Ohio EPA, Ohio Department of Natural Resources (ODNR) and Ohio Department of Health (ODH) are announcing that recent water quality sampling along the Grand Lake St. Mary’s beach area shows that levels of the previously detected algal toxin “microcystin” have fallen below the World Health Organization (WHO) provisional guideline for concern. Previously posted advisory signs will be removed from the beach areas until further notice. ODNR, in conjunction with the city of Celina, will begin bi-weekly sampling of Grand Lake St. Mary’s prior to Memorial Day weekend.

Water quality sampling throughout 2009 confirmed the presence of high levels of microcystin, a toxin which can cause minor to severe health issues for humans and animals. The WHO provisional guideline for low-risk recreational contact for microcystin levels is less than 20 parts per billion (ppb). In the summer of 2009, the levels in Grand Lake St. Marys were recorded as high as 82 ppb. Levels throughout the summer were consistently in the 40-60 ppb range. Science suggests that warm weather and sunlight contribute to higher levels of microcystin.

Given that the recent sampling results are below the WHO provisional guideline, Ohio EPA, ODNR and ODH believe that recreational use of the water is safe; however, the agencies recommend that lake users avoid, to the extent possible, ingesting untreated lake water. As warmer weather arrives, it is possible that microcystin levels will rise above the WHO risk provisional guideline. If this occurs, advisory signs will be re-posted. In either circumstance, there is no ban on swimming, boating, fishing or other recreational activities on the lake. Non-contact recreation, such as boating, fishing and sunbathing, are considered safe activities.

Most of the algae present in the lake is a blue-green algae called Planktothrix, which can produce the microcystin toxin, which in turn, can cause skin rashes, sore throat, runny eyes and nose or allergic reactions from inhaling water droplets; and gastro-intestinal distress (vomiting, diarrhea) from swallowing the water. It can sometimes cause death in small animals, such as dogs, that ingest water containing microcystin toxin. People should use similar precautions as they would when recreating in any non-chlorinated surface water, especially avoiding, to the extent reasonably possible, ingesting lake water.

The public drinking water supply in Celina remains safe; continued weekly testing conducted since last year indicates there is no microcystin present in the treated water. Due to the potential harm to the liver and kidneys from drinking significant quantities of microcystin, testing will continue on the city of Celina’s treated drinking water.

Additional information is available at the following Web links: The Great Lakes Sea Grant Extension Office at http://www.glerl.noaa.gov/seagrant/GLWL/Algae/HAB/HABFAQ.html; and the Centers for Disease Control at http://www.cdc.gov/hab/cyanobacteria/facts.htm.

Sampling results from May 2009 through March 2010 and other information are available at www.epa.ohio.gov/dsw/inland_lakes/index.aspx. Sampling data will continue to be updated at this link.