by Josephine Polifroni

Created on: June 03, 2010   Last Updated: June 04, 2010

It is easy to recognize a vehicle running on diesel fuel. Those black, sooty clouds puffing out and falling to the ground make them instantly recognizable. Diesel is the fuel of choice for millions of buses, trucks and automobiles worldwide. In addition, it is used in numerous off-road applications: in locomotives, agricultural equipment, construction and mining equipment, as well as commercial marine vessels.

Diesel is the fuel of choice for so many applications because it is reliable and cheap. It requires 25% -50% less fuel per mile than gasoline powered engines and therefore emits that much less CO2, (carbon dioxide), a known greenhouse gas.

It also burns more completely than gasoline for lower hydrocarbon and carbon monoxide emissions, but this does not mean it is problem free.

The problems for the environment with diesel are multi-layered as there are the initial chemical compounds emitted that then cause further reactions for a final, bewildering toxic soup that is bad for the environment and our health. Off-road engines are a particular problem, as they do not have state-of-the-art emission controls.

Overall, as an outdoor air pollutant, diesel exhaust is a leading cause of lung cancer, adding more risk than every other pollutant combined. Previous studies did not target diesel as a possible leading cause but more detailed studies have revealed diesel exhaust as a potent carcinogen

Diesel spews particulate matter that is especially small, <2.5 microns (compare to a human hair at 70 microns) that make it easy to inhale into the deepest part of the lungs. The small size of this particulate matter makes it easier to attract other toxic substances, such as nitrogen oxide, increasing the toxic effect. Particulates from diesel, soot or carbon particulates, because of their dark color, absorb heat and contribute to global warming.

Studies link this particulate matter to heart and lung problems, aggravating asthma, causing cancer and leading to premature mortality.

Diesel is responsible for a significant portion of the total NOx (nitrogen oxide) emissions in the U.S., particularly from off-road engines. NOx is a gas, a component of ground-level ozone and easily combines with particulates to form reddish-brown smog, leading to reduced visibility.

NOx also contributes to acid rain, the depletion of oxygen in lakes and streams and upsets the chemical balance necessary for aquatic wildlife to thrive. Some studies suggest these imbalances may be responsible for

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