| Pesticides in Surface Drinking-Water Supplies of the Northern Great Plains David B. Donald,1 Allan J. Cessna,2,* Ed Sverko,3 and Nancy E. Glozier4 1 Environment Canada, Regina, Saskatchewan, Canada; 2Agriculture and Agri-Food Canada, Saskatoon, Saskatchewan, Canada; 3National Laboratory for Environmental Testing, Environment Canada, Burlington, Ontario, Canada; 4National Hydrology Research Centre, Environment Canada, Saskatoon, Saskatchewan, Canada Abstract
Background: Human health anomalies have been associated with pesticide exposure for people living in rural landscapes in the northern Great Plains of North America. Objective: The objective of this study was to investigate the occurrence of 45 pesticides in drinking water from reservoirs in this area that received water primarily from snowmelt and rainfall runoff from agricultural crop lands. Methods: Water from 15 reservoirs was sampled frequently during the spring pesticide application period (early May to mid-August) and less frequently for the remainder of the year. Drinking water was sampled in early July. Sample extracts were analyzed for pesticide content using mass spectrometric detection. Results: We detected two insecticides and 27 herbicides in reservoir water. Consistent detection of a subset of 7 herbicides suggested that atmospheric deposition, either directly or in rain, was the principal pathway from fields to the reservoirs. However, the highest concentrations and number of herbicides in drinking water were associated with runoff from a localized 133-mm rainfall over 15 days toward the end of spring herbicide application. Water treatment removed from 14 to 86% of individual herbicides. Drinking water contained 3–15 herbicides (average, 6.4) . Conclusions: We estimated the mean annual calculated concentration of herbicides in drinking water to be 75 ng/L (2,4-dichlorophenoxy) acetic acid, 31 ng/L (2-chloro-4-methylphenoxy) acetic acid, 24 ng/L clopyralid, 11 ng/L dichlorprop, 4 ng/L dicamba, 3 ng/L mecoprop, and 1 ng/L bromoxynil. The maximum total concentration of herbicides in drinking water was 2,423 ng/L. For the seven herbicides with established drinking water guidelines, all concentrations of the individual chemicals were well below their respective guideline. However, guidelines have not been established for the majority of the herbicides found in drinking water or for mixtures of pesticides. Key words: drinking water, northern Great Plains, pesticides, reservoirs, water treatment. Environ Health Perspect 115:1183–1191 (2007) . doi:10.1289/ehp.9435 available via http://dx.doi.org/ [Online 15 May 2007]
Address correspondence to D.B. Donald, Environment Canada, Room 300 Park Plaza, 2365 Albert St., Regina, Saskatchewan, Canada, S4P 4K1. Telephone: (306) 780-6723. Fax: (306) 780-5311. E-mail: david.donald@ec.gc.ca *Current address: Environment Canada, National Hydrology Research Centre, Saskatoon, Saskatchewan, Canada. We thank the communities and their representatives who agreed to participate in this study. We appreciate the superb efforts of L. Mottle, R. Crosley, J. Syrgiannis, W. Aitken, D. Legault, and B. Holliday, who collected water from reservoirs and municipal facilities over a large geographic area, and J. Bailey for analysis of the water samples for sulfonylurea herbicides. This project was supported by the Pesticide Science Fund of Environment Canada. The authors declare they have no competing financial interests. Received 19 June 2006 ; accepted 15 May 2007.
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