I like the idea of diesels, I might even consider one as my next purchase. However, there is some information that is also important to think about other than CO2 emissions.

'The improved efficiency of diesel engines can also help reduce oil consumption. It should be noted, however, that it takes about 25% more oil to make a gallon of diesel fuel than a gallon of gasoline, so we should really look at how a vehicle does on fuel efficiency in terms of 'oil equivalents.' Thus, we need to adjust the mileage claims for diesel vehicles downward by about 20% when comparing them to gasoline-powered vehicles.'

'But when it comes to smog-forming pollutants and toxic particulate matter, also known as soot, today's diesels are still a lot dirtier than the average gasoline car.

TIERY-EYED

US tailpipe standards for diesel cars, which have historically been weaker than those for gasoline cars, are being updated to force diesel and gasoline vehicles to meet the same set of emissions standards. The tiered structure of the new 'Tier 2' standards, however, allows automakers to produce some cars that release two times more soot and smog-forming pollution than the average new vehicle and still meet their targets. Also, until the standards are fully implemented in 2009, existing loopholes allow some cars to pollute even more.

There are three size categories of soot particles:

* Large soot particles (>10 microns) deposit from the air into your nose, throat, and lungs, causing coughing and irritating your throat, and are ejected from your body through sneezing, coughing, and nose blowing.
* Coarse soot particles (~10 microns) are inhaled into your windpipe and settle there, causing more irritation and more coughing.
* Fine and ultra-fine soot particles (less than 2.5 microns) are the most successful at invading your body—they're small enough to travel deep into your lungs. Once there, these soot particles can irritate and mutate the most sensitive tissues in your lungs, your alveoli. These air sacs exchange oxygen and carbon dioxide from the air you breathe with blood in your capillaries, thus allowing your circulatory system to carry oxygen to the rest of your body. Soot particles, however, make this task more difficult because they cause inflammation and scarring of the alveoli. This also strains your heart because it must work harder to compensate for oxygen loss.

Soot also finds other ways to harm your body, including:

* chronic bronchitis,
* asthma,
* reduced ability of respiratory system to fight infections and remove foreign particles, and
* cancer.

All this means that diesel pollution can be deadly, causing premature mortality through cancer or heart and respiratory illnesses. The California Air Resources Board has concluded that diesel soot is responsible for 70% of the state's risk of cancer from airborne toxics. In the population as a whole, studies have shown a 26% increase in mortality in peopl