Chemicals higher, thyroid hormone lower in pregnant women near e-waste recycling.
Zhang, JQ, Y Jiang, J Zhou, B Wu, Y Liang, Z Peng, D Fang, B Liu, H Huang, C He, C Wang and F Lu. 2010. Elevated body burdens of PBDEs, dioxins and PCBs on thyroid hormone homeostasis at an electronic waste recycling site in China. Environmental Science and Technology http://dx.doi.org/10.1021/es902883a.
Pregnant women who live in areas close to electronic waste dismantling sites have higher exposures to persistent organic pollutants and depressed thyroid hormone levels than those who live farther away from the facilities, finds a study that compares women in two regions of China.
Despite the fact that they have no interactions with the e-waste facility, the recycling activities affect the women living adjacent to the sites. This study raises concerns about e-waste practices and health effects on both the mothers and the developing fetuses.
This is the first study to evaluate the levels of these three groups of pollutants in people who live near e-waste recycling sites and to determine their effect on thyroid hormone levels. The results of this study mostly agree with findings from the few prior studies that have also looked at the effects of the chemical groups – either alone or in pairs – on thyroid hormones.
PCBs and PBDEs are widely-used chemicals found in electronic products. PCDDs/Fs are typically formed when the electronic products containing these chemicals burn – as sometimes happens during their gutting and recycling. These chemicals have been either banned or phased out from use due to persistence, bioaccumulation and toxicity concerns.
Yet, the compounds are still present in residential areas and in consumer products. Electronic waste recycling – including burning, acid leaching and dismantling – can release the pollutants into the air, water and soil where people can be exposed to high levels.
All of the chemicals measured affect thyroid regulation in animal exposure studies. Several of these studies document significant associations between exposure to the contaminants and depression of thyroid hormone levels in both children and adults.
Steady thyroid hormone levels are critical to the developing fetus, particularly for physical and mental development. Low thyroid hormone levels can cause delays and brain and nervous system problems.
Fifty pregnant women who lived in two different regions in southeast China for at least five years participated in this study. One region is a well-known e-waste recycling area (zone A), in which recycling has been going on for more than 25 years. The second region represents a control reference site (zone B) and is located more than 250 kilometers away from the first region.
Researchers measured the levels of about 17 chlorinated dioxins (i.e. PCDDs and PCDFs), six polychlorinated biphenyls (PCBs) and six polybrominated diphenyl ethers (PBDEs) in cord blood collected during delivery. Thyroid hormone levels – T3, thyroxine (T4) and thyroid stimulating hormone (TSH) – were measured in the women’s blood samples taken during the sixteenth week of pregnancy.
In general, women living near the recycling facitlities had higher body burdens – and thus, higher exposures – to all three chemical classes than the women who lived farther away. Median concentrations of PCDDs/Fs, PCBs and PBDEs in cord blood collected from those who live close were 3 times, 5.4 times and 1.4 times higher, respectively, than the levels measured in cord blood collected from women who lived farther away.
Furthermore, total thyroxine and thyroid stimulating hormone (TSH) were significantly lower in women nearer the recycling activities. The researchers found that as PCDDs/Fs and PCBs levels increased, levels of T4 decreased. This association was statistically significant.
Results from this study warrant further research into human health effects of both employees in e-waste sites and for people living in cities with e-waste facilities from exposure to chemicals released during e-waste practices.
