For most people, swimming pools evoke images of leisurely summer days, family fun and physical fitness. Most of the time, that vision is a reality.
But pool water also can make people sick, a phenomenon that can put a damper on the public’s recreational activities.
Waterborne illness outbreaks associated with pools are on the rise, with outbreaks in the U.S. increasing from an average of 15 per year between 1993 and 2002, to 34 between 2003 and 2012, according to the U.S. Centers for Disease Control and Prevention.
Those are significant numbers considering a single outbreak can affect thousands of people.
A University of Wisconsin-Eau Claire researcher is a national leader in investigating the reasons behind this increase and exploring methods to help reverse the trend.
The most common illness associated with swimming pool use is cryptosporidiosis, whose symptoms include vomiting, diarrhea and nausea, said Dr. Laura Suppes, assistant professor of environmental public health in UW-Eau Claire’s Watershed Institute for Collaborative Environmental Studies.
The illness is caused by swallowing the pathogen Cryptosporidium in pool water, a pathogen that is resistant to chlorine.
“Some people believe swimming pools are sterile because they are treated with chlorine,” Suppes says. “Pool water is not sterile and pathogens can survive in it. Pathogens in pool water come from human or animal feces, and feces is shed more often than people probably realize.”
How often do people contract cryptosporidiosis from pools?
Research by Suppes and collaborators from the University of Arizona — recently published in the International Journal of Hygiene and Environmental Health — estimates that for every 100 swimmers in U.S. pools, between two and three become sick each year with the illness.
Children have a higher risk than adults because they swallow more water when swimming, Suppes says.
To stay healthy in pools, Suppes suggests that swimmers follow the guidelines included on the CDC's Steps of Healthy Swimming webpage.
Some key recommendations are:
- Do not swim or let your children swim if sick with diarrhea. You or they could be shedding Cryptosporidium or another pathogen that can make other swimmers sick.
- Become informed about your pool’s water quality by requesting pool inspection reports from your local health authority.
- Use pH and chlorine test strips to test pool water. These strips are inexpensive, easy to use and can be purchased at any local pool store. Chlorine should be at least 1 ppm in pools and 3 ppm in spas; and pH should be 7.2-7.8 in both pools and spas.
- Shower before swimming. Rinsing off for just one minute will do the trick.
“An additional recommendation from our study is to avoid swallowing pool water,” Suppes said. “Swimmers should also avoid splashing others in the face with pool water since research shows splashing other swimmers in the face makes them more likely to accidentally swallow water.”
While those recommendations are directed toward swimmers, pool directors, pool staff and coaches also must be vigilant about educating swimmers on the risks of swallowing pool water and the risks to others if they have less than stellar hygiene habits, Suppes said.
In addition, pool staff members need proper training in pool monitoring protocols and treatment, she said.
“Of the exposure factors we assessed, Cryptosporidium concentration in pool water had the most influence on risk of developing cryptosporidiosis, Suppes said. "This means it is very important to focus control efforts on preventing and reducing Cryptosporidium in swimming pool water.
“Improved monitoring protocols of fecal accidents for pool staff and continuous application of the coagulant polyaluminum chloride to reduce Cryptosporidium concentrations that may be present from unreported fecal contamination events are examples of prevention and control efforts."
Suppes — with the help of UW-Eau Claire environmental public health research students — continues to study the association between pool water and illness.
The research team’s latest project involves investigating the origins of pharmaceuticals and personal care products in pool water.
“The presence of fluoxetine, a prescription antidepressant, in 26 percent of pools and 0 percent of fill water samples indicates swimmers are introducing pharmaceuticals into pools,” Suppes said. “The flame retardant TCEP was present 48 percent more frequently in pool water than fill water, suggesting that swimmers introduce TCEP by skin or swimwear.”
Enforcing showering and bathroom breaks are recommended to reduce PPCP contamination from skin, swimwear and urine at swimming pools, Suppes said.
Suppes, who earned her bachelor’s degree in environmental public health from UW-Eau Claire before completing her master’s and doctoral degrees, currently serves as a consultant to the Council for the Model Aquatic Health Code on the CDC's national guidelines for public pools.
The Model Aquatic Health Code was published in 2014 so the guidelines have not been universally adopted across state and local health departments, she said.
Having national guidelines in place will go a long way in keeping pool water safe and people healthy, Suppes said.
Still, Suppes said, there is much more work to be done.
"What excites me about researching swimming pools and any environmental health topic is protecting public health," Suppes said. "There are so many unanswered questions about hazards in our environment, it is easy to stay motivated."
Photo caption: Dr. Laura Suppes is a national leader in investigating waterborne illness outbreaks associated with swimming pool use.