237 Airborne trichloramine in Swedish indoor swimming pools

Trichloramine is a disinfection by-product in chlorinated swimming pools, it can evaporate into air and cause irritation to eyes and airways. The aim of this study was to evaluate indoor air concentrations of trichloramine in different types of swimming pools across Sweden, and to investigate factors (determinants) that affect the levels. In total 72 swimming pools; 36 exercise-, 16 instruction-, 7 adventure-, and 13 rehabilitation pools were included. Stationary measurements were performed by the pool side using active sampling on quartz filters, analyzed using suppressed ion chromatography and conductivity detection. For public exercise pools the geometric mean concentration of trichloramine was 0.12 mg/m3 (range: 0.02-0.29 mg/m3). Geometric means for instruction- and adventure pools GM were 0.18 mg/m3 and 0.20 mg/m3, respectively. Trichloramine concentrations were statistically significantly lower in rehabilitation pools compared with the other pool types. For the exercise pools, a statistically significantly effect of time of the day for sampling was found, with higher levels during evenings compared with mornings and afternoons. Free but not combined chlorine in the pool water was associated with airborne trichloramine for exercise and rehabilitation pools while the opposite was found for the instruction pools. Number of swimmers in the pool during sampling was not identified as a significant determinant for airborne trichloramine, however, some of the highest concentrations were measured during intense pool activities. With repeated samplings the variability in measured concentrations could be estimated, and it was found that between- as well as within-pool variance contributed to the total variability of airborne trichloramine. The observed day-to-day variability encourages a repeated sampling strategy.