211B Research Group
Cars with diesel vs gasoline

TIER 1 REPORTS

To address the Tier 1 requirements, the Research Group and its contractor conducted a literature search of available health studies on substances in diesel exhaust, gasoline exhaust, and gasoline evaporative emissions. The Research Group also sponsored vehicle emissions testing for the gasoline baseline and non-baseline F/FAs, and conducted a literature review to characterize diesel exhaust emissions from heavy-duty vehicles.

To partially fulfill Tier 1 requirements, the Research Group contracted with EA Engineering, Science, and Technology, Inc. to conduct a literature search of available studies for health and welfare effects of substances in diesel exhaust, gasoline exhaust, and gasoline evaporative emissions (substances listed in Executive Summary – Tier 1 Chemicals ).  Relevant databases were searched back either 30 years or to their origins for health or welfare effects information on the following emission entities: diesel fuel exhaust, gasoline evaporative emissions, and gasoline exhaust, as the three primary emissions; select fractions or classes of compounds (16) associated with these emissions (ethers, alcohols, hydrocarbons, ketones, and aldehydes as "speciated emissions" along with 11 select naphtha fractions); and 173 individual chemicals found in these primary emissions.

For approximately 20 chemicals that had a large volume of information in the open literature, comprehensive reviews were used to identify prior relevant studies, with literature searches providing information on more recent, post-review studies. Unpublished studies provided by Research Group member companies were also reviewed. Information from studies identified as relevant and appropriate was then extracted to summary tables. Up to 15 combined health and welfare effects tables may exist per chemical or primary emission covering a wide variety of health or welfare effects.  Study summaries were organized into a single report and submitted to EPA (EA Engineering, 1997 ) along with completed copies of the underlying articles/studies.

In addition to the above described research on health effects of the primary emissions, the Research Group contracted with Southwest Research Institute to conduct vehicle emissions testing for the gasoline baseline and non-baseline F/FAs, and conduct a literature review to characterize diesel exhaust emissions from heavy-duty vehicles.

  • For diesel F/FA, an in-depth literature search concluded that sufficient data exist in the public domain to meet the requirements for the characterization of exhaust emissions from heavy-duty diesel vehicles, under 40 CFR Part 79, §79.52 (Southwest Research, 1996).
  • For the gasoline F/FA, exhaust and evaporative emission measurements were conducted using a 1996 Toyota Camry operating on a baseline ("industry average," RF-A) gasoline and six oxygenate/gasoline splash blends. The exhaust emissions portion of the test matrix consisted of triplicate Federal Test Procedure (FTP) emissions tests with the vehicle operating in each of three different configurations. The three configurations included: (1) original equipment manufacturer's configuration; (2) without catalytic converter; and (3) without evaporative emission canister (Southwest Research, 1997).
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