Sulphur Dioxide From Fossil Fuel Emissions Linked to Higher ALS Risk

Sulfur dioxide and ALS risk

A new study suggests that one element of fossil fuel emissions may be associated with a greater risk of the neurodegenerative disease ALS (amyotrophic lateral sclerosis).

Canadian researchers paired 304 people diagnosed with ALS with 1,207 healthy participants matched by age and sex. Using environmental data for the location of each person’s main home, they calculated individual exposure to pollutants.

The analysis focused particularly on sulphur dioxide (SO₂), a compound released when coal and oil-derived fuels are burned. Although this pollutant has previously been associated with brain damage, its potential relationship with ALS had not been investigated.

Within the study group, participants diagnosed with ALS had "a significantly higher history" of SO₂ exposure than the control group.

Air quality measures and pollutant exposure

Although the observed association cannot establish a direct causal relationship, it represents a strong and concerning connection. This is especially notable because every area included in the research was comfortably within official standards for ‘clean’ air quality.

"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," write the researchers in their published paper.

Nitrogen dioxide (NO₂), another pollutant produced by vehicle exhausts and coal-fired power plants, has already been associated with ALS risk. However, after the researchers accounted for other influences, including socioeconomic factors, this analysis found no meaningful link.

The team also determined that SO₂ levels before symptoms emerged were considerably more important than measurements from the years before diagnosis. This indicates that people may have reached a ‘point of no return’ by the time they were assessed by medical specialists.

"This is the first study to highlight that higher levels of ambient SO₂ in residential areas relate to an increased risk of ALS," write the researchers.

Understanding the effects of ALS

ALS is still uncommon, with approximately 1 to 2 new cases reported worldwide each year for every 100,000 people. Yet its consequences are severe: the disease progressively destroys nerve cells, resulting in paralysis, and is fatal within three years in most cases.

Scientists are continuing to learn about ALS, though its cause has not yet been established. There is usually no family history of the illness, for example. Certain risks, such as physical exercise and genetic mutations, have been identified, but the overall evidence remains unclear.

It is likely that several factors must act together to trigger the relevant mechanisms, and this study, alongside other research, indicates that air pollution is probably one of them. The same smog associated with modern life has also been linked with lung cancer and poorer mental health, among other health concerns.

The researchers responsible for the latest work want further studies to examine how pollutants affect ALS risk. They also argue for stricter air-quality rules while fossil fuels continue to be burned.

"There is a necessity for prevention strategies and improved regulatory intervention on behalf of public health on air pollution exposure levels," write the researchers.

The research was published in Environmental Research.