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The distribution and public health consequences of releases of chemicals intended for pool use in 17 states, 2001-2009.

Introduction

In 2009, swimming was the fourth most popular recreational sport in the U.S., with over 50 million individuals swimming at least six times within the year (U.S. Census Bureau, 2012). Various chemicals are used to maintain pool water quality and protect against the transmission of pathogens. These chemicals include bromine-based disinfectants (e.g., hypobromous acid), chlorine based-disinfectants (e.g., chlorine gas), and chemicals that adjust pH (e.g., soda ash) (De Haan & Johanningsmeier, 1997). Pool chemicals, which are safe when handled properly, can cause injury when mishandled. Depending on the severity, symptoms from exposure to hydrochloric acid, bromine, hypochlorites, and chlorine can include nose, eye, and throat irritation; dermatitis; abdominal pain; nausea; vomiting; headache; and dizziness (National Institute for Occupational Safety and Health, 2010).

Because the reporting of pool chemical incidents is not universally mandated, completely characterizing their public health impact is difficult (Agabiti et al., 2001; Thomas & Murray, 2008). Three publications describe a series of incidents involving various pool chemical releases in the U.S.; however, the articles have different measures and time frames. The first article, using data from the National Electronic Injury Surveillance System (NEISS), reported an annual median of 4,120 emergency department (ED) visits for injuries associated with pool chemicals for 1998-2007 (Centers for Disease Control and Prevention [CDC], 2009). The second article, using data from NEISS and the Sentinel Event Notification System for Occupational Risk (SENSOR), reported an annual average of 4,010 work-related illnesses or injuries associated with pool chemicals for 2002-2008 (CDC, 2011a). The third article reported data from three databases: the Hazardous Substances Emergency Events Surveillance (HSEES) had 92 pool chemical incidents that occurred at aquatic facilities during 2007-2008; NEISS reported a total of 4,574 ED visits resulting from pool chemical incidents for 2008; and the Waterborne Disease and Outbreak Surveillance System (WDOSS) reported 32 pool chemical incidents that occurred in Michigan and Maryland with two or more persons linked epidemiologically by time, location of water exposure, and illness characteristics and evidence implicating recreational water (CDC, 2011b).

Our analysis used data from the Agency for Toxic Substances and Disease Registry (ATSDR) HSEES program to describe the distribution and public health consequences of "pool chemical incidents," which are defined as incidents in any location involving any chemical intended for pool use. HSEES data differ from NEISS data, which focus on ED patients, and from SENSOR data, which are occupational. HSEES data are comprehensive and include chemical incidents with and without injuries and from all sectors including transportation.

Methods

Our study included data from the HSEES system from 2001 to 2009. During various periods within this time frame, 17 states participated in HSEES (Colorado, Florida, Iowa, Louisiana, Michigan, Minnesota, Mississippi, Missouri, New Jersey, New York, North Carolina, Oregon, Rhode Island, Texas, Utah, Washington, and Wisconsin). HSEES served as an active state-based surveillance system of hazardous substance incidents collected from multiple sources, including state and local environmental protection agencies, police and fire departments, poison control centers, hospitals, local media, and various federal databases (e.g., U.S. Department of Transportation Hazardous Material Incident Reporting Systems and the U.S. Coast Guard's National Response Center). States entered their data directly into a secure web-based application. A hazardous substance release was included in the HSEES system if it was an uncontrolled or illegal release of any hazardous substance, exclusive of petroleum-only incidents. Releases were included if they had to be cleaned up according to federal, state, or local law.

Pool chemical incidents involved at least one chemical intended to be used to maintain water quality or equipment at an aquatic venue (e.g., hot tub, water park, or pool). To identify potential pool chemical incidents, we queried the HSEES database for the following terms: "swim," "pool," "Jacuzzi," "spa," and "hot tub." We also queried pool chemicals mentioned in De Haan and Johanningsmeier's (1997) pool operator training manual: "algaecide," "bromide," "chlorinated isocyanurate," "cyanuric acid," "lithium hypochlorite," "hypobromous acid," "dichlor," "trichlor," "muriatic acid," "chlorine," "calcium hypochlorite," "hypochlorous solution," "hydrogen peroxide," "hydrochloric acid," "sodium hypochlorite," "potassium monopersulfate," "biguanide," "soda ash," "sodium bisulfate," and "copper sulfate."

We manually reviewed the incident records to confirm that pool chemicals were actually involved. We performed descriptive analysis of HSEES data by using SAS version 9.2. We used the North American Industry Classification System (NAICS) industry codes to identify sectors where pool chemical incidents occurred. Hereafter, NAICS industry codes will be referred to as sectors.

Results

Summary of Incidents

A total of 71,747 HSEES incidents occurred during 2001-2009. Pool chemical incidents were a small percentage of all HSEES incidents (400, 0.6%) but were a six-fold higher percentage (240, 3.6%) of the 6,642 HSEES incidents with injured persons. Pool chemical incidents had a higher percentage of evacuations than all HSEES incidents (21.0% vs. 6.7%, respectively) (Table 1). Pool chemical incidents also had a higher percentage of incidents with injuries than all HSEES incidents (60.0% vs. 9.3%, respectively). Of the 428 pool chemicals released in the 400 incidents, 61% were chlorine or chlorine-based disinfectants (calcium, sodium, or lithium hypochlorite; dichloro- or trichloroisocyanuric acid) (Figure 1).

Most pool chemical incidents occurred during the warmer months, May-September (70%), with the most in July (n = 93). Pool chemical incidents most frequently occurred at private residences (38.8%) (Table 2). Incidents occurring, however, in the public arts, entertainment, and recreation sectors injured the most persons (34.3%), followed by the accommodations sector (hotels) (23.6%). Both sectors are places that typically have a public pool or other aquatic venue. Other sectors where chemical incidents occurred and aquatic venues were likely to be were educational services (schools); real estate, rental, and leasing (apartment complexes); and health care and social assistance (i.e., retirement homes and hospitals). Sectors least likely to have aquatic venues included waste management and remediation services (disposal); utilities; construction; wholesale trade; transportation and warehousing; and administration of housing, urban planning, and community development.

The most commonly reported contributing factors to acute pool chemical incidents were human error (71.9%) and equipment failure (22.8%). The remaining primary contributing factors were intentional or illegal action (4.7%) and bad weather (0.5%). A more detailed secondary contributing factor was reported for 221 (55.3%) incidents. The most frequent secondary contributing factors were improper mixing (39.8%); improper filling, loading, or packing (12.2%); fire (10%); illegal or improper dumping (6.8%); and over-spray or misapplication (5.9%). Secondary factors for the remaining 25.3% of incidents included equipment failure; improperly performing maintenance; system process upset; improper system start-up or shutdown; power failure or electrical problems; illegal or intentional acts; vehicle or vessel collision; vehicle or vessel derailment/rollover/capsizing, explosion, load shift; or other.

Injured Persons

During 2001-2009, 732 persons were injured in pool chemical incidents. The one reported death was a suicide involving intentional chemical mixing. The following demographic groups were affected by pool chemical incidents: general public (67.4%), employees (23.2%), students (7%), and responders (2.4%). Age was reported for 485 (66.3%) injured persons (median: 17 years, range: <1-87 years). The majority of injured persons (63.5%) were treated at a hospital and released (Table 3). A total of 1,233 injuries/symptoms for the 732 injured persons were reported (Table 4). The most frequently reported injuries/symptoms were respiratory irritation (47.9%) and eye irritation (19.4%).

Personal Protective Equipment (PPE)

PPE use was reported for 19 injured persons: 13 responders, 3 employees, and 3 members of the public. All the responders wore the standard firefighter turnout gear (nine with respiratory protection, four without). The three employees wore level D PPE (a work uniform that provides minimum protection), and the three members of the public reported wearing other types of protection (i.e., gloves and/or eye protection).

Illustrative Case Reports

New York State

In 2003, a homeowner mixed calcium hypochlorite (pool shock treatment) and hydrochloric acid in an aluminum pan in the kitchen. The resulting reaction blew out the window and sent two adults to the hospital with breathing problems. The fire department called in the county hazmat team to neutralize the area. Four responders required decontamination after the incident. The homeowner was advised not to reenter the home until a hazmat contractor could complete the cleanup.

Wisconsin

In 2008, at a community care facility for the elderly, a swimming pool chlorine flow sensor malfunctioned, turning the pool water recirculation pump off and then back on. While the pump was off, "chlorine backed up in the apparatus; when the pump came back on, it delivered higher-than-normal amounts of chlorine into the water and air of the pool room." Two adult staff members and 42 school children using the facility became symptomatic. All 44 persons were decontaminated at the facility. One person received first aid at the facility, 42 received care in the ED but were not admitted, and one was admitted to the hospital. The majority of injured persons (42) reported respiratory issues; one reported skin irritation, one had gastrointestinal problems, and one reported having shortness of breath.

Discussion

This analysis provides data on 400 pool chemical incidents that occurred during nine years in 17 HSEES states and adds to the data published previously. These data illustrate the diversity of incident sectors where pool chemicals can be released including retail trade, educational services, real estate, waste management (disposal), construction, transportation, warehousing, and private residence. Similar to previous findings from WDOSS and NEISS (CDC, 2009, 2011a, 2011b), this report shows that a high proportion of pool chemical incidents resulting in injured persons (49.6%) occurred at private residences. Unlike the SENSOR and NEISS data, however, which show that most persons were injured at private residences (CDC, 2009, 2011b), our data show that incidents in public settings (recreation and hotels, 57.9%) resulted in more injured persons. Additionally, our data show that a higher portion of injured persons were under 18 years old (50.0%) compared to NEISS data (37.0%) (CDC, 2009).

The most commonly reported primary contributing factor was human error (71.9%). Many secondary contributing factors were related to mishandling (e.g., mixing of pool chemicals, such as the New York case report). Given the frequency of incidents occurring at residences and in public settings, pool chemical safety messages need to target both residential pool owners and public pool operators. Public health officials should collaborate with pool chemical retailers to educate residential pool owners and public pool operators about safe chemical storage and use. Particularly, important messages would be education about reading the label, following directions, and using PPE (CDC, 2009). The second most commonly reported primary contributing factor was equipment failure. Chlorine feed malfunction, such as the Wisconsin case report, is a common occurrence. Maintenance practices and engineering controls are available to prevent these types of incidents (CDC, 2009, 2011b, 2013).

Currently, only 25 states require pool operator training (National Swimming Pool Foundation, 2011), but training should be mandatory for all pool operators (Buss et al., 2009; CDC, 2010). The literature indicates that compared to noncertified operators, certified operators showed significant improvements in properly maintaining the pH level of pool water, the level of combined chlorine, and the compliance-chlorine standard (Johnston & Kinziger, 2007). The U.S. has neither nationally standardized regulations for pool management and operation nor a standardized national database to collect pool chemical release data in all states. Management and operation are regulated at the state or local level (CDC, 2003; Kaydos-Daniels, Beach, Shwe, Magri, & Bixler, 2008). Regulations might be effective in preventing releases in public venues and could be enforced through regular pool inspections. The Centers for Disease Control and Prevention (CDC) have reported, however, that because of lack of resources each pool is inspected only one to three times yearly (CDC, 2003, 2010).

In recent years, some initiatives have focused on proper pool chemical management and on preventing injuries associated with pool chemicals. When Wisconsin HSEES staff members found that 3% of their incidents for 1993-2003 involved chlorine and that those incidents resulted in 16% of all injured persons and 5% of all evacuees, they decided to conduct telephone outreach. They called major chlorine users, public pools, and 132 swimming pool operators, advising on safe-handling practices of chlorine products. Afterward, each pool operator received a follow-up questionnaire; 49% were returned. The majority of the operators (74%) stated that the telephone outreach resulted in a discussion among staff, and 70% stated that the telephone call was a useful reminder about swimming pool chemical safety practices (Kaye, Orr, & Wattigney, 2005).

In recent years, CDC and the U.S. Environmental Protection Agency (U.S. EPA) have developed resources to promote pool chemical safety, including recommendations for design of pool chemical storage areas and pump rooms, chemical storage, chemical handling, maintenance and repair of equipment, pool chemical training for aquatic facility staff, emergency response plans, and chemical packaging and labeling (CDC, 2009, 2013; U.S. EPA, 2001). U.S. EPA, which has regulatory authority over the labels on pool chemicals because they are considered pesticides, conducted consumer research to improve labels and developed downloadable posters and brochures as part of their "Read the Label First" campaign (U.S. EPA, 1996).

Recent studies have suggested, however, that the current regulated labels might not be sufficient to protect consumers (CDC, 2011a).

CDC is working with state and local public health officials and aquatic industry representatives to develop a Model Aquatic Health Code (MAHC). The MAHC consists of 14 modules and provides sample guidelines for design, construction, operation, maintenance, and management standards (www.cdc.gov/healthywater/swimming/ pools/mahc/index.html). In the absence of federal regulations, the MAHC will serve as a resource for local and state officials reviewing and updating their individual pools codes to promote healthy and safe swimming at public pools and other treated recreational water venues (CDC, 2011b, 2011c).

In 2010, ATSDR established the National Toxic Substance Incidents Program (NTSIP), a new surveillance program that expanded on the HSEES activities in a subset of states, placing a special emphasis on layered data analyses of the GIS location of chemically vulnerable areas and populations. Each of the seven NTSIP state programs (Louisiana, New York, North Carolina, Oregon, Tennessee, Utah, and Wisconsin) has analyzed multiple data sets (e.g., spills, chemical storage, U.S. Census, U.S. Department of Transportation data, and other data sources) to identify areas vulnerable to chemical incidents. New York NTSIP staff used GIS to map pool chemical incidents and the manufacturers, distributors, and retailers of pool chemicals and also mapped the locations of private pools at the zip code level to identify areas of greatest pool density in the state. These data are being used to identify the origins and distribution of pool chemicals and the areas with the highest density of private pools for targeted education and outreach. Based on the resulting data, New York NTSIP staff developed a set of fact sheets with detailed guidance on topics such as tips for safe pool chemical storage, preventing chemical wetting, and emergency response. To promote pool chemical safety, staff summarized key points about safe storage design, safe chemical handling, adjusting chemical levels, and emergency response into a single fact sheet that can be printed and posted in a suitable location for easy reference (www.health.ny.gov/environmental/chemicals/pool_chems/factsheet.htm). During the summer of 2012, the New York State Department of Health regularly released messages on pool chemical safety through Facebook and Twitter.

The HSEES data that were analyzed have some limitations. First, not all pool chemical incidents are reported to the HSEES states' notification sources, and some pool incidents may have been missed. This is particularly true for incidents that occurred at private residences but did not result in an emergency response. Some states, such as Florida, have been able to overcome this limitation by negotiating data-sharing agreements with local poison control centers, which identify more incidents at private residences. Poison control centers capture data only on incidents with potentially exposed persons; therefore, using this notification source increases the percentage of incidents with injuries. Second, although HSEES states are geographically and demographically diverse (Mary Kay O'Connor Process Safety Center, 2008), the surveillance system was not designed specifically to track pool chemical incidents. Therefore, HSEES pool chemical incidents might not be nationally representative. Also, because we had to rely on search terms to identify pool chemical incidents, some incidents might have been missed, particularly if the comments or synopsis field was blank or very brief and did not provide the details that would indicate a pool chemical incident. Third, misidentification of some chemicals during data entry might have occurred, particularly if "chlorine" was reported to HSEES when, in reality, the chemical was a chlorine-based disinfectant. Finally, because not all 17 states participated during 2001-2009, trend analysis could not be performed.

Conclusion

This analysis shows that about 60% of pool chemical incidents resulted in injured persons, a much higher number than the percentage of incidents with injured persons in all incidents in the HSEES database. We have concluded that many of these pool chemical incidents could have been prevented with the following: improved design and engineering; education and training that stress safe pool chemical handling and storage practices (available on material safety data sheets); and safe, preventive equipment maintenance.

Further, we believe that education targeting not only pool operators but also anyone involved in any phase of pool chemical handling, including transporters, retailers, wholesalers, warehousers, consumers, residential pool owners, and waste haulers, will reduce the frequency of these incidents.

Acknowledgements: The authors acknowledge the assistance of Thomas M. Lachocki, PhD, chief executive officer of the National Swimming Pool Foundation, for providing data on the states' requirements for pool operator training. The authors also wish to acknowledge Michele C. Hlavsa, MPH, Division of Foodborne, Waterborne, and Environmental Diseases, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, for her review and insightful suggestions.

References

Agabiti, N., Ancona, C., Forastiere, F., Di Napoli, A., Lo Presti, E., Corbo, G.M., D'Orsi, F., & Perucci, C.A. (2001). Short-term respiratory effects of acute exposure to chlorine due to a swimming pool accident. Occupational and Environmental Medicine, 58(6), 399-404.

Buss, B.F, Safranek, T.J., Magri, J.M., Torok, T.J., Beach, M.J., & Foley, B.P. (2009). Association between pool operator certification and reduced pool chemistry violations--Nebraska, 2005-2006. Journal of Environmental Health, 71(8), 36-40.

Centers for Disease Control and Prevention. (2003). Surveillance data from swimming pool inspections--selected states and counties, United States, May-September 2002. Morbidity and Mortality Weekly Report, 52(22), 513-516.

Centers for Disease Control and Prevention. (2009). Pool chemical-associated health events in public and residential settings--United States, 1983-2007. Morbidity and Mortality Weekly Report, 58(18), 489-493.

Centers for Disease Control and Prevention. (2010). Violations identified from routine swimming pool inspections--selected states and counties, United States, 2008. Morbidity and Mortality Weekly Report, 59(19), 582-587.

Centers for Disease Control and Prevention. (2011a). Acute illness and injury from swimming pool disinfectants and other chemicals--United States, 2002-2008. Morbidity and Mortality Weekly Report, 60(39), 1343-1347.

Centers for Disease Control and Prevention. (2011b). Surveillance for waterborne disease outbreaks and other health events associated with recreational water--United States, 2007-2008. Morbidity and Mortality Weekly Report, 60(SS12), 1-32.

Centers for Disease Control and Prevention. (2011c). Model aquatic health code (MAHC): A national model swimming pool and spa code. Retrieved from http://www.cdc.gov/healthywater/swimming/ pools/mahc/

Centers for Disease Control and Prevention. (2013). Recommendations for preventing pool chemical-associated injuries. Retrieved from http://www.cdc.gov/healthywater/swimming/pools/preventingpool-chemical-injuries.html

De Haan, W., & Johanningsmeier, J.S. (1997). Swimming pool pest management: A training manual for commercial pesticide applications and swimming pool operators. Retrieved from http://www. ipm.msu.edu/uploads/files/TrainingManuals_SwimmingPool/ SwimmingPool_WholeManual.pdf

Johnston, K., & Kinziger, M. (2007). Certified operators: Does certification provide significant results in real-world pool and spa chemistry? International Journal of Aquatic Research and Education, 1, 18-33.

Kaydos-Daniels, S.C., Beach, M.J., Shwe, T., Magri, J., & Bixler, D. (2008). Health effects associated with indoor swimming pools: A suspected toxic chloramine exposure. Public Health, 122(2), 195-200.

Kaye, W.E., Orr, M.F, & Wattigney, W.A. (2005). Surveillance of hazardous substance emergency events: Identifying areas for public health prevention. International Journal of Hygiene and Environmental Health, 208(1-2), 37-44.

Mary Kay O'Connor Process Safety Center (Chemical Engineering Department, Texas Engineering Experiment System, Texas A&M University System). (2009). Developing a roadmap for the future of national hazardous substances incident surveillance. Retrieved from http://pscfiles.tamu.edu/library/center-publications/ white-papers-and-position-statements/Developing%20a%20 Roadmap%20for%20the%20Future%20of%20National%20 Hazardous%20Substances%20Incident%20Surveillance.pdf

National Institute for Occupational Safety and Health. (2010). Pocket guide to chemical hazards. Retrieved from http://www.cdc. gov/niosh/npg/npgd0115.html

National Swimming Pool Foundation. (2011). Useful links to swimming pools and spa codes. Retrieved from http://www.nspf.org/en/ Resources/News_StateCodes.aspx

Thomas, H.L., & Murray, V. (2008). Review of acute chemical incident involving exposure to chlorine associated with swimming pools in England and Wales, June-October 2007. Journal of Public Health, 30(4), 391-397.

U.S. Census Bureau. (2012). Statistical abstract of the United States, 2011. Retrieved from http://www.census.gov/compendia/ statab/2012/tables/12s1249.pdf

U.S. Environmental Protection Agency. (1996). Consumer labeling initiative. Retrieved from http://www.epa.gov/pesticides/regulating/ labels/consumer-labeling.htm

U.S. Environmental Protection Agency. (2001). Chemical safety alert: Safe storage and handling of swimming pool chemicals. Retrieved from http://www.epa.gov/oem/docs/chem/spalert.pdf

Ayana R. Anderson, MPH

Division of Toxicology and Human Health Sciences Agency for Toxic Substances and Disease Registry

Wanda Lizak Welles, PhD

Bureau of Toxic Substance Assessment New York State Department of Health

James Drew

Bureau of Environmental and Occupational Health Wisconsin Department of Health Services

Maureen F. Orr, MS

Division of Toxicology and Human Health Sciences Agency for Toxic Substances and Disease Registry

Corresponding Author: Ayana R. Anderson, Public Health Analyst, Agency for Toxic Substances and Disease Registry, Division of Toxicology and Human Health Sciences, 4770 Buford Hwy., MS F58, Atlanta, GA 30341. E-mail: ing9@cdc.gov.
TABLE 1

Summary of Pool Chemical Incidents Compared With All Hazardous
Substances Emergency Events Surveillance Incidents, 2001-2009

Category Pool Chemical All Incidents
 Incidents

Events 400 71,747
Evacuations ordered 84 (21.0%) 4,796 (6.7%)
Total people 4,867 378,966
 evacuated (a)
Events with injured 240 (60.0%) 6,642 (9.3%)
 persons
Injured persons 732 18,468
Events with shelter 10 (2.5%) 680 (0.9%)
 in place order

(a) Number indicates the number of known evacuees. When
large areas were evacuated, not all the evacuees could be
counted, so the number for evacuees is an underestimate.

TABLE 2

Sectors Where Pool Chemical Incidents Occurred by Events
With Injured Persons and Number of Injured Persons, Hazardous
Substances Emergency Events Surveillance, 2001-2009

Sector (a) # Events % # Events
 With
 Injured %
 Persons

Private residence 155 38.8 119 49.6

Art, entertainment, 87 21.8 47 19.6
and recreation

Accommodation and 39 9.8 34 14.2
food services

Other (b) 29 7.3 12 5.0

Unknown sector 25 6.3 8 3.3

Retail trade 23 5.8 3 1.3

Educational services 16 4.0 8 3.3

Real estate, rental, 14 3.5 4 1.7
and leasing

Waste management 12 3.0 5 2.1
and remediation
services (disposal)

Total 400 100.3c 240 100.0

Sector (a) # Injured %
 Persons

Private residence 152 20.8

Art, entertainment, 251 34.3
and recreation

Accommodation and 173 23.6
food services

Other (b) 92 12.6

Unknown sector 9 1.2

Retail trade 21 2.9

Educational services 11 1.5

Real estate, rental, 7 1.0
and leasing

Waste management 16 2.2
and remediation
services (disposal)

Total 732 100.0

(a) Sectors are derived from the North American
Industry Classification System.

(b) Other includes utilities, construction,
wholesale trade, transportation
and warehousing, health care and social
assistance, and public administration.

(c) Total percentage total is greater
than 100 because of rounding.

TABLE 3

Medical Disposition of Injured Persons in Pool Chemical Incidents,
Hazardous Substances Emergency Events Surveillance, 2001-2009

Disposition Frequency %

Treated at hospital (not admitted) 414 63.5
Treated on scene (first aid) 106 16.3
Treated at hospital (admitted) 74 11.3
Seen by private physician within 24 hours 32 4.9
Injury reported by official 23 3.5
Observation at hospital, no treatment 2 0.3
Death 1 0.2
Total 652 (a) 100.0

(a) Data are missing for 80 persons.

TABLE 4

Frequency of Reported Injuries/Symptoms Occurring in Pool
Chemical Incidents, Hazardous Substances Emergency Events
Surveillance, 2001-2009

Injury Frequency %

Respiratory irritation 590 47.9
Eye irritation 239 19.4
Gastrointestinal problems 105 8.5
Skin irritation 97 7.9
Shortness of breath 96 7.8
Headache 48 3.9
Burns 17 1.4
Dizziness/central nervous system 15 1.2
 symptoms
Heart problems 8 0.6
Trauma 8 0.6
Other 7 0.6
Heat stress 3 0.2
Total 1,233a 100.0

(a) The total number of injuries exceeds the number of injured persons
(n = 732) because as many as seven injuries can
be reported for each injured person.

FIGURE 1

Frequency of Pool Chemicals Released (N = 428)

Dichlor/Trichlor 2%
Chlorine 46%
Hydrochloric/Muriatic 15%
Reactions 13%
Hypochlorites 13%
Mixtures 8%
Other 7%

Number of chemicals is greater than the number of events because
some incidents involved more than one chemical. "Other" includes
pool chemicals not otherwise specified (n = 4), sodium hydroxide (n
= 3), bromine (n = 2), cyanuric acid (n = 2), algaecide (n = 1),
peroxide (n = 1), sodium bicarbonate (n = 1), and sodium dichromate
(n = 1).

Note: Table made from pie chart.
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Title Annotation:ADVANCEMENT OF THE SCIENCE
Author:Anderson, Ayana R.; Welles, Wanda Lizak; Drew, James; Orr, Maureen F.
Publication:Journal of Environmental Health
Article Type:Author abstract
Date:May 1, 2014
Words:4294
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