Beach pollution is worst during new and full moon (Forwarded)

American Chemical Society
Washington, D.C.

Contact:
Michael Bernstein, 202-872-6042

FOR IMMEDIATE RELEASE: August 01, 2005

Beach pollution is worst during new and full moon

A new study of 60 beaches in Southern California suggests that water
pollution varies with the lunar cycle, reaching the highest levels when
tides are ebbing during the new and full moon. The findings could help
beachgoers and managers better assess the potential risk of swimming.

The report appears in the Aug. 1 issue of the American Chemical
Society's journal Environmental Science & Technology. ACS is the world's
largest scientific society.

Coastal water quality is controlled by a number of complex physical and
biological factors, including tidal cycles and seasonal rainfall. This
complexity makes beach water monitoring difficult, with levels of
bacteria in a certain area changing in just a few minutes.

For the new study, the researchers examined monitoring data compiled for
beaches throughout Southern California, keeping track of tidal patterns
and analyzing them for concentrations of enterococci -- bacteria that
allow scientists to estimate the risk of illness from swimming in marine
waters. "This is the largest array of beaches examined at the same time
for a similar pattern," says Alexandria Boehm, Ph.D., an environmental
engineer at Stanford University and lead author of the study.

She and her colleagues at the Southern California Coastal Water Research
Project found that in the full and new phases of the moon, levels of
enterococci were higher at the vast majority of the beaches studied.
Boehm found that during so-called "spring tides," when water levels vary
the most between high and low tides, a beach is twice as likely to be
out of compliance with water quality standards. Spring tides are
exceptionally high or low tides that take place during the full and new
moons, but have nothing to do with the season of the year.

The results are of immediate practical use to swimmers and beach
managers alike, according to Boehm. "The general public can use the
phase of the moon and the tide stage to assess the relative risk of
illness," she says. "It is riskier to swim during spring-ebb tides
[receding tide] compared to all other tidal conditions."

Beach managers can now use tides as they currently use rainfall to
assess warnings, Boehm suggests. When it rains, managers recommend that
swimmers not enter the water for three days. "They could also suggest
that during spring tides -- and especially spring-ebb tides -- water
quality is more likely to be impaired, and those who are risk-averse
should avoid swimming," Boehm says.

The results might also help managers identify potential sources of
pollution at beaches. "Most sources of enterococci at beaches are
unknown," Boehm says. "Because we found tidal signals in enterococci
densities at beaches with no obvious point source, like storm drains and
creeks, this suggests that there is a widespread tidally forced source
of enterococci at beaches."

Boehm suggests several candidates for this "mystery" source, including
beach sands, decaying plant material and polluted groundwater. "Beach
sands and wrack [piles of seaweed and animal remains that wash ashore]
have been shown at freshwater beaches to harbor fecal indicator bacteria
and even pathogenic bacteria," Boehm says. "Beach managers who want to
improve water quality at their beaches should investigate the potential
of these sources to be contributors of enterococci to marine waters."

Boehm cautions that enterococci from beach sands and wrack may not
correlate with health risk the same way as enterococci from runoff or
sewage. "We just don't know for sure, since no one has done an
epidemiological study to connect human illness to enterococci from
non-point sources other than runoff," Boehm says. "We need to do
additional work to understand the source of enterococci at all these
beaches."

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The online version of the research paper cited above was initially
published June 15, 2005, on the journal's Website
[http://pubs.acs.org/cgi-bin/abstract...s048175m.html].
Journalists can arrange access to this site by sending an e-mail to
or calling the contact person for this release.