Testing of a Model to Predict Human Exposures to Aldehydes Arising from Mobile and Point SourcesEPA Grant Number: R826787
Title: Testing of a Model to Predict Human Exposures to Aldehydes Arising from Mobile and Point Sources
Investigators: Raymer, James H. , Akland, Gerald G. , Clayton, C. Andrew , Johnson, Ted , Pellizzari, Edo D.
Current Investigators: Raymer, James H. , Akland, Gerald G. , Clayton, C. Andrew , Johnson, Ted , Michael, L. C. , Pellizzari, Edo D.
Institution: Desert Research Institute , TRJ Environmental Inc.
EPA Project Officer: Chung, Serena
Project Period: October 1, 1998 through September 30, 2002 (Extended to September 30, 2003)
Project Amount: $629,841
RFA: Urban Air Toxics (1998) RFA Text | Recipients Lists
Research Category: Air Quality and Air Toxics , Air
The main objective of the proposed program is to estimate human exposure to target aldehydes (formaldehyde, acetaldehyde, acrolein, propionaldehyde, butyraldehyde, crotonaldehyde, glyoxal, methylglyoxal) by means of microenvironmental and personal exposure monitoring for two urban areas. The main hypothesis to be tested is that a mathematical model (pHAP) can be used to predict personal exposure distribution to aldehydes. Additional hypotheses to be tested are that (a) personal exposure levels of aldehydes exceed outdoor concentrations; (b) indoor aldehyde concentrations exceed outdoor concentrations; and (c) the composition of oxygenated fuel results in significant differences in population exposures to aldehydes.
The primary objective of this study is to estimate the distribution of aldehyde exposures to residents living in two areas to determine if they are or are not impacted differently by the choice of oxygenated fuels used by mobile sources. Milwaukee, Wisconsin (because of the use of ethanol in the gasoline) and Sacramento, California (because of the use of methyl t-butyl ether or MTBE) have been chosen for the field studies. These two field studies, to be conducted for approximately 40 days each during the summers of 1999 and 2000, are both directed towards acquiring representative personal monitoring data which will be used to estimate the exposures of urban and suburban residents to selected aldehydes, VOCs, and carbon monoxide (CO). Aldehydes will be sampled using DNPH silica cartridges, VOCs (ethanol, MTBE, benzene, toluene, xylenes) will be sampled using sorbent tubes, and CO will be measured using real-time monitors. Through the collection and analysis of VOCs and CO in addition to the aldehydes, the design will permit a source apportionment of the aldehyde contribution to exposure that originates from direct emissions from mobile sources, those which are photochemically produced from mobile source emissions, combustion processes, and contributions of other sources and environments which also contribute to these exposures. The field design is model-based, that is, the monitoring field data are gathered for input into the model or to test and validate modeled predictions. Measured and predicted exposures will be compared for determining uncertainties of the modeled exposures.
Each field study will have two components. In the first component, integrated personal exposures for 40 volunteers will be measured once during a summer season. This study is similar in design to other personal exposure studies except that the volunteers will be randomly chosen according to selection criteria related to location of residence. The study population will be matched to the extent possible by age, race, sex as determined by the Census Bureau statistics, and according to spatial gradients away from the downtown area. Twenty four-hour measurements of the corresponding indoor and outdoor concentrations at the residence of each subject will also be made. In the second component the exposures of a technician to the same set of pollutants will be measured as the technician follows a set of prepared instructions, called scripts, to follow throughout the day. These scripts outline the activities and microenvironments to which the technician will be exposed on a given day, e.g., commuting downtown, driving in street canyons, walking inside, walking outdoors around a commercial area away from a roadway. The script provides instructions to the technician specifying (1) the duration of an air sample to be taken during each sampling period, (2) the general and microenvironmental location during the sampling period, and (3) the general activities undertaken during the period. Personal exposure monitors (aldehyde-DNPH, VOCs, and CO) will be used to measure 1-hr and 12-hr exposures to each compound as the technician simulates the activity patterns of typical city residents. Using the data generated from the scripted study and information about the activities of the study participants in the personal monitoring study, the exposures will be predicted using pHAP and compared to those measured.
Results of this research will be a characterization of aldehydes in urban microenvironments important to potential human exposure, information about the sources of aldehydes in the various microenvironments, information about personal exposures of individuals to aldehydes, the linkage of microenvironmental aldehyde concentrations to human exposures using a mathematical model, and suggesting improvements to the model.
Improvement in Risk Assessment or Risk Management: The personal exposure data and the microenvironmental data collected during the study will provide information about aldehyde exposures otherwise not available in the scientific literature, determine the extent to which these exposures might pose a health risk, and based on the study design, address the uncertainties of modeled exposures based on microenvironmental concentration data.