[Vwdiesel] Unenvironmental Diesels?

[Libbybapa at wmconnect.com]

A friend of mine has had it with his wasserboxer in his vanagon, and is keen 
on conversion.  I happen to own a vanagon converted to a 2.0 I4 jetta motor (I 
didn't do the conversion or it would be diesel).  My friend leans more toward 
gas than diesel primarily because he feels they are more environmental 
(according to EPA).
My understanding has always been that diesels emit more particulates, 
primarily carbon, but those particulates are less Toxic or environmentally unfriendly 
than many of the compounds emitted by gasoline motors.
This is a very important issue for me and I appreciate any input.  Links to 
further applicabe information and sites are greatly appreciated.
Andrew