Abstract
Residue levels of seven organophosphorus pesticides (OPPs), widely used as dairy cattle ectoparasiticides or in crops used for animal feed, were determined in raw milk and infant formulas. A total of 312 samples were collected (70 from infant formulas and 242 from raw milk) biweekly during a 24-month period. Pesticides were extracted by means of a solid phase system into acetone. An extract aliquot of acetone was injected into a gas chromatograph (GC) with a nitrogen-phosphorus detector. Recoveries of pesticides spiked in milk samples were 62.2 – 97.2 %. The frequency of total samples containing detectable levels of OPP residues was 6.73 % in total milk and 8.67 % in raw milk. The highest percentage incidence measured was for dichlorvos (5.78 %), followed by coumaphos (2.06 %), and parathion methyl (0.83 %). The range of positive results was calculated to be between 0.005 and 0.220 mg kg− 1. No residue was detected in the final product (infant formulas), so any risk to consumer health, especially to children's health, would be limited.