Green’s Dictionary of Slang

1. filth, dirt.

1959		P. Roth Goodbye Columbus 87: ‘You've got clean underwear? [...] Shmutz he lives in and I shouldn't worry’.
1963		Mad mag. Jan. 6/1: a pretty dolly by Karen Shmutz Age 5.
1978		L. Kramer Faggots 53: But is he not dealing in such schmutz!
2004		A. Kleinzahler Cutty, One Rock (2005) 10: While you’re at it, wipe the schmutz off your chin.

2. heroin [on the pattern of dirt n. (10b)].

1995

J. Stahl Permanent Midnight 250: I dropped the schmutz in the spoon [...] and drew in a full rig.