Organochlorine insecticide residues in Canadian foods - What are you really eating?

Dorothea F.K. Rawn, J. Brian Shields, Giacomo Conca
Food Research Division, Health Products and Food Branch, Health Canada, Ottawa, ON, K1A 0L2

Abstract

DDT and chlordane products have not been registered for use in Canada since 1985 and 1990, respectively. They are no longer considered to be pesticides in Canada, but rather classified as environmental contaminants, although these products are used as pesticides in other countries. These compounds are, however, detected in food samples, similar to those organochlorine insecticides still in use in Canada such as endosulfan and lindane. In general, pesticide residue data in food samples are determined for compliance purposes rather than exposure assessments. Health Canada, however, does collect food samples for surveillance purposes as part of the Total Diet Study. As part of this study, food is collected on an annual basis from different Canadian cities in order to determine pesticide levels in the average Canadian diet. Additionally, pesticide residues are measured in infant and junior food samples collected from across Canada to determine infant exposure to these compounds. Sample extraction has been performed using acetone: hexane (2:1) with gel permeation chromatography and Florisil cleanup. Analyses have been performed using gas chromatography - high resolution mass spectrometry. OC insecticides are generally detected at higher levels in lipid rich foods, than foods with a low lipid content. Total DDT ( o,p'-DDT, p,p'-DDT, o,p'-DDD, p,p-DDD and p,p'-DDE) and total chlordane ( heptachlor, heptachlor epoxide, oxychlordane, trans-nonachlor, -chlordane and -chlordane) concentrations were determined to range between 0.01 ng/g lipid and 450 ng/g lipid, and 0.02 ng/g lipid and 69 ng/g lipid, respectively in total diet samples. Total HCH ( -HCH, -HCH and -HCH) was observed at levels ranging from 0.02 ng/g lipid to 64 ng/g lipid in total diet samples. Endosulfan ( endosulfan I, endosulfan II and endosulfate) levels in total diet samples ranged from below detection limits to 2.5 ng/g lipid, while levels in infant and junior foods were at levels below detection limits to a maximum concentration of 6.3 ng/g lipid. Total DDT concentrations in baby foods ranged between 5.3 ng/g lipid and 95 ng/g lipid. Highest concentrations of total chlordane were found in infant custard samples (2.8 ng/g lipid), whereas total HCH levels were greatest in junior chicken and vegetable samples (20 ng/g lipid). In general, residue concentrations were found in decreasing order of appearance: DDT> chlordane > HCH > endosulfan . The concentrations observed in the food samples studied to date are below the maximum residue limits (MRL) identified in the Canadian Food and Drug Regulations.