Quantitative Estimation of Persistent Organochlorine Pesticide Residues in Milk and Some Traditional Dairy Products in the City of Tobruk, Libya

Abstract

Persistent organochlorine pesticides (OCPs) are environmental contaminants that pose significant health risks due to their bioaccumulation and long-term persistence. This study quantitatively assessed residues of seven OCPs in fresh milk and traditional dairy products (butter and ghee) from Tobruk, Libya, and evaluated the associated health risks. Thirty samples (10 fresh milk, 10 national butter, 10 national ghee) were collected from local markets in August 2025. Residues were extracted using acetonitrile/hexane for milk and hexane for butter and ghee, followed by purification on Florisil columns. Analysis was performed using high-performance liquid chromatography with UV detection (HPLC-UV). Method validation showed recovery rates between 85% and 105%, and calibration curves exhibited correlation coefficients (R²) greater than 0.998. Detectable residues were found in 53.3% of samples, with α-HCH being the most prevalent and concentrated contaminant, reaching 0.612 ppm in ghee. Total mean pesticide concentrations increased with fat content: 0.022 ppm in milk, 0.170 ppm in butter, and 0.791 ppm in ghee. The lipid accumulation factor (LAF) for α-HCH in ghee was 57.03, and the relative risk index (RRI) reached 35.57, indicating substantial concentration during processing. Although 90% of samples complied with Codex Alimentarius maximum residue limits (MRLs), three ghee samples exceeded permissible levels for α-HCH and p,p’-DDT. The findings confirm that traditional processing methods concentrating milk fat also concentrate lipophilic contaminants, leading to elevated residues in high-fat products. While general consumption appears relatively safe, chronic intake of contaminated ghee may pose health risks, underscoring the need for regular monitoring and source control.