Algae blooms may add to air pollution, a greater threat than previously thought

Every summer, thick algae beds in freshwater lakes and coastal bays kill animals and pets by poisoning their organs and nervous systems. Last month, The News & Observer reported a dog’s death linked to algal blooms in Jordan Lake.

With climate change driving more extreme heat events that raise water temperatures and causing heavier rains that flush pollutants into waterways, algal blooms are becoming a more frequent and longer-lasting global problem.

Lethal blue-green algae, or cyanobacteria, feed on fertilizer pollutants and grow atop standing bodies of water in clumps large enough to see. These bacteria produce varied chemicals, some of which can be toxic.

Scientists from the University of North Carolina at Chapel Hill are studying if the bacteria’s poisons also escape into the air, worsening air quality and risking the health of humans who simply walk near pond scum.

The U.S. Environmental Protection Agency has set guidelines for ingesting or coming in contact with harmful algal blooms, advising people not to drink or touch algae-contaminated water.

But the EPA, the Centers for Disease Control and Prevention and the World Health Organization do not have guidelines for bacterial toxins in the air, as scientists are still figuring out how much toxin people must breathe in to be sickened.

There are numerous cyanobacteria that produce various toxic chemicals. It’s been difficult to determine which bacteria are doing what in a lake.

What’s in the air?

UNC environmental scientist Haley Plaas, an author of the new study, is looking for microcystins, a specific toxin that cyanobacteria produce that the EPA considers a potent liver toxin and possible human carcinogen.

“The cyanobacteria love the hot temperatures and they can thrive in a low nutrient [pollutants] environment,” said Plaas.

According to Plaas, the toxins are likely to escape into the air when a water spray occurs on contaminated water bodies. The air trapped beneath the water creates tons of bubbles that absorb chemicals from algae. When the bubbles burst, the chemicals in the water escape into the air.

Plaas and her team installed air filter devices to capture poisons between the summer and fall of 2020 in the Chowan River and Albemarle Sound. This area has been renowned for algae blooms since Hans Paerl, Plaas’ research adviser, became the first N.C. researcher working on algae growth problems in the 1980s.

According to the Albemarle Resource Conservation and Development Council’s website, cyanobacteria blooms flared up in the Chowan River and its tributaries from 2015 to 2020 for the first time in almost 30 years, triggering state advisories against swimming and eating fish.

Like Plaas and Paerl, scientists across the U.S. are expanding their research into algae toxins and air pollution. Researchers on Nantucket Island in Massachusetts are studying which toxin is in the air and if weather affects how algae and toxins become airborne. In Michigan, Great Lakes scientists are creating a risk system that would help people avoid poor air quality caused by algal blooms.

So far, the Albemarle Sound team has good news — they didn’t see microcystins floating in the air in eastern North Carolina.

The filter devices Plaas and her team installed can trap drifting particulates, which the cyanobacteria and microcystins are likely to bind to if they enter the air.

Researchers analyzed the composition of the particles and didn’t find microcystins, which is “good news,” according to Plaas.

But the absence of toxins doesn’t guarantee that the air quality is safe from the bacteria and toxins lurking in the water.

Tiny particles can cause serious health problems

Researchers found that algal blooms may increase the level of air contaminants of small particles that harm the environment and human respiratory system.

The particles studied had a diameter of less than 2.5 micrometers, or PM 2.5, which is invisible to human eyes but threatens human respiratory health. Researchers found more particles in the air during the bloom period than during the non-bloom period, and these particles are dangerous air pollutants.

Because they are so small, these particles can travel deep into the respiratory tract. Exposure to PM 2.5 can irritate the lungs and heart, causing difficulty in breathing, heart attacks and death. People suffering from asthma or other respiratory illnesses are particularly vulnerable.

The N.C. Department of Environmental Quality monitored PM 2.5 air quality across 16 counties in 2020, down from 30 counties in 2013. Durham and Wake counties are among those being monitored. Chowan County, where UNC researchers are studying, has not been on the monitoring list.

The more small airborne particles there are in the air — as the researchers have found linked to blue-green bloom timing — the greater the threat to human health.

Plaas said the microcystins may still stay within the cyanobacteria cells because the bacteria don’t easily break up and may mass together to create larger clumps than previously believed.

She and her colleagues are preparing a research article that they hope to share by the end of July. Meanwhile, to hunt down the toxins and bacteria that they didn’t find in North Carolina, the researchers are getting their feet wet in freshwater and bays where thicker beds of algae bloom.

Researchers are collecting data on blooms from the Delta Bay area of California, which has a similar static water body to Albemarle Sound, only worse.

Reservoirs and canals that keep water from flowing into coastal rivers and bays, causing water to stagnate, are “the perfect conditions for algae [growth] 24-7,” Plaas said.

She added that because the area is surrounded by agricultural activities that feed abundant nutrient pollutants into waterways, she should be able to collect more evidence of where algal blooms take place.

Plaas has just returned from the Delta Bay area where she and other California researchers installed air sampling devices.

She is also deploying more devices on N.C.’s coastal streets. Beginning in July, there will be new air samplers spanning from Elizabeth City near Albemarle Sound to Northampton County. Northampton, about 100 miles northeast of Raleigh, is not monitored by DEQ’s air quality system.

“We hope to keep these air sensors up and running for as long as they’ll survive, which is five to 10 years,” she said.

Plaas noted that living organs naturally produce biochemical compounds: Just as human bodies make hormones when they are happy or stressed, bacteria’s “toxic” compounds are essential for their survival.

Treating algal blooms is possible, Paerl said in an interview with UNC, but taking action “needs a will.”

“That will is ever increasing because of our need for good water quality,” he added.