UNIVERSITY PARK, Pa. — Pollutants known as “contaminants of emerging concern” or chemicals that could potentially harm human health and have been found in the environment, including pesticides, ingredients from personal care products, pharmaceuticals and perfluoroalkyl substances (PFAS), are increasingly found in streams and lakes. A team led by researchers at Penn State recently demonstrated the accuracy and utility of a new method to find even very low levels of these substances in surface waters. They reported their findings in the Science of the Total Environment.

Emerging contaminants, which flow into streams from wastewater treatment plants, agricultural runoff and industrial discharges, as well as from septic tanks, pose serious threats, according to team leader Heather Preisendanz, professor of agricultural and biological engineering at Penn State. Among them are risks for human health, including potential effects on the endocrine, immune and reproductive systems. For example, bisphenol-A (BPA), phthalates and certain pharmaceuticals have been linked to hormonal disruptions and developmental abnormalities, while antibiotics may contribute to the development of antibiotic-resistant bacteria. 

“Aquatic species are at risk, as well, including effects on growth, reproduction and behavior,” she said. “For instance, PFAS have been linked to developmental abnormalities in fish and exposure to antidepressants has been shown to alter the behavior of fish and other aquatic organisms.”

The researchers reported that their new method — which employs cell-based bioassays that measure the concentration or potency of substances by their effect on living cells — detected potential ecological hazards in water samples that conventional tests that target and measure concentrations of specific chemicals did not. Using samples collected from nine sites in three central Pennsylvania streams, the researchers compared results of the two methods. 

With the conventional targeted chemical concentration analysis, the team evaluated water samples for 47 contaminants of emerging concern, including pesticides, ingredients in personal care products, and veterinary and human pharmaceuticals. The contaminants examined were based on previous research in the studied watershed and included 21 pharmaceuticals, 15 pesticides and 11 personal care products. 

The researchers used an exposure-activity ratio for each chemical, which indicates chemical concentrations that might cause cellular damage, and a toxicological prioritization index, which is a tool that helps assess the threat posed to aquatic life from chemicals by integrating data from multiple sources and displaying it in a visual profile. With this data, the researchers determined that the pharmaceutical carbamazepine, typically used to treat seizure disorders; the pesticide carbaryl, used to control ticks, fleas and more; and the herbicide atrazine, used to kill and prevent weeds, posed the greatest concerns.

However, the alternate method, using cell-based bioassays, indicated the presence of contaminants beyond the 47 evaluated with the conventional analysis at all nine sampling sites. Because there is such a wide range of chemicals present in the stream water comprising a complex mixture, chemical analysis alone is insufficient to monitor potentially impacted ecosystems, according to first author Jack Vanden Heuvel, professor of molecular toxicology in the College of Agricultural Sciences at Penn State. 

Instead, he explained, the researchers applied the alternate methods: bioassays designed to be predictive of potential adverse events caused by contaminants to assess the cumulative chemical activity in stream waters. The bioassays, he said, allowed the team to assess the threat posed by complex mixtures of chemicals.

“Predicted activity based on individual chemical analysis and calculated exposure-activity ratio were different than those measured by bioassays, indicating that biologically active chemicals are present in the samples that were not included in the targeted analyses,” said Vanden Heuvel. “Taken together, these data show that chemical analysis and exposure activity ratio analysis are beneficial for prioritization of chemicals and pollution sites, whereas cell-based bioassays are more inclusive of known and unknown chemical contaminants, making them more useful for overall water quality analysis.”

Contributing to this research at Penn State were Megan Granda, research associate in the Department of Veterinary and Biomedical Sciences, and Francesca Ferguson, doctoral student in ecology; and Scott Glaberman, School of Biosciences, University of Birmingham, United Kingdom.

The U.S. Department of Agriculture’s National Institute of Food and Agriculture financially supported this work.