Simulated gut system to test soil contaminated with arsenic

Washington, Oct 8 : A team of scientists have simulated a gastrointestinal system in order to test soil contaminated with arsenic for its potential to harm humans, a method that is likely to save time and money for people hoping to repurpose land with an industrial past.

Chronic exposure to arsenic can cause cancer, impaired nerve function, kidney and liver damage, and skin lesions.

Most testing for potential arsenic exposure is conducted in recognition of the fact that humans unknowingly eat a little bit of soil each day. For children who might play on contaminated soil and ingest dirt, the testing is considered particularly important.

An in-vitro method that simulates digestion of arsenic-laden dirt in a glass flask has been shown in comparison studies at Ohio State University to be as effective as arsenic testing in young pigs, the most common animal model used for this purpose.

This phase of testing is meant to determine how much of the ingested soil arsenic dissolves during digestion and eventually enters the bloodstream.

Some soils can bind up arsenic, preventing the compound from dissolving, which reduces the exposure risk.

"We can't tell you how much arsenic gets absorbed into the blood with the in-vitro method, but we can tell you how much dissolves from the soil in the gastrointestinal tract. Arsenic can't get into the blood unless it dissolves," said Nicholas Basta, professor of soil and environmental chemistry and lead developer of the testing method.

"And right now, we tell people that under worst-case assumptions, any arsenic that gets dissolved also gets absorbed," he added.

Basta and colleagues combine enzymes and other chemicals in a simple glass flask to simulate stomach contents.

After introducing arsenic-contaminated soil to the solution, the scientists stir the contents to mimic a churning stomach and adjust the pH level to maintain proper acidity.

The researchers later simulate the introduction of the solution to the small intestine, where absorption would occur in the body.

The method can't mimic the animal absorption of arsenic into the blood, so the scientists instead determine how much arsenic has dissolved during the process.

The more that dissolves, the more likely the contaminated soil is dangerous to humans and requires treatment or remediation.

Basta and colleagues are continuing to refine the method, but have already put it to use testing between 20 and 50 soil samples each year.

ANI