Occurrence of glyphosate in surface waters of Southern Ontario.

Glyphosate in surface waters of southern Ontario (Canada) was studied over a 2-year period. A small percentage of samples exhibited glyphosate concentrations greater than the analytical limit of quantitation (17 microg a.e./L), and the maximum concentration of glyphosate measured was 40.8 microg/L. No samples of roughly 500 analyzed exceeded the Canadian Water Quality Guideline of 65 microg a.e./L considered protective of aquatic life. Typical concentrations of glyphosate in amphibian habitats were well below a range of toxicity thresholds for aquatic organisms, and were thus judged to be unlikely to pose a substantial risk to either sensitive amphibian larvae or other aquatic biota.