The Full Story
Summer is here, which means backyard barbecues, fireworks, and trips to the swimming pool! Whether it's in your backyard or at a local community center, keeping a swimming pool clean and properly maintained is important to limit people's exposure to recreational water illnesses (RWIs). According to the Centers for Disease Control and Prevention (CDC), RWIs are caused by bacteria and other germs that spread by swallowing, inhaling, or making skin contact with contaminated water. The most common RWI is diarrhea, which can be caused by organisms such as Cryptosporidium, E. coli, and norovirus. In the last two decades, there has been an increase in the number of RWI outbreaks associated with swimming pools. According to the CDC, reported RWI Cryptosporidium cases increased by over 200% from 2004 to 2008.
Chlorine and chlorine derivatives are the most commonly used disinfectants to treat swimming pools. Pool chlorinating agents are either inorganic (ex. calcium hypochlorite) or organic (ex. chlorinated isocyanurates like trichloroisocyanuric acid or potassium dichloroisocyanurate).
Pool owners and maintenance teams must keep the chlorine concentration within a range that is high enough to effectively kill germs yet low enough to avoid injury to swimmers. The CDC recommends keeping a free chlorine concentration of at least 1 ppm in pools and 3 ppm in hot tubs. Maintaining an optimal pH also contributes to protecting swimmers from the spread of germs in pool water. If the pH or chlorine concentration is out of the recommended range, it can sometimes cause mild irritation to the skin and eyes of swimmers.
Now you might be thinking, "What about the strong chemical odor that I smell when I'm at the pool? Is that safe?" The strong odor is not actually from the chlorine alone. When chlorine is added to a pool, it mixes with other things in the water, particularly from swimmers themselves (think sweat, dirt, and yes, even urine and feces). The mixing of chlorine and these compounds creates chloramines. Chloramines are irritants that are formed from the reaction of mixing the free chlorine (hence "chlor") and amine groups (hence "amine") from organic matter. These are what cause extreme irritation to the skin and eyes after prolonged exposure. Additionally, the fumes induce irritation of the respiratory tract causing coughing and breathing trouble. Because chloramine gas is heavier than air, it settles on top of the water, making it problematic for both swimmers and those nearby. It can be especially troublesome for people who spend many hours in a pool (e.g., competitive swimmers) or those with pre-existing health problems (e.g., asthma or COPD). Indoor pools increase the risk of experiencing irritation from the accumulation of these fumes because of limited ventilation.
As pool-goers and owners, there are some preventative measures that can be taken to help keep the experience safe.
For swimmers, consider wearing swim goggles and practice sanitary swimming pool etiquette:
Do not go into the water if you have diarrhea.
- Do not urinate or defecate in the pool.
- Rinse off in a shower before you enter the pool.
- Do not drink the water.
For pool owners/operators:
- Use chlorinating agents according to the product instructions.
- Ensure adequate ventilation for indoor pools and hot tubs.
- Use test kits frequently to keep chlorine and pH levels within recommended ranges.
- Store all pool chemicals in temperature-controlled environments and away from public access, direct sunlight, and water.
- Always wear personal protective equipment (e.g., gloves, goggles) when handling pool chemicals.
For pool staff and maintenance teams, proper training on the handling and storage of chemicals is key. All aquatic facilities should have specific rules and procedures in place to ensure everyone's safety. Most brief exposures result only in mild irritation, but if left unaddressed or from larger scale exposures, chemical burns, burns to the surface of the eye, and serious respiratory illness have occurred. If someone has been exposed to a pool chemical, it's important to immediately move them from the area to fresh air. Most often, skin and eye exposures will respond to immediate irrigation of the affected area.
As a pool-goer, it's important to be aware of the potential health effects from exposure to excess amounts of chloramine. If you or someone you know starts feeling irritation from the fumes, immediately move away from the water and into fresh air. If there is irritation to the skin, rinsing off in a shower should help reduce discomfort. If the eyes are red and burning from direct exposure, irrigation with water in a shower or at an eye station for 15 minutes is recommended. If anyone starts experiencing difficulty breathing, shortness of breath, wheezing, chest tightness, or any persistent pain or discomfort of the skin or eyes, then seek medical attention immediately. These symptoms can be addressed at an urgent care center or an emergency room with a breathing treatment and further eye irrigation.
There is nothing more refreshing than cooling off on a hot summer day with a dip in the pool. By knowing the potential risks and best preventative practices, we can all do our part to keep this fun activity safe and enjoyable for everyone. And remember…Don't pee in the pool!
If you are worried about exposure to a pool chlorinating agent, check the webPOISONCONTROL® online tool for guidance or call Poison Control at 1-800-222-1222. Whether you log on or call, expert assistance is available 24 hours a day.
Kristina Yee, PharmD, BS
Certified Specialist in Poison Information