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Water Today Title October 30, 2020

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Update 2018/2/1
Blue-green algae


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By Michelle Moore

Cyanobacteria can cause harmful algae blooms (HABs) to grow on the surface of water leaving it unfit to drink and swim in. The negative effects on human health are well documented and include skin irritations, gastrointestinal and respiratory issues, liver failure, and in a few cases even death. Widely recognized routes of exposure are through the skin (dermal) and through ingestion (oral). For instance, people who swim in water contaminated by HABs or eat shellfish contaminated with cyanotoxins can become ill, sometimes requiring hospitalization.

Another lesser known, but equally recognized route of exposure is through inhalation. While inhalation has certainly not been investigated to the extent that oral and dermal exposure has, there is scientific evidence that it can cause illness. With the rapid proliferation of HABs, and with more people living in lakeside areas, scientists have recently delved in to this relatively new area of study to explore the effects of cyanotoxins through inhalation more seriously.

Water can become aerosolized by disturbances in the water, be it waves crashing up on shore, people engaging in water sports, hydro-electric dams, evaporation or other factors. Studies conducted by the Lovelace Respiratory Research Institute (LRRI) confirm that along with the water itself, "algae cells, bacteria, and waterborne toxins can be aerosolized by a bubble-bursting process with a wind-driven white-capped wave mechanism," meaning that if toxins are present in the water, and if it becomes aerosolized, they can be inhaled.

While not every algal bloom is toxic, "it has been suggested that worldwide, an average of 60% of the cyanobacterial bloom samples investigated have been positive for cyanobacterial toxins," according to the World Health Organization. Furthermore, studies referred to this reporter by Health Canada point to the fact that following a bloom, which usually lasts for one to two weeks, much of the toxicity remains in the water during a short period after the bloom is no longer visible.

Tricia Lynn at the Office of Public Affairs for the U.S. Environmental Protection Agency (EPA) said that the "aerosolization of cyanotoxins can be a potential source of exposure to people who may be near, on, or in recreational waters." When asked about monitoring, Lynn said "monitoring of HABs is the responsibility of the state or local jurisdiction where the bloom occurs."

Dr. Lorraine Baker, senior scientist at the National Center for Environmental Health for the Centers for Disease Control and Prevention (CDC) gave a similar response, specifying that little research exists as to the effects of this type of exposure. It is true that many studies focus on recreational exposure which may include oral, dermal and inhalation as possible routes of exposure. This can make it difficult to attribute symptoms to any one source of exposure.

However, she did share a case that had been reported to the Kansas Health Department in 2011 that was associated with inhalation exposure. The person reported suffering from eye and upper respiratory tract irritation beginning twenty-four hours after knee-boarding. The Kansas Health Department report itself cites a lack of awareness among the public of cyanobacterial blooms in general, and the need to further educate the public and health care providers.

Backer also stated that "people with asthma and other respiratory conditions should probably avoid being around cyanobacterial blooms under circumstances where the blooms and/or toxins could become aerosolized, such as in windy conditions or choppy waters."

Dr. Eva Pip is a recently retired professor at The University of Winnipeg and has published many studies on toxic cyanobacteria. Dr. Pip explained that microcystins, a liver toxin, and anatoxins, a neurotoxin, "can be present in Lake Winnipeg at unsafe concentrations that coincide with concurrent cyanobacterial bloom conditions." She added, "these toxins can be ingested while swimming or with drinking water, they can be absorbed through the skin through contact with algal mats or water containing the algae, and they can be inhaled, which is a little known fact. I always tell people: if you can smell the mats, you are being exposed."

Dr. Pip said symptoms caused by microcystins are considered to be fast-acting. Someone who comes into contact with the toxins would develop symptoms the same day. She said, "if you have inhaled it then your primary symptoms will start out as respiratory symptoms. Some people experience difficulty in breathing, they might experience irritation in their nose and throat so in that case it might look like some kind of chest infection, even though there is no actual infection, it's just the irritation that's causing that."

Dr. Wayne Carmichael is a retired Professor of Aquatic Biology and Toxicology from the Department of Biological Sciences at Wright State University. His research focused on freshwater cyanobacteria their toxins and toxicology. Dr. Carmichael said, "anytime you have a bloom and you're having water sports whether you're skiing or water boarding, in the waves out on the shore you will be exposed to some level of aerosol particles for inhalation and if there are toxins present there will be a risk and that risk will depend on the concentration and the exposure time and the type of toxin that's present too."

A 1992 study published in the Journal of Environmental Management reported that people who were dinghy sailing in a river with HABs complained of upper respiratory and gastrointestinal symptoms as well as skin rash, ear pain, and eye irritation. The study began after the National Rivers Authority in the United Kingdom determined that the water body exceeded the "concentration threshold for a potential to cause harm".

Published in the same journal, a 2006 epidemiology study involved over 1300 people who had used a water craft on lakes with different levels of HABs contamination. Water samples were collected and participants completed questionnaires beforehand. After 3 days people who had been on lakes with higher levels were 2.1 times more likely to report respiratory symptoms.

When asked just how serious this exposure could be Dr. Carmichael said, "in all these situations, an aerosol exposure is going to have fairly low toxin concentration, so it would probably be more an immediate reaction and then it wears off fairly quickly once you leave the area. But some day there's going to be a situation where the bloom is fairly toxic and it might be a mixture of neurotoxins and liver toxins and people may become more acutely poisoned just from the situation and that wouldn't clear up necessarily once they left the lake. So, there is that risk."

Dr. Pip expressed the need for more public awareness about this source of exposure and the effects of cyanotoxins overall, pointing out that often people experiencing symptoms rarely recognize it as such. In addition, she believes that there is a lot of unawareness among health care professionals which causes cyanotoxin exposure to get misdiagnosed, saying that "in medical schools there needs to be more taught on this problem because it will only get worse."

She further stated that "we know for a fact that this stuff is toxic so right there that means that we have to pay attention and especially government regulatory agencies should pay attention. But governments should pay also attention to how we address the cause of this problem which is how the nutrients is going into the water." Dr. Carmichael agreed with the sentiment, saying "we've got water quality issues that are not going to go away and we do have to pay attention to it."

Dr. Pip said the aerosols could definitely be carried inland and suggests that people avoid water bodies while there is a bloom if they can. For people living lakeside, she specified that anything the aerosol comes into contact with has the potential to become contaminated. On that same note, Dr. Carmichael said "I would close windows during a bloom where there's a storm or wind that's making wave action and it depends on how close they are, I think if they are a few hundred yards or meters away from the shoreline there is certainly less risk than if they are 50 feet from the shoreline. It might also come down to if people are experiencing skin or eye irritation, that would be a clue too to stay inside."

When asked just how far cyanobacteria can travel, both Dr. Pip and Dr. Carmichael said that to their knowledge there have been no specific studies on this area. However, Dr. Carmichael said "cyanobacteria are pretty resistant, even when they tend to dry out they can be carried long distances." In the case of do not swim advisories that are posted at recreational lakes during blooms, Carmichael said "these warnings usually say avoid swimming, bathing, keep pets in particular away from the water I think it would be appropriate to also make a statement about aerosols during high wave action."

A 2011 study conducted by the Cawthron Institute, the largest independent science organization in New Zealand, reported that "nasally applied microcystin appears to have a 10-fold higher availability and toxicity than orally ingested toxins, suggesting that aerosolized toxins could represent a major risk for human populations close to lakes with cyanobacterial blooms." Although their results did not appear to demonstrate a hazard for human health, they concluded that their "peak values may (have been) underestimated. Aerosolized toxins should be considered when developing risk assessments particularly for lakeside populations and recreational users."

The Centre for Applied Microbiology and Research in the United Kingdom echoed these finding in their study on mice wherein they examined the toxicity of microcystin during seven days of inhalation exposure. It determined that "laboratory investigations into the intranasal exposure of mice to microcystin-LR have shown sensitivity to be about 10 times greater than gastric intubation (oral route)."

The exposure resulted in the degeneration and necrotization of nasal and respiratory passages and indicated the presence of liver and neurotoxins. The authors concluded that "these findings and the, albeit limited, environmental observations, indicate that the possibility of exposure to cyanobacterial toxins via inhalation should be considered during at-risk activities," which included showering and doing water sports in cyanobacteria contaminated water.

When asked about these studies in particular, Dr. Pip said "...your mucous membranes like in your nose, your eyes, those mucous membranes are much more absorptive than just regular skin so yes if you do inhale it, all of that mucous membrane, there is a lot of surface area there and so yes, it can be a significant source of exposure."

For his part, Dr. Carmichael commented that "routes of exposure vary tremendously with the toxin and not just the cyanobacterial toxins but any kind of toxin exposure... inhalation, because the mucous membranes of the nose and the lung, they absorb things a lot better than your skin does or your stomach does, so it is not surprising that yes that route of exposure, inhalation would be high up on the list of risk factors so even though the concentration might be very low compared to an oral ingestion, you might literally get more toxin into the bloodstream."

While inhalation is considered to be a possible route of exposure alongside ingestion and skin contact, much of the specifics surrounding it remain to be discovered. Mainly, how far exactly can it travel, and what concentration causes symptoms of what degree? As the issue of cyanobacteria and the blooms themselves continue to grow, the need for more research will become increasingly evident. However, for now and in the midst of the winter season, we remain on ice.


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