ARB Research Seminar

This page updated August 10, 2015

Environmental Fate of Low Vapor Pressure - Volatile Organic Compounds from Consumer Products: A Modeling Approach

Photo of Deborah H. Bennett, Ph.D.

Deborah H. Bennett, Ph.D., Department of Public Health Sciences, University of California, Davis

September 22, 2015
Cal EPA Headquarters, 1001 "I" Street, Sacramento, CA

Research Project


The formation of ground-level ozone is caused by the gas-phase interactions of emitted volatile organic compounds (VOCs) and oxides of nitrogen in the presence of sunlight. Low vapor pressure-volatile organic compounds (LVP-VOCs) are exempt from the VOC content limits for consumer products and are defined in the California Code of Regulations. To evaluate the availability of LVP-VOCs that may contribute towards ozone formation from the use of consumer products, we developed modeling tools for two potential modes of releases during the use of consumer products (i.e., direct release to the outdoor air and disposed down the drain).

For the fate of LVP-VOCs found in some consumer products used in down-the-drain applications (e.g., laundry detergents, fabric softeners, dishwashing detergents, and other laundry products), we applied a wastewater treatment plant (WWTP) fate model to predict the fraction of LVP-VOCs that may volatilize at WWTPs. For the portion of the LVP-VOCs volatilized to air during product use, we applied a multi-compartment mass-balance model to track the fate of LVP-VOCs in a multimedia urban environment. Based on the modeling results for the selected 33 LVP-VOCs, loss by volatilization in a WWTP is negligible for most compounds, suggesting that a majority of the LVP-VOCs will not be available for ozone formation reactions in the atmosphere once they are disposed down the drain. In contrast, for the LVP-VOCs in a consumer product that is volatilized to air and is assumed to be in the gas phase, greater than 90% will remain in the air and may participate in photochemical reactions either at the source location or in the downwind areas. Comparing results from these two modes of releases emphasizes the importance of determining the fraction of LVP-VOCs volatilized versus the fraction disposed down the drain when a product is used by consumers. The results from this study can provide important information and modeling tools to evaluate the impact of LVP-VOCs on air quality.

Speaker Biography

Deborah H. Bennett, Ph.D., is an Associate Professor at the Department of Public Health Sciences, University of Caifornia, Davis. Dr. Bennett's research focuses on the fate, transport, and exposure of particulate matter and compounds in multi-scale applications, including direct consumer product use, and indoor and outdoor multimedia environments within the context of both environmental epidemiology and environmental risk assessment. She utilizes both modeling and measurement techniques, bridging the gap between these two lines of inquiry. Dr. Bennett is conducting an intervention study to determine if high filtration of indoor air improves air quality and subsequent systems in pediatric asthmatics. Research interests also include development of methods to assess exposures in autism epidemiology studies for compounds found in consumer products and exposures to particulate matter, endotoxins, and pesticides among farmworker populations. She also conducts exposure studies focusing on flame retardants, hazardous air pollutants, and perfluorinated compounds. This work on exposure has received support from the California Air Resources Board and describes the development of modeling tools for two potential modes of releases during the use of consumer products (i.e., direct release to the outdoor air and disposed down the drain) to evaluate the availability of low vapor pressure-volatile organic compounds (LVP-VOCs) that may contribute towards ozone formation from the use of consumer products. She received her Ph.D. in Mechanical Engineering from UC-Berkeley in 1999 and was an assistant professor at Harvard School of Public Health before joining the UCD faculty in 2005.

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