Benzenes measurement in indoor air and its human exposure assessment in four cities of southern China

Objective To investigate the pouution levels of benzene, toluene, ethylbenzene and xylene (BTEX) in indoor air at residences and offices in four cities of southern China, to analyze the potential sources of BTEX and to estimate the population exposure levels of BTEX through indoor inhalation.

Methods Tenax TA sampling tubes were used to collect BTEX samples in the indoor air of residences and offices. Thermal desorption technique and GC-MS analysis were combined to measure the mass concentration of BTEX. Relative component ratios of benzene, toluene and ethylbenzene were used to identify the BTEX sources, and exposure assessment model was used to evaluate the population exposure levels of BTEX.

Results The mean mass concentrations of benzene, toluene, ethylbenzene, and xylene were 20.7, 16.3, 9.1 and 29.9 μg/m³ respectively in offices and were 15.4, 52.6, 39.3 and 97.8 μg/m³ respectively in residences. The air pollution levels of toluene, ethylbenzene and xylene in residences were higher than those in offices. Source apportionment of BTEX showed that BTEX pollution in both offices and residences was mainly generated from the release of solvent in decoration materials. Exposure assessment based on the exposure parameters of Chinese population showed that daily average exposure dose to toluene, ethylbenzene and xylene in the residential environment was significantly higher than that in the office environment, and no significant benzene exposure difference was detected between the two types of places. The exposure to BTEX in the office and residential environment was far less than the threshold.

Conclusion The overall BTEX exposure risk in the four cities in the southem china is low, but the benzene mass concentrations in some residents and offices were higher than the benzene limit in the newly issued "indoor air quality standard (GB/T 18883-2022)". As people spend more time indoors than outdoors, it is necessary to further strengthen the pollution control and personal protection in the indoor air environment to ensure the health of the population.