Particulate penetration of the respiratory tract (click for larger image)

Diesel pollution can be broken into two primary sections: gases and particulates. The gases that are damaging directly or indirectly include nitrogen oxides, carbon monoxide and carbon dioxide. The particulates include unburned and partially burned fuel, carbonized solids and more.

Particulate matter is the collective term for the non-gaseous emissions group. These can be solids and/or liquid in droplet form. Particulate matter emissions are principally divided up and categorized by size. The range of particles of greatest concern are the PM10s (particles of 10 nanometers in diameter) and lower as these are readily inhaled and can be absorbed into the blood stream through the lung tissue?

A recent study conducted in North Eastern USA found that black carbon, a constituent of particulate mass in engine exhaust damages the developing brains of children. (See the article in New Scientist magazine.)

Particulates are built up with polycyclic aromatic hydrocarbons (PAH's, also called polynuclear aromatic hydrocarbons) that are produced within the combustion chamber by the incomplete burning of the hydrocarbon fuel. There are sixteen PAH's that are of concern to government bodies such as the US EPA. One of the criteria for listing a PAH as concerning is the effect it has on health.

The polycyclic aromatic hydrocarbon family includes naphthalene. This chemical is known to have a number of impacts on health. One such impact is the destruction of red blood cells, the body's oxygen carriers. This effect leads to fatigue, loss of appetite even jaundice, nausea and blood in the urine. Another impact is the mutagenic and carcinogenic effect of the PAH. Cancers of the nose and lungs have been documented in lab mice exposed to naphthalene as well as adenomas (growths of glandular origin), which typically are benign but can become malignant.

In addition to the above grave issues many of these particulates are irritants. When inhaled they can irritate the walls of the air passages. This causes the asthma like symptoms of swollen tissue and excess mucus production, both of which inhibit respiration. Prolonged exposure is believed to contribute to the development of asthma in both children and the elderly. Some asthmatics find that exposure to diesel exhaust can initiate attacks of varying severity.

Both D3 and G1 reduce particulate emissions. For more details of this see 'How It Works'