Trihalomethanes in exhaled air, indoor air and water: A parallel design trial in chlorine and ozone-chlorine disinfected swimming pools

We measured the concentrations of Trihalomethanes (THMs), Chloroform (TCM), Bromodichloromethane (BDCM), Dibromochloromethane (DBCM) and Bromoform (TBM), in water, indoor air and exhaled air before and after using chlorine and ozone-chlorine disinfected swimming pools from September 2020 to January 2021. Two parallel panels of adult subjects swam for 60 min in a chlorine and an ozone-chlorine indoor swimming pool. The concentration of total THMs (tTHMs) in water samples of chlorine and ozone-chlorine swimming pools were in the ranges of 170.8–192.5 μg/L and 161.3–180.4 μg/L, respectively which exceeded the WHO guideline value. High levels of THMs were found in indoor air at the height of 10 cm compared to 150 cm above water surface. We found a statistically significant correlation between the concentration of THMs in water and indoor air samples. The results showed that the levels of all detected THMs in participant’ exhaled air after 60 min swimming were 11–13 times higher than those of before exposure. A statistically significant linear correlation was observed between THMs levels in the exhaled air and indoor air at the height of 10 cm above the water surface, but not with the levels at the height of 150 cm. We also found that the levels of THMs in exhaled air were associated with the energy expenditure, swimming distance and time, but not correlated with BMI and skin area. [Display omitted] •TCM was the most dominant compound in water, indoor air, and exhaled air samples.•THMs concentrations in water samples exceeded the WHO guideline values.•Indoor air THMs levels were much higher at the breathing zone.•THMs levels in exhaled air significantly increased after 60 min exposure in both pools.