Project at a Glance

Title: Indoor concentrations of polycyclic aromatic hydrocarbons in California residences.

Principal Investigator / Author(s): Sheldon, L

Contractor: Research Triangle Institute

Contract Number: A033-132

Research Program Area: Health & Exposure

Topic Areas: Indoor Air Quality, Toxic Air Contaminants


The purpose of this study was to obtain information on indoor and outdoor air concentrations of polycyclic aromatic hydrocarbons (PAHs) and carbon monoxide in California residences. Additional objectives were to investigate the relationship between compounds and different types of indoor combustion sources and to explore relationships among the measured compounds. To meet these objectives, a single season field monitoring study was conducted in 280 homes in northern California. Homes were selected to represent specific combustion source categories including tobacco smoking, fireplaces, woodstoves, and gas heat. For each home, 24-hour indoor and outdoor air samples were collected and analyzed for 13 PAHs and quinoline, a nitrogen substituted PAH. Air exchange measurements were also made. In a subset of -75% of the homes, indoor and outdoor carbon monoxide measurements were made over the same period. Information was gathered on use of combustion sources and other activities during the monitoring period. Summary statistics were calculated by source categories for indoor air concentration, outdoor air concentration, indoor/outdoor air concentration ratio, and source strength. Statistical models were developed to evaluate the relationship between measured PAH concentrations and source usage. Results indicate that, in the absence of strong indoor combustion sources, most homes had higher outdoor than indoor air concentrations of PAHs. Among indoor sources, cigarette smoking appeared to have the strongest effect on indoor levels of PAHs. Fireplaces, woodstoves and kerosene heaters also contributed to elevated indoor PAH concentrations. Infiltration of outdoor air into the home was also a major contributor to PAH concentrations in indoor air. Outdoor levels of PAHs correlated highly with each other. However, indoor PAHs behaved differently: correlations were high only for those PAHs of similar volatility. Only a few homes showed elevated levels of carbon monoxide; most were associated with the use of gas heat and fireplaces.

For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753

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