The Northern Front Range Air Quality Study concluded that for the Denver metropolitan area during 1996 and 1997, 55% of particles with an aerodynamic diameter 50% cutpoint of 2.5 μm (PM2.5) were attributable to motor vehicle exhaust particulates. The health effects of PM2.5 are currently unknown, but are under investigation. It is of vital interest to understand the chemistry, morphology, size distribution and microstructure of motor vehicle exhaust. The techniques of transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS) appear to be well suited for the analysis of the microstructure, morphology and microchemical composition of particulate matter. Previous electron microscopy observations of particulate matter from a variety of sources have found that the chemical composition and crystal structure are characteristics of the source of the particles.
As part of an ongoing research project into the health effects of motor vehicle particulate matter, Southwest Research Institute (SWRI) is performing chassis dynamometer tests of a variety of vehicles and collecting samples from the exhaust stream for analysis.