Today's air pollution mix is different from that which plagued the industrial world 70 years ago. The historic culprit was coal burnt in homes, factories and power plants; you could smell it and see it in the tiny bits of carbon or unburned fuel that collected on clothes. Air Pollution now is colorless, odorless and tasteless, and mainly comes in particles so small they can pass through facemasks.
Exposure to particles is linked to higher levels of respiratory and cardiovascular disease, chronic bronchitis, acute asthma, decreased lung function, lung inflammation, cancer, reduced birth weight, infant mortality and premature death in adults. More than 7 million deaths, or one in eight of all deaths, are linked to it according to the World Health Organization (WHO).
The Problem with Particulate matter
Particulate matter (PM) is formed by the incomplete combustion of fossil fuels, biofuels, and biomass. Diesel engines emit large amounts of fine PM. 90 % of these particles are less than 1 micron in diameter, too small to see (by contrast, the typical human hair is about 70 microns in diameter). These tiny particles evade our respiratory defenses and get stuck in the deepest recesses of our lungs, where they can cross into the bloodstream.
Diesel particles carry Black Carbon (BC) and toxic heavy metals, sulfates, and dozens of other chemicals known to cause cancer, including arsenic, benzene, and formaldehyde. PM2.5 from traffic, especially from diesel engines, is the predominate pollution source in cities. PM2.5 is the most dangerous pollutant to human health. The size of particulates is directly linked to their potential to cause health problems.
Diesel is also a major environmental hazard, resulting in 20-25% of the world's black carbon (BC). BC is the second most powerful man-made contributor to global warming, accelerating the melting of Arctic ice and mountain glaciers worldwide, and has been found to contribute to climate change twice as much as previously estimated.
BC influences climate through multiple mechanisms:
* Direct effect: BC absorbs both incoming and outgoing radiation of all wavelengths, which contributes to warming of the atmosphere and dimming at the surface.
* Snow/ice effect: BC deposited on snow and ice darkens the surface and decreases reflectivity, thereby increasing absorption and accelerating melting.
* Other effects: BC also alters the properties and distribution of clouds, affecting cloud reflectivity and lifetime ("indirect effects"), stability ("semi-direct effect"), and precipitation.
It's a global problem - Europe
* In Europe one reason for the increased air pollution is that there are now far more diesel cars.
* Gasoline engines emit large amounts of CO and relatively small amounts of particulate matter, while diesel engines do the opposite. Diesel engines also co-emit other pollutants including nitrogen oxides (NOx), sulfur dioxide (SO2) and organic carbon.
* 50% of NOx in European countries is from traffic sources (up to 80% at highly polluted sites)
* Diesel cars have spread on the streets resulting in 20 fold NOx emissions compared to it's alternative (gasoline).