Polybrominated diphenyl ethers (PBDEs) are used as flame retardants in many types of consumer products. Perhaps as a result of their widespread use and their lipophilicity, these compounds have become ubiquitous in the environment and in people. This review summarizes PBDE concentrations measured in several environmental media and analyzes these data in terms of relative concentrations, concentration trends, and congener profiles. In human blood, milk, and tissues, total PBDE levels have increased exponentially by a factor of ∼100 during the last 30 yr; this is a doubling time of ∼5 yr. The current PBDE concentrations in people from Europe are ∼2 ng/g lipid, but the concentrations in people from the United States are much higher at ∼35 ng/g lipid. Current PBDE concentrations in marine mammals from the Canadian Arctic are very low at ∼5 ng/g lipid, but they have increased exponentially with a doubling time of ∼7 yr. Marine mammals from the rest of the world have current PBDE levels of ∼1000 ng/g lipid, and these concentrations have also increased exponentially with a doubling time of ∼5 yr. Some birds' eggs from Sweden are also highly contaminated (at ∼2000 ng/g lipid) and show PBDE doubling times of ∼6 yr. Herring gull eggs from the Great Lakes region now have PBDE concentrations of ∼7000 ng/g lipid, and these levels have doubled every ∼3 yr. Fish from Europe have ∼10 times lower PBDE concentrations than fish from North America. From these and other data, it is clear that the environment and people from North America are very much more contaminated with PBDEs as compared to Europe and that these PBDE levels have doubled every 4−6 yr. Analyses of the relative distributions of the most abundant PBDE congeners (using category averages and principal component analysis) indicated that these patterns cannot yet be used to assign sources to these pollutants.

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The differential environmental fates and toxicities of the various hexachlorocyclohexane (HCH) isomers including lindane and isomers in the technical mixture will be the focus of this review. HCHs are one of the most widely used and most readily detected organochlorine pesticides in environmental samples. The relatively high volatility of HCH has led to global transport, even into formerly pristine locations such as the Arctic. Certain HCHs cause central nervous system, reproductive, and endocrine damage. Because γ-HCH is rapidly metabolized, the β-HCH isomer is consistently found in higher concentrations in human fat, blood, and breast milk. In contrast, Rand γ-HCH are the most prevalent isomers in soil, water, and air samples. The ratio of the Rto γ-isomers can be used to track global transport of HCHs. A new area of HCH research focuses on the selective degradation of the two R-HCH enantiomers in various environmental matrices. These HCH issues and recommendations for future HCH research are presented in this review.

A highly chlorinated flame retardant, Dechlorane Plus (DP), was detected and identified in ambient air, fish, and sediment samples from the Great Lakes region. The identity of this compound was confirmed by comparing its gas chromatographic retention times and mass spectra with those of authentic material. This compound exists as two gas chromatographically separable stereoisomers (syn and anti), the structures of which were characterized by one- and two-dimensional proton nuclear magnetic resonance. DP was detected in most air samples, even at remote sites. The atmospheric DP concentrations were higher at the eastern Great Lakes sites (Sturgeon Point, NY, and Cleveland, OH) than those at the western Great Lakes sites (Eagle Harbor, MI, Chicago, IL, and Sleeping Bear Dunes, MI). Atthe Sturgeon Point site, DP concentrations once reached 490 pg/m3. DP atmospheric concentrations were comparable to those of BDE-209 at the eastern Great Lakes sites. DP was also found in sediment cores from Lakes Michigan and Erie. The peak DP concentrations were comparable to BDE-209 concentrations in the sediment core from Lake Erie butwere about 30 times lower than BDE-209 concentrations in the core from Lake Michigan. In the sediment cores, the DP concentrations peaked around 1975-1980, and the surficial concentrations were 10-80% of peak concentrations. Higher DP concentrations in air samples from Sturgeon Point, NY, and in the sediment core from Lake Erie suggest that DP's manufacturing facility in Niagara Falls, NY, may be a source. DP was also detected in archived fish (walleye) from Lake Erie, suggesting that this compound is, at least partially, bioavailable.

The global distribution of 22 potentially harmful organochlorine compounds was investigated in more than 200 tree bark samples from 90 sites worldwide. High concentrations of organochlorines were found not only in some developing countries but also in industrialized countries, which continue to be highly contaminated even though the use of many of these compounds is restricted. The distribution of relatively volatile organochlorine compounds (such as hexachlorobenzene) is dependent on latitude and demonstrates the global distillation effect, whereas less volatile organochlorine compounds (such as endosulfan) are not as effectively distilled and tend to remain in the region of use.

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Polybrominated diphenyl ethers (PBDEs) are widely used as flame retardants in consumer goods, such as plastics, electronics, textiles, and construction material. PBDEs have been found in human milk, fat, and blood samples. Rodent studies indicate that PBDEs may be detrimental to neurodevelopment, possibly by lowering thyroid hormone concentrations in blood. In the present study, we determined concentrations of PBDEs and thyroid hormones in human fetal and maternal serum. Patients presenting in labor to Indiana University and Wishard Memorial County hospitals in Indianapolis, who were older than 18 years, were recruited to participate. Twelve paired samples of maternal and cord blood were obtained and analyzed using gas chromatographic mass spectrometry; thyroid hormone concentrations were determined by radioimmunoassay. Six congeners of PBDE were measured in maternal and fetal serum samples. The concentrations of total PBDEs found in maternal sera ranged from 15 to 580 ng/g lipid, and the concentrations found in fetal samples ranged from 14 to 460 ng/g lipid. Individual fetal blood concentrations did not differ from the corresponding maternal concentrations, indicating that measurement of maternal PBDE blood levels is useful in predicting fetal exposure; similarly, other reports have shown a high correlation between PBDE in mother's milk and fetal exposure. In accord with reports on other biologic samples, the tetrabrominated PBDE congener BDE-47 accounted for 53-64% of total PBDEs in the serum. The concentrations of PBDEs found in maternal and fetal serum samples were 20-106-fold higher than the levels reported previously in a similar population of Swedish mothers and infants. In this small sample, there was no apparent correlation between serum PBDEs and thyroid hormone concentrations. Our study shows that human fetuses in the United States may be exposed to relatively high levels of PBDEs. Further investigation is required to determine if these levels are specific to central Indiana and to assess the toxic potential of these exposure levels. Key words: brominated diphenyl ethers, cord blood, human, pregnancy, serum.