The scoop: tell your guests why they should shower before swimming, and they probably will.(Chemistry Corner)

Should guests be asked to shower before entering a public pool? The debate has gone on for years. But there is no doubt among some pool professionals that a soapy scrub in the bathhouse prior to taking the plunge makes good sense.

"There are two major reasons why we require swimmers to shower," says John Whitmore, recreation superintendent of leisure services for the City of Denton (Texas) Department of Parks and Recreation. "The first is that during the day, people will perspire and the byproducts from this perspiration build up on the skin. If they enter a pool without showering, those byproducts will automatically wash off and combine with chlorine to create chloramines, the compounds that cause most of the eye irritations in pools.

"The second reason is that before going into the water, most people don't take a real cleansing shower, that is, washing every crack and crevasse--literally.... All these little 5-year-olds don't quite 'complete the paperwork' at the end of a potty session. That 'material' is washed off in the pool when they get in."

Lili McGovern, manager of NRPA's National Aquatic Branch, seconds the recommendation. "I agree that the greater concern among the pool staff today is to not introduce any water-borne pathogens," she says, "and a good wash with soap helps to clean the area down there."

According to McGovern, the Centers for Disease Control and Prevention in Atlanta have done several studies on the transmission of illness through pool water. These studies show that diarrhea, the most frequently reported symptom, is caused by germs such as cryptosporidium, E. coli and parasites such as giardia, released into the water or on a pool deck through contact with fecal matter. Chlorine works well at quickly eliminating some of these "bugs," but not all.

"The CDC says that if you take the average residue left in the water and multiply that by the number of people in the pool, you end up with a couple of fairly good-sized stools," Whitmore says. "Most people don't realize that, which is a good thing to some extent, because it might scare off a lot of people."

The city pools in Cincinnati strongly encourage showering for another reason, says Jincey Yemaya, aquatics director of the Cincinnati ...