The public-health advisory against water contact at Lost Creek Lake ended Wednesday after tests showed a blue-green algae bloom has dissipated in time for the busy Fourth of July weekend.
Water sampled last week showed that the cyanobacteria levels that were once 32 times above state public-health standards had all but disappeared from Jackson County's largest and most popular reservoir, according to the U.S. Army Corps of Engineers.
And Corps officials Wednesday received toxicology tests that showed no unsafe levels of toxins associated with the cyanobacteria in the sampled water, said Jim Buck, the Corps' Rogue Basin project manager.
The results were reviewed Wednesday afternoon by Oregon Health Authority officials, triggering the lifting of the volunteer advisory against water contact there.
"I am removing the advisory this afternoon," Buck said Wednesday. "The lake looks substantially better."
Twice-annual blooms of cyanobacteria, typically a strain called Anabaena flos-aquae, and subsequent advisories have been commonplace at Lost Creek Lake since the Oregon Health Authority began issuing advisories in the early 2000s.
The warnings are advisory only and not mandatory bans from water contact, but they keep many would-be visitors away.
The current advisory was issued June 3 and was the first of the summer algae-bloom season in Oregon, according to the OHA.
When lifted Wednesday, the 24-day-old advisory was two days short of a June 2009 bloom that is currently the shortest advisory ever issued for Lost Creek Lake.
Corps officials were hoping to get the advisory lifted in time for the Fourth of July holiday, which is one of the busiest boating days on Southern Oregon's most popular reservoir.
Anabaena flos-aquae can produce potentially dangerous toxins, particularly when the bloom dies off. But not all blooms become toxic.
During advisories, people and pets are warned to avoid water contact. Anglers are encouraged to practice catch-and-release fishing during advisories.
Toxins cannot be filtered by standard camp filters or by boiling the water. In-home filtering systems cannot cleanse the water, though public treatment plants can reduce algae toxins through filtration and disinfection.
Exposure to toxins can produce numbness, tingling and dizziness that can lead to difficulty breathing or heart problems that require immediate medical attention. Symptoms of skin irritation, weakness, diarrhea, nausea, cramps and fainting should also receive medical attention if they persist or worsen.
Children and pets are at increased risk for exposure because of their size and level of activity.
No confirmed human illnesses have been tied directly to an algae outbreak in Oregon. However, at least four dogs have died in recent years from toxins in water near the Umpqua River near Elkton.
Reach Mail Tribune reporter Mark Freeman at 541-776-4470, or email at email@example.com.