Project at a Glance

Title: Development of integrated bioassay and chemical methods to characterize heavy-duty diesel exhaust. Final report.

Principal Investigator / Author(s): Hsieh, Dennis

Contractor: UC Davis

Contract Number: 92-342 & 94-335

Research Program Area: Emissions Monitoring & Control, Health & Exposure

Topic Areas: Health Effects of Air Pollution, Mobile Sources & Fuels, Toxic Air Contaminants


The emissions from heavy-duty diesel-powered vehicles contains both particle and vapor-phase associated compounds. With respect to particulate matter (PM), diesel-powered vehicles are a major source in California. PM has especially been studied for potential adverse health effects to humans. Almost all diesel PM emitted is smaller than 10 m (PM 10) aerodynamic diameter and typically submicron in size. These particles can penetrate the deepest portions of the human lung, and in turn can lead to adverse health effects such as respiratory problems, mortality, and association with cancer. Diesel PM is considered a probable human carcinogen, and a complex mixture of toxic compounds can be adsorbed to these particles. Although many toxicological studies have focused on diesel PM, few studies have focused on vapor-phase toxic compounds, especially those emitted from the combustion of fuels available in California. These vapor phase compounds are more volatile than those typically found in the particulate phase. We investigated the particle-and vapor-phase emissions from a heavy-duty diesel engine using a California Pre-October 1993 fuel (Fuel 1) and a newer fuel (Fuel 2) that was available from the MTA storage tanks during the Main Study sampling period in March 1995. Emissions were collected under the controlled conditions of an engine dynamometer and dilution tunnel (a facility where engine exhaust is diluted and measured). The particle-and vapor-phase emissions were chemically analyzed using gas chromatograph/mass spectral (GC/MS) analyses and by bioassay using a Salmonella microsuspension assay. For the particulate-phase, the mass of PAHs per mass of particulate matter (g/g), or concentration of PAH were determined for a series of 15 PAHs, and from this value, emissions (g PAH/mg PM) of most of the PAHs in the particle phase was higher for Fuel 2 emissions. When the emission values for the PM samples were calculated, emissions of pyrene and benzo[a]pyrene were approximately 30% higher from the use of the Fuel 2 than from use of Fuel 1. Overall, for both fuel types, the highest relative emissions were for phenanthrene and pyrene. For the vapor-phase, numerous PAHs and PAH containing substituent groups were detected.

For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753

Stay involved, sign up with CARB's Research Email Distribution List