California Beach Safety -
Avoid Beach Waters
after the New Moon
Avoid Swimming in
the Pacific Ocean after it rains.
Beach germs, tides
New study points to an odd lunar pattern in ocean contamination.
People worried about exposure to bacteria might want to avoid swimming in
the ocean during new or full moons, according to a new study.
The study, of 60 beaches from Point Zuma to Corona del Mar, showed that
counts of one type of bacteria associated with human sewage rise at certain
times during the lunar cycle. And so far, no one knows why.
The effect was noted in 2002 at Huntington Beach by Alexandria Boehm, a
Stanford University environmental engineer.
Boehm wondered if it was a peculiarity of Huntington Beach or something more
widespread. So she analyzed ocean-water sampling data up and down the coast,
and found that almost all showed the same pattern.
The tides that occur during new or full moons are known as spring tides,
when high and low tides are at their extremes. (The term has nothing to do
with the season.)
"My friends ask me – 'cause I study dirty beaches – 'When should I go to the
beach?'" Boehm said Friday. "I say, if you're worried about it, I wouldn't
go to the beach during spring tides."
The effect was strongest, she said, when the tide was ebbing during a spring
Monica Mazur, a senior environmental-health specialist at the Orange County
Health Care Agency, said others have been noticing that effect since at
least 1999. But she believes it is often too small an effect to be useful
for regulation of beaches, such as by issuing warnings about bacteria.
The bacteria, enterococcus, is one of three measured by regulators to
determine whether human sewage is present in a water sample. But it can also
be found in decaying plants and the feces of animals, including birds.
Another possible source, said Boehm: polluted groundwater just beneath the
surface near the coast.
For now, experts say, the finding is an interesting result that will require
further research. Boehm's study, which she worked on with the Southern
California Coastal Water Research Project in Westminster, appears in the
Aug. 1 issue of Environmental Science & Technology, a journal published by
the American Chemical Society.
are free swimming, colorless, and range in size from a few inches to three
feet in diameter. They sometimes appear during the summer months. Their
tentacles cause an uncomfortable reaction when they come in contact with
human skin. Although jellyfish do not cause serious risk, if stung, report
to the nearest staffed lifeguard station for first aid. If an allergic
reaction occurs, dial 911 immediately.