Exposure to air pollutant sulfur dioxide tied to greater ALS risk
Study: Being exposed to other forms of pollution not associated with disease
Long-term exposure to sulfur dioxide (SO2), a gaseous air pollutant generated by the burning of fossil fuels, significantly increases the risk of developing amyotrophic lateral sclerosis (ALS), according to a study in Canada.
Exposure to other forms of air pollution, including nitrogen dioxide (NO2), ground-level ozone (O3), and PM2.5 , was not associated with ALS, the data suggested. PM2.5 is fine particulate matter with a diameter of 2.5 micrometers or less.
“Our findings support the association between long-term exposure to air pollutants, particularly [sulfur dioxide], and the development of ALS, supporting the need for improved air pollution control measures,” researchers wrote.
Their study, “Associations between long-term air pollution exposure and the development of amyotrophic lateral sclerosis: A matched case-control study,” was published in Environmental Research.
Odds of ALS higher with increasing sulfur dioxide exposure
Both genetic susceptibility and environmental exposures are thought to play a role in the development of ALS, a rare neurological disorder marked by the progressive loss of voluntary muscle function.
Prior research has supported a relationship between exposure to air pollution and the development of other neurological conditions, such as Parkinson’s and Alzheimer’s diseases. However, there have been few studies examining a potential connection between air pollution and ALS risk.
To learn more, a team of researchers in Canada analyzed data from 304 people with ALS and 1,207 matched healthy individuals, who served as controls. Participants were 64 years old on average, a little more than half were men (52%), and 39% lived in rural areas.
“It was hypothesized that long-term exposures to environmental factors in the surrounding residential area of individuals played a role in the development of ALS,” the researchers wrote.
The team used available information about participants’ residences and pollution levels in various locations. Air pollutants investigated included NO2 and SO2, which are both produced by the burning of fossil fuels, as well as O3, a byproduct of NO2. PM2.5 — the sources of which include smoke, soot, dust, and pollen PM2.5 — was also assessed.
This is the first study to highlight that higher levels of ambient SO2 in residential areas relate to an increased risk of ALS.
The analysis revealed that the median annual levels of SO2 were significantly higher around the residences of ALS individuals compared with those of controls, but that was not the case for all other air pollutants.
After adjustments for other factors that could influence the risk of ALS, the odds of an ALS diagnosis significantly increased by 1.23-fold for a 0.14 part-per-billion increase in SO2 exposure. This relationship was significant for SO2 exposures from five to 10 years before the onset of ALS. No associations were found between ALS and exposure to NO3, O3, or PM2.5.
Further analysis suggested the odds of ALS were higher with increasing exposure to SO2, with the highest exposure being significantly different from the lowest. Still, the relationship was not linear, meaning, for example, that a twofold increase in SO2 exposure did not double the ALS risk.
“This is the first study to highlight that higher levels of ambient SO2 in residential areas relate to an increased risk of ALS,” the researchers wrote. “More research is thus needed to determine if SO2 exposure is a key causal element for the development of ALS or merely accelerating an already self-perpetuating neurodegenerative process.”
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