What sound pressure levels are considered dangerous to hearing these days?
SPL level depends on exposure and type of sound. It is not well understood. The fact that people almost always go deaf or at least slightly deaf as they get older complicates our understanding.
So regular hunting without ear defenders is a no no. Once in the while firing a hot gun...not likely to cause damage for most people but will make your ears ring for a couple of hours.
Firing artillary without ear defenders may give you instant damage.
Long exposure to high levels of music (musicians and club workers and rodies) with several hours a night - definitely bad.
Sitting at the wrong place for an entire rock concert (in front or speakers at 115 DB SPL ) - bad news for ears - permanent damage may be expected.
Long exposure levels of 90 DB SPL and more 8 hours a day - day in day out = BAD for hearing but again it may depend on type of sound - if it is not bang in the midrange then it may be less damaging (for example Ultra LF at 90 db SPL is barely audible).
You going to a nightclub once in a while or cranking your stereo from time to time or listening to a few rock songs at high volume with your iPod in the gymn (less than an hour) - no worries mate!
In general your body/brain will tell you - just be senstive to when you feel you have had enough and your ears need a rest!