Occupational exposure to chlorinated solvents and risk of amyotrophic lateral sclerosis: a Chinese case-control study: abstract

Objectives Previous studies on the association between occupational exposure to chlorinated solvents and the risk of amyotrophic lateral sclerosis (ALS) have shown inconsistent results. We aim to examine the association in a Chinese case-control study. Methods We conducted a hospital-based case-control study, recruiting 430 newly diagnosed ALS cases and 1,033 controls. Occupational exposure to trichloroethylene (TCE) and perchloroethylene (PCE) was estimated using semi-quantitative job-exposure matrices (JEMs), developed from routine industrial hygiene monitoring datasets, published literature, international JEMs, and expert input. Logistic regression models were used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for ALS risk in relation to various exposure metrics, adjusting for age, sex, education, residential distance to hospital, and pesticide exposure. Results TCE and PCE exposures were highly correlated (r = 0.93, P < 0.001), and exposure-associated ALS risk showed similar patterns. Ever exposure to TCE was associated with a lower risk of ALS compared to unexposed (OR: 0.55, 95%CI: 0.38-0.79). When cumulative TCE exposure was categorized into quartiles based on the control distribution, adjusted ORs (95%CI) for ALS risk were 0.43 (0.21–0.83), 0.46 (0.20–0.98), 0.38 (0.15–0.82), and 0.89 (0.49–1.56) across increasing quartiles. Exposure-response trend was not significant when excluding non-exposed individuals (Ptrend = 0.143). In sensitivity analyses limited to job titles with higher certainty of TCE exposure, inverse associations remained but were less precise. Discussions Our preliminary findings suggest a potential inverse association between occupational chlorinated solvents exposure and ALS risk, particularly at lower exposure levels. However, the lack of a consistent exposure-response and imprecision in sensitivity analyses warrant cautious interpretation. This is the first study to assess lifetime occupational exposure specifically to TCE and PCE and ALS risk in Asian populations using semi-quantitative JEMs. These results contribute to a growing body of evidence on chlorinated solvents-related neurotoxicity.
Abstract from: 30th Epidemiology in Occupational Health Conference (EPICOH 2025), Hosted by Institute for Risk Assessment Sciences, Utrecht University, 6–9 OCTOBER 2025, Utrecht, the Netherlands