Rheumatoid arthritis (RA) is a systemic autoimmune disorder characterized by chronic inflammation and immune dysregulation, leading to progressive joint destruction and involvement of multiple organ systems

whose pathogenesis remains uncertain. Nonetheless, environmental factors may play a pivotal role. Large-scale use of pesticides may be partly responsible for the occurrence of RA, yet the association between dichlorophenol (DCP) exposure and the incidence of RA is still poorly understood. 

Data used in the present study was originated from the US National Health and Nutrition Examination Survey (NHANES). Exposure levels of DCP were evaluated by concentrations of 2,4-dichlorophenol (2,4-DCP) and 2,5-dichlorophenol (2,5-DCP) in urine. A multivariate logistic regression model was established to evaluate the relationship between DCP exposure and RA risk in American adults. To determine whether there was a nonlinear correlation between DCP exposure and RA morbidity, a restricted cubic spline plot was employed.

7514 subjects with 536 RA patients were included. Compared to non-RA subset, DCP concentration in RA subset was significantly higher. 2,4-DCP and 2,5-DCP in the highest quartile were correlated with an increased risk of RA compared to the lowest quartile after adjustment for potential covariates (odds ratio [OR]: 1.59, 95% CI: 1.00-2.53, P for trend = 0.029) and OR: 1.53, 95% CI: 1.02-2.28, P for trend = 0.035). In male patients and people aged 40 to 59, a significant correlation was found between DCP level and the prevalence of RA. The restricted cubic spline model showed a linear correlation between DCP exposure and the occurrence of RA. 

Our study indicated a significant difference in DCP concentration between healthy and RA people. DCP exposure was correlated with an increased risk of RA. Higher DCP levels were linearly associated with an increased incidence of RA. These findings provide novel epidemiological evidence for the relationship between environmental pollution and arthritis, suggesting that controlling the DCP exposure may represent an effective strategy for arthritis prevention.