EPA issues guidance on algal toxins in public drinking water supplies

Last summer’s shutdown of Toledo’s drinking water supply raised questions among municipal drinking water utilities nationwide. New EPA Health Advisory will help.

If you live in certain areas of southeast Michigan and receive your drinking water from Lake Erie, you no doubt remember the concern and inconvenience caused by a harmful algae bloom in the western basin of the lake. Drinking water supplies to thousands of homes in Toledo and other cities were interrupted for several days during August of 2014.

The contamination of drinking water supplies drawn from western Lake Erie was caused by what aquatic scientists refer to as a Harmful Algal Bloom (HAB). According to Michigan State University Extension most algal blooms that occur in aquatic systems are green algae – true plants that are fed upon by fish and other aquatic organisms. Though sometimes a nuisance, green algae blooms are harmless to human health. But the algal bloom that shut down drinking water supplies was blue-green algae -- technically not algae but cyanobacteria. Cyanobacteria blooms may be referred to as HABs because some species of cyanobacteria are capable of producing toxins that can pose health risks to people and animals.

To date, the U.S. Environmental Protection Agency (EPA) has not issued federal, regulatory drinking water standards for cyanotoxins in public water supplies due to lack of conclusive, quantitative evidence of risk to human health. Research to determine health effects are ongoing at institutions across the country as HABs in surface waters is a widespread problem. However, the Toledo shutdown added new urgency -- drinking water utilities across the country are asking for guidance.

Based on the best available science, EPA has determined cyanotoxin levels in tap water that are “protective of human health” and has recently issued a Health Advisory for public drinking water supplies. A fact sheet, explaining the new Health Advisories, is now available. These guidelines come just in time for summer, which is prime season for algal blooms in surface waters because of warmer temperatures.

The EPA points out that Health Advisories are not regulatory standards, but provide technical guidance to help state and local officials and managers of water systems protect public health. They identify concentrations of contaminants above which adverse health effects are possible and provide testing methods and treatment techniques. Health Advisories are not legally enforceable federal standards and are subject to change as new information becomes available.

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