Indoor phthalate concentration and exposure in residential and office buildings in Xiʹan, China

Indoor phthalate levels were investigated in 28 buildings, including 14 office and 14 residential buildings in Xiʹan, China. Phthalate esters in the gas-, particle-, and dust- phase were measured separately. Four phthalates including dimethyl phthalate (DMP), diisobutyl phthalate (DiBP), di-n-butyl phthalate (DnBP) and di(2-ethylhexyl) phthalate (DEHP) were detected. The detection frequency of DnBP and DEHP was more than 90%. The concentrations of total phthalate esters ranged from 0.20 to 8.29 μg m−3 for the gas- phase, from 0.09 to 14.77 μg m−3 for the particle- phase and from 123 to 9504 μg g−1 for the dust- phase. The individual phthalate with the highest concentrations of 6.17 μg m−3, 7.97 μg m−3 and 7228 μg g−1 respectively for gas-, particle- and dust- phase in all investigated rooms is all DiBP. The median concentration of the gas- and particle-phase DiBP (0.52 and 0.72 μg m−3) and dust-phase DEHP (582 μg g−1) were the highest. It was also found that the average concentrations of individual phthalates in residential buildings were often higher than in office buildings, and correlation analysis indicated that DiBP, DnBP and DEHP might come from the same sources. Based on the gas- and particle-phase concentrations measured, the particle-air partition coefficients of phthalates were estimated, and their logarithm values were found to be linearly correlated with the logarithm values of their octanol-air partition coefficients. Finally, the total daily exposure to indoor phthalates in air and dust was calculated, and ranged from 2.6 μg kg−1 day−1 (for adults) to 7.4 μg kg−1 day−1 (for toddlers).