Co-exposure to perchlorate, nitrate, thiocyanate, and per- and polyfluoroalkyl substances (PFAS) mixtures is...

Humans are concurrently exposed to a variety of environmental endocrine-disrupting chemicals (EDCs), which include such widespread substances like urinary perchlorates, nitrates, thiocyanates, and serum per- and polyfluoroalkyl substances (PFAS). The vast majority of the previous studies were devoted to individual chemicals or certain groups of chemicals, but the impact of co-exposure to mixtures of EDCs was also not thoroughly studied. The objective of this study is to identify the relationship between these EDC mixtures and prevalence of rheumatoid arthritis (RA) based on NHANES database.

We used three types of regression models with individual chemical effects, weighted quantile sum (WQS) regression, and Bayesian kernel machine regression (BKMR) in 2005-2012 to analyze results of individuals aged ≥ 20 years. Age and gender subgroup analyses were also done.

A total of 4219 patients were analyzed, and 215 (5.10%) of them had RA. Multivariate logistic regression demonstrated that there was a significant relationship between thiocyanate (as a continuous variable) and the prevalence of RA. The upper quartile of perchlorate, nitrate as well as thiocyanate and MPAH showed correlation with elevated prevalence of RA. The effects of specific chemicals were stronger among the older subjects and females. WQS and BKMR models showed a positive association between co-exposure to these chemicals and RA, with thiocyanate as the primary contributor. These associations were especially strong in young adults and females.

This study provides the first evidence that co-exposure to a mixture of EDCs is positively correlated with RA, with a stronger effect in young adults and females. Thiocyanate is identified as a key contributor. Limiting exposure to EDCs may be beneficial for potentially reducing RA risk. Key Points • We assessed the association between a mixture of ten chemicals and the risk of incidence of RA. • The co-exposure of chemical mixtures were positively associated with RA by WQS and BKMR models. • Thiocyanate was the key contributor in these mixtures. • The associations were more pronounced among young adults and females.