Background/Purpose:

Studies have suggested a potential association between traffic pollutants and rheumatoid arthritis (RA), but findings have been inconclusive. We therefore assessed the risk of RA from occupational exposure to combustion products in a large population-based case-control study.

Methods:

We included participants living in Sweden from 2006 to 2013. Incident cases of RA were enrolled from the Swedish Rheumatology Quality Register. Ten controls per case, matched on sex, age and county, were enrolled from the total population register. Work histories were available through population and housing censuses. We estimated exposure to asphalt fumes, diesel engine exhaust and polycyclic aromatic hydrocarbons from 1955 to 1995 with job-exposure matrices. Conditional logistic regression was used to estimate the risks of two histological subtypes of RA (seropositive or seronegative RA) from exposure to either of the combustion products taken separately or all of them combined. All main exposures were adjusted for potential confounding from each other as well as from respirable crystalline silica dust and household disposable income. The results are presented for men and women separately.

Results:

We analyzed 9 180 cases and 81 367 controls. Ever exposure to diesel engine exhaust in men was associated with a marginally higher risk of seropositive RA (OR: 1.11, 95 % CI: 1.00-1.23), which was slightly higher among workers with at least 20 years of exposure (OR: 1.22, 95 % CI: 1.00-1.49). More than 20 years of asphalt fumes exposure was also associated with a higher risk estimate for seropositive RA among men (OR: 1.87, 95 % CI: 1.05-3.31). Being exposed to asphalt fumes, diesel engine exhaust or polycyclic aromatic hydrocarbons combined for more than 20 years resulted in an OR of 1.22 (95 % CI: 1.03-1.45) among men for seropositive RA and 0.98 (95 % CI: 0.77-1.23) for seronegative RA.

Women were less likely than men to have been exposed to combustion products during work and few female workers had been exposed for a longer period of time. Ever exposure to polycyclic aromatic hydrocarbons in women was associated with a potentially higher risk of seropositive RA (OR: 1.22, 95 % CI: 1.00-1.48). Women exposed to asphalt fumes, diesel engine exhaust or polycyclic aromatic hydrocarbons combined for more than 20 years had an OR of 0.91 (95 % CI: 0.36-2.29) for RA overall.

Conclusion:

Long-term exposure to combustion products may increase the risk of seropositive RA among men after adjustments for potential confounders.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/occupational-exposure-to-combustion-products-and-risk-of-developing-rheumatoid-arthritis/