Assessing polybrominated diphenyl ethers (PBDEs) in indoor environments : concentrations in dust, human serum and the effect of regulations

Yang, Jinyu and Sweetman, Andrew and Li, Hong (2019) Assessing polybrominated diphenyl ethers (PBDEs) in indoor environments : concentrations in dust, human serum and the effect of regulations. PhD thesis, Lancaster University.

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Abstract

Polybrominated diphenyl ethers (PBDEs) are synthetic chemicals used in consumer products as additive flame retardants. There has been concern about these substances amongst regulators and policy makers as a result of their persistence in the environment and bioaccumulation in human and wildlife, as well as their ability to undergo long range atmospheric transport. PBDE contamination has been reported in most parts of the outdoor environment (such as sediment, soil, air, water and wildlife), as well as the indoor environment (dust and air) and human body (blood, breast milk, hair and so on). These chemicals have also raised concerns as they are human toxicants since they have been reported to affect thyroid hormones, neurobehavioural development, disruption to endocrine systems and possibly causing cancer. The overall hypothesis for this study was that the government regulatory intervention has differed between regions and countries. This has led to variations in the use of consumer goods containing PBDEs which directly affects contaminant levels in indoor environments which may be detrimental to human health with different timing and severities. The aims of the study were to discuss the development of regulations in Europe, North America and China, and through a sampling campaign and investigation, determine concentrations of PBDEs in the indoor environment of private homes across China. The final part of the study investigated the possible correlation between human serum concentrations and thyroid hormone function. In the initial part of this study, previously published studies of PBDEs in indoor environments and human exposure were used to summarize and compare temporal and spatial patterns across Europe, the USA and China. This was followed by the collection of dust samples in private homes in December, 2016 to January 2017, from five main cities in China, Dalian, Beijing, Shanghai, Xiamen and Guangzhou. Serum samples were collected from patients diagnosed with thyroid function abnormalities in Kunming, China. All samples were analyzed by gas chromatography and mass spectrometry (GC/MS). As a result of the variation in regional restrictions of the production/usage of commercial PBDEs, the concentration and PBDE profile composition were found to be different between Europe, the USA and China. Data from this study also showed variations in PBDE concentration between cities, within a city region and within individual dwellings. For example, a significant positive correlation was found between total PBDE concentration in dust collected from air conditioner (AC) filters and floor dust samples, which suggests they have a common source. AC filters may be a good place to collect samples in future as it represents the status of the general indoor environment. However, no significant association was found between total PBDEs in dust collected from foam furniture and floor dust. Differences were also observed between urban, suburban and rural locations. Serum samples from patients with abnormal thyroid function from Kunming were evaluated for PBDE contamination to assess exposure and possible interactions. The results identified BDE47 to be the major congener present in human serum. The concentrations of ∑7PBDE were similar to those from previous studies for general population groups including both adults and children, and at the same order of magnitude as European data, but lower than in the USA. Multiple linear regressions were used to examine the associations between PBDE congeners and the 5 thyroid hormone parameters. BDE153 showed significant positive correlation with Thyroxine (T4) and a negative correlation with Triiodothyonie (T3), whilst BDE47 showed a negative correlation with Free Thyroxine (FT4). The β-coefficients also suggested that a log-unit increase in ∑7PBDE was associated with an increase of FT4 and T4 levels and a decrease of TSH, T3 and free triiodothyonine (FT3). Further research is required, preferably using an increased sample size from thyroid patients, to investigate this possible relationship.