Could Living Near Algal Blooms Raise Your ALS Risk?

In recent years, the threat of harmful algal blooms (HABs) in freshwater lakes and rivers has become a growing public health concern for many communities worldwide. Often driven by a mix of warming temperatures, excess nutrient pollution and changing weather patterns, these vivid green blooms are far more than just an eyesore; they can pose significant health risks to people and animals alike.

A newly published study by Michigan Medicine has added a worrying piece to this puzzle: people living near cyanobacterial blooms could face a heightened risk of developing ALS, or amyotrophic lateral sclerosis, a progressive neurodegenerative disease with no known cure.

For communities that rely on lakes for water supply, fishing, swimming or other recreation, this emerging evidence underlines an uncomfortable truth: protecting freshwater ecosystems is not just an environmental issue, it’s a public health priority that could have far-reaching consequences for how we live, work and manage our local waterways.

What Are Cyanobacteria and Why Do They Bloom?

Emerging research links toxic algal blooms like this one to serious health risks, including ALS.

Cyanobacteria, also known as blue-green algae, are ancient microorganisms that are naturally found in almost every freshwater ecosystem worldwide. Under typical conditions, they play a vital ecological role: producing oxygen through photosynthesis, forming part of the base of aquatic food chains, and helping to cycle nutrients.

However, when the balance is disturbed, usually by an influx of nutrients and warm, still water, these organisms can multiply rapidly, forming thick surface mats that choke off light, deplete oxygen, and release toxins into the environment. These blooms can discolour water, create foul smells, and in severe cases, kill fish and other aquatic life by depleting dissolved oxygen.

One of the primary causes of excessive blooms is nutrient runoff. When agricultural fertilisers, livestock waste and untreated sewage find their way into rivers and lakes, they deliver nitrogen and phosphorus, the perfect fuel for explosive algal growth. Warmer temperatures and stagnant water conditions can accelerate this process even further.

As the climate warms, heavy rainfall events are becoming more common, washing even more nutrients off farmland and into water bodies. Meanwhile, longer, hotter summers extend the growing season for cyanobacteria, meaning blooms appear earlier, last longer, and occur in places they historically did not. Together, these trends mean that cyanobacterial harmful algal blooms are now a seasonal fixture for many freshwater communities.

How Do Algal Bloom Toxins Affect People?

Not every bloom is toxic, but many species of cyanobacteria produce potent toxins, and it only takes small concentrations to pose health risks to humans and wildlife. Three of the most studied cyanobacterial toxins are microcystins, anatoxins, and BMAA (β-Methylamino-L-alanine).

Microcystins primarily affect the liver and can cause nausea, vomiting, diarrhoea, and long-term liver damage if exposure is repeated. Anatoxins are neurotoxins that can interfere with nerve function and, in high enough doses, be fatal to animals and pets who drink contaminated water. BMAA is especially concerning because some studies suggest a link to neurodegenerative diseases such as ALS, though more research is needed to understand this connection fully.

Could the water near your home be increasing your risk? The science says it’s time to pay attention.

Human exposure to these toxins can occur through several pathways. Swimming, paddling, or fishing in bloom-affected water may lead to direct skin contact or accidental swallowing. When algal scum dries on shorelines, toxins can become airborne, creating a risk of inhalation. For people who rely on private wells near lakes, the danger is that toxins can seep into groundwater if proper filtration and testing are not carried out. Eating fish or shellfish from contaminated waters can also be a route of exposure if toxins build up in edible tissue.

All these pathways highlight the hidden threat of freshwater toxin exposure, a risk that is easy to overlook but may have long-term consequences for local communities.

Inside the Michigan Medicine Study

To better understand the possible link between cyanobacterial harmful algal blooms and ALS, scientists at Michigan Medicine undertook a major population-based study. By analysing satellite imagery of lakes, rivers and reservoirs across a broad geographic area, they mapped bloom frequency and density near where ALS patients lived.

They then compared this environmental data with patient medical records and lifestyle information, such as whether people used private wells, swam regularly in local lakes, or ate locally caught fish. This multi-pronged approach gave researchers a clearer picture of how real-world exposure might work.

Their findings were striking: living closer to lakes with frequent blooms and relying on untreated or lightly treated well water appeared to increase the likelihood of toxin exposure. People engaged in frequent water-based activities, such as swimming, boating, or fishing, had higher cumulative contact. More alarmingly, the study found hints that such exposure may not only influence the risk of developing ALS but could also affect disease progression and survival times.

Although the research does not yet prove a direct cause-and-effect relationship, it strongly supports the idea that blue-green algae health risks go far beyond simple skin irritation or short-lived stomach upsets. It suggests that long-term or repeated exposure may play a role in complex, life-altering diseases, an unsettling but crucial insight for anyone living near bloom-prone water bodies.

The ALS Exposome: How the Environment Shapes Risk

For decades, ALS was viewed primarily through a genetic lens. While genes do play a significant role, recent advances have shown that the environment is equally critical in understanding who develops ALS and how fast it progresses. This broader view is captured by the idea of the exposome, the totality of all environmental exposures a person experiences from conception onwards.

Unlike isolated exposures, the exposome acknowledges that risks add up over time and interact in complex ways. For lakeside residents, repeated low-level contact with cyanobacterial toxins could become just one piece in a much larger puzzle of ALS environmental risk factors. The presence of BMAA, in particular, has sparked concern because it may accumulate in the brain and spinal cord over decades, possibly triggering or accelerating neurodegeneration in people who are genetically predisposed.

Understanding these connections opens the door for prevention and early intervention. By controlling and monitoring exposure to known hazards like cyanobacterial toxins, communities may be able to reduce the overall burden of ALS and other related diseases.

Why the Midwest and Coastal Regions Face Higher Threats

Across the United States, certain regions are more prone to harmful algal blooms than others. The Great Lakes, for instance, are home to some of the largest freshwater HAB events in North America. Warm, nutrient-rich shallows, coupled with intensive agriculture and urban development, create a perfect environment for blooms to thrive.

Midwestern states, where large-scale farming is common, contribute significant nitrogen and phosphorus runoff, while coastal states face their challenges with heavy rainfall and warm coastal estuaries. In both cases, outdated water treatment facilities may struggle to remove toxins completely, especially during peak bloom periods.

These regional hotspots mean millions of people are potentially at higher risk of freshwater toxin exposure, especially households using private wells or small-scale water systems that lack advanced filtration. As climate change brings hotter summers and more extreme rainfall, the need to tackle this issue at both local and national levels is becoming harder to ignore.

A Real-World Example: Lakeside Communities at Risk

This isn’t just ugly — it’s dangerous.

Picture a rural community in the heart of the Midwest. Families here enjoy a peaceful lifestyle near a scenic fishing lake that supports local recreation and tourism. Many residents draw drinking water from private wells drilled just metres from the shoreline. In summer, children swim, boat, and fish almost daily. The local economy benefits from holidaymakers who flock to the area when the weather warms.

Yet beneath this idyllic surface lies a risk that few residents fully appreciate. When a toxic bloom develops, it may not always be obvious to the naked eye, especially in the early stages. Parents might not realise that letting children swim in affected coves could mean repeated skin contact with microcystins or anatoxins. Fish caught and eaten may contain low levels of BMAA that build up slowly over months and years.

Without regular well testing, families could unknowingly consume contaminated water for weeks at a time. Combined with other ALS environmental risk factors, such hidden exposures could add up to a real health threat over the long term. This scenario is not isolated; it reflects the lived reality for many small, lakeside communities across the United States.

What Can We Do About It?

While the research linking harmful algal blooms to ALS is still evolving, there are clear and practical actions that residents, councils and policymakers can take today.

• Regular Well Testing

Households that rely on private wells should test their water regularly, especially during summer months when blooms are most active. Home water filters should be properly maintained and, where possible, upgraded to systems certified for toxin removal.

• Timely Information

Local councils and public health departments should provide up-to-date bloom warnings and easy-to-understand health advisories. Mobile alerts, local news bulletins and visible lakefront signage can help families make safe choices.

• Better Runoff Management

Farmers, industries and municipalities all have a role in controlling nutrient runoff. Measures like cover cropping, riparian buffers, wetland restoration, and improved wastewater treatment can help reduce the nitrogen and phosphorus entering waterways.

• Community Awareness

Education campaigns can build understanding of blue-green algae health risks and encourage precautionary habits. Simple steps, like avoiding swimming during visible blooms, rinsing off thoroughly after lake activities, and cooking fish well, can help lower the risk.

Key Takeaways

Cyanobacterial blooms are more than a seasonal nuisance; they are an increasingly significant public health issue. For those living near affected lakes and rivers, the risks range from short-term illness to possible links with serious neurodegenerative diseases like ALS.

The evidence so far points to an urgent need for proactive action: improved monitoring, stronger environmental protections, better water management, and informed communities. By taking simple steps now, residents and local authorities can reduce harmful exposures and help safeguard future generations from avoidable risks.

Stay Informed, Work With Hydro Synergy

Hydro Synergy is committed to helping councils, rural communities, and lakeside residents tackle the hidden dangers of harmful algal blooms. From double-power ultrasonic control systems and nutrient-eating bacteria to non-toxic UV-blocking dyes, our solutions are designed to reduce bloom risks and protect your local water supply.

If you’re ready to take practical steps to safeguard your water, your health and your community, get in touch with our team today. Email us at support@hydrosynergy.co.nz or call 0800-NOALGAE (662 5423) to learn more about our tailored services for freshwater toxin prevention.