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EPA New England  Diesel Particulate Matter  What is Diesel
Particulate Matter?  Diesel particulate matter is part of a
complex mixture that makes up diesel exhaust. Diesel exhaust is
commonly found throughout the environment and is estimated by
EPA's National Scale Assessment to contribute to the human
health risk in New England. Diesel exhaust is composed of two
phases, either gas or particle and both phases contribute to the
risk. The gas phase is composed of many of the urban hazardous
air pollutants, such as acetaldehyde, acrolein, benzene,
1,3-butadiene, formaldehyde and polycyclic aromatic
hydrocarbons. The particle phase also has many different types
of particles that can be classified by size or composition. The
size of diesel particulates that are of greatest health concern
are those that are in the categories of fine, and ultra fine
particles. The composition of these fine and ultra fine
particles may be composed of elemental carbon wit