Hazardous Air Pollutant Mixtures: Measuring and Modeling Complex ExposureEPA Grant Number: R827928
Title: Hazardous Air Pollutant Mixtures: Measuring and Modeling Complex Exposure
Investigators: Adgate, John L. , Church, Timothy , Pratt, Greg , Ramachandran, Gurumurthy , Sexton, Ken , Zhang, Junfeng
Institution: University of Minnesota , Minnesota Pollution Control Agency , University of Medicine and Dentistry of New Jersey
EPA Project Officer: Chung, Serena
Project Period: December 20, 1999 through December 19, 2002 (Extended to June 19, 2004)
Project Amount: $510,012
RFA: Urban Air Toxics (1999) RFA Text | Recipients Lists
Research Category: Air Quality and Air Toxics , Air
Description:This research, which builds upon previous STAR grant air pollution research in the Minneapolis-St. Paul Metropolitan area, has two objectives: (a) to examine the relationships between ambient monitoring (i.e., outdoor central sites), residential indoor air monitoring, and personal exposure monitoring for a mixture of selected hazardous air pollutants (HAPs), i.e., 8 Volatile Organic Chemicals (VOCs) and 6 particle-bound metals in the PM2.5 size fraction; and, (b) examine the relationships between modeling results and monitoring results for exposures to VOCs and metals.
The Twin Cities Hazardous Air Pollution Study, which was funded in part by the 1996 STAR Grant AMeasurement and Source Apportionment of Human Exposures to Toxic Air Pollutants in the Minneapolis-St Paul Metropolitan Area@ (Grant Number R825241; PI: Greg Pratt, Minnesota Pollution Control Agency) focused on dispersion and source apportionment modeling as well as indoor and personal sampling for VOCs. The field portion of the study was augmented with indoor and personal PM2.5 monitoring conducted with funds received as part of a faculty development grant from the University of Minnesota. This previous study had three objectives: 1) to apportion the relative contributions of point, area, and mobile sources to measured ambient concentrations of selected toxic air pollutants, specifically a suite of VOCs in three communities; 2) to apportion the relative contributions of measured ambient concentrations and indoor residential concentrations to measured personal exposures to VOCs and PM2.5; and 3) to examine the relationship between VOC and PM2.5 levels collected at a central monitoring sites in three communities, inside the residences, and by personal exposure monitoring.
Approach:Concurrent measurements of VOCs (benzene, carbon tetrachloride, chloroform, 1,4-dichlorobenzene, methylene chloride, styrene, tetrachloroethylene, and toluene) and PM2.5 were made at a central monitoring site in each community as well as indoors and outdoors at subject=s homes. Residents from three communities, each with different socio-demographics and HAPs source profiles, wore personal VOC and PM2.5 monitors for 6-12 days in 3 seasons between May and November 1999. This new research funds additional analyses and will use the following approaches to examine relationships between different classes of HAPs:
Analyze personal and indoor PM2.5 samples for 6 metals (As, Cd, Cr, Pb, Mn and Ni) using inductively coupled plasma mass spectroscopy (ICP-MS).
Develop an integrated database that merges data on metals concentration with the data from the previous study, i.e., indoor, outdoor and personal VOC concentrations, indoor, outdoor and personal total mass concentration of PM2.5, and outdoor and indoor continuous measures of PM2.5, and time-activity and source questionnaire data.
For these various ambient, indoor, and personal measures of PM2.5 and VOCs, construct models that examine relationships a) between and among metals in the PM2.5 fraction and VOCs, b) between continuous and integrated PM2.5 measures, and c) between ambient measured/modeled levels and indoor and personal measured/modeled levels.
Expected Results:Data on outdoor, indoor, and personal concentrations will be combined with information from time-activity diaries, a socio-demographic questionnaire, and emission inventories to construct a comprehensive data base, which can be used to answer fundamental questions (who? how? what? where? when?) about complex exposures to HAPs mixtures. This database will provide a novel opportunity to develop and test predictive models for estimating human exposure to a combination of VOCs and metals.
Despite the fact that all of us are constantly exposed to a wide variety of low-level chemicals in the air we breathe, for practical reasons most exposure studies have traditionally measured only a single chemical (e.g., benzene) or single class of chemicals (e.g., VOCs). We therefore know relatively little about the magnitude, duration, and frequently of actual exposures to real-world mixtures of HAPs. This study is one of the first to conduct concurrent measurements of outdoor concentrations, indoor residential concentrations, and personal exposures to a mixture of VOCs and metals. Consequently, results will provide a unique chance to investigate how, where, when, and why people are exposed to HAPs mixtures, allowing us to develop improved knowledge and better understanding of cumulative exposures and related health risks. A key feature of the proposed research is the development and verification of models to accurately predict actual human exposures to real-world mixtures of VOCs and metals; a critical step in fostering more realistic risk estimates for HAPs.