NOx and PM

Emission limits cover in particular nitrogen oxides (NOx) and particulate matter (PM) which pose the most serious health problems. NOx can lead to respiratory illnesses and contributes to acid rain. Particulate matter can come from many sources. Generally, any activity which involves burning of materials or any dust generating activities is a source of PM. Vehicles of all types produce particulates. PM can be found in the air in different sizes, for instance 10 microns in diameter (PM 10) or 2.5 microns in diameter (PM 2.5). The latter are particularly harming for the human body as they are small enough to get inhaled.

PM can alter the body's defence systems against foreign materials, damage lung tissues, aggravate existing respiratory and cardiovascular disease, and can lead to cancer. PM of 10 or 2.5 microns and less can pass from the lung into the blood supply. These particles are dangerous because the body has no efficient mechanisms for removing them.

Diesel vs. Petrol

Diesel cars used to be considered cleaner than gasoline cars because they emit significant less carbon dioxide (CO) due to their lower fuel consumption. However, emissions of NOx and PM from diesel vehicles are higher than those for petrol vehicles. They are considered to pose the most serious health and environmental problems and are therefore at the core of emission control legislation. Emissions standards therefore tend to concentrate on petrol vehicles, allowing diesel cars much higher levels of noxious fumes such as NOx and PM. more >>