VOCs in industrial, urban and suburban neighborhoods, Part 1: Indoor and outdoor concentrations, variation, and risk drivers

Abstract

Information regarding indoor and ambient concentrations and exposures of volatile organic compounds (VOCs) is limited in terms of the number and types of compounds measured, the spatial and temporal variation of concentrations, and the significance of indoor and outdoor emission sources. This study characterizes a wide range of VOCs across three communities that represent a gradient of population density and industrial activity. Monitoring was conducted in two seasons inside and outside of 159 residences in industrial, urban and suburban cities located in southeast Michigan, USA. Passive samplers were deployed at each location, and analyzed for 98 compounds. Outdoors, 46 different VOCs were detected. Benzene, toluene, p, m-xylene and carbon tetrachloride had the highest concentrations (medians from 1 to 2 μg m −3). Concentrations were elevated in winter in the suburban community, and levels were the highest in the industrial community. Indoors, 53 VOCs were detected, and benzene, toluene, p, m-xylene, n-heptane, α-pinene and d-limonene had the highest concentrations (medians from 1 to 17 μg m −3). Seasonal changes were small or inconsistent. Median indoor levels among the three communities generally followed outdoor rankings. Indoor/outdoor ratios varied from 1 to 10 for most compounds, but up to 100 for several compounds, e.g., d-limonene. Over a quarter of residences had benzene, naphthalene, chloroform and carbon tetrachloride at levels giving a chronic lifetime cancer risk above 10 −5 and sometimes much higher; outdoors, these compounds gave risks exceeding 10 −6. The study identifies a number of indoor emission sources associated with specific and sometimes very high VOC exposures, reports on several VOCs that have not been measured in previous indoor and outdoor studies, and shows the importance of both indoor and outdoor sources. Measured concentrations were at an intermediate level with respect to recent measurements elsewhere in the US, suggesting that study results are broadly representative.