Exposure to hazardous air pollutants in underground car parks in Guangzhou, China

Abstract

Volatile organic compounds (VOCs), carbon monoxide (CO), and PM10 were studied by field sampling in six underground car parks beneath multi-level buildings in Guangzhou, China. CO and PM10 in the car parks range from 3.0 to 69.0 ppm and 0.087 to 0.698 mg m−3, with mean concentrations of 10.8 ppm and 0.228 mg m−3, respectively. Overall mean concentrations of methyl tertiary-butyl ether (MTBE), benzene, toluene, ethyl-benzene, and xylene (BTEX) are 90.5, 54.8, 239.9, 47.7, and 189.3 μg m−3, respectively. Indoor air pollutants in the car parks show an obvious seasonal variation and are higher in winter than in summer. The total estimated cancer risks of occupational exposure for car park staff and casual exposure for parking users are 3.73 × 10−4 and 5.60 × 10−6, indicating definite and possible risks, respectively. The hazard quotient of target VOCs is 4.33, implying a definite risk for people using underground car parks. Indoor/outdoor (I/O) ratios for MTBE and BTEX are significantly higher than one, reflecting strong emission sources in underground car parks. The BTEX to MTBE ratios in the car parks are almost the same as those in tunnel air, indicating that indoor aromatic hydrocarbons were mainly from engine emissions and gasoline evaporation. With increasing urbanization in China, more attention should be paid to the exposure of staff and users to hazardous air pollutants in underground car parks.