Haloacetic acids (HAAS) are the main groups of disinfection by-products that have high health risks. In this investigation, determination of thrichloroacetic acid and dichloroacetic acid as two main product of chlorination procedure of water treatment was measured in some swimming pools of Zanjan city-Iran. After sampling, gas chromatography tandem mass spectroscopy method (GC/MS) was used for analyzing of these two chlorinated by-products. Six samples of swimming pools were studied in two summer and winter seasons. The average amount of thrichloroacetic acid and dichloroacetic acid concentration was ranged between not detectable (ND) to 6.80 µg L-1 and 0.06 to 1.45 in summer, and 0.29–5.13 and 0.27-17.12 in winter. The concentration of these haloacetic acids in tap water sample was lower than swimming pools and observed 0.26 µg L-1 and not detectable (ND) for dichloroacetic acid and thrichloroacetic acid, respectively.
