I'm working on a translation of The catcher in the Rye and Holden seems to prefer the word crumby to other adjectives to describe, well, dirty stuff:
That isn’t too far from this crumby place, and he comes over and visits me practically every week end.
"I don’t feel like walking on your crumby nails in my bare feet tonight."
"He started shaving himself all over again. He always shaved himself twice, to look gorgeous. With his crumby old razor."
He also uses dirty quite often:
His teeth were always mossy-looking, and his ears were always dirty as hell, but he was always cleaning his fingernails.
He got up off me, and I got up, too. My chest hurt like hell from his dirty knees. “You’re a dirty stupid sonuvabitch of a moron,” I told him.
As a non-native English speaker, looking at dictionaries and context seems to indicate they are very close in meaning. But well, there are never really synonyms, are there? How do they differ?