Cyanobacteria - Info for Health Care Providers
Background
Cyanobacteria, also called "blue-green algae" or "pond scum" grow in warm, shallow or slow-moving water. Even though cyanobacteria are colloquially known as blue-green algae, blooms can range in colour from green to red. New blooms smell like mown grass and older blooms smell like rotting garbage.
Health effects
Some species of cyanobacteria produce toxins that have negative effects on human health. Approximately 50 to 70 percent of cyanobacterial blooms produce toxins, so avoiding all blooms is prudent. It is not possible to identify which blooms are toxin-producing or when they will produce toxins by visual inspection alone.
The most commonly detected toxin in cyanobacterial blooms is microcystin, which, at very high levels of exposure, can have hepatotoxic effects. Adverse health effects of other cyanobacterial toxins can include headaches, visual disturbances, rashes and pruritus, diarrhea, nausea and vomiting, respiratory irritation, and flu-like symptoms.
Routes of exposure include inhalation of contaminated water droplets, ingestion of contaminated fish or water, and absorption through skin or mucosal membranes.
The health effects of cyanobacterial toxins often overlap with bacterial, protozoal or viral infections, which may also result from water exposures. Further complicating diagnosis, diagnostic tests for human exposure to cyanobacterial toxins are not readily available.
Children are more at risk of health effects than adults. Patients undergoing dialysis are also at a higher risk if their dialysate fluid is contaminated with cyanobacterial toxins. This can occur if the dialysate fluid contains water contaminated with cyanobacterial toxins; however, this is highly unlikely in the KFL&A area because municipal water treatment methods provide an effective barrier to these toxins. Further, the Kingston General Hospital regularly tests dialysate fluid for cyanobacterial toxins.
Preventive measures for patients
Most people avoid exposure to water contaminated with cyanobacteria because of its unsightly colour and smell. For patients who may not or do not wish to avoid contaminated water, health care providers can make the following recommendations:
- Recreational water activities: Recommend that your patients avoid recreational water activities during cyanobacterial blooms. If your patient wants to continue recreational water activities during a cyanobacterial bloom, recommend lower-exposure activities, like canoeing or sailing. Higher-exposure activities include swimming, water skiing, and wind surfing.
- Fishing: Recommend that your patients avoid eating fish from areas where a cyanobacterial bloom is visible. If your patient still wants to continue eating fish, recommend that they discard the organs, as this is where most of the toxins accumulate. Advise patients that cooking does not inactivate most cyanobacterial toxins.
- Drinking water: If your patient obtains water from a surface water source that might be contaminated with cyanobacteria, recommend that they contact the Ontario Ministry of the Environment's Spills Action Centre at 1-800-268-6060 or 416-325-3000. Conventional water treatment and boiling are not effective at removing cyanobacterial toxins.
Further questions?
Contact a public health inspector at KFL&A Public Health by visiting our office or calling 613-549-1232, ext. 1231.
Revised: 2014-01-21