Blue-green algae threatens drinking and recreational water in United States

15/09/2015

     Blooms of toxic cyanobacteria, or blue-green algae are reported tobe a poorly monitored and underappreciated risk to recreational and drinking water quality in the United States, and may increasingly pose a global health threat.      Several factors are contributing to the concern. Temperatures and carbon dioxide levels have risen, many rivers have been dammed worldwide, and wastewater nutrients or agricultural fertilizers in various situations can cause problems in rivers, lakes and reservoirs.      No testing for cyanobacteria is mandated by state or federal drinking water regulators, according to scientists from Oregon State University, nor is reporting required of disease outbreaks associated with algal blooms. But changes in climate and land use, and even increasing toxicity of the bacteria themselves, may force greater attention to this issue in the future, the researchers said.          An analysis outlining the broad scope of the problem has been published in Current Environmental Health Reports, by scientists from OSU and the University of North Carolina. The work was supported by the U.S. Geological Survey and the National Science Foundation.      The researchers also noted that problems with these toxins reach their peak during the heat of summer - as they are doing right now.      In 2015, drought and low snow pack throughout the West has led to large and toxic algal blooms earlier than in previous years. Toxic blooms have occurred for the second consecutive year in the Willamette River near Portland, Ore., and Upper Klamath Lake and most of the Klamath River have health warnings posted.      In a related marine concern, all along the West Coast many shellfish harvests are closed due to an ongoing event of domoic acid shellfish poisoning, producing what is thought to be the largest algal bloom in recorded history.      Cyanobacteria are ubiquitous around the world, and a 2007 national survey by the EPA found microcystin, a recognized liver toxin and potential liver carcinogen, in one out of every three lakes that were tested. Some of the toxic strains of cyanobacteria can also produce neurotoxins, while most can cause gastrointestinal illness and acute skin rashes.      Exposure to cyanobacteria is often fatal to pets or wildlife that drink contaminated water, and there have been rare cases of human fatalities. Last year the drinking water supply was temporarily shut down in Toledo, Ohio, a city of 500,000 people, due to cyanobacterial contamination of water taken from Lake Erie.   Phạm Đình