Key Takeaways & Executive Findings
- •• • Median serum ∑8PBDEs was 10.2 ng·g⁻¹ lw (range: 0.13–2089.4 ng·g⁻¹ lw), with BDE-209 contributing 59.7% of total, indicating dominant exposure to this high-molecular-weight congener in the Shenzhen cohort. • • A 1.7-fold increase in serum BDE-153 was associated with a 0.4% increase in FT3 (P<0.05), suggesting a potential stimulatory effect on thyroid hormone synthesis or release. • • A 1.7-fold increase in serum BDE-183 was associated with a 0.9% decrease in T3 and a 0.7% decrease in FT3 (P<0.05), indicating a suppressive effect on thyroid hormone levels. • • BKMR and WQS models revealed that mixed PBDE exposure was negatively associated with TSH at high exposure levels and with T3 and T3/FT3 ratio, with BDE-153 and BDE-183 as key contributors, underscoring the importance of assessing cumulative effects.
Abstract
This study characterized the body burden of polybrominated diphenyl ethers (PBDEs) in a physical examination population in Shenzhen and evaluated its impact on thyroid function. Serum samples from 368 residents were analyzed for eight PBDE congeners using atmospheric pressure gas chromatography-tandem mass spectrometry (APGC-MS/MS). The median concentration of ∑8PBDEs was 10.2 ng·g⁻¹ lipid weight (lw), ranging from 0.13 to 2089.4 ng·g⁻¹ lw, with BDE-209 predominating (59.7% of total). Multiple linear regression revealed that a 1.7-fold increase in serum BDE-153 was associated with a 0.4% increase in free triiodothyronine (FT3) (P<0.05), while a 1.7-fold increase in BDE-183 was associated with a 0.9% decrease in total triiodothyronine (T3) and a 0.7% decrease in FT3 (P<0.05). Bayesian kernel machine regression (BKMR) indicated a negative correlation between mixed PBDE exposure and thyroid-stimulating hormone (TSH) at high exposure levels. Weighted quantile sum (WQS) regression showed that mixed exposure was associated with decreased T3 levels and T3/FT3 ratio, with BDE-153 and BDE-183 as the primary contributors. These findings suggest that PBDE exposure may adversely affect thyroid function and disrupt thyroid hormone homeostasis, with BDE-183 and BDE-153 playing key roles. This study provides a scientific basis for PBDE health risk assessment and thyroid protection.
1. Introduction
Polybrominated diphenyl ethers (PBDEs) have been extensively used as flame retardants in electronics, furniture, and building materials since the 1980s, with global cumulative usage exceeding 500,000 tons. Their persistence, bioaccumulation, and potential toxicity led to their inclusion in the Stockholm Convention in 2009 and China's List of Key Controlled New Pollutants since 2022. Despite regulatory actions, PBDEs remain ubiquitous in the environment and human tissues, raising concerns about endocrine disruption, particularly thyroid function. However, epidemiological evidence on the association between PBDE exposure and thyroid hormone levels has been inconsistent, partly due to the complexity of mixed exposures and the use of traditional regression models that do not account for non-linear and interactive effects.
This study addresses these gaps by employing advanced statistical approaches—multiple linear regression, Bayesian kernel machine regression (BKMR), and weighted quantile sum (WQS) regression—to evaluate both individual and joint effects of eight PBDE congeners on thyroid function in a cohort of 368 Shenzhen residents. By integrating these methods, the study aims to identify the most influential congeners and characterize the shape of the exposure-response relationship, thereby providing more robust evidence for health risk assessment and regulatory decisions.
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CHEN Yang, ZHOU Chenyu, ZHAN Zijian, MA Shuai, ZENG Xiaopeng, JIANG Yousheng, PENG Jinling, SONG Jiayi, ZHANG Jianqing (2026). Body Burden of Polybrominated Diphenyl Ethers and Joint Effects on Thyroid Function in a Physical Examination Population in Shenzhen. Environmental Chemistry. https://doi.org/10.7524/j.issn.0254-6108.2025121602
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Frequently Asked Questions
What is the rationale for using BKMR and WQS models in addition to multiple linear regression?
Multiple linear regression assesses individual congener effects but assumes linearity and independence. BKMR and WQS models capture non-linear and interactive effects of mixed exposures, providing a more realistic assessment of joint toxicity. In this study, BKMR revealed a negative association between mixed PBDEs and TSH only at high exposure levels, which would be missed by linear models. WQS identified BDE-153 and BDE-183 as primary contributors to decreased T3 and T3/FT3 ratio, offering insight into which congeners drive the mixture effect.
How do the serum PBDE concentrations in this Shenzhen cohort compare with other populations?
The median ∑8PBDEs of 10.2 ng·g⁻¹ lw is within the range reported in other Chinese and global studies, though direct comparison is complicated by differences in congener panels and analytical methods. The dominance of BDE-209 (59.7%) is notable, as this congener is often less prevalent in Western populations, reflecting regional differences in PBDE usage patterns.
What are the potential clinical implications of the observed associations between BDE-153 and BDE-183 and thyroid hormone changes?
The 0.4% increase in FT3 per 1.7-fold increase in BDE-153 and the 0.9% and 0.7% decreases in T3 and FT3 per 1.7-fold increase in BDE-183, respectively, may seem small but could be clinically relevant at the population level. Chronic shifts in thyroid hormone levels, even within the normal range, can influence metabolic rate, cardiovascular health, and neurodevelopment. The negative association with TSH at high exposure levels suggests potential disruption of the hypothalamic-pituitary-thyroid axis.
What are the limitations of this study in terms of causal inference?
This is a cross-sectional study, so causality cannot be established. Residual confounding from unmeasured factors (e.g., other environmental chemicals, lifestyle, genetic predisposition) is possible. Additionally, the sample size (n=368) may limit statistical power for detecting subtle effects, and the use of a single serum sample may not reflect long-term exposure. Future prospective studies with repeated measurements are needed to confirm these findings.
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