Document Type



The frequent and heavy use of pesticides in agriculture has led to the contamination of surface and ground waters worldwide. Many questions have arisen about the human health effects of exposure to these pesticides and their mixtures. Most of the information about the adverse human health effects due to environmental contaminants comes from studies that focus on exposure to single rather than multiple contaminants since many of the environmental regulations regarding levels of xenobiotic contamination refer only to individual compounds. In this study, MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) cell proliferation assays were performed with normal human fibroblasts to test the toxicity of environmentally relevant levels of three of the most heavily used pesticides in the United States: atrazine, metolachlor and diazinon, either alone or in binary mixtures. MTT analysis showed a statistically significant decrease in cell proliferation compared to the control at low levels of each of the three single pesticides tested (> 0.8 ppb (parts per billion) atrazine, > 1.6 ppb metolachlor and > 1.6 ppb diazinon) as well as with binary mixtures of either atrazine and metolachlor or atrazine and diazinon. When experimental results were compared to predictions of toxicity based on the response addition model, the mixture of atrazine and metolachlor was shown to generally be antagonistic, while the mixture of atrazine and diazinon resulted in additive responses. These findings, along with other studies, indicate that current regulatory standards for pesticides in drinking water may not sufficiently protect human health.

Publication Date


Journal Title

International Journal of Global Health





First Page


Last Page



©2003 International Journal of Global Health



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Public Health Commons



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