Associations between long-term air pollution exposure and the development of amyotrophic lateral sclerosis: A matched case-control study

There is increasing evidence of an association between air pollution, particularly nitrogen dioxide (NO₂), and the development of amyotrophic lateral sclerosis (ALS). However, investigation into sulfur dioxide (SO₂) remains understudied. Also, empirical identification of confounding variables to adjust for in ALS environmental studies is largely absent. Thus, we created a multifactorial database, mapped hypothesized direct effects of air pollutants, and conducted a matched case-control study in New Brunswick, Canada to investigate the association between long-term exposure to various air pollutants and the development of ALS. Odds of ALS onset was significantly associated with increased SO₂ exposure (OR = 1.23; 95 % CI: 1.02-1.47, per IQR increase of 0.14 ppb) in adjusted direct effect models, but not associated with exposure to NO₂ (OR = 1.09; 95 % CI: 0.87-1.41, per IQR increase of 2.79 ppb), ozone (O₃) (OR = 0.99; 95 % CI: 0.80-1.22, per IQR increase of 2.31 ppb), fine particulate matter (PM_2.5) (OR = 0.99; 95 % CI: 0.80-1.23, per IQR increase of 0.52 μg/m³) or PM_2.5(smoke) (OR = 1.05; 95 % CI: 0.83-1.35, per IQR increase of 0.68 μg/m³). As for recency models, SO₂ remained significantly associated with ALS in both 5-year (OR = 1.21; 95 % CI: 1.03-1.43) and 10-year prior to onset sensitivity models (OR = 1.23; 95 % CI: 1.02-1.47). Our findings support the association between long-term exposure to air pollutants, particularly SO₂, and the development of ALS, supporting the need for improved air pollution control measures.