Grantee Research Project Results
2000 Progress Report: Transformations of Selected Organic Urban HAPs: Mechanistic and Modeling Studies to Identify Cancer and Non-Cancer Human Health Risk
EPA Grant Number: R826247Title: Transformations of Selected Organic Urban HAPs: Mechanistic and Modeling Studies to Identify Cancer and Non-Cancer Human Health Risk
Investigators: Jeffries, Harvey E. , Chien, Chao-Jung , Sexton, Ken , Liu, Xiaoyu
Current Investigators: Jeffries, Harvey E.
Institution: University of North Carolina at Chapel Hill
EPA Project Officer: Chung, Serena
Project Period: December 8, 1997 through December 7, 2000
Project Period Covered by this Report: December 8, 1999 through December 7, 2000
Project Amount: $540,000
RFA: Ambient Air Quality (1997) RFA Text | Recipients Lists
Research Category: Air Quality and Air Toxics , Air
Objective:
The three objectives of this project are to: (1) advance fundamental knowledge of atmospheric transformation of organic hazardous air pollutants (HAPs)?initially, 1,3-butadienes, aromatics and epoxides will be studied and, in subsequent years, this will expand to other HAPs; (2) include the large variety of organic HAPs in modern air quality models by extensions of the newly developed "morphecules" concept; and (3) design and prepare a HAPs mixture of testing HAPs behavior in an urban-like environment and for evaluating the allomorphic/morphecule representation and other mechanisms for air quality models.Progress Summary:
Progress has been made in several areas, including: (1) HAPs emissions data have been obtained from several sources, and HAPs mixtures have been designed for smog chamber tests; (2) smog chamber tests have been conducted with the HAPs mixtures; (3) chemical analysis by gas chromatography and mass spectrometry show many products from transformation of key HAPs and HAPs mixtures; and (4) mechanism development and modeling studies have been conducted with previous experiments.Design of HAPs Mixtures: Types of Mixtures and Composition Tables. Several sources of information, which can be used to determine relative composition of ambient toxic chemicals, were consulted. These include reports published by and accessible from the EPA (see Relevant Web Sites below), such as the Toxic Release Inventory (TRI), the EPA Integrated Urban Toxics Project (EPA HAPs List), and the National Vehicle Toxics Emissions project. The resulting mixtures designed and used for smog chamber tests are shown in a table in the University of North Carolina (UNC) Web site listed below. While the composition is based on the published reports data, the exact composition of the mixtures is not critical as long as it is known and can be specified in simulation models, and resulting yields of products can be determined relative to the starting parent compounds. The goal was to conduct experiments with known major HAPs in chamber experiments; the first of these should not be too complex and should reflect relative contributions, based on mass or toxicity, found in the atmosphere. Most of the HAPs are constituents of the SynUrban mixture, which is based on the EPA's national ambient volatile organic compound (VOC) measurements also used to conduct experiments for this project. Also, individual aldehyde HAPs were compared directly with the SynUrban mixture to check the light assumptions used to model these experiments and to study some important HAPs, which have never been studied individually before.
Chamber Experimental Results Using HAPs Mixtures, Including Decay Rates and Transformation to Other Products: Smog Chamber Experiments. Tables at the UNC Web site for this project list the chamber experiments conducted during this last year, including both those using individual HAPs and the HAPs mixtures. The experiments are daytime ones starting at sunrise and lasting for about 10 hours, or nighttime ones to study chemistry without photolytic processes. Results for each experiment are in a file containing documentation and physical and time-concentration data. Each experiment listed in the tables is linked to a plot of the time-concentration data for NOx and O3, and basic physical data of sunlight, temperature, and dewpoint. The smog chamber facilities are described in another hypertext link and in a downloadable document.
Data processing is continuing, including analysis of mass spectra of products formed during the chamber experiments' photochemically induced transformations of the parent HAPs. Photooxidation or decay rates of the parent HAPs will be compared relatively to the more studied HAPs as well as absolutely to known OH rates as a way to determine the presence of other significant chemistry.
Mechanism Development and Modeling Studies of Previous Experiments. Modeling efforts to date have focused on individual HAPs, such as the dienes and their major products, and the aromatic 1,4 unsaturated dicarbonyl products. Progress and success are mixed. As an example, the simulations are good in reproducing the experimental observations for the parent hydrocarbons in the case of dienes and their primary products such as methacrolein, but the simulations of the organic acids are under-predicting the observations (in which we have high confidence). Progress has been made in the testing and further development of the chemistry of the 1,4 unsaturated dicarbonyl products, and it is clear that more experimental work is needed.
Conclusions, Research Needs Identified, and Recommendations for Future Work. We have shown that the use of bench-top gas chromatography and mass spectrometry systems coupled to smog chambers provide realistic photochemical experiments, allow for the discovery of new HAPs oxidation products, and contribute to the understanding of the atmospheric fate of these compounds under conditions more like the atmosphere. However, the use of these systems requires pure standards for confirmation of compound identity and quantification. Synthesis of proposed and known, but commercially unavailable, product compounds are needed for this purpose and for additional study. Additional studies needed with these synthesized compounds include chamber experiments of the individual compounds and in mixtures, basic kinetics, and photolysis absorption cross-sections and quantum yields determinations.
Computer simulations of some of the experiments conducted for this project have shown that the current state of knowledge is fairly good for simulating the primary oxidation of the parent HAPs and formation of several major products, and incomplete and unsuccessful for other major products.
Future Activities:
The future activities will include preparing the final report and publications.Journal Articles:
No journal articles submitted with this report: View all 13 publications for this projectSupplemental Keywords:
atmospheric degradation, oxidation products, polar products, aromatic products, toxic products of atmospheric HAPs, fate of atmospheric HAPs., RFA, Health, Air, Toxics, air toxics, HAPS, Risk Assessments, tropospheric ozone, cancer risk, ambient air quality, atmospheric, fate and transport, health effects, model, monitoring, risk, risk assessment, urban air toxics, urban air, exposure and effects, air pollutants, aldehydes, morphecules, outdoor smog chamber, ketone, air quality models, ambient air, hazardous air pollutants, air quality criteria, ambient monitoring, atmospheric transformation, chemical composition, modeling, smog, urban air pollutants, air pollution models, air quality data, human exposure, cancer, carcinogens, hazardous air pollutants (HAPs), urban air pollution, epoxides, ketones, environmental effects, human health, photochemical reaction mechanism, cancer risk assessment, molecular biology, 1, 3-Butadiene, atmospheric chemistry, transportRelevant Websites:
http://airchem.sph.unc.edu/research/projects/epaprojects/thaps/
Exit
http://toxnet.nlm.nih.gov/ Exit
Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.