Organohalogen contaminants in humans with emphasis on polybrominated diphenyl ethers

Abstract

The occurrence and distribution of organohalogen compounds, including polybrominated diphenyl ethers (PBDEs), in humans was investigated. For this purpose, the previously used method for analysis of organochlorine compounds was modified for the analysis of PBDEs and hydroxylated metabolites of polychlorinated biphenyls (OH-PCBs) in breast milk, matemal and cord blood plasma, liver and adipose tissue.

PBDEs and PCBs were found in all samples. The PCB levels were approximately 100 times higher than those of PBDEs. Among the PBDEs, 2,2',4,4'-tetraBDE (BDE-47) was the predominant congener in breast milk, adipose tissue, matemal and cord blood, while in liver samples 2,2',4,4',5pentaBDE (BDE-99) occurred at similar concentrations as BDE-47. The PCB congener profile was similar in all samples. 2,2',4,4',5,5'-hexaCB (CB-153), 2,2',3,4,4',5'-hexaCB (CB-138) and 2,2',3,4,4',5,5'-heptaCB (CB-180) were the dominant congeners.

OH-PCBs constituted 30-50% of the sum of PCBs in blood samples, 1-10% in liver and 0.03-0.4% in adipose tissue, while the levels of OH-PCBs in breast milk were inconsiderable. Matrix specific differences were observed in OHPCB congener distribution. 2,2',3,4',5,5',6-heptachloro-4-biphenylol (4-OH-CB187) and 2,2',3,4',5,5'-hexachloro-4-biphenylol (4-0H-CB146) were the most dominant congeners in blood samples, 2,2',3,4,4',5'-hexachloro-3'-biphenylol (3'-OH-CB138) and 2,2',3,3',4,5'-hexachloro-4'-biphenylol (4'OH-CB130) in liver, 3´-OH-CB138 and 2,3,3',4',5,5',6-heptachloro-4-biphenylol (4-OH-CB 193) in adipose tissue.

The presence of PBDEs, PCBs and OH-PCBs in cord blood demonstrates that placenta is not an effective barrier for the transfer of these compounds to the foetus. consequently, infants are exposed to organohalogen compounds already before they are born and additionally later via breast milk. Due to the low levels, postnatal exposure to OH-PCBs via breast milk in the present study subjects was considered of a minor importance.

Temporal trends in contaminants have been investigated by analysing breast milk from different time periods. The levels of oganochlorine compounds: PCBs polychlorinated naphtalenes, dibenzo-rho-dioxins, dibenzofurans and several pesticides decreased to different extent from 1972 to 1997. During the same time period increasing levels of PBDEs were found. However, from 1998 to 2000 a decrease in PBDE levels was observed. The change in the trend was mainly due to the decrease of the most dominant PBDE congener, BDE-47. No large difference was noticed in levels of higher brominated PBDEs. During the same time period the levels of organochlorine contaminants in breast milk continued to decrease.