Harvard University released a study that suggests the more someone is exposed to diesel exhaust, the greater the likelihood they develop amyotrophic lateral sclerosis, or ALS. The researchers also found that risk may increase with length of exposure.

Researchers analyzed 1,639 Danish National Patient Registry entrants who were diagnosed with ALS between 1982 and 2013. The average age of diagnosis was 56. Researchers compared every diagnosed person with 100 people of the same age and sex who did not have ALS, and looked at employment history to estimate diesel exposure before their diagnosis. They divided the pool into four groups, depending on what their estimated diesel exposure rate was. They found that men exposed to a lot of diesel exhaust 10 years before their diagnosis were 20 percent more likely to develop ALS than men who weren’t. One particular group of men had more than a 50 percent chance of being exposed to a lot of diesel exhaust in their jobs, and that group of men was also 45 percent more likely to develop ALS than their peers who were not exposed to a lot of exhaust. This study found that the association between diesel exhaust and ALS did not hold as true for women, which researchers associate with differences in job tasks.

The Occupational Safety and Health Administration (OSHA) offers resources on diesel exhaust and diesel particulate matter. Workers in mining, transportation, construction, agriculture, maritime, and manufacturing industries may be exposed to diesel exhaust from vehicles and heavy machinery.

Scientists think that genetic and environmental factors can play a role in the development of ALS, but until this study scientists had only pointed to smoking as an environmental factor linked to ALS. No study had yet to look at the relation between diesel exhaust exposure and ALS. A limitation of this study could be that researchers did not have a measurable amount of diesel exhaust exposure and instead estimated it for participants.

The study results will be presented at the American Academy of Neurology’s 70^th Annual Meeting this April.

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