ARB Research Seminar

This page updated July 26, 2013

Emissions of Toxic Pollutants From Compressed Natural Gas and Ultra-Low Sulfur Diesel Fueled Transit Buses With and Without After-Treatment Devices

Norman Kado, Ph.D., Air Resources Board and University of California, Davis; with Paul Rieger, Air Resources Board

October 24, 2003
Cal EPA Headquarters, 1001 "I" Street, Sacramento, CA



A series of studies were conducted to determine the toxic particulate matter (PM) and vapor-phase emissions from heavy-duty transit buses powered by compressed natural gas (CNG) and new ultra low sulfur diesel (ULSD) fuel formulations. Chemical analyses for toxic pollutants and biological analyses for mutagenic activity were conducted on both CNG-fueled and ULSD-fueled heavy-duty transit buses tested on a chassis dynamometer over three transient driving cycles and a steady-state cruise condition. In the initial study, the CNG bus had no after-treatment device. The diesel bus was first equipped with an oxidation catalyst (OC) and then with a catalyzed diesel particulate filter. Emissions were analyzed for PM, volatile organic compounds, polycyclic aromatic hydrocarbons (PAHs), and mutagenic activity. In a subsequent study, the CNG bus was equipped with an OC, and the emissions were analyzed for these same components over two test cycles. The results from these studies will be discussed.

Speaker Biography

Norman Kado received his Ph.D. from the University of California, Berkeley, Department of Biomedical and Environmental Health. Dr. Kado is a Staff Toxicologist in the Health Exposure Assessment Branch of the Research Division, Air Resources Board and an Associate Adjunct Professor in the Department of Environmental Toxicology, University of California, Davis. Dr. Kado's research interests include environmental toxicology of air pollutants and exposure analyses of pollutants.

Paul Rieger received his Masters of Science Degree in Chemistry from the California State University at Los Angeles. Mr. Rieger is the Chief Chemist of the Southern Laboratory Branch (SLB) of the Air Resources Board where he oversees the development and implementation of test methods for the measurement of pollutants in motor vehicle exhaust. Currently, the SLB is building a laboratory to measure the toxic components of PM in motor vehicle exhaust.

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