More swimmers means more pathogens in the water

Jul 02, 2007

The levels of potentially harmful waterborne microorganisms in rivers, lakes and other recreational waterways may be highest when the water is most crowded with swimmers. Researchers at the Johns Hopkins Bloomberg School of Public Health completed two studies at the Hammerman beach area along Maryland’s Gunpowder River that linked the number of swimmers using the water with the levels of microsporidian spores and the parasites Cryptosporidium parvum and Giardia lamblia. The studies were made available online in advance of publication in the scientific journals Applied and Environmental Microbiology and Water Research.

Exposure to microorganisms like C. parvum and G. lamblia can cause nausea, vomiting and diarrhea. They can be particularly harmful to people with compromised immunity.

“Our research suggests it would be best to test the water when the beach is active to determine if it is safe for recreational use,” said Thaddeus K. Graczyk, PhD, co-author of both studies and associate professor with the Bloomberg School’s Department of Environmental Health Sciences and Center for Water and Health. According to Graczyk, health officials typically conduct water sampling when there is little human activity.

For both studies, researchers sampled the water at the Hammerman area for 11 weeks during the summer of 2006. Samples were taken on Wednesdays, when beach activity was typically low, and on Saturdays, when activity was usually high. The researchers also counted the number of swimmers in the water at the time the water was sampled.

The concentration of microsporidian spores, C. parvum and G. lamblia were highest during the weekends, when the beach was busiest. Water turbidity was also highest on the weekends. The findings indicate that the swimmers stir up pathogens resting in the sediment.

The Environmental Protection Agency does not require testing for microsporidian spores, C. parvum or G. lamblia in recreational waters, because of the cost and difficulty in measuring these pathogens. Regulations do require that water be tested for E. coli and enterococci as bacterial indicators of fecal contamination.

“Monitoring for E. coli and enterococci may not be reliable in monitoring for waterborne protozoan pathogens,” said Graczyk.

Source: Johns Hopkins University Bloomberg School of Public Health

Explore further: More than one-third of kids in England are overweight/obese

add to favorites email to friend print save as pdf

Related Stories

Sheriffs want popular police-tracking app disabled

36 minutes ago

Sheriffs are campaigning to pressure Google Inc. to turn off a feature on its Waze traffic software that warns drivers when police are nearby. They say one of the technology industry's most popular mobile ...

Warm ocean melting East Antarctica's largest glacier

50 minutes ago

The largest glacier in East Antarctica, containing ice equivalent to a six-metre (20-foot) rise in global sea levels, is melting due to warm ocean water, Australian scientists said on Monday.

British lawmakers demand freeze on fracking

51 minutes ago

A committee of British lawmakers demanded a national moratorium on fracking due to environmental concerns on Monday, ahead of a crucial vote intended to boost the shale gas industry.

China's online population nears 650 million

51 minutes ago

The number of Internet users in China has risen to nearly 650 million, authorities said over the weekend, as the world's largest online population continues to rise.

Recommended for you

Some doctors won't see patients with anti-vaccine views

4 hours ago

With California gripped by a measles outbreak, Dr. Charles Goodman posted a clear notice in his waiting room and on Facebook: His practice will no longer see children whose parents won't get them vaccinated.

Obamacare Co-ops show promise and peril

5 hours ago

The Affordable Care Act includes a program designed to promote greater competitiveness in the health insurance marketplace by creating health insurance cooperatives. There are now more than 20 such entities serving 26 states ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.