My understanding from articles that I have read in various newpapers over the years, (Not that makes the content factual or accurate in anyway) was that USofA and California regulatory agencies take a different approach then their European counterparts.The Europeans overlook some of the pollution output of diesels in exchange for their efficency, where as our regulatory agencies (EPA, and CARB) tend to be more restrictive concerning the range and quanity of pollutants emitted from cars in general and especially diesels.

It seems that each subsequent study of diesel particulates, finds that they are worse then previously thought, and that certain size particulates thought to be relatively "inert" are pretty harmfull in how and where they lcan odge in the lungs.

I am just sharing the "Big picture" that I have gotten from the mass media, wether it is correct, factual, etc. I have no idea, but it seems to be pretty consistantly repeated.

As for the issues mentioned by many poster in this thread concerning CARB and the EPA, you may be correct, all I know is that when I use to visit/drive in LAX region in the early 80's, I physically would get sick, and you could rarely see the mountains around L.A. even when you could, you could not take a picture of them, as a camera could not pick the image up, through the smog filter. It am told it was common place for CHP officers to get a "Black Lung" type disease from breathing in all the pollutants present on Southern California freeways. Having lived in L.A. in the late 90's I cannot believe just how much cleaner the air appeared at that time. This improvement came with more people crowded into roughly the same area, far more cars on the road, being driven more miles then before. Something has made a dramatic improvement in the quality of peoples lives in this region of America.

Not trying to start a pissing match here, just some food for thought.