At least as safe as fermenting acidic substances in it and drinking substances containing ethanol. More likely safer than the latter.
HDPE is marked foodsafe and rated to 110-120 deg so I reckon I'll be dying from something else long before nc gets me.
Anyone paranoid about hdpe and other plastics should be using ss or glass.
I know what's in various kinds of plastic by the way. It's what comes out in contact with boiling water that I doubt you'll find much evidence for (speaking about hdpe here).