Time tendency of organochlorine pesticide residues in cow's milk from agricultural region of Veracruz (Mexico)

Organochlorine pesticide levels in 150 cow's milk samples collected from a central agrarian region of Veracruz State during 1996 were determined. p,p'-DDE was detected in all samples with a mean level of 0.053 mg/kg, beta-HCH was found in 99% of the samples analyzed at a mean level of 0.104 mg/kg followed by p,p'-DDT detected in 97% of the samples with a mean level of 0.085 mg/kg. The gamma-HCH mean levels were higher on March and December due to anti-livestock ectoparasite programs during the dry season. Meanwhile, p,p'-DDT mean levels were significantly higher in February, June, September and October due to anti-malaria actions.