PCDD/Fs, DL-PCBs, and NDL-PCBs in Dairy Cows: Carryover in Milk from a Controlled Feeding Study

摘要

A feeding study was carried out to investigate the kinetics in cow milk of the 17 polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), the 12 dioxin-like polychlorinated biphenyls (DL-PCBs), and the 6 non-dioxin-like PCBs (NDL-PCBs) regulated by the European (EU) legislation. A fortified ration (Sigma PCDD/Fs and DL-PCBs: 24.68 ng TEQ/clay/cow; Sigma NDL-PCBs: 163.99 mu g/day/cow) was given to the animals for 49 days, followed by 42 days on clean feed. EU maximum limit for TEQPCDD/F+DL-PCB was exceeded in milk after 1 week of exposure, while for Sigma NDL-PCBs, after 5 weeks. Milk compliance was restored after 1 week on clean feed, but to return to the basal TEOPCDD/F+DL-PCB it took 42 days. At the end of the study, Sigma NDL-PCBs had not yet reached the basal level. The carryover rate of Sigma NDL-PCBs was 25.4%, while the carryover rate of TEOPCDD/F+DL-PCB was 36.9%. The latter was mainly affected by the 12 congeners contributing most to the toxic equivalent (TEQ) level, explaining the fast overcome of the maximum limit in milk.