One of the dutch subscribers to apug sells B&W films, papers and chemistry. But he has a dayjob in a computer manufacturing plant. He recently assured me that digital is way more toxic than B&W analog, because the manufacturing of digital equipment involves masses of VERY toxic chemicals and waste.
Aside from the silver in used fixer, all other normal B&W chemicals are harmless if disposed off intelligently. I don't know if this is true for color processing or toners too.