Pesticides in fresh potatoes sold in farmers' markets in Alberta, Canada.

Fresh potatoes (228 samples) from 34 farmers' markets in Alberta were analyzed for 29 pesticides. Residues of three different pesticides were found in the samples tested with chlorpropham being most frequently detected (n = 13) at concentrations ranging from 15 to 7,600 μg kg(-1). Azoxystrobin (n = 11) and imidacloprid (n = 8) were found at concentrations ranging from 0.6 to 5.1 and 15-31 μg kg(-1), respectively. All pesticide concentrations were below Canadian maximum residue limits as established for potatoes. No pesticide residues were detected in 23 potato samples obtained from certified organic farmers.