Blue-green algae is a growing threat to US water supplies say scientists
Blooms of blue-green algae on lakes and other bodies of water are poorly monitored and underestimated as a risk to recreational and drinking water quality in the US and may be a threat to health globally according to recent research.Testing for the algae - cyanobacteria - is not mandated by state or federal drinking water regulators, according to Oregon State University (OSU) researchers nor is reporting of algal bloom-related disease outbreaks. But changes in climate and land use, and possible increases in the toxicity of the bacteria themselves, may create a demand for greater attention to cyanobacteria in the future, the researchers said.
"The biggest health concern with cyanobacteria in sources of drinking water is that there's very little regulatory oversight, and it remains unclear what level of monitoring is being voluntarily conducted by drinking water utilities," said Tim Otten, a OSU Department of Microbiology scientist and lead author on the study.
Cyanobacteria-associated illnesses are not required to be reported under the Centre for Disease Control and Prevention's guidelines, as most pathogens are. This makes accurate assessments of the incidence and severity of adverse health outcomes difficult to determine.
Researchers said modern water treatment does a reasonably good job of making drinking water safe, but the lack of required or widespread monitoring remains a problem.
The researchers said rising temperatures and carbon dioxide levels have caused many rivers worldwide, to be rendered un useable and wastewater nutrients or agricultural fertilizers can exacerbate problems in rivers, lakes and reservoirs. Problems with blue green algal toxins peak during the summer.
Drought and low snow pack throughout the West has led to large and toxic algal blooms developing earlier this year than in previous years. West coast shellfish harvests have been closed due to shellfish poisoning. Cyanobacteria are ubiquitous around the world, and a 2007 national survey by the EPA found microcystin, a Cyanobacteria- associated liver toxin and potential liver carcinogen, in one third of all lakes tested.
Last year the drinking water supply was temporarily shut down in Toledo, Ohio due to cyanobacterial contamination of water taken from Lake Erie. Many large, eutrophic lakes such as Erie are plagued by algal blooms that are visible from space.
"At this point we only have toxicology data for a handful of these toxins, and even for those it remains unclear what are the effects of chronic, low-dose exposures over a lifetime," Otten said. "We've really scratched only the surface with regard to understanding what the health effects may be for the bioactive metabolites produced by these organisms."
Researchers have fear that the nutrients that fuel these blooms may select for the more toxic populations of cyanobacteria creating a cycle whereby he danger becomes ever more intense.