Measurement and Modeling of Exposure to Selected Air Toxics for Health Effects Studies and Verification by Biomarkers

EPA Grant Number: R832347C143
Subproject: this is subproject number 143 , established and managed by the Center Director under grant R832347
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).

Center: Health Effects Institute (2005 — 2010)
Center Director: Greenbaum, Daniel S.
Title: Measurement and Modeling of Exposure to Selected Air Toxics for Health Effects Studies and Verification by Biomarkers
Investigators: Harrison, Roy M
Institution: University of Birmingham , Health Effects Institute
EPA Project Officer: Hunt, Sherri
Project Period: April 1, 2005 through March 31, 2010
RFA: Health Effects Institute (2005) RFA Text |  Recipients Lists
Research Category: Health Effects , Air Quality and Air Toxics , Air

Objective:

Air toxics are a diverse group of air pollutants that are known or suspected, with sufficient exposure, to cause adverse health effects including cancer, damage to the immune, neurologic, reproductive, developmental, or respiratory systems, or other health problems. Limited monitoring has been performed by some state and local agencies, but substantial uncertainty regarding exposure to air toxics remains, largely because of their presence in the ambient environment at low concentrations. Although environmental exposures to air toxics are generally low, the potential for widespread chronic exposure and the large number of people who are exposed have led to concerns regarding their impact on public health. Estimation of the health risks of exposure to air toxics is complicated by the fact that there are multiple sources of air toxics. These may be outdoor and indoor (e.g., environmental tobacco smoke, building materials, consumer products, and cooking).

The overall objective of the Investigators was to quantify the magnitude and range of individual personal exposures to a variety of air toxics and to develop models for exposure prediction on the basis of time–activity diaries. The specific research goals were (1) to use personal monitoring of non-smokers at a range of residential locations and exposures to non-traffic sources to assess daily exposures to a range of air toxics, especially volatile organic compounds (VOCs*) including 1,3-butadiene and particulate polycyclic aromatic hydrocarbons (PAHs); (2) to determine microenvironmental concentrations of the same air toxics, taking account of spatial and temporal variations and hot spots; (3) to optimize a model of personal exposure using microenvironmental concentration data and time–activity diaries and to compare modeled exposures with exposures independently estimated from personal monitoring data; (4) to determine the relationships of urinary biomarkers with the environmental exposures to the corresponding air toxic.

Approach:

Dr. Roy Harrison investigated personal exposures to a broad group of air toxics, with the goal of developing detailed personal exposure models that take various microenvironments into account. In order to provide important information on personal exposures to air toxics, the study was designed to capture adequate variation in exposure concentrations. Repeated measurements of exposure to selected air toxics were made for each of 100 healthy adult nonsmoking participants residing in urban, suburban, and rural areas of the United Kingdom expected to have different traffic exposures. Measurements included five repeated 24-hour measurements of personal exposure to volatile organic compounds (VOCs; including 1,3-butadiene), per participant; five urine samples collected to test for urinary biomarkers (polycyclic aromatic hydrocarbon [PAH] metabolites, cotinine, and trans-3'-hydroxycotinine) per participant; and one 24-hour measurement of particle-phase PAHs per participant; plus concurrent measurement of microenvironmental exposures at participants’ homes and workplaces—a total of 200 VOC, 190 1,3-butadiene, and 168 PAH samples, as well as measurements in other major microenvironments. Dr. Harrison developed models to predict personal exposures on the basis of microenvironmental concentrations and data from time–activity diaries, and compared measured personal exposures with modeled estimates of exposure. The goal was to use these data to produce a scheme for categorizing exposure (by compound) according to the location of residence and other lifestyle and exposure factors, including environmental tobacco smoke, for use in the design of health studies of cancer incidence.

Expected Results:

Personal exposures were most heavily influenced by the home microenvironment and were higher in the presence of fossil fuel combustion, environmental tobacco smoke, solvent use, use of selected consumer products, and commuting. After the home microenvironment, the workplace and commuting were the largest contributors to personal exposure. The reported concentrations of selected air toxics and levels of personal exposure were somewhat lower than those observed in other studies.

Investigators used an innovative approach to modeling to predict personal exposures on the basis of microenvironmental concentration data and time–activity diaries, with the idea that models could inform the design of future health studies.The most predictive statistical models did only a fair-to-moderate job of predicting personal exposures, however. Statistical models based on microenvironmental factors and lifestyle were able to explain a fair amount of the variance in personal exposures for selected VOCs but were less predictive of PAH exposures. While part of the inability to effectively model exposures may be due to the lack of measured characteristics of home ventilation, particularly air exchange rates in the home, this study underscores the challenges of accurately predicting personal exposures. Personal exposure monitoring requires extensive time and equipment, but the science is not yet at a point at which exposures to VOCs and PAHs can be reliably predicted from time–activity patterns and microenvironmental concentrations alone.

Supplemental Keywords:

Health Effects, Air Toxics, VOCs, PAHs,  urban air toxics, indoor air, epidemiology, mobile-source air toxics, carcinogens, exposure models, tobacco smoke

Relevant Websites:

http://pubs.healtheffects.org/getfile.php?u=515 Exit


Main Center Abstract and Reports:

R832347    Health Effects Institute (2005 — 2010)

Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
R832347C135 Mechanisms of Particulate Matter Toxicity in Neonatal and Young Adult Rat Lungs
R832347C136 Uptake and Inflammatory Effects of Nanoparticles in a Human Vascular Endothelial Cell Line
R832347C138 Health Effects of Real-World Exposure to Diesel Exhaust in Persons with Asthma
R832347C140 Extended Follow-Up and Spatial Analysis of the American Cancer Society Study Linking Particulate Air Pollution and Mortality
R832347C141 Air Pollution Effects on Ventricular Repolarization
R832347C143 Measurement and Modeling of Exposure to Selected Air Toxics for Health Effects Studies and Verification by Biomarkers
R832347C144 Genotoxicity of 1,3-Butadiene and Its Epoxy Intermediates
R832347C145 Effects of Concentrated Ambient Particles and Diesel Emissions on Rat Airways
R832347C147 Atmospheric Transformation of Diesel Emissions