Here is link to a French car magazine study results : http://www.automobile-magazine.fr/ac...e_pollution__1
(sorry, it's in French)

the car ranking is based on their true environment impact, that includes CO2 and even the other bad gazous stemed from the fuel combustion.
This study was made in order to criticize French CO2 bonus policy : French custumers obtains an ecologic bonus when they buy a "green" car which has a low CO2 emission, but this policy takes into account only the CO2 and not all the pollutant agents.... My regret : they didn't study the Toyota Prius gaz emissions.

This study shows big differences between the "official" ranking and the real one ! as an example : The ADEME (understand the French agency for energy) gives the Smart fortwo cabrio 0,8 dci 45 ch FAP as the best Diesel car, but this study ranked it only 138th...

PS : sorry for my poor and bad English...

 

Interesting article, thanks for the link.