During January–March 2007 patrons and lifeguards at a hotel indoor waterpark resort in Ohio complained of respiratory and eye irritation. After testing exposure to airborne trichloramine in the waterpark was suspected as the cause of the symptoms. 

CDC’s Morbidity and Mortality Weekly Report
Respiratory and Ocular Symptoms Among Employees of a Hotel Indoor Waterpark Resort — Ohio, 2007

Lifeguards reported significantly more work-related symptoms (e.g., cough, wheezing, shortness of breath, chest tightness, and eye irritation) than unexposed hotel employees. Lifeguards also reported significantly more eye irritation and cough on days when hotel occupancy was high versus low.

Insufficient air movement and distribution likely led to accumulation of trichloramine and exacerbation of symptoms. Based on recommendations to increase air movement and distribution at pool deck level, hotel management modified the ventilation system extensively, and subsequently no new cases were reported.

Chloramines are disinfection by-products formed when chlorine combines with nitrogen-containing compounds such as sweat and urine. They include monochloramine, dichloramine, and trichloramine.

Trichloramine is the main chloramine compound present above chlorinated water surfaces  and has been suspected as the cause of outbreaks of eye and respiratory irritation at indoor pools. Increased bather load has been associated with increased trichloramine levels, most likely because of increased nitrogen compounds from bathers.

Other factors affecting airborne trichloramine concentration include water chemistry, air recirculation, and aerosolization of water contaminants from splashing and spraying.  Trichloramine is a strong mucous membrane irritant and has been associated with eye and respiratory tract irritation and asthma in swimmers and pool attendants.

The World Health Organization recommends an airborne trichloramine concentration of 0.5 mg/m3 as a provisional value. Currently, no NIOSH or Occupational Safety and Health Administration (OSHA) occupational exposure limits exist for airborne trichloramine.