Key Takeaways & Executive Findings
- •• • Inside the legacy production site, HBCD concentrations reached up to 1.18×10⁶ ng·g⁻¹ dw in surface soils, exceeding outside levels by orders of magnitude (outside range: ND–6.90×10² ng·g⁻¹ dw), indicating severe point-source contamination requiring immediate remediation. • • Vertical profiling showed a sharp decline with depth: from 1.08×10⁴–1.18×10⁶ ng·g⁻¹ dw at the surface to 1.05–93.5 ng·g⁻¹ dw at ~4 m depth, suggesting limited vertical migration and potential containment feasibility. • • Cumulative environmental burden analysis revealed that 23.7% of the total HBCD load is within 2 km, 40.1% within 2.81 km, 60.0% within 4 km, and 87.1% within 6 km, quantifying the spatial footprint and guiding risk-based management zones. • • Health risk assessment identified oral ingestion as the dominant exposure pathway, with localized high-contamination areas inside the plant posing significant non-carcinogenic risks, while risks for children outside the plant remained acceptable, supporting differential remediation priorities.
Abstract
Although the production and use of hexabromocyclododecanes (HBCDs) have been completely banned in China since December 2021, historical production activities may still leave high-concentration residual contamination in localized areas. This study investigated a typical legacy site of historical HBCDs production in eastern China. Surface and core soil samples were systematically collected both inside and outside the former plant area to characterize the occurrence, spatial distribution, and environmental burden of HBCDs, and to evaluate associated human health risks. Results showed that HBCD concentrations in soils outside the plant area ranged from below detection limit to 6.90×10² ng·g⁻¹ dw, while those inside the plant area were substantially higher, reaching up to 1.18×10⁶ ng·g⁻¹ dw. γ-HBCD was the dominant isomer; however, its relative abundance was lower than that reported in commercial HBCD mixtures and in previous studies conducted near production facilities. Outside the plant, HBCDs concentrations in soil generally decreased with increasing distance from the site, yet remained detectable at a distance of approximately 10 km (15.2 ng·g⁻¹ dw). Within the plant area, HBCDs concentrations in soil cores decreased with depth, declining from 1.08×10⁴–1.18×10⁶ ng·g⁻¹ dw in surface soils to 1.05–93.5 ng·g⁻¹ dw at depths of about 4 m. Analysis of the relative cumulative environmental burden indicated that although HBCDs loads were highest in the near-source area, they gradually accumulated over a broader spatial scale. Approximately 23.7%, 40.1%, 60.0%, and 87.1% of the total estimated burden accumulated within 2 km, 2.81 km, 4 km, and 6 km from the site, respectively. Health risk assessment indicated that oral ingestion of soil was the primary exposure pathway for different populations. Localized high-contamination zones within the plant area contributed significantly to non-carcinogenic risks, while overall risks for children outside the plant area were at acceptable levels.
1. Introduction
Hexabromocyclododecanes (HBCDs) are brominated flame retardants that have been widely used in polystyrene foams and textiles. Despite their ban under the Stockholm Convention and in China since December 2021, historical production and use have left legacy contamination in soils, particularly at former manufacturing sites. Existing remediation efforts often overlook the spatial heterogeneity and depth distribution of HBCDs, leading to inaccurate risk assessments and inefficient resource allocation. The challenge lies in characterizing the extent of contamination and quantifying the associated health risks to prioritize intervention.
This study addresses this bottleneck by conducting a systematic investigation of a typical historical HBCDs production site in eastern China. By analyzing surface and core soil samples both inside and outside the plant area, the research provides high-resolution data on concentration gradients, isomer profiles, and cumulative environmental burdens. The findings enable a precise health risk assessment, distinguishing between high-risk zones within the plant and lower-risk surrounding areas. This approach offers a template for managing legacy POPs sites, integrating empirical data with risk-based decision-making.
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YANG Jing, WU Kaixuan, QI Li, YANG Wenlong, ZHU Chaofei, MAO Yanqing, LIU Haoran, LI Jingchen, YAN Yan, DU Bing, LIU Wenbin (2026). Occurrence Characteristics and Health Risk Assessment of Hexabromocyclododecanes in Soils from a Historical Production Legacy Site. Environmental Chemistry. https://doi.org/10.7524/j.issn.0254-6108.2026020207
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Frequently Asked Questions
What is the maximum HBCD concentration found in soil at the legacy production site, and how does it compare to background levels?
The maximum concentration inside the plant area reached 1.18×10⁶ ng·g⁻¹ dw, while outside concentrations ranged from below detection limit to 6.90×10² ng·g⁻¹ dw. This indicates a concentration gradient of over three orders of magnitude, highlighting the severity of point-source contamination.
How does the vertical distribution of HBCDs in soil cores inform remediation strategies?
Concentrations decreased sharply with depth, from 1.08×10⁴–1.18×10⁶ ng·g⁻¹ dw at the surface to 1.05–93.5 ng·g⁻¹ dw at ~4 m depth. This suggests that contamination is primarily confined to the top layers, allowing for targeted excavation or in-situ treatment of the upper soil zone, reducing costs and disturbance.
What is the spatial extent of contamination beyond the plant boundary, and what are the implications for surrounding populations?
HBCDs were detectable up to 10 km away (15.2 ng·g⁻¹ dw), with cumulative burden analysis showing that 87.1% of the total load is within 6 km. This indicates a significant dispersion footprint, necessitating monitoring and potential risk communication for communities within this radius.
Which exposure pathway dominates health risks, and what are the risk levels for children outside the plant?
Oral ingestion of soil is the primary exposure pathway. For children outside the plant, overall non-carcinogenic risks were at acceptable levels, but localized high-contamination zones inside the plant contributed significantly to risks, emphasizing the need for restricted access and remediation in those hotspots.
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