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Background: Increasing evidence has shown that environmental factors play a crucial role in the pathogenesis of periodontitis. Humans are simultaneously exposed to a variety of environmental brominated flame retardants (BFRs). However, the relationship between BFRs in periodontitis remains unclear. This study aimed to investigate the overall association between BFRs and periodontitis in a nationally representative US population and to further identify important chemicals., Methods: Data from 3322 NHANES participants from 2009 to 2016 were used. Serum BFRs were registered, including PBDE-28, PBDE-47, PBDE-85, PBDE-99, PBDE100, PBDE-153, PBDE-154, PBDE-183, PBDE-209 and PBB-153. Survey weighted generalized logistic regression models, restricted cubic splines (RCS) were conducted to assess single BFRs exposure with periodontitis. Meanwhile, weighted quantile sum (WQS) regression and Bayesian kernel machine regression (BKMR) were used to evaluate the overall association of BFRs mixtures with periodontitis and to identify significant chemicals., Results: A total of 3322 participants were included in the study, of whom 1795 had periodontitis. After adjusting for potential confounders, multiple logistic regression analysis revealed significant positive associations between serum levels of PBDE-28, PBDE-47, PBDE-85, PBDE-99, PBDE-100, PBDE-154, PBDE-183, and PBB-153 and the risk of periodontitis (all P < 0.05). A dose-response relationship was observed for many of these BFRs, with higher quantiles associated with an increased risk of periodontitis. WQS regression identified PBDE-183 (38.60%), PBDE-153 (21.20%), PBDE-209 (14.40%), and PBDE-99 (11.90%) as the BFRs with the largest weights contributing to the overall mixture effect on periodontitis risk. BKMR analysis further supported the positive association between serum BFRs and periodontitis, with most individual BFRs showing a positive trend, except for PBDE-153. Restricted cubic spline analysis revealed a generally increasing probability of periodontitis with increasing concentrations of BFRs, albeit with some nonlinear patterns for certain compounds., Conclusion: In conclusion, this study provides compelling evidence of a significant association between exposure to brominated flame retardants (BFRs) and an increased risk of periodontitis in a nationally representative sample of U.S. adults. Elevated serum levels of several BFRs, including PBDE-28, PBDE-47, PBDE-85, PBDE-99, PBDE-100, PBDE-154, PBDE-183, and PBB-153, were found to be positively associated with periodontitis, exhibiting a dose-response relationship., Competing Interests: Declaration of competing interest The authors declare that they have no competing interests., (Copyright © 2024 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

The kinetics of elemental mercury (Hg 0 ) release from fly ashes and hydrated fly ash cement pastes was investigated using a homemade Hg measurement system. Three types of fly ash (FA) and ordinary Portland cement (OPC) were used to prepare cement pastes. After standard curing for 28 days, the hydrated cement paste (HCP) was ground into a fine powder for Hg emission measurements. Detectable Hg 0 was found released from both fly ashes and hydrated fly ash cement pastes. The results show that elevated temperatures and evaporation of the capillary pore water in wet HCP samples accelerate Hg 0 release. Both desorption of Hg 0 from the particle surface of HCP powder and migration of Hg 0 from the inner pores contribute to Hg 0 release. The kinetic calculation indicates that the hydration products of hydrated fly ash cement have little immobilization effect on Hg 0 , which is mainly physically encapsulated in the HCP particles by hydration products., (Copyright © 2019 Elsevier Ltd. All rights reserved.)