liver injury were increased by high-fat diet and VC co-exposures only in males. Taken together, the results suggested that VC inhalation led to sex-dependent liver and metabolic toxicity.To learn more about this research, please refer to the following sources:
- Wahlang B, Hardesty JE, Head KZ, Jin J, Falkner K, Prough RA, Cave MC, Beier JI. 2019. Hepatic injury caused by the environmental toxicant vinyl chloride is sex-dependent in mice. Toxicol Sci 174(1):79-91. doi:10.1093/toxsci/kfz236 PMID:31774537 PMCID:PMC7043220
Researchers Provide New Insights in Gene Expression Regulation
Researchers from the Texas A&M SRP Center examined how estrogen regulates gene expression at the cell level and found that individual cells in a population respond differently to estrogen stimulation at both the single cell and allele level. Their work provides novel insights about the complexity of gene regulation in mammals.
The researchers treated human breast cancer cells with estrogen in the lab and looked at expression of two well-characterized genes, GREB1 and MYC, whose activity is regulated by estrogen. As expected, they found that estrogen activated GREB1 and MYC genes within 15 minutes. However, unexpectedly, there were large differences in the level of gene activation between different individual cells and even between alleles within the same cell.
They explored the possibility that estrogen receptor regulators were involved in modifying the response to estrogen. Using automated high throughput technologies, they tested a collection of small molecule inhibitors of the estrogen receptor regulators and identified one, called MS049, that markedly increased the response of individual alleles to estrogen.
The researchers altered estrogenic response by inhibiting estrogen receptor regulators, establishing a previously unrecognized regulation path for estrogen to activate genes at the single cell level. According to the authors, the findings provide novel insights into the complex ways that cells maintain variability in response to stimuli, an important adaptation strategy for cell populations.To learn more about this research, please refer to the following sources:
- Stossi F, Dandekar RD, Mancini MG, Gu G, Fuqua SA, Nardone A, De Angelis C, Fu X, Schiff R, Bedford MT, Xu W, Johansson HE, Stephan C, Mancini MA. 2020. Estrogen-induced transcription at individual alleles is independent of receptor level and active conformation but can be modulated by coactivators activity. Nucleic Acids Res 48:1800-1810. doi:10.1093/nar/gkz1172 PMID:31930333 PMCID:PMC7039002
Challenges with Co-Contamination at Clean Up Sites
Researchers from the University of California, Berkeley SRP Center studied the efficiency of groundwater cleanup at sites contaminated with both arsenic and trichloroethylene (TCE), two chemicals commonly found together at National Priorities List sites.
Cleanup of TCE-contaminated groundwater is often conducted using anerobic bacteria, which break down TCE and arsenic in the absence of oxygen. Arsenic hinders the effectiveness of this method because it becomes more mobile and toxic as it is broken down.
The researchers assessed arsenic and its more toxic breakdown product at various concentrations. They also evaluated its effect on the bacteria and rate of TCE cleanup. Initially, arsenic concentrations did not impact cleanup. However, as breakdown products of arsenic began accumulating and the researchers added more arsenic, TCE cleanup slowed.
According to the researchers, adding amino acids could help bacteria clean up these contaminants more efficiently by enhancing their tolerance to arsenic breakdown products. This study could inform the design of additional strategies to deal with sites contaminated by both arsenic and TCE.To learn more about this research, please refer to the following sources:
- Gushgari-Doyle S, Alvarez-Cohen L. 2020. Effects of arsenic on trichloroethene-dechlorination activities of dehalococcoides mccartyi. Environ Sci Technol 54(2):1276-1285. doi:10.1021/acs.est.9b06527 PMID:31913608
New Strategies to Enhance Contaminant Removal
Researchers from the University of California, Berkeley SRP Center recently described the underlying mechanisms involved in cleaning up contaminants using in situ chemical oxidation (ICSO) and identified new strategies to adjust treatment conditions to enhance contaminant removal.
When hydrogen peroxide is used for ICSO, petroleum products and other organic contaminants, such as phenols, are oxidized and broken down as the hydrogen peroxide decomposes into hydroxyl radicals. However, depending on the environmental conditions, this process may not work efficiently.
Using nuclear magnetic resonance, the team identified a new oxidative chemical formed in carbonate-rich environments as part of a chemical reaction with hydrogen peroxide. The chemical, called peroxymonocarbonate, can enhance the breakdown of certain contaminants when too few hydroxyl radicals are being formed for oxidation.
According to the authors, these fundamental results have broad implications or other sites undergoing cleanup.To learn more about this research, please refer to the following sources:
- Yang X, Duan Y, Wang J, Wang H, Liu H, Sedlak DL. 2019. Impact of Peroxymonocarbonate on the transformation of organic contaminants during hydrogen peroxide in situ chemical oxidation. Environ Sci Technol Lett 6:781-786. doi:10.1021/acs.estlett.9b00682
PAH and Hypoxia Exposures May Lead to Mitochondrial Dysfunction
Duke SRP Center researchers provided new insights into how two common stressors, PAHs and limited oxygen, interact to produce toxic effects in fish. Although both stressors have been studied extensively on their own, less is known about their interaction.
Researchers exposed zebrafish embryos to a PAH mixture and to limited oxygen, alone and in combination, to evaluate changes in the function of mitochondria, the powerhouse of cells. A decrease in mitochondria function can disrupt energy production and metabolism.
Individually, each stressor negatively affected zebrafish mitochondria and energy production. However, when the fish were exposed to PAHs and limited oxygen together, the authors found no evidence of worsened effects.
The researchers explained that one stressor can make the zebrafish more vulnerable to the other stressor. For example, when mitochondrial functioning is altered by limited oxygen, the zebrafish may be less able to respond to PAH toxicity. Because PAHs and limited oxygen are common environmental stressors that often occur together, the authors stress the importance of understanding how they interact to harm fish.To learn more about this research, please refer to the following sources:
- Lindberg C, Di Giulio RT. 2019. Polycyclic aromatic hydrocarbon and hypoxia exposures result in mitochondrial dysfunction in zebrafish. Aquat Toxicol 216:doi:10.1016/j.aquatox.2019.105298 PMID:31586484 PMCID:PMC6917040
Calcium Assists Uranium Transport in Plants
UNM SRP Center researchers reported for the first time that calcium is crucial to enhance uranium transport inside plant root cells. These findings provide new insight into how uranium is transported and accumulated in plants, which has important implications for using plants to clean up contaminants in the environment and for human exposure.
Researchers exposed Brassica juncea, a plant known to accumulate high levels of contaminants, to uranium and calcium carbonate. In the absence of calcium carbonate, the team reported that uranium accumulated primarily in the plant roots. As the calcium concentration increased, more uranium was found in the shoots of the plants and less was found in the roots.
They also identified the specific pathway, called the symplast pathway, that causes uranium to move from the roots to the shoots in the presence of calcium. According to the authors, understanding how uranium is transported in plants under different environmental conditions and how to increase its accumulation in plant tissues may improve how plants are used to clean up contaminants and better protect human health.To learn more about this research, please refer to the following sources:
- Hayek EE, Brearley AJ, Howard T, Hudson P, Torres C, Spilde MN, Cabaniss S, Ali AS, Cerrato JM. 2019. Calcium in carbonate water facilitates the transport of U(VI) in brassica juncea roots and enables root-to-shoot translocation. ACS Earth Space Chem 3(10):2190-2196. doi:10.1021/acsearthspacechem.9b00171 PMID:31742240 PMCID:PMC6859903
Accumulation of Methylmercury in Wood Frogs and Spotted Salamanders
Dartmouth SRP Center researchers showed that vernal pools are important hotpots where amphibians accumulate a more toxic and readily absorbed form of mercury known as methylmercury. Vernal pools are seasonal wetlands that fill up with rainwater during winter and spring but may be dry for part of the year.
Vernal pools are known to provide ideal conditions for mercury to convert to methylmercury, due to relatively high dissolved organic carbon, fluctuating water levels, and low pH and dissolved oxygen. However, little was known about how that translates to accumulation in vernal pool animals and nearby ecosystems. In a study in Vermont, the researchers investigated bioaccumulation of methylmercury in wood frog and spotted salamander eggs, larvae, and adults.
They researchers found that spotted salamander larvae rapidly accumulated methylmercury, with concentrations 1.5 to 2 orders of magnitude greater than their eggs, while wood frog larvae accumulated methylmercury more moderately, one order of magnitude greater than their eggs.
According to the authors, the research suggests that predators that feed on amphibian larvae in these ephemeral systems may be exposed to relatively high concentrations of methylmercury. The findings demonstrate the importance of vernal pools as a source of methylmercury bioaccumulation, and that larvae from the pools may lead to higher concentrations of methylmercury in the terrestrial ecosystem.To learn more about this research, please refer to the following sources:
- Faccio SD, Buckman KL, Lloyd JD, Curtis AN, Taylor VF. 2019. Bioaccumulation of methylmercury in wood frogs and spotted salamanders in Vermont vernal pools. Ecotoxicology doi:10.1007/s10646-019-02068-4 PMID:31243636
Metals and Fine Sediments Influence Recovery at Contaminated Sites
Water quality improvements at Superfund sites aren’t the only factor driving the success of restoration, according to a new study led by James Ranville at the Colorado School of Mines. The study findings suggest that sediment quality plays an important role, and that different communities of aquatic insect larvae respond differently to physical and chemical stressors, such as from fine sediments and metals.
The team combined field studies and mesocosm studies in the lab to predict how aquatic insect larvae, such as mayflies and caddisflies, would recover following the removal of acid mine waste from the North Fork of Clear Creek, a Superfund site in Colorado. They specifically evaluated how fine sediment and metals from mining operations influence the diversity and abundance of aquatic insects, an important indicator of ecosystem health.
Over 30 days in the field, they found the overall abundance of insect larvae was significantly lower in the metal-contaminated sediments compared to sediments that weren’t contaminated, and that insects were slower to colonize the contaminated sediment. They also found distinct communities of insect species in contaminated versus control sediments, and that fine sediment impacted insect groups differently. The mesocosm studies in the lab showed similar results.
The authors suggest that after water quality improvements, fine sediment and metals can still reduce the recovery potential for certain groups of insects, particularly those that are less mobile and able to avoid patches of habitat with more contamination.To learn more about this research, please refer to the following sources:
- Dabney B, Clements WH, Williamson JL, Ranville JF. 2018. Influence of metal contamination and sediment deposition on benthic invertebrate colonization at the North Fork Clear Creek Superfund Site, Colorado, USA. Environ Sci Technol 52:7072-7080. doi:10.1021/acs.est.7b06556 PMID:29812923 PMCID:PMC6008246
Enterosorbents Added to Food and Water to Reduce Toxicant Exposure During Disasters
Humans and animals can be exposed to mixtures of chemicals from food and water, especially during disasters such as extended droughts, hurricanes, and floods. Researchers at the Texas A&M SRP Center have developed a technology that can bind to mixtures of these hazardous chemicals in the body after exposure, reducing the amount that can be absorbed by the body. This technology, known as broad acting enterosorbent materials, can be added to food or water following natural disasters and other emergencies.
Food is susceptible to contaminants during droughts and extended periods of heat, when fungi can reach their optimal growth conditions for the production of toxins, such as aflatoxin B1 and zearalenone (ZEN). During disasters such as hurricanes and floods, water and food can be contaminated with potentially harmful chemicals because heavy rain and wind can mobilize toxic soil and sediments containing chemicals including pesticides, such as glyphosate.
The enterosorbent materials are made of nutrient-enriched calcium and sodium clays and were shown to effectively bind to aflatoxins, ZEN, and glyphosate, reducing their availability in the body. According to the authors, the enterosorbents may be able to decrease exposures to other chemical contaminants as well, including additional pesticides, polycyclic aromatic hydrocarbons, polychlorinated biphenyls, dioxins, and metals.To learn more about this research, please refer to the following sources:
- Wang M, Hearon S, Phillips TD. 2019. Development of enterosorbents that can be added to food and water to reduce toxin exposures during disasters. J Environ Sci Health B 54:514-524. doi:10.1080/03601234.2019.1604039 PMID:31014207 PMCID:PMC6681816
Collaborative Cross Mice Can Fill Data Gaps in Risk Assessment: PERC as an Example
The Collaborative Cross (CC) mouse model, developed using eight different strains of mice to capture over 90% of the known genetic variation in mice, can address susceptibility differences when studying effects of chemicals, according to new research from the Texas A&M SRP Center. Researchers used the CC mouse model to measure individual variability in kidney toxicity caused by tetrachloroethylene (PERC), a solvent frequently used in dry cleaning solutions, adhesives, and metal degreasers.
The EPA uses human health risk assessments to determine safety thresholds for exposures to harmful chemicals, often calculated based on studies in rodents. To protect the general human population, mathematical uncertainty factors are applied, which lower the safety threshold to account for data limitations such as differences between humans and rodents and differences between individuals in a population.
People with different genetic make-up may metabolize chemicals differently, making them more or less likely to experience harmful health effects based on how those metabolites are distributed within the body and interact with cells and organs. To better estimate differences in PERC toxicity within a population, the team used the CC mouse model to characterize how PERC exhibits kidney toxicity and how much the toxicity varies within the population of mice.
Mice exposed to PERC had lower kidney weight and markers of kidney injury. Among the 45 CC strains tested, the team found variation in PERC metabolism and toxicity. According to the authors, the default values used to account for variation protect 95% of the population, but perhaps not the most sensitive individuals. This study illustrates how the CC mouse population can be used to fine-tune protective adjustment factors for population variability in risk assessments.To learn more about this research, please refer to the following sources:
- Luo Y, Cichocki JA, Hsieh N, Lewis L, Wright FA, Threadgill DW, Chiu WA, Rusyn I. 2019. Using Collaborative Cross mouse population to fill data gaps in risk assessment: A case study of population-based analysis of toxicokinetics and kidney toxicodynamics of tetrachloroethylene. Environ Health Perspect 127(6):67011. doi:10.1289/EHP5105 PMID:31246107 PMCID:PMC6792382
Cost-Effective Solutions to Reduce Arsenic Exposure from Drinking Water in Bangladesh
According to a new study from the Columbia University SRP Center, long-term funding of free well testing on a massive scale can reduce exposure to arsenic. In Bangladesh, about 20 million people drink well water containing more than 50 micrograms per liter of arsenic, the Bangladesh drinking water standard. The study focuses on a population of 380,000 in rural Araihazar, Bangladesh over 18 years.
The researchers found that in Araihazar, testing drinking water for arsenic alone reduced the population exposed to arsenic in the short term by about 130,000. Testing helped communities identify the subset of low arsenic wells that could be shared at a total cost of less than US$1 per person. Testing also had a longer-term impact, as 60,000 exposed people inhabitants lowered their exposure by installing new wells to tap aquifers low in arsenic, costing US$30 per person.
In contrast, the installation of over 900 deep wells and a single piped-water supply system by the government reduced exposure of about 7,000 inhabitants at a cost of US$150 per person. According to the authors, the findings make a strong case for long-term funding of free well testing on a massive scale with piped water or groundwater treatment only as a last resort.To learn more about this research, please refer to the following sources:
- Jamil N, Feng H, Ahmed KM, Choudhury I, Barnwal P, van Geen AF. 2019. Effectiveness of different approaches to arsenic mitigation over 18 years in Araihazar, Bangladesh: Implications for national policy. Environ Sci Technol 53(10):5596-5604. doi:10.1021/acs.est.9b01375 PMID:31033281 PMCID:PMC6535723
Comparing Fish and Worm Models to Screen Contaminants for Neurotoxicity
According to a new study from the OSU SRP Center, combining data from zebrafish and flat worms may be useful in understanding how hazardous substances impact development and behavior.
Researchers exposed zebrafish and flat worms to 87 chemicals from five different chemical classes, including pharmaceutical drugs, flame retardants, polycyclic aromatic hydrocarbons, and pesticides. Negative effects caused by the chemicals included developmental delays, physical abnormalities, death, and altered behavior. Effects were observed in zebrafish for 86 of 87 chemicals, while worms exhibited impacts for 50 out of the 87.
Though zebrafish experienced effects from more chemicals compared to flat worms, both provided valuable information about chemical impacts during development. Studies in zebrafish revealed more information about physical abnormalities caused by chemicals, whereas flatworms demonstrated more behavioral impacts. The researchers also compared their results to 28 of the chemicals that had previously been tested with rodents. They found most chemicals that were toxic to rodents were also toxic to zebrafish and flat worms.
According to the authors, although zebrafish and flat worm models are unlikely to capture all chemicals that are hazardous to human health, they may be beneficial as a primary screening tool to prioritize chemicals for further study. Combining data from alternative model organisms, such as fish and worms, may be more cost-effective and time-efficient than carrying out chemical toxicity studies on rodents.To learn more about this research, please refer to the following sources:
- Hagstrom D, Truong L, Zhang S, Tanguay RL, Collins ES. 2019. Comparative analysis of zebrafish and planarian model systems for developmental neurotoxicity screens using an 87-compound library. Toxicol Sci 167(1):15-25. doi:10.1093/toxsci/kfy180 PMID:30011007 PMCID:PMC6317421
Measuring Uptake of Contaminants in Fish and Blue Crabs
Passive samplers have emerged as a promising tool to measure the availability of chemicals and estimate their potential for accumulation in animals based on exposure from sediment at contaminated sites. In a new study, researchers at the University of Rhode Island SRP Center described their analysis of a variety of contaminants, including pesticides, polybrominated diphenyl ethers (PBDEs), and polychlorinated biphenyls (PCBs) in sediment, porewater, and river water using low-density polyethylene passive samplers. They also measured contaminants in 11 different finfish species and blue crab from the lower Passaic River. In addition, they measured per- and polyfluoroalkyl substances (PFAS), specifically perfluorinated alkyl acids (PFAAs), in water samples, sediment, and fish.
They found that the best predictors of accumulation of contaminants in animals, or bioaccumulation, were porewater concentrations for PCBs and pesticides, and sediment organic carbon for PBDEs and PFAAs. Although banned decades ago, contamination by legacy pollutants is widespread in the aquatic environment of the lower Passaic River. The results of the study indicate that concentrations of contaminants in porewater and river water, and in sediments for some chemicals, can be used to estimate concentrations in fish and crabs.
The results also imply that in certain systems, bioaccumulation needs to be considered to predict concentrations of contaminants in top predators. Measured tissue concentrations of certain types of PFAS were 1.4 to 2.7 times higher in fish than what was predicted from sediments.To learn more about this research, please refer to the following sources:
- Khairy M, Noonan GO, Lohmann R. 2019. Uptake of hydrophobic organic compounds, including organochlorine pesticides, polybrominated diphenyl ethers, and perfluoroalkyl acids in fish and blue crabs of the lower Passaic River, New Jersey, USA. Environ Toxicol Chem 38(4):872-882. doi:10.1002/etc.4354 PMID:30614049 PMCID:PMC6475076
PFAS Exposure is Associated with Liver Cell Death but not Inflammation in Humans
University of Louisville SRP Center researchers led by Matthew Cave have reported that PFAS exposures are associated with liver disease. They further revealed the underlying mechanism of this association where PFAS exposure was linked to liver cell death and changes in adipocytokines, which are small proteins secreted by fat tissues and are involved in inflammatory and metabolic responses.
PFAS are man-made chemicals that have been used extensively in consumer products due to their grease, stain, and water-resistant properties. Using banked blood samples from the C8 Health Study, a population of individuals in Ohio and West Virginia who were exposed to PFAS-contaminated water over a period of approximately 20 years, the team evaluated the relationship between PFAS and biological markers of liver disease.
They reported a positive association between PFAS exposure and CK18 M30, an indicator of liver cell death, and adiponectin, a protein hormone involved in regulating glucose levels and the breakdown of fatty acids. They also found an inverse relationship between PFAS exposure and tumor necrosis factor alpha and interleukin 8, both of which are cytokines involved in inflammation. The study is the first report that PFAS exposure can lead to liver cell death without increasing the inflammatory immune response.
According to the authors, this study provides evidence that PFAS exposure can be linked to fatty liver disease, though longitudinal studies are needed to better understand the impacts of PFAS exposure on the liver.To learn more about this research, please refer to the following sources:
- Bassler J, Ducatman A, Elliott M, Wen S, Wahlang B, Barnett J, Cave MC. 2019. Environmental perfluoroalkyl acid exposures are associated with liver disease characterized by apoptosis and altered serum adipocytokines. Environ Pollut 247:1055-1063. doi:10.1016/j.envpol.2019.01.064 PMID:30823334 PMCID:PMC6404528
Resilience Through Regeneration: The Economics of Repurposing Vacant Land with Green Infrastructure
In a new study, Texas A&M SRP Center Community Engagement Core co-leader Galen Newman used landscape performance measures to evaluate the cost and flood performance of green infrastructure projects for three neighborhoods in Houston, Texas. Results suggested that when using green infrastructure to regenerate vacant properties, flood risk continually decreases, upfront economic costs increase in the short term when compared to conventional development, but the long-term economic return on investment is much higher.
Many urban areas affected by flood disasters are also becoming increasingly ecologically and socially fragmented due to the accumulation of vacant properties. While redevelopment is often viewed as the primary objective in regenerating vacant properties, they can also potentially provide ecological and hydrological land uses. This research examined the hydrological and economic effects of green infrastructure as a strategy for vacant land regeneration.
Three design projects were carried out independently in three underserved neighborhoods in Houston following a “Resilience through Regeneration” approach. Resilience through Regeneration refers to a design approach which seeks to mitigate community-scaled flood effects through repurposing efforts of vacant properties around green infrastructure. This approach incorporates both public engagement and site-specific programming.To learn more about this research, please refer to the following sources:
- Newman G, Dongying L, Rui Z, Dingding R. 2019. Resilience through regeneration: the economics of repurposing vacant land with green infrastructure. Landsc Archit Front 6:10-23. doi:10.15302/J-LAF-20180602 PMID:30761217 PMCID:PMC637032
Reusable Sorbents Offer Strategy to Remove PFAS from Water
Researchers from the Texas A&M University SRP Center have recently developed reusable hydrogel sorbents to remove PFAS from water. PFAS are industrial compounds that have been used in many consumer products, such as non-stick cooking pans, due to their unique oil and water repellent properties and are widely found in the environment. Exposure to PFAS has been linked to developmental problems, liver and kidney damage, and cancer in animal studies.
These innovative sustainable sorbents were found to remove all five of common PFAS tested, perfluorooctanoic acid (PFOA), perfluorooctanesulfonic acid (PFOS), perfluorobutanesulfonic acid (PFBS), perfluorobutanoic acid (PFBA), and GenX, from solution. These PFAS represent both long-chain PFAS that have been used widely in the past, and newer short-chain PFAS that were developed to replace them. Traditional approaches to clean up PFAS have not performed well for short-chain PFAS, like GenX, in particular.
Their results indicate that PFAS removal and desorption to regenerate the sorbent material depends on the specific properties of each chemical and chemical interactions between the PFAS and the sorbent. According to the authors, the ability to regenerate sorbents after use will reduce the overall treatment costs for PFAS.To learn more about this research, please refer to the following sources:
- Huang P, Hwangbo M, Chen Z, Liu Y, Kameoka J, Chu K. 2018. Reusable functionalized hydrogel sorbents for removing long- and short-chain perfluoroalkyl acids (PFAAs) and GenX from aqueous solution. ACS Omega 3(12):17447-17455. doi:10.1021/acsomega.8b02279
Links Between Prenatal Arsenic Exposure, Gestational Age, and DNA Methylation
Prenatal arsenic exposure is inversely associated with birth gestational age, according to a new SRP study. The study shows that methylation of specific regions of DNA in cord blood were linked with this effect on gestational age.
The researchers examined associations between arsenic exposure and DNA methylation, which modifies the way genetic information is expressed without directly changing the genetic code stored in DNA. They also examined how differences in exposure and DNA methylation were linked to reproductive outcomes in an established prospective birth cohort recruited in Bangladesh. They utilized a two-stage approach to test the hypothesis that methylation at specific regions of DNA would mediate the association between prenatal arsenic exposure and reproductive health outcomes. This two-stage approach was economical and potentially reduced the possibility of false discoveries.
The results support the hypothesis that arsenic exposure in utero can disrupt fetal programming that may play a role in the developmental origins of health and disease. Furthermore, this experimental framework for the discovery and validation of candidate methylation regions as mediators of exposures and health outcomes could be extended to other exposures and health outcomes.To learn more about this research, please refer to the following sources:
- Bozack AK, Cardenas A, Quamruzzaman Q, Rahman M, Mostofa G, Christiani DC, Kile ML. 2018. DNA methylation in cord blood as mediator of the association between prenatal arsenic exposure and gestational age. Epigenetics 13(9):923-940. doi:10.1080/15592294.2018.1516453 PMID:30175652 PMCID:PMC6284783