Pool Chemical–Associated Health Events in Public and Residential Settings — United States, 2003–2012, and Minnesota, 2013

Michele C. Hlavsa, MPH; Trisha J. Robinson, MPH; Sarah A. Collier, MPH; Michael J. Beach, PhD


Morbidity and Mortality Weekly Report. 2014;63(19):427-430. 

In This Article


Pool chemicals are added to treated recreational water venues (e.g., pools, hot tubs/spas, and interactive fountains) primarily to protect public health by inactivating pathogens and maximizing the effectiveness of disinfection by controlling pH. However, pool chemicals also can cause injuries when handled or stored improperly. To estimate the number of emergency department (ED) visits for injuries associated with pool chemicals in the United States per year during 2003–2012, CDC analyzed data from the U.S. Consumer Product Safety Commission's National Electronic Injury Surveillance System (NEISS). This report summarizes the results of that analysis. In 2012 alone, an estimated 4,876 persons (95% confidence interval [CI] = 2,821–6,930) visited an ED for injuries associated with pool chemicals. Almost half of the patients were aged <18 years. This report also describes a pool chemical–associated health event that occurred in Minnesota in 2013, which sent seven children and one adult to an ED. An investigation by the Minnesota Department of Health (MDH) determined the cause to be poor monitoring of or response to pool chemistry. Pool chemical–associated health events are preventable. CDC's Model Aquatic Health Code (MAHC)[1] is a resource that state and local agencies can use to optimize prevention of injuries and illnesses associated with public treated recreational water venues, including pool chemical–associated health events.

NEISS captures data on ED visits for injuries associated with consumer products, including product codes (e.g., pool chemical code: 938); the most severe diagnosis; the most seriously injured body part; incident location; disposition, age, sex, and race/ethnicity of the patient; and two 71-character narrative fields to describe events 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 the hospital being selected, and the weights were summed to produce national estimates; 95% CIs were calculated, accounting for the sample weights and complex sampling design. Rates per 100,000 person-years were calculated using these estimates and U.S. Census Bureau population estimates.[2]

In the United States during 2003–2012, the median estimated number of persons visiting an ED for pool chemical–associated injuries per year was 4,247 (range = 3,151–5,216) (Figure). In 2012, an estimated 4,876 persons (95% CI = 2,821–6,930; 1.6 per 100,000 person-years) visited an ED for injuries associated with pool chemicals ( Table ). Almost half (46.9%) of the patients were aged <18 years (an estimated 2,289 persons [95% CI = 965–3,613]; 3.1 per 100,000 person-years). The most frequent diagnosis was poisoning (an estimated 2,167 injuries [95% CI = 1,219–3,116]; 0.7 per 100,000 person-years). Of the 50 actual visits to NEISS-participating EDs resulting in a poisoning diagnosis, 46 (92.0%) stemmed from inhalation of vapors, fumes, or gases rather than ingestion. More than a third (36.1%) of the injuries occurred at a residence. Of the total 109 actual visits to NEISS-participating EDs, 79 (72.5%) occurred over the summer swim season (Saturday of Memorial Day weekend through Labor Day); 47 (43.1%) occurred on a Saturday or Sunday. No deaths were documented. Patients were injured when handling pool chemicals without using personal protective equipment such as goggles (especially while opening containers), when pool chemicals were added to the water just before the patient entered the water (frequently in residential and hotel settings), and when pool chemicals were not secured away from children.


Estimated number of emergency department (ED) visits for injuries associated with pool chemicals — United States, National Electronic Injury Surveillance System, 2003–2012

In December 2013, a mother notified MDH that multiple persons had developed rashes and symptoms of respiratory illness after attending a child's birthday party on the previous Saturday in December at an indoor hotel swimming pool and spa. MDH conducted a cohort study and enrolled all 12 party attendees, who were interviewed by telephone using a standardized questionnaire. Eight of the 12 reported developing a raised, red rash all over their body. Ill persons also reported headache, cough, sore throat, vomiting, and difficulty urinating. The eight ill persons reported illness onset 5.5–7.0 hours after first exposure to the swimming pool or spa. All eight ill persons sought medical attention at an ED, where their signs and symptoms were clinically diagnosed as chemical burns. Inspection by an MDH environmental health specialist 2 days after the birthday party revealed free chlorine* levels ≥15–30 ppm in both the swimming pool and spa, exceeding the state limit of 5.0 ppm. The pH was measured at 9.0 in both bodies of water, exceeding the state pH maximum of 8.0. Review of the daily log for the previous 10 days indicated the combined chlorine level had been 10–17 ppm in the pool and 0.8–8.4 ppm in the spa, exceeding the state limit of 0.5 ppm. No remediation steps were documented. As a result of this outbreak investigation, the hotel installed new automated controllers and liquid chlorine feeders to ensure chemical disinfectant levels were kept within regulatory limits.

* Chlorine in water (found as an aqueous mixture of hypochlorous acid and hypochlorite anion) that can serve as an effective disinfectant (also referred to as free available chlorine or residual chlorine).
Chlorine that has reacted with organic or inorganic compounds in the water is no longer an effective disinfectant, and might cause ocular and respiratory irritation.