Contaminants in natural aquatic systems are often persistent and therefore have the potential to induce toxicity in humans through drinking water ingestion. Exposure to more than one contaminant at a time is common and often more detrimental to overall health than exposure to a single substance. This study examines the combinatorial effects of two classes of compounds found ubiquitously in drinking water across the U.S., namely pesticides and metal ions. Glyphosate (N-(phosphonomethyl)glycine), a hydrophilic compound, is the active ingredient in several herbicides. Lead acetate is chemically stable, an anthropogenic pollutant, and is ubiquitous in natural aquatic systems. Zebrafish (<i>Danio rerio</i>) embryos were used in this study as a model for investigating developmental delays after controlled exposures. Embryos were exposed to six increasing concentrations, including a control, of glyphosate (ranging 0.001 ppm to 10 ppm) and lead acetate (ranging 0.5 ppm to 4 ppm) as single inoculation exposures followed by co-exposures of both glyphosate and lead acetate simultaneously at similar dosing regimens (ranging 0.001:0.5 ppm to 10:4 ppm). Sublethal endpoints such as hatching, spine curvature, somite formation, coagulation, and evidence of non-detached tail were quantified to determine potencies. Preliminary testing indicates that the higher concentrations of the individual chemicals (10 ppm for glyphosate and 4 ppm for lead acetate) correlate with a later hatching abundance (5 days post fertilization) while the higher concentrations of the chemicals as co-exposures correlates with earlier hatching abundance (4 days post fertilization). A trend of increased bent spine abundance was observed following lead acetate exposures when compared to co-exposures, suggesting potential antagonistic effects induced by glyphosate. Increased levels of coagulation were observed following the co-exposure as compared to the individual exposures, suggesting potential synergistic effects. Glyphosate and lead acetate are just two of hundreds of contaminants found in U.S. drinking water. These results support the urgent need to test the effects of pesticides in drinking water systems that also contain heavy metal species.

Combinatorial effects of glyphosate and lead acetate in the development of zebrafish (<i>Danio rerio</i>) embryos

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Combinatorial effects of glyphosate and lead acetate in the development of zebrafish (Danio rerio) embryos