Pool Chemical Injuries in Public and Residential Settings

United States, 2008-2017, and New York, 2018

Kayla L. Vanden Esschert, MPH; Tadesse Haileyesus, MS; Amanda L. Tarrier, MPH; Michelle A. Donovan; Gary T. Garofalo; Joseph P. Laco, MS; Vincent R. Hill, PhD; Michele C. Hlavsa, MPH


Morbidity and Mortality Weekly Report. 2019;68(19):433-438. 

In This Article

Abstract and Introduction


Pool chemicals are added to water in treated recreational water venues (e.g., pools, hot tubs/spas, and water playgrounds) primarily to protect public health. Pool chemicals inactivate pathogens (e.g., chlorine or bromine), optimize pH (e.g., muriatic acid), and increase water clarity, which helps prevent drowning by enabling detection of distressed swimmers underwater. However, pool chemicals can cause injuries if mishandled. To estimate the annual number of U.S. emergency department (ED) visits for pool chemical injuries, CDC analyzed 2008–2017 data from the National Electronic Injury Surveillance System (NEISS), operated by the U.S. Consumer Product Safety Commission (CPSC). During 2015–2017, pool chemical injuries led to an estimated 13,508 (95% confidence interval [CI] = 9,087–17,929) U.S. ED visits; 36.4% (estimated 4,917 [95% CI = 3,022–6,811]) of patients were aged <18 years. At least 56.3% (estimated 7,601 [95% CI = 4,587–10,615]) of injuries occurred at a residence. Two thirds of the injuries occurred during the period from Memorial Day weekend through Labor Day. This report also describes a toxic chlorine gas incident that occurred at a public pool in New York in 2018. Pool chemical injuries are preventable. CDC's Model Aquatic Health Code (MAHC) is an important resource that operators of public treated recreational water venues (e.g., at hotels, apartment complexes, and waterparks) can use to prevent pool chemical injuries.

NEISS captures data on ED visits for injuries, including those associated with consumer products. NEISS records include data on consumer products (swimming pool chemical product code = 938); patient age, sex, and race/ethnicity; the most severe diagnosis; the most seriously injured body part; patient disposition; incident location; and two 71-character narrative fields to describe the incident leading to injury. These data are collected from a nationally representative probability sample of approximately 100 hospitals across the United States, and thus, can be used to calculate national estimates. Each case was weighted based on the inverse probability of hospital selection, and the weights were summed to produce national estimates; 95% CIs were calculated according to CPSC's direct variance method, accounting for the complex sampling design.[1] Rates per 100,000 population were calculated using weighted NEISS point estimates and U.S. Census Bureau population estimates.[2] Descriptive analyses of 2015–2017 data were conducted to characterize the most recent pool chemical injuries and increase national estimate stability. Data analyses were conducted using SAS (version 9.4; SAS Institute).

During 2008–2017, the median estimated annual number of U.S. ED visits for pool chemical injuries was 4,535 (range = 3,151–5,215) (Figure). During 2015–2017, pool chemical injuries led to an estimated 13,508 total ED visits (95% CI = 9,087–17,929; rate = 1.4 per 100,000 population) (Table), with persons aged <18 years accounting for 36.4% of patients (estimated 4,917 [95% CI = 3,022–6,811]). An estimated 93.9% (95% CI = 8,480–16,899) of patients seeking care in an ED for pool chemical injuries were either treated in the ED and released or examined in the ED and released without treatment. An estimated 5,245 patients (95% CI = 3,135–7,355; rate 0.5 per 100,000 population) had their injury diagnosed as poisoning. NEISS report narratives indicated that approximately 90% of patients who received a diagnosis of poisoning were injured via inhalation rather than ingestion. The poisoning diagnosis contributed to "all parts of the body (>50% of the body)"* being the most affected body part. An estimated 3,745 injuries (95% CI = 2,497–4,994) were diagnosed as dermatitis or conjunctivitis, and an estimated 2,588 (95% CI = 644–4,533]) were diagnosed as chemical burn. No deaths were documented. At least 56.3% (estimated 7,601 [95% CI = 4,587–10,615]) of injuries occurred at a residence. Among the estimated 9,065 injuries for which incident location data were captured, 83.8% (7,601 [95% CI = 4,587–10,615]) occurred at a residence. Approximately two thirds (64.5%) of all ED visits occurred during the summer swim season (Saturday of Memorial Day weekend [late May] through Labor Day [first Monday in September]). Narratives for NEISS reports noted that patients were most frequently injured when inhaling chemical fumes or dust (particularly while opening containers), when pool chemicals were not secured away from children, or when pool chemicals were added to the water just before the patient entered the water.


Estimated number of emergency department (ED) visits for pool chemical injuries, by year — National Electronic Injury Surveillance System, United States, 2008–2017

New York mandates operators of public treated recreational water venues to report onsite illness or injury incidents to permitting officials within 24 hours of occurrence (https://www.health.ny.gov/regulations/nycrr/title_10/part_6/subpart_6-1.htm). In August 2018, maintenance personnel at an outdoor pool in upstate New York noticed a yellow substance seeping into the pool through the inlets (e.g., water jets). Lifeguards cleared the pool of swimmers, and the maintenance personnel examined the equipment room. There they discovered that the recirculation pump was not running, resulting in no water flow in the recirculation system.§ The operator turned the pump back on, which resulted in resumption of water flow in the recirculation system. Consequently, substantially more of the yellow substance entered the pool; a pungent odor developed; and lifeguards evacuated the pool area. Investigation of the event suggested that a power outage in the area the previous night could have shut down the recirculation pump; however, the water flow monitoring system, which deactivates the chemical feeders when there is no water flow, failed. The failure to automatically shut off the chemical feeders allowed concentrated chlorine and acid to mix, and thus, generated toxic chlorine gas in the recirculation system. Persons in the pool area reported blisters, nausea, vomiting, or irritation of the face or eyes, and a few followed up with a health care provider.

* For a poisoning injury diagnosis, NEISS requires that affected body part be coded as "all parts of the body (>50% of the body)."
This includes incidents that result in death, require resuscitation, or require referral to a hospital or other facility for medical attention or where illness is associated with bathing water quality.
§ The recirculation system transports water from a treated recreational water venue via outlets (e.g., the main drain). Via the venue plumbing, the water passes through the filter. Subsequently, chemical feeders add chlorine or bromine and further along in the plumbing, a pH-adjusting chemical (e.g., muriatic acid). This means chemical dilution occurs before mixing. Finally, the recirculation system returns treated water into the venue via inlets.