Diesel engines and catalytic converters

The World Health Organization recently declared diesel exhaust (specifically nano-particles) to be carcinogenic.  Can anyone tell me why it is that diesel engines don't have catalytic converters (or equivalent)?  Are any of our governments pursuing means to protect us from this carcinogen?  Are our governments being lobbied by big-oil and big auto makers?  Trains; trucks; ships; they're all mostly diesel.  Is anyone seriously working to replace them with something else?