Proximity to Algal Blooms May Worsen ALS Outcomes
New research reveals a concerning link between living near harmful algal blooms and a faster progression of amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig’s disease. The study suggests that exposure to cyanobacteria toxins found in these blooms may negatively impact the life expectancy of those with ALS.
Algal Blooms and ALS: A Connection
A recent study from Michigan Medicine indicates that residing close to cyanobacterial harmful algal blooms can accelerate the rate of mortality from ALS. These blooms, prevalent nationwide but particularly common in coastal and Great Lakes states, involve dense, uncontrolled growth of cyanobacteria, also known as blue-green algae. These organisms generate toxins that can pose risks to both human health and the environment.
Researchers at the University of Michigan Pranger ALS Clinic examined participants with ALS. They assessed the duration and extent of each participant’s exposure to harmful algal blooms by examining their residential and health records. They also used satellite data from the Cyanobacteria Assessment Network.
Living Near Blooms and ALS Progression
The study revealed that many participants resided within three miles of a harmful algal bloom. Living near blooms, especially if engaging in activities such as swimming, boating, or utilizing a possibly contaminated local water source, was linked to dying from ALS almost a year sooner. These findings have been published in the International Journal of Environmental Research and Public Health.
“Harmful algal blooms are a growing problem across the country, and it is not uncommon for people to live near them,”
—Stephen Goutman, MD, Harriet Hiller Research Professor, director of the Pillory as a clinic and associate director of the ALS Center of Excellence at University of Michigan
People may encounter cyanobacteria toxins through ingestion, inhalation, and skin contact. The study found that people with the most significant exposure lived near harmful blooms and used private wells for their water source. The Centers for Disease Control and Prevention report that between 2009 and 2010, over 350 people in the United States died from harmful algal blooms (CDC, 2025).
The Science Behind the Link
Cyanobacteria generate various toxic agents connected to neurodegenerative diseases, including ALS, Alzheimer’s, and Parkinson’s. One such toxin, ß-methylamino-L-alanine, has been detected in brain and cerebrospinal fluid samples of ALS participants. The research emphasizes that exposure to cyanobacteria toxins from these water bodies may influence ALS progression.
While genetics play a role in ALS, environmental factors also significantly influence the disease. The accumulation of exposures to toxins and pollutants, collectively known as the ALS exposome, includes elements like pesticides and volatile organic compounds. Cases of ALS are most common in the Midwest, which researchers believe may be partly due to extensive industrial and agricultural practices.
“If exposure to cyanobacteria toxins is a meaningful risk factor for ALS, the large number of inland lakes from to such bacteria in the Midwest may partly explain why the disease incidence is much higher than other parts of the country,”
—Stuart Batterman, PhD, professor of environmental health sciences at the U-M School of Public Health
The study underscores the importance of considering environmental exposures throughout one’s life when studying ALS. Further research will provide insight into the factors contributing to the onset and progression of the disease.
