Page 3: Guidelines for Canadian Drinking Water Quality: Guideline Technical Document – Chlorpyrifos


Chlorpyrifos was not detected in a survey of 511 samples from municipal and private drinking water supplies encompassing Metropolitan Toronto (1971 to 1982), Manitoba (1986) and Alberta (1978 to 1985) (detection limits 0.20 and 0.04 µg/L).Footnote 9 It was not found in 446 samples taken from surface waters of the Grand River and Thames River basins, although nearly 3000 and 7500 kg/year, respectively, had been used in these areas (detection limit 0.1 µg/L).Footnote 10

Based on the residue tolerance limits set by the Food Directorate of the Department of National Health and Welfare,Footnote 11 the theoretical maximum daily intake of chlorpyrifos from food is 0.07 mg/d, which represents 10% of the acceptable daily intake (ADI) of 0.7 mg/d for a 70-kg adult.Footnote 12 Chlorpyrifos was detected in only 49 of 6391 domestic food samples in the United States, 94% of which had concentrations below 2.0 ppm; in imported foods, chlorpyrifos was detected in 1777 of 12 044 samples, with all but five samples containing concentrations at or below 0.5 µg/g.Footnote 13 The average daily dietary intake of chlorpyrifos has been estimated to be 0.241 µg, based on the U.S. market basket survey.Footnote 14

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