Blue-Green Algae Health Concerns

As the incidence of blue-green algae blooms increases across North America so do concerns about human and animal health impacts of exposure to it. Blue-green algae (cyanobacteria) have the potential to produce algal toxins. Not all blue-green algae will produce toxins but it is impossible to tell whether there are toxins present just by looking at it and even if the toxins are not present one day, they could be the next. In May 2015, a dog died from swimming in a Minnesota lake that appeared to have clear water, so there was not the usual warning that comes with the appearance of algae on the surface. In general, people are advised to use caution both for themselves and for their pets or livestock if there is an algal bloom evident.

Dog eyeing blue-green algae at Minaki, Ontario 2011 - courtesy of Todd Sellers

Dog eyeing blue-green algae at Minaki, Ontario 2011 – courtesy of Todd Sellers

Exposure to the toxins in blue-green algae can occur either through ingesting it, inhaling it or having skin contact with it. It can cause rashes, skin and eye irritation, allergic reactions, gastrointestinal upset, and other effects.  At high levels, the exposure can result in serious illness or death. There have been several dog deaths reported in many locations across North America over the past decade but no human deaths have been reported to date. Since exposure to the toxins is not limited to simply ingesting or drinking the water, when a bloom is present people are advised not to swim, water ski or participate in other activities that could result in inhaling or being spayed by the water.
Blue-green algae can produce several toxins, but two types of toxins are of particular concern and are generally tested for: Microcystins and Anatoxin-A. Microcystins are a group of hepatoxins (toxins that affect the liver). Microcystins are considered to be the most commonly-found cyanobacterial toxins in water and are the toxins most responsible for human and animal poisonings. Anatoxin A is a potent neurotoxin (toxins that affect the nervous system) which can cause lethargy, muscle aches, confusion, memory impairment, and, at sufficiently high concentrations, death.
Recently, some attention is being paid to the possibility that BMAA, a toxin found in some blue-green algae, is related to the onset of motor neuron disease diseases like Alzheimers, ALS and Parkinsons.  The possible link was first investigated in Australia and now researchers in New England and Vermont are looking at clusters of cases of ALS around a few lakes, wondering if there is any connection to the blue-green algae.
There is no central reporting or tracking of blue-green algae blooms in either Canada or the United States. Each province and each state have different mechanisms for doing so, some more comprehensive than others. This lack of consistent tracking impedes the public’s awareness of both the problem and the solutions. There is also no consistent requirement to report illnesses related to exposure to blue-green algae so determining the extent of the problem is difficult. In a study released in 2013 by researchers at the University of Oregon, they found that the toxicity in algal blooms was increasing and therefore the health concerns will also be increasing. Consistent reporting of both bloom occurrences and health incidents needs to begin throughout North America.



  1. […] of the HABs that you will find in the US Great Lakes are blue green algae.They are not technically algae. These organisms are cyanobacteria that include chlorophyll, which […]

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