2001 Progress Report: 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 Period Covered by this Report: October 1, 2000 through September 30, 2001
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 this research project 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: (1) personal exposure levels of aldehydes exceed outdoor concentrations; (2) indoor aldehyde concentrations exceed outdoor concentrations; and (3) the composition of oxygenated fuel results in significant differences in population exposures to aldehydes.
Sample analysis continued and was completed for the Milwaukee phase of the study and work on the database continued. Enhanced effort on completing the Sacramento database and, later in the year, the Milwaukee database was put forward, given the needs of the American Petroleum Institute (API) and the additional funding provided by the Environmental Protection Agency (EPA) for this purpose.
Prior to the completion of the statistical analysis and stepwise linear regression analyses planned, some summary statistics were prepared for the scripted studies for both aldehydes and volatile organic compounds (VOCs) in all of the Sacramento and Milwaukee microenvironments. To better compare microenvironments across the two study locations, the sum of all of the aldehydes and of the VOCs in each microenvironmental sample was calculated to represent a "total" aldehyde or VOC amount. These total values were analyzed to permit the evaluation of those microenvironments that contribute the greatest to the total exposures. Total aldehyde concentrations as a function of microenvironment for Sacramento and Milwaukee are shown in Figures 1 and 2, respectively. In each figure, the number at the top of each bar represents the number of measurable values across the microenvironmental setting. The locations with the highest median total aldehyde concentrations in Sacramento were indoors at a residence (median approximately 98 µg/m3), indoors at a restaurant (median approximately 60 µg/m3), and indoors at a grocery store (median approximately 50 µg/m3). In Milwaukee, the highest median concentrations were measured indoors at a grocery store (approximately 43 µg/m3), indoors in a public building (approximately 36 µg/m3), and indoors at a restaurant (approximately 25 µg/m3).
Figure 1. Total Aldehyde Concentrations as a Function of Microenvironment. Numbers above the bars indicate the number of measureable values across all microenvironments of that type.
Figure 2. Total Aldehyde Concentrations as a Function of Microenvironment. Numbers above the bars indicate the number of measureable values across all microenvironments of that type.
Tables 1 and 2 show a breakdown of analytes for both cities in a high-exposure microenvironment (see Table 1, restaurant), and a much lower exposure microenvironment (see Table 2, outdoors within 10 yards of a street). The data of Table 1 show similar aldehydes in both cities, yet much higher concentrations of acetaldehyde measured in Sacramento restaurants as compared to those in Milwaukee; acetaldehyde and formaldehyde are responsible for the majority of the total concentrations. Acetaldehyde is the initial metabolite of ethanol and is likely exhaled by individuals drinking alcohol. It also is known that various aldehydes are produced as a result of deep-frying foods or cooking foods in hot oil, as in stir fry. Table 2 shows that aldehydes also were higher in Sacramento than in Milwaukee at outdoor locations near a street. The significance of these differences will be examined more closely in future work.
a Not applicable
a Not applicable
b Not Detected
The VOC concentrations measured in the scripted studies also were much higher in Sacramento than in Milwaukee. In Sacramento, the highest median values were measured indoors at a restaurant (approximately 580 ng/L), outdoors at a service station (approximately 760 ng/L), and indoors at a residence (approximately 440 ng/L). Maximum values of 9,100 ng/L and 2,900 ng/L were measured indoors at a restaurant and outdoors within 10 yards of a street, respectively. In Milwaukee, the highest median concentrations were measured indoors at a public building (approximately 130 ng/L), although there were only two of these microenvironments; indoors at a grocery store (approximately 95 ng/L), and indoors at a restaurant (approximately 40 ng/L).
A closer comparison was made of the VOCs in two microenvironments. In the restaurants, ethanol was the predominant VOC (490 ng/L in Sacramento; 71 ng/L in Milwaukee) and was probably the result of the consumption of alcoholic beverages. Methyl t-butyl ether (MTBE) concentrations also were much higher in Sacramento and are consistent with the use of gasoline containing MTBE. In the outdoor microenvironments near a street, ethanol (260 ng/L) and MTBE (29 ng/L) were the main VOCs from the Sacramento study. Although MTBE would be expected in Sacramento given that MTBE was used as a fuel additive at that time, the reason for the large amount of ethanol is unclear. Except for the one measurement of MTBE (43 ng/L) in Milwaukee, all other VOCs were unremarkable.
During the fourth year of the project, we will: (1) complete entries of metadata into the database (quality assurance of entries); (2) complete questions for API; (3) resume and complete statistical analysis of combined Sacramento/Milwaukee database; and (4) prepare the final report.