Congener-specific accumulation of PCDD/Fs, PCBs, and PBDEs in sheep (Ovies aries) liver and muscle

Abstract

Polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs) are persistent organic pollutants (POPs). Their emission from anthropogenic and non-anthropogenic sources pollutes the environment. Sheep are exposed to those chemicals as they graze on contaminated areas, accumulating POPs in tissue. The paper explores the congener-specific accumulation of PCDD/Fs, PCBs, and PBDEs in tissue samples of sheep exposed to background levels. Paired liver and muscle samples from 29 sheep (Ovis aries) were analyzed using the isotopic dilution method and the HRGC-HRMS technique. Sequestration differences between liver and muscle were correlated with regional factors and distinctive congener patterns, which was supported by principal component analysis. There tended to be transfer of 2,3,7,8-tetrachlorinated dibenzo-p-dioxin to muscle, and PCDDs had an affinity for the liver which rose with the number of chlorine atoms. Except for 2,3,7,8-tetrachlorinated dibenzofuran, the retention of PCDFs in the liver was greater than that of PCDDs. While PCB-126 was heavily retained in the liver, other PCBs tended to be transferred to muscle. The geometric structure of PCB molecules seemed to play the most crucial role in their sequestration, while the number of chlorine atoms played none. Generally, PBDEs accumulated in muscle rather than the liver, except for BDE-209. The higher levels of BDE-209 in the liver than in muscle may have been related to its greater environmental prevalence and faster elimination. The concentration of 3 PCDD/Fs and 6 PCBs in muscle rose with increasing muscle-to-liver fat ratio. The investigation of POP sequestration in animal tissue with new statistical methods seems crucial.