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Microcystin Toxin Information

During 2017, the Illinois Environmental Protection Agency (IEPA) expanded their Ambient Lake Monitoring Program to include a subset of Public Water Supply intakes to be monitored for Harmful Algal Blooms.  IEPA biologists collected cyanobacterial toxin samples between the months of June through October 2017 at two of the three Highland Park intakes.  Samples collected on June 13, 2017 showed there was no detection of the microcystin toxin in either intake.  Samples for the third intake were collected on June 21, 2022, and showed no detection of the microcystin toxin. 

On May 6, 2015, the U.S. Environmental Protection Agency (EPA) issued a health advisory for the cyanobacterial toxins, microcystins and cylindrospermopsin in drinking water. The advisories describe concentrations of the two algal toxins in drinking water at or below which adverse human health effects are not anticipated to occur over a ten-day exposure period. The health advisory values for algal toxins recommend 0.3 micrograms per liter for microcystin and 0.7 micrograms per liter for cylindrospermopsin as levels not to be exceeded in drinking water for children younger than school age. For all other ages, the health advisory values for drinking water are 1.6 micrograms per liter for microcystin and 3.0 micrograms per liter for cylindrospermopsin. Potential health effects from longer exposure to higher levels of algal toxins in drinking water include gastroenteritis and liver and kidney damage.

Health advisories are not regulations 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. 

Microcystins and cylindrospermopsin are toxins produced by cyanobacteria. Cyanobacteria are also known as blue-green algae and are frequently found in surface water when conditions are favorable for growth and formation of algal blooms. Cyanobacteria release toxins upon cell death or lysis. 

These blue-green algae flourish in warm fertile waters. These conditions are common in Lake Erie, especially at the mouth of the Maumee River which brings fertilizer laden water from the near-by agricultural region. This high nutrient input and shallow depths of the system makes it particularly susceptible to algal blooms. This is the reason on Saturday, August 2, 2014, residents of Toledo, Ohio and surrounding areas were issued a do not drink water advisory after the water tested positive for microcystin toxins and why the health advisory was issued the following year. 

The City of Highland Park along with neighboring communities along Lake Michigan are fortunate to not have significant sources of fertilizer (nitrogen and phosphorous) required to produce these algal blooms. There is no drainage from agricultural areas and no direct municipal sewage plants discharge into Lake Michigan. 

That Sunday, August 3, 2014, Chicago Department of Water Management collected samples from Lake Michigan and lab results showed there was no detection of the microcystin toxin that was found in the Toledo water. Chicago routinely tests for the presence of toxic algae two to three times per week with negative results. 

Along with several neighboring communities Highland Park also conducted screening for microcystin toxins. A sample collected on August 11, 2014, from our intake from Lake Michigan showed there was no detection of the microcystin toxin.

For more information on the two cyanobacterial toxin health advisories, including the health effects support documents, visit EPA’s health advisory website.

For more information on the support document for managing cyanotoxins in drinking water, visit EPA’s CyanoHABs website.

Listed below are links to EPA and other research documents on microcystins: 

USEPA Drinking Water Treatability Database:  Microcystins

USEPA Article:  Harmful Algal Blooms & Drinking Water

World Health Organization Guidelines for Drinking Water Quality, Cyanobacterial Toxins:  Microcystin-LR in Drinking Water

As always, residents with any water quality questions are encouraged to call our Water Treatment Plant at 847.433.4355.