The clastogenic potential of triazine herbicide combinations found in potable water supplies.

Pesticide contamination of drinking water supplies has increased over the past decade. A major concern is how exposure to combinations of low levels of pesticides, especially herbicides, could affect public health. Flow cytometric analysis was performed to determine the clastogenic potential of herbicide interaction on Chinese hamster ovary (CHO) cells. The cells were exposed to atrazine, simazine, cyanazine, and all possible combinations of these chemicals for 48 hr. Two concentrations were used for each sample: the U.S. EPA maximum contamination level (MCL) and the highest contamination level found in Illinois water supplies. Nuclei were isolated from the cells and analyzed by flow cytometry. The effects of clastogenicity were measured by the coefficient of variation (CV) of the G1 peak of whole cells and the change in CV of the largest chromosome in the flow karyotype. At both levels tested, atrazine caused chromosomal damage to the CHO cells. Simazine was observed to induce whole-cell clastogenicity but not flow karyotype damage. Cyanazine did not induce any measurable chromosomal damage in either analysis. Each of the herbicides, although all three were triazines, had different effects with respect to chromosome damage as measured by flow cytometry. CHO cells treated with a combination of atrazine and simazine, or atrazine and cyanazine, were observed to have whole-cell and flow karyotype damage. This damage was, however, equal to or less severe than the damage caused by either atrazine or simazine alone. No synergy was observed. When all three herbicides were combined, three of the four possible combinations gave no observable clastogenic response.