Organochlorine pesticide residues in cow's milk from a tropical region of Mexico

A monitoring study was conducted to assess the magnitude of DDT [(1,1,1-trichloro-2,2-bis(p-chlorophenyl) ethane)] and HCH ( hexachlorocyclohexane) contamination of bovine milk from the central tropical region of Mexico as the chemicals are extensively used in livestock and public-health programmes. Among pesticide residues analysed, the milk samples collected from Tlalixcoyan showed a mean level of gamma-HCH (0.128 mg kg(-1)), which was significantly higher than residues in milk samples from Medellin (0.049 mg kg(-1)) and Paso San Juan (0.022 mg kg(-1)). The mean level of pp'-DDE in Medellin samples (0.039 mg kg(-1)) was significantly higher than in Paso San Juan (0.018 mg kg(-1)) and Tlalixcoyan (0.024 mg kg(-1)) milk samples. The pp'-DDT mean level from Medellin milk samples (0.089 mg kg(-1)) was significantly higher than the levels detected in the other two areas. The highest mean Sigma-DDT level detected in Medellin samples (0.146 mg kg(-1)) was three times the FAO/WHO tolerance level. The highest acceptable daily intakes calculated for Sigma-DDT were 0.017 mug kg(-1) bw day(-1) for adults and 0.530 mug kg(-1) bw day(-1) for infants; for gamma-HCH residues, they were 0.021 mug kg(-1) bw day(-1) for adults and 0.666 mug kg(-1) bw day(-1) for infants, indicating that infants are more exposed to pesticide residues. Results indicate that cattle exposure to HCH and DDT results in high levels in dairy milk and a potential health risk for consumers.