Pool Chemical Injuries: Thousands of Emergency Visits a Year, Mostly at Home

This report was published in 2019 and covers injuries up to 2017 and one incident in 2018. The Model Aquatic Health Code it mentions has been revised since; see CDC's current edition.

The chemicals added to pools, hot tubs and spas, and water playgrounds are there mainly to protect health. Chlorine or bromine kills germs, chemicals such as muriatic acid keep the pH right, and clear water lets lifeguards see a swimmer in trouble below the surface. Handled carelessly, the same chemicals injure people.

How many injuries

CDC looked at 2008–2017 data from the National Electronic Injury Surveillance System (NEISS), run by the U.S. Consumer Product Safety Commission. NEISS draws on a nationally representative sample of approximately 100 hospital emergency departments, and each record carries the product involved (swimming pool chemicals have their own code, 938), the patient's age, sex and race or ethnicity, the most severe diagnosis, the most seriously injured body part, what happened to the patient, where the injury happened, and two short free-text fields describing the incident. Weighting the sample gives national estimates.

In 2008–2017 the median estimated number of emergency department visits for pool chemical injuries was 4,535 a year, ranging from 3,151 to 5,215. For 2015–2017, the most recent years:

About 90% of the poisoning cases, according to the narratives, came from breathing chemicals in rather than swallowing them. Where the location was recorded — an estimated 9,065 injuries — 83.8% happened at a residence. About two thirds (64.5%) of visits fell in the summer swim season, from the Saturday of Memorial Day weekend to Labor Day.

The narratives point to three common situations:

• breathing fumes or dust, especially while opening a container;
• chemicals left where children could reach them;
• chemicals added to the water just before the person got in.

A chlorine gas release in New York

New York requires public pool and spa operators to report illness or injury on site to permitting officials within 24 hours. In August 2018, maintenance staff at an outdoor pool in upstate New York saw a yellow substance seeping into the pool through the inlets, the jets that return treated water.

Some background on how the plumbing works: a recirculation system draws water out through outlets such as the main drain, passes it through a filter, then adds chlorine or bromine from one chemical feeder and, further along, a pH-adjusting chemical such as muriatic acid, so each is diluted before they meet. The treated water then returns to the pool.

Lifeguards cleared the swimmers, and staff found the recirculation pump was off, so no water was flowing. When the operator restarted it, much more of the yellow substance entered the pool, a sharp smell developed, and lifeguards evacuated the pool area. A power cut the night before had probably stopped the pump. The flow-monitoring system, which should have shut off the chemical feeders when the water stopped, had failed, so concentrated chlorine and acid mixed in the pipes and made toxic chlorine gas. People at the pool reported blisters, nausea, vomiting and irritation of the face or eyes, and a few saw a health care provider.

The pool stayed closed for the rest of the 2018 season, and the flow indicator was replaced. With the New York State Department of Health, the venue planned new procedures for 2019: checking the recirculation system, testing water chemistry and recording the results every 2 hours while the pool is open.

Preventing injuries

Getting the health benefits of swimming means keeping both chemical injuries and germs to a minimum. The number of injuries, the share among children and how many happen at home all call for more awareness among public operators and home pool owners alike.

For public pools, hot tubs and water playgrounds, CDC's Model Aquatic Health Code (MAHC), which state and local jurisdictions can adopt voluntarily in whole or in part, recommends:

• training operators in pool chemical safety, including how to read product labels, which say which chemicals must not be mixed (chlorine and acid, for example) and what protective equipment to wear;
• chemical feeders that switch off automatically when water flow in the recirculation system stops or runs low — the safeguard that failed in New York.

State and local officials have less authority over home pools, but environmental health practitioners can offer owners pool chemical safety training; CDC's recommendations are generally the same for home and public pools.

Swimmers and parents can help too. Chloramines — chlorine combined with nitrogen compounds from urine, feces, sweat and dirt — irritate eyes and lungs and use up chlorine that would otherwise kill germs. To keep them down:

• take a rinse shower before getting in;
• do not urinate or defecate in the water;
• take children on bathroom breaks or check diapers every hour.

Healthy and Safe Swimming Week, the week before Memorial Day, is a good time to spread these messages.

Limits of the data

NEISS covers only injuries that reach an emergency department. Its records have little detail and some missing fields, such as location. It keeps only the most severe diagnosis, so some pool chemical injuries may be missed. The chemical may be misidentified — eye irritation blamed on chlorine may really come from chloramine. And water chemistry changes quickly, which makes causes hard to pin down.

Sources

Based on "Pool Chemical Injuries in Public and Residential Settings — United States, 2008–2017, and New York, 2018," by Kayla L. Vanden Esschert and colleagues (CDC; Oak Ridge Institute for Science and Education; New York State Department of Health), Morbidity and Mortality Weekly Report 68(19), published by the Centers for Disease Control and Prevention; rewritten in hubnx's own words.

• The report's chart of annual visits is not reproduced.
• The report's call for change requests to the 2021 edition of the MAHC (deadline January 6, 2020) has passed and is left out.