Human serum parabens levels and their associations with rheumatoid arthritis

Abstract Parabens are widely used in consumer products resulting in frequent exposure to humans. To date, little is known about the association between human paraben exposure and rheumatoid arthritis (RA). In this study, a case-control cohort (n = 290) was established in Hangzhou, China, aiming to quantify the concentrations of methyl paraben (MeP), ethyl paraben (EtP), propyl paraben (PrP), and butyl paraben (BuP) in serum samples and to determine their associations with RA risks. MeP (mean 4.7 ng/mL, range < LOD–20 ng/mL) was the predominant paraben in human serum, followed by PrP (1.9 ng/mL, < LOD–24 ng/mL), EtP (1.4 ng/mL, < LOD–10 ng/mL), and BuP (1.09 ng/mL, < LOD–10 ng/mL). Human serum concentrations of MeP were correlated with the levels of rheumatoid factors [adjusted β = 0.19, 95% confidence interval (CI): 0.12, 0.46], anti-cyclic citrullinated peptide antibody (adjusted β = 0.30, 95% CI: 0.26, 0.58), immunoglobulin G (adjusted β = 0.24, 95% CI: 0.21, 0.30). Significant associations between serum MeP (adjusted β = 0.15, 95% CI: 0.037, 0.28) and PrP (adjusted β = 0.23, 95% CI: 0.080, 0.38) levels were associated with C-reactive protein levels. In addition, an association between serum MeP levels and the incidence of RA (odds ratios (OR)crude = 1.337, CI: 1.110, 1.624, p = 0.03; ORadjusted = 1.866, CI: 1.321, 2.636, p = 0.02) was positive and significant. Based on the measurements of serum parabens concentrations, this work supports the evidence for the significant associations among parabens exposure, change of specific immune marker, and RA risks.