NEW YORK (Reuters Health) - Swimming teachers and other people who spend a lot of time near chlorinated pools face an increased risk of breathing problems, Dutch researchers report.

Chlorine reacts with substances such as urine and sweat to create byproducts that can irritate the respiratory tract, most importantly chloramines, explain Dr. Jose Jacobs of the University of Utrecht in The Netherlands and colleagues in a report in the European Respiratory Journal.

The research team surveyed 624 swimming pool employees and sampled air at six swimming pools. They measured trichloramine levels at all 38 pools included in the study to estimate long-term exposure among employees. Trichloramines are the most volatile type of chloramine, and are known to irritate the eyes and upper respiratory tract.

Compared to pool workers with the least exposure to trichloramines, such as catering employees or receptionists, swimming instructors were 2.4 times as likely to suffer frequently from sinusitis or sore throat, and faced a 3.4-fold greater risk of chronic cold, the researchers found.

Employees with high levels of exposure were at greater risk of a number of other respiratory symptoms compared to the general Dutch population, ranging from a 40 percent increased risk for tightness of the chest to a more than sevenfold greater likelihood of suffering breathlessness while walking with a person of the same age.

People who reported excessive humidity or inadequate ventilation at work were also more likely to report breathing problems.

Trichloramine exposure is the most likely explanation for the breathing problems identified in the study, given that levels poolside can be three times higher than the established comfort level, the researchers write. The chemicals could boost a person's risk of asthma, allergies and other breathing problems, they suggest, by making the airways more permeable.

Health and safety regulations for chlorinated pools address water quality, but not air quality, Jacobs and colleagues point out. One possible way to reduce levels of trichloramines might be to improve hygiene among pool users, they add, although enforcing compliance could be difficult.