DEPARTMENT OF HEALTH AND HUMAN SERVICES

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

Summary 

Lifeguards and patrons in the rapidly growing indoor waterpark industry can be exposed to numerous disinfection byproducts (DBP) 

and microorganisms that can cause 

adverse health effects such as eye 

and respiratory irritation, skin rashes, and flu-like symptoms. NIOSH 

provided technical assistance to a 

county health department to investigate the cause of symptoms 

reported by employees of a large 

indoor waterpark. This document 

addresses issues that pool managers, designers, and public health officials should consider to reduce illness at indoor water parks.

Reducing Illnesses at Indoor

Waterparks

Description of

Exposure

The mixture of disinfectants, such as 

chlorine, and compounds found in 

pool water can produce many DBPs, 

which can dissipate into the air; microorganisms may also be present in 

water and can make people sick. Also, 

indoor waterparks have many splash 

and spray features that can aerosolize contaminants from the water into 

the air, where patrons and employees 

can inhale them (see Figures 1 and 2). 

These features can make managing this 

environment more difficult than in stillwater pools. 

Waterparks can have high numbers of patrons, including young children, spending long lengths of time in the waterpark 

area, which can be a major contributing factor to DBP production because 

they produce sweat and urine. The average amount of urine, which contains 

nitrogenous compounds, released into 

pool waters per bather is 25 to 30 milliliters [Gunkel and Jessen 1988], and 

each liter of sweat contains one gram of 

nitrogen [WHO 2006]. As more sweat 

and urine are released into the pool water, the nitrogen-containing compounds 

also increase which can chemically mix 

with disinfectants to create irritating 

DBPs in the air. 

Lifeguards and employees working inside 

an enclosed waterpark for long durations 

may be at higher risk of having symptoms 

of exposure to DBPs because they work 

long hours with fewer breaks than those 

who work outside the enclosed area.

Chloramines and

Endotoxins

Chloramines are DBPs that form 

when chlorine combines with nitrogencontaining compounds from sweat or 

urine. Chloramines, specifically trichloramine, are suspected as a primary 

cause of reported irritation symptoms 

based on exposure monitoring studies 

[Hery et al. 1995; Massin et al. 1998]. 

People exposed to trichloramine may 

experience respiratory symptoms such 

as cough, chest tightness, wheezing, and 

eye irritation. In addition to the number 

of people using the pool, other factors 

that affect the chloramine concentration in indoor waterparks include water chemistry parameters (e.g., chlorine 

concentration, pH, temperature), aerosolization of particles caused by splashing and spraying, and air recirculation 

from the ventilation system [Hery et al. 

1995; Massin et al. 1998]. 

Endotoxin, which is found in the cell 

wall of certain bacteria, is released 

when the bacterial cell breaks down 

or multiplies. It has been found in 

various industrial and nonindustrial settings associated with bacterial 

contamination, humidifiers, air conditioners, and other water-associated 

processes. It can cause airway and alveolar inflammation as well as chest 

tightness, fever, and malaise and 

acute reduction in lung function. 

Case Study

NIOSH assisted a local heath department to investigate eye and respiratory 
irritation symptoms at an indoor waterpark resort. This 

waterpark was newly opened, and within a month, the 

county health department received about 80 reports of 

eye and respiratory irritation from patrons and employees. Symptoms included red, burning or itchy eyes; itchy 

or runny nose; cough; wheezing; shortness of breath; 

chest tightness; or sore throat. Initial tests revealed normal water chemistry as well as air chlorine concentrations below NIOSH and OSHA occupational exposure 

limits. Management added supply diffusers to the ventilation system to increase air movement at the deck level, increased the frequency of water chemistry checks, 

and added more fresh water to all systems to reduce 

symptom reports; however, the county health department continued to receive health complaints prompting 

a technical assistance request to NIOSH. Because the 

NIOSH mission is to promote occupational safety and 

health, the investigation focused on the employees.

This waterpark measures approximately 80,000 square 

feet, and has a maximum occupancy of 3,746 persons. It 

contains 11 waterslides, two activity pools, two hot tubs, 

a wave pool, a leisure river, a four-story interactive play 

system, and several features that splash, spray, and aerate 

large amounts of water. Water flows by gravity through 

the main drains and gutter systems from the pool into 

designated surge tanks. The water is pumped out of the 

surge tank and filtered. An automated chemical controller tests and adjusts the water’s pH and chlorine concentration as needed by adding a sodium hypochlorite solution (to disinfect) and sulfuric acid (for pH adjustment).

NIOSH investigators tested pool water for pH, microbials, sulfites and sulfates, and free and total chlorine and 

reviewed facility plans to assess water and ventilation 

system designs. Endotoxin were also tested for in air and 

water. To assess the effect of the number of occupants 

in the pools (bather load), NIOSH investigators collected samples of air in several deck areas to test for trichloramine concentrations on high (more than 1,000 guests) 

and low bather load days (fewer than 100 guests) as approximated by hotel occupancy. 

NIOSH investigators also conducted a survey of lifeguards working inside the waterpark (exposed) and 

hotel employees working outside the waterpark (unexposed). All participants filled out an initial questionnaire concerning demographics, work and medical history, and work-related symptoms occurring within the last 

month. Symptoms were considered work-related if they 

occurred on work days and improved on days off work. 

The following findings were noted:

From the medical assessment:

 Lifeguards had more work-related symptoms than unexposed employees.

 Lifeguards had more work-related cough and eye irritation on days when the number of people using the 

indoor pool area was high.

From the industrial hygiene assessment:

 Trichloramine concentrations were similar to those 

found in other indoor swimming pool studies, and 

concentrations at some pools were at levels reported 

to cause mucous membrane irritation.

 Air endotoxin were found at concentrations that have 

been associated with cough and fever.

 No fecal contamination, Legionella, mycobacteria, or 

sulfites were found in the pool water.

From the ventilation assessment:

 The ventilation system design may not have provided 

adequate air movement and distribution to adequately 

capture and remove air contaminants at the pool and 

deck level. Because all facilities are unique, ventilation 

system design should be evaluated case-by-case.

From the water system assessment:

 Water chemistry results met state and local standards.

 Spray feature piping drew water prior to the filtration 

and treatment cycle.

Recommendations

Below are specific steps/practices that waterpark/pool managers, designers, and public health officials can consider and/

Figures 1 and 2. Aerosolizing spray features of 

waterpark.
or adopt to eliminate or minimize exposure to DBPs and 

endotoxin and reduce respiratory, skin, and mucous membrane irritation potentially related to these exposures.

Patron and employee education:

 Provide education and training to employees on recognizing the symptoms and signs of eye and respiratory 

irritation, skin rash, and asthma that may be attributed to DBP exposures.

 Encourage employees to report symptoms to management. 

 Encourage patrons to shower before entering and after 

leaving the pool area.

 Encourage children to take frequent bathroom breaks 

to decrease the amount of nitrogenous waste released 

into pool water [Dziuban et al. 2006].

Water chemistry considerations:

 Keep combined chlorine levels as low as possible and 

continue to maintain water chemistry within recommended guidelines.

 Assess water system treatment design, such as ensuring that spray features draw water that has been adequately filtered and treated.

 Allow water to drain out of spray features during periods of disuse because research has shown that microbials can amplify in them overnight [Rose et al. 1998].

 Reduce aerosolization of potential contaminants by 

using nozzles that produce larger droplets and reduce 

spray feature cycle times.

Ventilation considerations:

 Place supply and return ducts in locations that allow 

the ventilation systems to provide enough air movement and remove contaminants properly.

Follow Up

Waterpark management made extensive changes to their 

ventilation system including, adding additional supply 

diffusers and lowering return air vents closer to deck level and aerosolizing spray features. The air handling units’ 

volume of airflow was increased, and ductwork changes were made to increase air movement to the front and 

back areas of the waterpark. A full year after changes 

were made, the county health department shared that no 

further chloramine-related symptoms had been reported.

Acknowledgments

The principal contributors to this publication were Lilia 

Chen, Division of Surveillance, Hazard Evaluations, and 

Field Studies, NIOSH; and Ellen Galloway, Division of 

Creative Services, Centers for Disease Control and Prevention. 

To read the full HHE report, visit the following Web 

site: http://www.cdc.gov/niosh/hhe/reports/pdfs/2007-

0163-3062.pdf

References

Dziuban EJ, Liang JL, Craun GF, Hill V, Yu PA, Painter 

J, Moore MR, Calderon RL, Roy SL, Beach MJ [2006]. 

Surveillance for waterborne-disease outbreaks associated with recreational water—United States, 2003–

2004. MMWR 55(SS12):1–2.

Gunkel K, Jessen HJ [1988]. The problem of urea in 

bathing water. Z Gesamte Hyg 34(4):248–224.

Hery M, Hecht G, Gerber JM, Gendre JC, Hubert G, 

Rebuffaud J. [1995]. Exposure to chloramines in the 

atmosphere of indoor swimming pools. Ann Occup 

Hyg 39(4):427–443.

Massin N, Bohadana AB, Wild P, Héry M, Toamain JP, 

Hubert G [1998]. Respiratory symptoms and bronchial responsiveness in lifeguards exposed to nitrogen trichloride in indoor swimming pools. Occup 

Environ Med 55(4):258–263.

Rose CS, Martyny JW, Newman LS, Milton DK, Talmadge EK, Beebe JL, McCammon JB, Hoffman RE, 

Kreiss K [1998]. “Lifeguard lung”: endemic granulatomous pneumonitis in an indoor swimming pool. Am J 

Public Health 88(12):1795–1800.

WHO [2006]. Guidelines for safe recreational water environments. Volume 2, Swimming pools and similar environments. Geneva, Switzerland, World Health Organization.
DEPARTMENT OF HEALTH AND HUMAN SERVICES

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

4676 Columbia Parkway

Cincinnati, OH 45226–1998

Official Business

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As part of the Centers for Disease Control and Prevention, 

NIOSH is the Federal agency responsible for conducting research and making recommendations to prevent work-related 

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Reducing Illnesses at Indoor Waterparks DHHS (NIOSH) Publication No. 2010–138

Safer • Healthier • PeopleTM March 2010