Superfund Research Program

May 2024

Hot Publication

Researchers from the University of Arizona SRP Center revealed how cadmium and arsenic, two toxic metals that frequently occur in soils together, may interact inside the human body. The effects of each individual metal on the digestive system have been studied, but little is known about how the contaminants behave when ingested simultaneously.

The team used an artificial gastrointestinal (GI) tract, developed in a lab, to measure the amount of arsenic or cadmium that could enter the bloodstream, called bioaccessibility. They exposed the GI tract to cadmium only, arsenic only, and a mixture of both contaminants. They also added ferrihydrite, an iron mineral commonly found in dust, and pepsin, an enzyme responsible for protein digestion, as variables to better capture realistic conditions in the human body.

The team reported that cadmium bioaccessibility increased with the addition of arsenic, while arsenic bioaccessibility decreased with the addition of cadmium. However, arsenic transformed into a more toxic form in the presence of cadmium.

Using advanced spectroscopy techniques, the researchers found that each metal formed complexes with ferrihydrite. However, the presence of both metals promoted the release of cadmium from ferrihydrite complexes but inhibited the release of arsenic. Bioaccessibility of both metals increased when pepsin formed soluble, or dissolvable, complexes with the metals.

By improving understanding of interaction between metal contaminants, the study could inform health risk assessments, according to the authors. The study may also inform regulatory strategies for soils and dust contaminated with toxic metal mixtures.

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