Seasonal Variation in Residues of DDT and HCH in Dairy Milk in Punjab, India

The seasonal variation in the concentration of DDT and HCH residues in dairy milk in Ludhiana and Patiala districts of Punjab is reported. Average concentration of Σ-DDT residues in samples from Ludhiana district declined from January to July, showed a sharp increase during August-September and remained almost steady up to December. Those from Patiala remained at low level throughout the year. Ninety two per cent of the samples from Ludhiana district as compared to 2.8% from Patiala district exceeded the maximum residue limit of 0.05 mg kg⁻¹ of Σ-DDT. About 94 and 55% of the samples from Patiala and Ludhiana districts respectively exceeded the maximum residue limit of 0.02 mg kg⁻¹ for β-HCH. The trend of Σ-DDT residues correlated mainly with DDT usage for control of mosquito-vectors of malaria. The fluctuation in Σ-HCH residues was attributable to iti usage both in agriculture and public health.