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This information provided by the Environmental Toxicology section of the Office of Environmental Public Health.
Algae bloom in Ross Island lagoon is not harmful to health
September 8, 2003
An unusually dense, visible algae bloom is occurring in the Willamette River
near the Ross Island lagoon but it does not constitute a health hazard, according
to public health officials in the Oregon Department of Human Services (DHS).
"The algae bloom is highly visible because of its bright green and blue-green
colors," said Dave Stone, Ph.D., toxicologist in DHS. "Understandably,
this has created some questions and caused some concern."
The algae bloom is called Microcystis aeruginosa and is the result of warm
water and abundant nutrients. In addition to the algae that is present in the
lagoon, river currents are also transporting algae downriver, according to Stone.
"Under certain conditions, Microcystis aeruginosa is capable of producing
a liver toxin called microcystin, which is harmful to humans and animals using
the water," Stone said. "Ingestion of the water is the most significant
hazard, but direct skin contact with algae may also result in adverse skin reactions."
However, Stone said the Oregon Department of Environmental Quality has been
testing water in this area and results indicate that microcystin toxin is present
at concentrations below the public health advisory threshold of 1.0 part per
billion (ppb).
"Based on current testing results, no public health advisory will be issued,"
Stone said. "However, it is advisable for people and their pets to avoid
contact with the water in areas with visible algae and not use the water for
household purposes such as drinking, food preparation or other ingestion purposes."
Stone said that DHS and DEQ will continue to monitor the water until the algae
bloom has died off. "Changes in weather or other conditions in a water
body influence the growth of blue-green algae. Generally, cooler weather, increased
rainfall and reduced sunshine lead to reductions in algae growth and toxin levels,"
he said.
Low flows in the Willamette River and unusually warm temperatures may have
contributed to the current algal blooms, Stone said.
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