Synonyms for Dirtying:

n.

act (noun)
soiling, soilure.
dirtying (noun)
soiling, soilure.

v.

dirtying (verb)
Besmirching, Tainting, Muddying, Befouling, contaminating, Smearing, Smudging, Putrefying, smirching, staining, Streaking, soiling, Sullying, Defiling, Fouling, Polluting, Tarnishing.

Other synonyms:

Other relevant words:
soilure.