Found this on the net:
CHARACTERISTICS OF DIESEL EXHAUST
Diesel fuel is a mixture of many different hydrocarbon molecules. The combustion, both complete and incomplete, of diesel fuel forms a complex mixture of hundreds of organic and inorganic compounds in the gas and particle phases.
Gaseous Components of Diesel Exhaust:
Carbon dioxide
Oxygen
Nitrogen
Water vapor
Carbon monoxide
Nitrogen compounds
Sulfur compounds
Low-molecular-weight hydrocarbons
Toxicologically Relevant Gaseous Components:
Aldehydes (formaldehyde, acetaldehyde, acrolein)
Benzene
1,3-butadiene
Polycyclic aromatic hydrocarbons (PAHs)
Nitro-PAHs
Particulate Component of Diesel Exhaust (Diesel Particulate Matter - DPM):
Elemental carbon
Adsorbed organic compounds
Small amounts of sulfate, nitrate, metals, and other trace elements
Toxicologically Relevant Compounds Adsorbed on DPM surfaces:
(PAHs and their derivatives are adsorbed on the surface DPM
(Figure 1)
Polycyclic Aromatic Hydrocarbons
Nitro-PAHs
Oxidized PAH Derivatives
(For in-depth analysis of these DE components, go to this link:
http://oaspub.epa.gov/eims/eimscomm.getfile?p_download_id=36255 )
The components of diesel exhaust (DE) emissions are a public concern for the following reasons:
* Emissions from diesel engines include over 40 substances that are listed by the EPA as hazardous air pollutants.
* Components of DE contain potential cancer causing substances such as arsenic, benzene, formaldehyde, nickel, and PAHs.
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* The diesel particulate matter (DPM) is very small (90% are less than 1um by mass), making DPM easy to respire into the deep lung.
* DPM has hundreds of chemicals adsorbed to their surfaces, including many known or suspected carcinogens.
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* There are many irritants and toxic chemicals in the gaseous phase of DE.
* Oxides of nitrogen, component of urban smog, are in the gaseous phase of DE.
* There is a likelihood that people in both ambient and occupational settings can be exposed to DE.
* DE has the potential to cause adverse health effects including cancer, pulmonary and cardiovascular diseases.
* Studies show workers exposed to higher levels of DE are more likely to develop lung cancer.
* In 1990, the state of California identified DE as a chemical known to cause cancer.
* The International Agency for Research on Cancer has concluded that DE probably causes cancer in humans.
* The EPA has proposed classifying DE as a probable human carcinogen.
Despite all of these concerns, it is difficult to understand the nature of DE and to measure the exposures from DE and it壮 health effects with certainty. DE is only one of various sources of particulate matter and gaseous air pollution in the atmosphere and workplace. Though the evidence is persuasive that DE has the potential to cause adverse health effects, there are uncertainties. There are gaps and assumptions in the data about human exposures to DE. An assessment of how the physical and chemical nature of past exposures compare to current exposures is not possible since available data are not sufficient. Also, much is not known about DE toxicity and carcinogenicity in humans. DE exposure could have synergistic or additive behaviors occurring with exposures to other air pollutants. More definitive data and more research is needed to improve our understanding of the nature of DE, DE exposure, and potential human health effects to DE. And finally, it is difficult to assess DE exposure because of improvements in engine design, fuel grade, and emissions technology relating to the nature of DE.
