PM2.5 composition and disease aggravation in amyotrophic lateral sclerosis

Background: Long-term exposure to fine particulate matter (PM2.5) has been associated with disease aggravation in amyotrophic lateral sclerosis (ALS). In this study, we characterized long-term exposure to six major PM2.5 components and their individual association with disease aggravation in ALS. Methods: We leveraged 15 years of data from the New York Department of Health Statewide Planning and Research Cooperative System (2000–2014) to calculate annual ALS first hospitalizations in New York State. We used the first hospital admission as a surrogate of disease aggravation and a prediction model to estimate population-weighted annual black carbon, organic matter (OM), nitrate, sulfate, sea salt, and soil concentrations at the county level. We used a multi-pollutant mixed quasi-Poisson model with county-specific random intercepts to estimate rate ratios (RR) of 1-year exposure to each PM2.5 component and disease aggravation in ALS, adjusting for potential confounders. Results: We observed 5,655 first ALS-related hospitalizations. The annual average hospitalization count per county was 6.08 and the average PM2.5 total mass concentration per county was 8.1 μg/m3—below the United States’ National Ambient Air Quality Standard of 12 μg/m3. We found a consistent positive association between ALS aggravation and OM (1.17, 95% confidence intervals [CI], 1.11, 1.24 per standard deviation [SD] increase) and a negative association with soil (RR = 0.91, 95% CI, 0.86, 0.97). Conclusion: Our findings suggest that PM2.5 composition may influence its effect on ALS. We found that annual increases in county-level particulate OM may be associated with disease aggravation in ALS, even at PM2.5 levels below current standards.