Microscopic danger can lurk in pools Contamination: E-coli bacteria infection can -- and did -- occur in a park with chlorinated water.


Pool water has that smell and taste, that artificially aquamarine look, for a reason: state-regulated standards of biocidal chlorine, bromine and other disinfectant chemicals.

But on June 24, at least nine children caught a virulent strain of E-coli bacteria in a wading pool at White Water Recreation Park in Atlanta - the first reported instance in the nation of E-coli contamination in a chlorinated public pool.

The pool was regulated with an automatic chlorination system, but a toddler infected with E-coli 0157:H7 reportedly defecated in the pool, contaminating the water. At least three children are now suffering from hemolytic uremic syndrome, a disease known to cause kidney failure. The bacteria had to have been ingested for transmittance, according to Dr. Dennis Lang of the National Institute of Allergy and Infectious Diseases.

How could this happen? Are chlorinated pools no longer safe?

Though E-coli 0157:H7 is a mutated strain, it is unlikely that the strain has mutated to a point where it could resist chlorine, says David Roberts, chief of the Division of Community Services at Maryland's State Department of Mental Health and Hygiene.

"If the water quality and disinfection level is maintained properly, this organism would not be able to survive," he says. "But it does take time for the chlorine to kill the organism."

A few organisms, such as giardia and Cryptosporidium, are fairly resistant to chlorine and require minutes to kill, but most bacteria are killed within seconds, including E-coli. The danger lies, though, in what Roberts calls a "shielding effect." When fecal material is fairly concentrated, it can create a shield around the bacteria, prolonging the time it takes for chlorine to contact the bacteria.

White Water Recreation Park spokeswoman Deedie Dowdle says the park adheres to the county's pool disinfection rules, which require 1 to 3 parts per million of free chlorine. An automatic chlorination system continuously adjusts and corrects the levels within minutes. "The chlorine level on June 11 was 1.5 to 2 parts per million," says Dowdle, but "this doesn't mean the levels won't drop. It does mean that the system will correct it."

Baltimore's public pools require 1.5 parts per million of free chlorine, and public wading pools require three parts per million, says Roberts. Maryland state law requires each pool to have certified pool operators who test and sample the water every two hours. The pool operators must also keep records of their tests.

As for private pools, it is up to the homeowner to regulate the disinfection levels using guidelines published by organizations such as the National Spa and Pool Institute.

"There's actually a very good public-health lesson to be learned here," says Lang, "and that is that parents with sick children should not bring their children to public pools."

According to Roberts, Maryland law prohibits anyone with diarrhea from using a public pool. "That, again, is very difficult to control," he says.

White Water Park is now requiring that all children sport plastic, sealed pants when entering the kiddie pools. Although these are not hermetically sealed, they are closely fitting pants that should prove helpful, Roberts says.

The strain 0157:H7 is a fecal contamination usually spread through beef products contaminated during slaughter.

"The organism is uncommon as a contaminant in swimming pools, because it is an infrequent infection in children," says Lang.

Pub Date: 7/05/98

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