Thecontributionoftraffictoindoorconcentrationsofpolycyclicaromatic hydrocarbons { SARA D. DUBOWSKY, a LANCE A. WALLACE b AND TIMOTHY J. BUCKLEY a a Johns Hopkins School of Hygiene and Public Health b US Environmental Protection Agency A photoelectric aerosol sensor (PAS) was used to measure real-time indoor concentrations of polycyclic aromatic hydrocarbons (PAHs) at three residences. Semi-quantitative measurements of total indoor particle-bound PAH and temperature were collected continuously every minute for approximately 2 weeks at each location. The purpose of this study was to examine the effect of traffic on indoor concentrations of PAHs. This was accomplished by collecting indoor measurements at an urban, semi-urban, and suburban residential location with varying levels of, and proximity to, traffic. Since the homes were occupied, the effects of cooking, the dominant indoor source, were also examined among the three nonsmoking households. The results indicate that traffic was the main outdoor source of PAH concentrations measured indoors for all locations. In fact, a significant (p<0.001) traffic-related trend in weekday PAH concentration was detected with a geometric mean concentration at the urban location (31 ng/m 3 ) nearly two times that at the semi-urban location (19 ng/m 3 ) and over three times larger than the suburban location (8.0 ng/m 3 ), once adjusted for indoor sources. Hourly average concentration profiles also revealed weekday rush hour peaks of PAHs at all locations. No pronounced peaks and significantly lower concentrations (10, 10, and 4.9 ng/m 3 ) were seen during the weekends for all locations i.e., the urban, semi-urban and suburban locations, respectively. Indoor sources including frying/saute Âing, broiling, and candle-burning were characterized by peak concentration, duration of PAH elevation, and potential dose. This analysis suggests that cooking, and especially frying/saute Âing, may be an important source of indoor PAH concentrations. Keywords: cooking, exposure, indoor air, polycyclic aromatic hydrocarbons (PAH), potential dose, traffic. Introduction With a rising concern over human exposure to airborne particles, there is a growing interest in the chemical constituents of particulate matter, including high molecular weight polycyclic aromatic hydrocarbons (PAHs) (US EPA, 1996). High molecular weight PAHs are primarily sorbed to the particulate respirable fraction (e.g., <2.5 m) and many have been identified as mutagens (Lewtas et al., 1992) and carcinogens (Chiddihy et al., 1984; Rannug and Sundvall, 1985; Cassarett and Doull, 1991; DHHS, 1995). Because of this toxicity and the ubiquitous occurrence of PAHs throughout the environment, exposure to PAHs is of significant public health concern. Environmental exposure occurs primarily through dietary ingestion and secondarily through inhalation (Buckley and Lioy, 1992; Buckley et al., 1995). More recent data suggest that nondietary ingestion of contaminated house dust may also be an important route of exposure especially for children due to their increased contact with house dust and increased hand-to-mouth activity (Wilson et al., 1994; Roberts and Dickey, 1995). The indoor air-inhalation pathway is of particular concern with respect to respiratory effects including lung cancer. PAHs from mobile sources have been shown to be more mutagenic than PAHs from other sources such as wood stoves (Lewtas et al., 1992; Cupitt et al., 1994). PAHs are products of incomplete combustion and are often generated through open burning, incineration, in- dustrial power generation, and vehicle emissions (DHHS, 1995). While these particular sources are found outdoors, indoor sources must also be considered. In fact, it has been well-documented that indoor PAH concentrations are influenced by both indoor and outdoor sources. Activities such as cooking, residential heating, smoking cigarettes, and burning candles are known to generate significant levels of PAHs (Waldman et al., 1990; Chuang et al., 1991; Nabinger et al., 1995; Ott and Klepeis, 1995; Ott et al., 1994; Wallace et al., 1997). As people spend approximately 1. Abbreviations: PAH, polycyclic aromatic hydrocarbons; PAS, photo- electric aerosol sensor. 2. Address all correspondence to: Timothy J. Buckley, Ph.D., Johns Hopkins School of Hygiene and Public Health, Department of Environmental Health Science, RM 6010, 615 N. Wolfe Street, Balti- more, MD 21205. Tel.: (410)614-5750. Fax: (410)955-9334. E-mail: tbuckley@jhsph.edu y This paper has been reviewed in accordance with the US Environmental Protection Agency's peer and administrative review policies and approved for presentation and publication. Mention of trade names or commercial products does not constitute endorsement or recommendation for use. Received 3 June 1998; revised 25 November 1998. Journal of Exposure Analysis and Environmental Epidemiology (1999)9,312±321 # 1999 Stockton Press All rights reserved 1053-4245/99/$12.00 http://www.stockton-press.co.uk