Living near toxic algal blooms tied to shorter survival in ALS patients
Study: Link stronger for people who swam or fished, had private wells
Living close to water bodies with blue-green algae blooms, or cyanobacteria, is linked to significantly reduced survival among people with amyotrophic lateral sclerosis (ALS), according to a new study.
The association was significantly stronger in people who used private well water or participated in water-related activities such as swimming or fishing, which shortened lifespans by up to 0.89 years.
“Our study shows a clear link between living in close proximity to cyanobacteria blooms over the course of one’s life and adverse outcomes of ALS,” Stephen Goutman, MD, the study’s lead author and associate director of the ALS Center of Excellence at the University of Michigan, said in a university news story.
The study, “Life Course Exposure to Cyanobacteria and Amyotrophic Lateral Sclerosis Survival,” was published in the International Journal of Environmental Research and Public Health.
‘Harmful algal blooms are a growing problem across the country’
A combination of genetics, environmental exposures, and lifestyle habits is thought to underlie the development of ALS, a progressive neurological disorder marked by the death of motor neurons, the nerve cells that control voluntary movements.
Cyanobacterial algal blooms occur in freshwater, marine, and terrestrial waters, and their size can vary widely depending on many factors, including the watershed, weather, and nutrients.
When these algae grow dense and out of control, they release toxic agents that can poison people, animals, and the environment. Thus, people living near such water bodies are likely to be affected by these toxins — either by ingesting contaminated water or seafood, by participating in water-related activities such as swimming or fishing, or by inhaling aerosols downwind of contaminated water.
Even though the World Health Organization has established exposure guidelines to protect people and the environment from these toxins, the understanding of exposures and the impact of cyanobacterial algal blooms on human health remains limited.
Because current evidence suggests there’s a link between exposure to cyanobacteria toxins and a greater risk for developing ALS, Goutman and colleagues set out to determine whether living close to cyanobacterial algal blooms also impacted ALS progression.
“Harmful algal blooms are a growing problem across the country, and it is not uncommon for people to live near them,” Goutman said.
ALS patients with less exposure to toxic algal blooms lived longer
The team compiled the residential and health histories of individuals with ALS and then measured the duration and extent of each person’s exposure to cyanobacterial algal blooms using satellite data from the Cyanobacteria Assessment Network. Residences in the study were primarily located in Michigan, but there were also patients living in other states.
The survival assessment focused on 309 ALS patients, with a median age at diagnosis of 64 and a median time between diagnosis and death of 2.3 years.
Our study shows a clear link between living in close proximity to cyanobacteria blooms over the course of one’s life and adverse outcomes of ALS.
According to the analysis, up to 20 years of exposure to algal blooms before an ALS diagnosis significantly increased the risk of death after disease onset by up to 20%, particularly for those who lived within 5 km (3 miles) of water bodies.
Overall, ALS patients with less exposure, based on annual average cyanobacteria levels, lived a median of 4.7 months longer than those who were more exposed (median 2.53 vs. 2.14 years).
“Our study shows a clear link between living in close proximity to cyanobacteria blooms over the course of one’s life and adverse outcomes of ALS,” Goutman said.
ALS incidence markedly higher in Midwest
When the team examined different water sources, shorter survival for ALS individuals living within 5 km of algal bloom events was partly driven by the use of private wells for drinking water, which decreased survival up to 8.8 months.
Significantly shortened survival, of up to 10.7 months, was also found for those who fished or swam in cyanobacteria-contaminated water bodies within 5 km of their home.
“While there is still limited research into the mechanism by which cyanobacteria toxins affect neurodegenerative diseases, our findings suggest living near or participating in activities in these water bodies may influence the progression of ALS,” Goutman said.
The team also noted that these findings might explain the regional patterns of ALS incidence, which is markedly higher in the U.S. Midwest region (Michigan, Wisconsin, Minnesota, Illinois, and Indiana) than in other U.S. regions.
“If exposure to cyanobacteria toxins is a meaningful risk factor for ALS, the large number of inland lakes prone to such bacteria in the Midwest may partly explain why the disease incidence is much higher than other parts of the country,” said Stuart Batterman, PhD, the study’s first author and professor of environmental health sciences at the University of Michigan School of Public Health.
Still, researchers said exposure to cyanobacteria toxins is a modifiable risk factor of ALS progression. “By avoiding high-risk activities associated with this exposure, ALS survival (and possibly ALS risk) might be improved,” they concluded.
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