Public Swimming Pools: How Dirty Are They?

Public swimming pools have earned a bad rep as unsanitary perti dishes of infectious diseases – but is this reputation unfounded or well deserved?

One-in-eight public swimming pools was immediately shut down after inspection due to dirty water or other serious code violations, such as missing safety equipment, according to a 2008 government report. The Centers for Disease Control and Prevention (CDC) analyzed samples from more than 120,000 public swimming pools in 13 states and conducted water quality tests -- the largest study ever done by the CDC on pool water.

Most troubling is the fact that the venues with the most disinfection violations were kiddie or wading pools and water play areas.

Each year, about 15 to 20 outbreaks of diseases, including stomach bugs and diarrhea, are blamed on dirty public pools, according to the CDC. A quarter of theses outbreaks are caused by bacteria, parasites and viruses that could have easily been prevented had the pools been properly chlorinated and monitored.

And don't trust your nose.

"Many people think that when a pool smells of chlorine, that means that it's clean," said Mary Ostrowski, director of the Chlorine Issues at the American Chemistry Council, a trade organization. "But that smell is actually chloramines, a substance that results from a mix of chlorine and bacteria, urine and sweat."

So that strong chemical smell actually signifies that the pool's water is exceptionally dirty and should have its chlorine and pH levels tested and adjusted, Ostrowski told Life's Little Mysteries. A perfectly healthy pool would be odorless, and if chloramines levels have reached a point where they can be smelled, the pool water may act as an irritant to a swimmer's eyes, skin and nose.

Harmful germs such as Giardia, E. coli and cryptosporidium (crypto) parasites can spread in public pools that have insufficient chlorine and too-low pH levels. Symptoms of all three illnesses include diarrhea, weight loss, nausea, vomiting, dehydration and stomach cramps.

Pool operators need to monitor the chlorine levels frequently, and there is even a current promotion by the Water Quality and Health Council providing free water-testing strips, so that pool-goers can test the chlorine levels in public pools and report any problems to pool managers.

However, more does not always equal better, as chlorine should be added in moderation or else it will harm the swimmers as well as the germs. Improperly chlorinated water puts swimmers at risk for dermatitis, skin infections and rashes caused by the chemical, according to the CDC.

Other tips provided by the American Chemistry Council to prevent the spread of recreational water illnesses (RWIs) include:

  1. Avoid swallowing pool water
  2. Shower before going into a pool
  3. Take small children on frequent bathroom breaks
  4. Wash hands after going to the bathroom
  5. Touch the tiles of the pool – they should feel smooth, not slimy
  6. Listen for the sound of a working pool pump
  7. Make sure that the pool's bottom is clearly visible
Remy Melina was a staff writer for Live Science from 2010 to 2012. She holds a bachelor’s degree in Communication from Hofstra University where she graduated with honors.