Seasonal and Spatial Variation of Ambient Air Volatile Organic Compounds in Pathumwan District, Bangkok, Thailand

Abstract

Ambient air pollution, mainly from motor vehicle emissions, is a serious problem in Bangkok, Thailand, and in many other cities. Ambient levels of the volatile organic compounds (VOCs) benzene, toluene, ethylbenzene and xylene (BTEX) and 12 carbonyl compounds (CCs) were evaluated at university and roadside areas in Pathumwan District, central Bangkok, Thailand, during wet and dry seasons in 2012 and 2013. Toluene was the most abundant BTEX while formaldehyde and acetaldehyde were the most abundant CCs. Benzene levels were highest in the university area in the wet season. Benzene, xylene, formaldehyde and acetaldehyde levels were significantly higher in the wet season than in the dry season (p<0.001). The ranges of toluene to benzene ratio (T/B) and formaldehyde to acetaldehyde ratio (F/A) in both seasons were 1.49-2.05 and 2.50-2.89, respectively. The urinary trans,trans-muconic acid (t,t-MA), hippuric acid, formaldehyde, acetaldehyde and formic acid of 287 outdoor workers in the study area were measured in both seasons. Urinary t,t-MA and formaldehyde at roadside areas were significantly higher in the wet season than in the dry season (p<0.001 and p<0.01). The same was true for urinary formic acid. While urinary formic acid of workers in both areas were significant higher in wet season than dry season. Overall, ambient VOC levels were higher in roadside areas than in the university area, and were higher in the wet season than in the dry season. There were associations of ambient levels of benzene, toluene, formaldehyde and acetaldehyde with urinary biomarkers of t,t-MA, hippuric acid, formaldehyde and acetaldehyde respectively.