Microcystins are among the toxins that blue-green algae produce, and they can be quite harmful. Also known as cyanobacteria, these algae show up in surface water when the conditions are right for algal blooms to develop, according to the U.S. Environmental Protection Agency.
When the blue-green algae die, they release toxins into the surrounding environment, and the toxins can remain there for months. The most dangerous toxins they release are microcystins, the majority of which are hepatotoxins, or liver toxins. If people consume water that has these toxins, they target the liver although microcystins also irritate the throat, eyes and skin, as stated by the U.S. Environmental Protection Agency.
When water pH is between 6 and 9, and water temperature is between 40 and 85 degrees Fahrenheit, conditions are favorable for blue-green algae blooms, assuming that enough nitrogen and phosphorus are present. The majority of blooms take place during the late summer and early autumn. The implication is that microcystins are generally present in supplies of surface water that are present in sunny, warm climates, notes the U.S. Environmental Protection Agency.
The federal government does not currently regulate microcystins in drinking water, but they appear on the government's Contaminant Candidate Lists 1 and 2 as cyanobacteria and related toxins. Several specific microcystins appear on Contaminant Candidate List 3. The World Health Organization has set a provisional guideline of 1 microgram per liter for microcystin-LR, states the U.S. Environmental Protection Agency.