Application of radioimmunoassay in the screening of polychlorinated biphenyls in cowʹs milk

Total polychlorinated biphenyls (PCBs) were determined by microcolumn radioimmunoassay (RIA) in extracts from milk samples collected from 723 supply routes in 39 districts of the Czech Republic. Analysis of 1491 milk and 99 body fat samples collected from dairy cows have demonstrated that RIA is a reliable and sensitive method for the determination of PCBs in the tested matrices. A good correlation of results of RIA and gas chromatography (r = 0.97, in = 27) was found within the concentration range 0.1–5.58 mg Delor 106 (Aroclor 1260) kg-1 fat. The permissible concentration of 0.3 mg PCB kg-1 fat was exceeded in 40 milk supply routes, i.e., 5.5% of the total number of the routes tested at the entries into dairy plants. Findings of PCB concentrations exceeding the permissible level in bulk milk samples allowed the identification of contaminated herds. The pattern of contamination allowed herd operators to reduce the existing milk losses by managerial actions. Thus PCB RIA has proven to be a useful tool for some managerial decisions in contaminated herds.