Characterization of Factors Determining Personal Exposure to Volatile Air Toxics in Urban EnvironmentsEPA Grant Number: R826786
Title: Characterization of Factors Determining Personal Exposure to Volatile Air Toxics in Urban Environments
Investigators: Esmen, Nurtan A. , Hall, Thomas A. , Johnson, D. L. , Phillips, M. L.
Current Investigators: Esmen, Nurtan A. , Hall, Thomas A. , Johnson, D. L. , Lynch, Robert A. , Phillips, M. L. , Wang, D.
Institution: University of Oklahoma Health Sciences Center
EPA Project Officer: Chung, Serena
Project Period: October 1, 1998 through September 30, 2001 (Extended to September 30, 2002)
Project Amount: $559,352
RFA: Urban Air Toxics (1998) RFA Text | Recipients Lists
Research Category: Air , Air Quality and Air Toxics
Previous studies have provided valuable information regarding which sources actually contribute significantly to personal exposure to ambient air toxics, and what factors affect the relative weighting of these sources. However, in order to develop generalized models for estimating personal exposure within and among broad populations, it is necessary to employ a more advanced study design that will investigate the effects of external factors on personal activity patterns and exposure levels. The primary objective of this project is to investigate how external factors influence the relationship between personal exposures and area measurements of air toxics.
Using a multi-city, multi-season, two-level fractional factorial design, we will study the distribution of personal exposures in relation to eight dichotomous macroenvironmental and household factors which are hypothesized to influence personal activity and exposure patterns. The factors studied will be: size of urban area, degree of industrialization, high vs. low and mild vs. extreme seasonal temperature, presence or absence of precipitation, workday vs. leisure day, presence or absence of children in the household, and socioeconomic status. The highly efficient factorial design will allow the effects and interactions of these factors to be assessed using at most 256 monitoring periods spread over about two years. The monitoring will be conducted in about 100 volunteer households recruited in four Oklahoma cities. Only non-smoking households in single-family dwellings will be included. One adult 21-50 years of age in each household will be selected randomly for personal exposure monitoring. Personal and area hazardous air pollutant (HAP) exposure measurements will be performed indoors and outdoors over 24-hr periods for a number of volatile organic compounds (VOC), including benzene, toluene, ethylbenzene, xylenes, styrene, n-hexane, and 2,2,4- trimethylpentane. VOC concentrations will be assessed for 12-hr periods. Subjects will keep diaries to document personal activities of study subjects, and diaries will be supplemented by precise location tracking using Global Positioning System (GPS) technology. In addition, residences will be characterized regarding resistance to infiltration/exfiltration. A pilot study on the use of multi-stage piezoelectric microbalance impaction for the characterization of hourly indoor and outdoor fine particulate matter size distributions will also be performed at study residences.
The primary expected outcome of this work is a resolution of fundamental questions regarding the underlying assumptions of previous HAP exposure assessment approaches. The extensive number of well-planned measurements will also have ancillary benefits. By introducing eight contrasts and five generic measures, with the exposure values split into two 12-hr segments, we will be in a position to estimate relative contribution levels for HAP sources.
Improvement in Risk Assessment or Risk Management: The results are expected to produce a model that can be used to define exposure models for other populations. Both as a fundamental study and as an applied investigation of exposure parameters and levels, the data generated are expected to provide a significant scientific basis for understanding exposure mechanisms to air toxics.