Algae bloom increase linked to climate change

Long-term health effect on humans uncertain

SALEM, Ore. — The words blasted to cellphones around Oregon’s capital city were ominous: “Civil emergency. Prepare for action.”

Within half an hour, a second official alert clarified the subject wasn’t impending violence but toxins from an algae bloom detected in Salem’s water supply.

Across the U.S., reservoirs that supply drinking water and lakes used for recreation are experiencing similar events with growing frequency. The trend represents another impact of global warming and raises questions about the effects on human health, researchers say.

“When water bodies warm up earlier and stay warmer longer … you increase the number of incidents,” said Wayne Carmichael, a retired Wright State University professor.

Technically called cyanobacteria, the organisms thrive in warm, still bodies like lakes and ponds. They also create a unique class of toxins, the impact of which on humans is only partly understood.

Long linked to animal deaths, high doses of the toxins in humans can cause liver damage and attack the nervous system.

But less is known about exposure at lower doses, especially over the long term.

Small studies have linked exposure to liver cancer, and others have pointed to potential links to neurodegenerative disease. But definitively proving those links would require larger studies, said Carmichael, who helped the World Health Organization set the first safe exposure standards for the toxins.

Because they prefer warm water, higher summer temperatures and more frequent heat waves help the organisms. More frequent droughts also cause reservoirs to be shallower in summer, causing them to warm faster.

In Utah, a 2016 algae bloom in a recreational-use lake sickened more than 100.

In Lake Erie, a major bloom in 2014 caused authorities to warn against drinking tap water in Toledo, Ohio, for more than two days.

Now blooms happen every year in Utah and Ohio. Officials in both states say they’ve largely been able to stop them from toxifying drinking water. But the blooms can still sicken people and pets that go in the water, and they often hit recreation businesses that depend on lake access.

Other blooms have been logged in recent years in New York, Florida and California.

In Oregon, officials lifted Salem’s drinking water advisory after several days, but then had to re-issue the warning.

Officials also warned that dozens of other water supplies could be vulnerable, and when workers from the city of Cottage Grove inspected another reservoir, they found a bloom, according to a report by Oregon Public Broadcasting.

Testing for the blooms isn’t required by either federal or state law, officials noted.

Rick Egan The Associated Press A potentially toxic blue-green algae bloom June 12 in Provo Bay in Provo, Utah. A 2016 bloom on a Utah lake left more than 100 people sick.