BDAG lists two senses for ἀκαθαρσία]:
(1) Lit., any substance that is filthy or dirty,
For the nuance, "impurity," cp. Num. 19:13 with Mt.
(2) Fig., a state of moral corruption, immorality,
vileness, esp. of sexual sins. See Rom. 1:24; 2 Cor.
12:21; Col. 3:5; Eph. 4:19; 5:3.
Moulton-Milligan (Vocabulary of the Greek Testament)
also has an interesting citation from POxy VIII.
1128.25 (A.D. 173):
PARADOTW TOUS TOPOUS KAQAROUS APO KOPRIWN KAI PASHS
M-M also supplies this information:
"In a literal sense the noun [ἀκαθαρσία] occurs in a
formula used in agreements for renting houses, which
the tenant undertakes to leave in good condition"