October 19, 2018

Low levels of cyanotoxin detected in Siltcoos Lake near Florence

People who draw water directly from the lake, use in-home treatment, should find alternative drinking source after harmful algae bloom found

The presence of cyanotoxins caused by harmful algae blooms is prompting the Oregon Health Authority to recommend that people who draw water directly from Siltcoos Lake use an alternative drinking source for vulnerable family members and pets.

OHA environmental health officials say low levels of cyanotoxins, produced by cyanobacteria found in harmful algae blooms, were discovered in the water body located about seven miles south of Florence off U.S. Route 101 (Oregon Coast Highway) in Lane and Douglas counties.

Public drinking water advisory levels are very different from levels used for recreational advisories. This is because the amount of water people incidentally swallow while recreating (swimming, water skiing, etc.) is much lower than when people use it as a primary source of drinking water. Therefore, separate advisories are issued for drinking water or recreational use as data warrant. Private intakes and in-home treatment systems are not tracked or regulated by OHA Drinking Water Services, so advisories for these systems are not issued.

Cyanotoxin levels at Siltcoos Lake are well below OHA recreational use values for human exposure. As a result, a recreational use health advisory was not issued. Because toxins have not been found in finished or treated drinking water, a drinking water advisory from the city also is not necessary. However, analyses of raw water from samples taken weekly by the South Coast Water District at the agency’s drinking water intake within the lake show a level of toxin above drinking water values for vulnerable populations, including children younger than 5, pregnant and nursing women, the elderly and those with compromised immune systems. The levels can be a health issue for people who are not on a public drinking water system.

South Coast Water District is monitoring Siltcoos Lake because prior sampling confirmed the presence of cyanotoxins above drinking water advisory values in the lake water. Individuals on private intakes and using in-home treatment systems will be notified when toxin levels in the raw (lake) water are confirmed to be below drinking water advisory values.

For information about cyanobacteria, cyanotoxins, exposures or illnesses (people or pets), health advisories and other related topics, contact the Oregon Health Authority at 971-673-0440, the toll-free information line at 877-290-6767, or visit the Harmful Algae Blooms website at http://healthoregon.org/hab and select "Algae Bloom Advisories."

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