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Ambient air concentrations of pesticides used in potato cultivation in Prince Edward Island, Canada.

Ambient air concentrations of nine selected pesticides used in potato cultivation were investigated on Prince Edward Island by collecting samples during the summer of 1998 at three potato farm sites and one non-agricultural site. In 1999, air samples were collected at a single potato farm site during local application of pesticides. The fungicide chlorothalonil was the only pesticide detected in every sample in both years, even in samples with a duration as little as 5 h. In 1998, maximum (45-458 ng m(-3)) and mean (22-193 ng m(-3)) concentrations of chlorothalonil from composite 42 h samples were one to two orders of magnitude greater at agricultural sites than at the non-agricultural site (3.9 and 2.5 ng m(-3), respectively). Maximum and mean concentrations of chlorothalonil from combined 24 h samples at the farm site in 1999 were higher than those measured in 1998 (636 and 284 ng m(-3), respectively). The ubiquitous presence in air of relatively high concentrations of chlorothalonil in agricultural areas on Prince Edward Island is likely related to its repeated use on potato farms where fungicides account for 80-90% of pesticides applied. Eight of nine pesticides were detected at farm sites in 1998 and they are ranked by mean concentration from highest to lowest as follows: chlorothalonil, methamidophos, azinphos-methyl, alpha-endosulfan, beta-endosulfan, pirimicarb, metobromuron, metribuzin, metalaxyl and fluazifop-P-butyl. Concentrations of metalaxyl, pirimicarb, metobromuron and fluazifop-P-butyl in air are among the first reported values for these pesticides. Five pesticides were detected at the Summerside farm in 1999, but only two fungicides (chlorothalonil and metalaxyl) were used locally, while the presence of metribuzin, alpha-endosulfan and methamidophos in air was not associated with local application. Evidence of pesticide drift was observed for chlorothalonil, alpha-endosulfan and methamidophos, and these pesticides were identified as being of high concern in terms of potential wildlife exposure on the Island.