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High
Levels of Unhealthy Bacteria Found in Sand at L.A. Area Beaches
Date: May 23, 2006
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UCLA
Engineering professor Jennifer Jay and researcher Christine
Lee.
Credit: Reed Hutchinson
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Sunbathers heading for a
day at the beach in Southern California may have more to worry
about than sunscreen. A new study by researchers at the UCLA
Henry Samueli School of Engineering and Applied Science shows
that bacteria known as Escerichia coli and enterococci
are prevalent in the top layer of sand at some of the area's most
popular beaches, even when the surrounding ocean water tests
"clean."
UCLA civil and environmental
engineering professor Jennifer Jay and graduate researcher
Christine Lee conducted a survey of beaches in the Santa Monica
Bay, ranging from Redondo Beach to Malibu. Their research study,
due to be published in an upcoming issue of the journal Water
Research, shows that while the water bacteria levels at area
beaches may meet state health standards, the sand itself may act
as a source of bacteria. More disturbing, however, is that the
bacteria were found in their highest concentrations in the sand
of enclosed beaches often favored by parents with toddlers
because of their lack of surf and more protected coastline.
Usually associated with feces,
both Escerichia coli and enterococci bacteria
levels are used routinely to determine the quality of water at
recreational beaches, and both are used as indicators of the
possible presence of other harmful microorganisms. But while
water quality at local beaches is monitored on a daily basis by
local city officials, the microbial quality of beach sand is
continuously overlooked.
(click
image for larger version)
Enterococcus
Faecium Bacteria on Human Skin
Photocomposite of
Enterococcus faecium on the surface of human skin (epidermis)
with hair emerging from hair follicle. Enterococcus faecium
is a gram-positive, VRE, coccus prokaryote (dividing) which
causes skin and wound infections. Bacteria at a magnification
of x800 and human skin at a magnification of x260.
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(click image for
larger version)
E. Coli
Bacteria
Group of Escherichia coli bacteria under an
electron microscope. Each rod of the bacteria, found in human
intestines, is approximately one micron in size, equal to
1/100th of a human hair.
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"Southern Californians
are aware of swimming advisories and beach closings due to
contamination of the water. But what is startling about our
findings is that even when the water shows low bacteria levels,
there are still high levels of bacteria that persist in the
sand," Jay said.
"This is particularly
relevant when we're talking about sheltered beaches such as
'Mother's Beach' and the enclosed part of Cabrillo Beach, for
example, which appear to be more conducive to the persistence of
these bacteria. The levels of enterococci were
approximately 1,000 times higher than the levels observed at the
beaches open to the ocean," Jay said.
Other high offenders included
the enclosed portion of Cabrillo Beach in San Pedro, and Topanga
Beach, just north of Topanga Canyon Road in Malibu. High levels
of bacteria also were found at Santa Monica Beach near the pier.
Both Malibu's Surfrider Beach and Redondo Beach showed lower
levels of bacteria relative to the other test sites.
"Due to their enclosed
nature, 'pocket' or enclosed beaches show the highest levels of
bacteria present in the sand. These more enclosed locations are,
for good reason, popular with families. As a parent of two young
infants, I know firsthand children tend to put things in their
mouths, including sand," Jay said. "That concerns me."
Because health standards for
beach sediments have not been developed, there is no strict
standard to evaluate exactly how much of a health risk these
bacteria actually pose.
"The survival of these
'indictor bacteria' organisms in sand points to the persistence
of other disease-causing organisms in the sand, which could be
very significant," Jay said. "But we don't yet have
enough data to know how significant. More research needs to be
done in this area."
"What this study
ultimately shows is the importance of monitoring bacteria in the
sand as well as the water, particularly at enclosed recreational
beaches," Jay said.
The beaches tested by UCLA
Engineering's study include Malibu's Surfrider Beach, Topanga,
Will Rogers Beach, Santa Monica (north and south), Dockweiler,
Venice Beach, Manhattan Beach, Redondo Beach, Cabrillo (open and
enclosed) and Mother's Beach (enclosed).
Jay and her researchers are now
working on a second study that will focus on the persistence of
viruses in beach sediments.
Source
/ credit: UCLA
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