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Final Progress Reports: University of California-Davis: Immunoassays for Human and Environmental Health Monitoring

Superfund Research Program

Immunoassays for Human and Environmental Health Monitoring

Project Leader: Bruce D. Hammock
Grant Number: P42ES004699
Funding Period: 1995-2023
View this project in the NIH Research Portfolio Online Reporting Tools (RePORT)

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Final Progress Reports

Year:   2014  2009  2004  1999 

To understand the potential health effects of environmental exposures on people, rapid, accurate methods to measure the amount of exposure are needed. Immunoassays are ideal methods for rapid screening when there are a large number of samples to analyze, for example in studies monitoring environmental or human exposure. This project makes and uses immunoassays for chemicals that have the potential for widespread exposure and impact on human health, particularly pesticides, polybrominated diphenyl ether flame retardants (PBDEs) and antimicrobial compounds. Immunoassays have been used for more than 30 years, thus researchers also develop novel reagents to improve the sensitivity, increase the throughput of analysis and make the assays more robust for analysis of any type of environmental or biological sample.

Recently, researchers have focused on two classes of insecticides called pyrethroids and phenylpyrazoles. Although less toxic to mammals than some insecticides, pyrethroids and phenylpyrazoles are toxic to non-target organisms like aquatic invertebrates. These insecticides are also used in the home, on pets and in the garden as well as by pest control operators; exposure to the general population is likely. Researchers have developed assays to the insecticides and the expected human metabolites of these insecticides. The metabolite assay is currently being used to identify the pathways of exposure to pyrethroids in farmworker families living in the Central Valley of California. Results from this study will improve farmworker health by suggesting behaviors and activities to reduce pesticide exposure.

PBDEs are newly emerging environmental contaminants found in many furniture foams and plastics used in electronics. Cell-based and animal model studies suggest that PBDEs affect the nervous system. The immunoassay for PBDE-47, one structural analog found in high abundance, will be used to understand the relationship between PBDEs and potential effects on humans by measuring PBDEs in foam, serum and dust from homes with and without children with autism spectrum disorder. Other emerging contaminants of interest are triclocarban and triclosan that are used as antimicrobial agents in many personal care products. These compounds appear to be resistant to sewage treatment and thus accumulate in sewage sludge. Sludge is sometimes used as a fertilizer, thus there are concerns about build up in soil, leaching to groundwater or translocation to crops. Immunoassays have been developed for use in environmental monitoring and efforts are now directed toward development of assays for human monitoring.

Novel nanoparticles that are magnetic and fluorescent have been used in a variety of applications, for example to measure several chemicals simultaneously. The most important characteristic of the nanoparticles is that their intrinsic fluorescence provides a method of internal standardization greatly improving the precision and accuracy of the analysis. Additional improvements to the nanoparticles to increase brightness are also under way.

Researchers have developed mimics of key reagents in the assay using a molecular biology technique called phage display. Use of these reagents allows them to detect lower amounts of chemical as well as to detect the chemical with less interference from similar chemicals. These advancements mean that human and environmental monitoring studies will have more rapid, sensitive and ultimately more portable assays. For example, the PBDE assay has been developed to include the phage display reagents and formatted into a simple dipstick. A very simple method to extract PBDEs from furniture foam has been developed. Along with the dipstick, this will allow onsite assessment of furniture foam contamination by PBDE-47. Such tools allow researchers to gather more comprehensive information on the relationship of human exposure to environmental contaminants.

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