Is soot (from a chimney or boiler) harmful to pets?

My dad was cleaning out the boiler today and as a result a lot of soot was released. He tracked some with his feet into the bathroom when he went to wash his hands. My cat went into the bathroom to eat his food and I noticed when he came out his little paws were gray-ish black- he has white paws. Now he's sitting here cleaning himself and I tried to stop him but of course he wouldn't and I don't know what to clean him with (if he'll let me). Is this soot harmful to his insides? And, what can I clean him with should I happen to end up cleaning him. Thanx for your help!!