Researchers Find That Algae Blooms Can Spew Dangerous Toxins into the Air


Algae blooms and the toxins they produce have become an increasingly common problem. Scientists now say the harmful algal blooms maybe even more damaging than we thought, indicating that they could even poison the air.

As per a recent press release, scientists from the Massachusetts University have for the first time detected an airborne instance of the algal toxin anatoxin-a (ATX), also known as the “very fast death factor.” They have already been shown to kill the fish that swim in the water they infest or the animals that drink from it. The study was published in Lake and Reservoir Management. Study lead author Dr. James Sutherland of the Nantucket Land Council said in a press release:

“ATX is one of the more dangerous cyanotoxins produced by harmful algal blooms, which are becoming more predominant in lakes and ponds worldwide due to global warming and climate change,” 

Airborne Under Certain Environmental Conditions

ATX is a toxin made by cyanobacteria or blue-green algae. Despite their name, these single-celled organisms are not plants but rather bacteria that can photosynthesize. The toxin can cause loss of coordination, muscular twitching, and respiratory paralysis. It has been known to kill livestock, pets, and other animals that drink contaminated water. The study authors wrote:

“Although no previous studies have documented the capture of airborne ATX molecules or cyanobacteria cells containing ATX, we hypothesized that ATX could become airborne under certain environmental conditions.” 

To test this idea, the scientists devised a way to sample the air above a pond in Nantucket, Massachusetts, dealing with a harmful algal bloom (HAB). They brought an air sampling device to the shore on windy days and collected airborne particles on filters. They also tested the water for the presence of the toxin.

Potential Human Health Exposure

The scientists collected their samples between July and October of 2019. They detected ATX in the water at concentrations as high as 21 nanograms per milliliter, Science Alert reported. And, on one foggy and windy day in September, they detected it in the air also. They recorded an average of 0.87 nanograms per filter on their air sampling device, which would equal an airborne exposure of 0.16 nanograms per meter squared.

The researchers are not sure how the toxin ended up in the air but think the wind might have blown it in tiny droplets from the pond, and then the fog allowed it to persist for longer than usual. In any case, it is a problem worth investigating further. The researchers wrote:

“These findings indicate that emission of ATX molecules, or cyanobacteria containing ATX, during HABs presents a potential human health exposure not previously examined.” 

Cyanobacteria Prefer Warmer Water Temperatures

Harmful algal blooms are a problem for many other reasons, of course. They can deprive water of oxygen as they decompose, killing fish and degrading water quality, the press release explained. They are also made worse by human activity, according to Science Alert. They are fed partly by excess nutrient pollution from agricultural runoff. As Sutherland noted, they are also exacerbated by the climate crisis. The cyanobacteria prefer warmer water temperatures, and heavy rain from extreme weather events can wash more fertilizer and other nutrients into bodies of water. Sutherland said in the press release:

“People often recreate around these lakes and ponds with algal blooms without any awareness of the potential problems […] direct contact or inhalation of these cyanotoxins can present health risks for individuals, and we have reported a potential human health exposure not previously examined.”

Exposure Route Is Via Inhalation

The global expansion of harmful cyanobacterial blooms (CyanoHABs) poses an increasing threat to public health. CyanoHABs are characterized by the production of toxic metabolites known as cyanotoxins. Human exposure to cyanotoxins is challenging to forecast, and perhaps the least understood exposure route is via inhalation. 

While the aerosolization of toxins from marine harmful algal blooms (HABs) has been well documented, cyanotoxins’ aerosolization in freshwater systems remains understudied. In recent years, spray aerosol (SA) produced in the Laurentian Great Lakes’ airshed (the United States and Canada) has been characterized, suggesting that freshwater systems may impact atmospheric aerosol loading more than previously understood. 

Cyanobacteria, also referred to as blue-green algae, are microscopic organisms that live primarily in fresh water and saltwater, at the surface and below. They usually multiply and bloom when the water is warm, stagnant, and rich in nutrients (phosphorus and nitrogen) from sources such as fertilizer runoff or septic tank overflows.

Dangerous To People, Marine Life, And the Environment

An algal overgrowth is referred to as an “algal bloom.” Cyanobacterial blooms are usually blue-green, but algal blooms can vary in color, ranging from red to brown. When a bloom occurs, scum (a layer of extraneous foul matter) might float on the water surface, resulting in a rotten plant-like odor. Blooms typically occur during late summer or early fall but can occur anytime during the year.

Not all algal blooms are harmful. A cyanobacterial algal bloom can be detrimental when the toxins (cyanotoxins) produce in air and water reach concentrations that are dangerous to people, marine life, and the environment.

Domestic animals, especially dogs, maybe early victims of a toxin-producing bloom. Dogs become engaged in outdoor activities and do not differentiate between clean or contaminated water. Effects seem to be more severe in animals than in humans. This might be the result of higher ingested doses or a difference in the reaction to toxins.

The most frequently reported symptoms in dogs exposed to cHABs are gastrointestinal, such as vomiting and foaming at the mouth. Exposure can also cause lethargy and neurologic symptoms, including stumbling, behavior changes, spastic twitching, loss of coordination, ataxia, violent tremors, partial paralysis, and respiratory paralysis.

Wash Cyanobacteria off Pets and Livestock

Hepatoenteritis, toxic liver injury, hepatic lesions with necrosis, and petechial hemorrhages of the heart have been reported in animals. Exposure has caused death in fish, dogs, cattle, and birds. People should learn to use clean, fresh water to immediately wash cyanobacteria off pets and livestock that contact a bloom. They should also prevent the animal from licking cyanobacteria off its fur.

People should also keep their pets or livestock from grazing near, drinking, or swimming in water with a bloom. Always contact a veterinarian if the animal shows any signs or symptoms of illness after suspected or known exposure to cHABs or potentially contaminated water. Signs and symptoms include loss of energy or appetite, vomiting, stumbling or falling, foaming at the mouth, diarrhea, convulsions, excessive drooling, tremors, or other unexplained sickness.


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