Occupational Exposure to Petroleum-Derived Lubricants and Risk of Multiple Sclerosis

Background and Objectives Lung irritants such as smoking and organic solvents are established risk factors of multiple sclerosis (MS), with effects influenced by genetic susceptibility, particularly leukocyte antigen (HLA) DRB1*15:01 and HLA-A*02:01 . Petroleum-derived lubricants represent another widespread occupational exposure with potential inflammatory properties, yet their contribution to MS etiology remains unclear. This study investigated associations between occupational exposure to petroleum-based lubricants and MS risk, including interactions with smoking and HLA genotypes. Methods This investigation was based on a Swedish population-based case-control design. Incident MS cases were consecutively recruited by neurologists at 40 clinics (2005–2015). Inclusion criteria comprised residence in Sweden, age 16–70 years, and a diagnosis of MS confirmed by a neurologist according to the McDonald criteria. Controls were randomly selected from the national population register using density sampling and frequency-matched to cases by age, sex, and residential area. Exposure to petroleum-derived lubricants was assessed using questionnaire data. Logistic regression was used to estimate odds ratios (ORs) and 95% CIs for MS in relation to occupational exposure to petroleum-derived lubricants. Interactions with smoking, HLA-DRB1*15:01 , and absence of HLA-A*02:01 were assessed on the additive scale using the attributable proportion due to interaction (AP). Results The study population comprised 2,872 incident MS cases and 6,122 controls (mean age: 34.6 years; 72% female). Occupational exposure to petroleum-derived lubricants was associated with increased MS risk (OR 1.38, 95% CI 1.16–1.65), with a modest exposure-duration response. The association persisted when applying a 7-year exposure lag (OR 1.55, 95% CI 1.27–1.90). A positive interaction was identified between petroleum exposure and smoking (AP 0.34, 95% CI 0.10–0.55). Among the subset with available HLA data (2,070 cases and 2,899 controls), petroleum exposure interacted with the absence of HLA-A*02:01 (AP 0.32, 95% CI 0.05–0.59). A similar interaction was observed with HLA-DRB1*15:01 (AP 0.19, 95% CI -0.08-0.46), although this estimate did not reach statistical significance. Discussion Occupational exposure to petroleum-derived lubricants was associated with MS risk, with stronger associations among smokers and participants with established genetic susceptibility. These findings add to the evidence that lung irritants and gene-environment interactions contribute to MS susceptibility but require replication in independent populations.