Study Finds Airborne Release of Toxin from Algal Scum

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Cyanobacteria, or blue-green algae, can release harmful toxins and deplete oxygen levels in the lakes and ponds where they bloom. For the first time, scientists have observed the release of blue-green algae toxins into the air.

According to a report published in the Journal Lake and Reservoir Management, researchers measured traces of the algal toxin anatoxin-a, or ATX, sometimes called the Very Fast Death Factor, at a Massachusetts pond that frequently hosts large algal blooms. ATX is produced by cyanobacteria, a type of photosynthesizing bacteria. Though not technically algae, cyanobacteria are often called blue-green algae.

ATX has been blamed for the deaths of livestock, waterfowl, and dogs. Acute exposure can cause loss of coordination, muscular twitching, and respiratory paralysis. Lead author James Sutherland, an environmental scientist with the Nantucket Land Council, said in a news 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.”

Bacteria That Can Photosynthesize

ATX is produced by single-celled organisms known as cyanobacteria, which can form harmful algal blooms – when vast amounts of cyanobacteria grow in lake surface waters. Blooms are exacerbated by fertilizer run-off entering lakes or ponds from nearby fields or improperly treated wastewater and can stimulate growth and high water temperatures. Cyanobacteria, which also are known as blue-green algae, are a type of bacteria that can photosynthesize.

Cyanobacterial blooms can also lead to low oxygen conditions, further degrading water quality. When the algae in these large blooms die, they sink to the lake bottom and decompose, which can use up all the oxygen in the water, killing fish and other animals. The blooms also can release toxins into the water that can prove fatal for these animals.

Though airborne algal toxins had never been measured before, Sutherland and his colleagues hypothesized algal blooms could release toxins into the air under certain conditions. During the late summer and early fall in 2019, researchers regularly collected air samples using a glass fiber filter at Capaum Pond’s edge on Nantucket Island in Massachusetts.

Adverse Health Effects

Scientists screened for an array of toxins using an analytical technique called liquid chromatography-tandem mass spectrometry. On a windy but foggy day, several samples revealed the presence of ATX in the air. Researchers measured concentrations as high as 21 nanograms of ATX per milligram of air and captured an average of 0.87 nanograms of ATX in each filter.

Brisk winds likely helped the toxins get airborne, while the surrounding fog prevented the toxins from being dispersed beyond detectable levels by the wind. Scientists aren’t sure how exactly the toxins are becoming airborne, whether the ATX molecules are enveloped in aerosolized water droplets or attaching themselves to other aerosolized particles.

When people are exposed to cyanotoxins, adverse health effects may range from a mild skin rash to severe illness or, in rare circumstances, death. Acute diseases caused by short-term exposure to cyanobacteria and cyanotoxins during recreational activities include hay fever-like symptoms, skin rashes, respiratory and gastrointestinal distress. Exposure to drinking water contaminated with elevated concentrations of microcystin and cylindrospermopsin could cause liver and kidney damage. The table below summarizes the health effects caused by the most common toxin-producing cyanobacteria.

Death Can Occur Within Hours

High biomass blooms, whether of toxic or nontoxic species, can lead to deficient oxygen levels in the water column (hypoxia), resulting in higher mortality rates in local fish and shellfish invertebrate and plant populations. The blooms may also affect benthic flora and fauna due to decreased light penetration. Toxic blooms from some cyanobacteria genera may lead to inhibition of other phytoplankton and suppression of zooplankton grazing, leading to reduced growth and reproductive rates and community structure changes composition.

CyanoHABs can also harm pets, wildlife, and livestock. Pets and other animals can be poisoned by drinking toxin-contaminated water or swimming in waters with a cyanoHAB. Several dog and livestock deaths have been reported after exposure to cyanotoxins in water. Symptoms of exposure to HABs in pets can include excessive salivation, fatigue, difficulty breathing, vomiting, diarrhea, and seizures. Death can occur within hours to days of exposure.

No matter how it’s happening, researchers say the phenomenon is a threat to humans and wildlife’s health and safety. Sutherland said:

“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.”

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