Ok, after being taken to the wood shed let see if we can inject some common sense (not very common)into this diacussion.
I stated I used WD 40 externally to prevent corrosion. All my regulators are metal, I don't have any plastic. Plastic doesn't corrode, no need for corrosion protection. I use it after the regs are rinsed and dried before they are stored away On a first stage if the protective cap is on none will enter the regulator. If there is a swivel such as at the
1st or 2nd stage hose connection and the swivel doesn't leak air when in use than none will enter it. Just don't spray it on or into the mouthpiece. In regards to rubber parts. Neoprene hoses, nitrile, and silicone O rings are used to transport and seal many pretroleum products, gasoline, lubricating oil, hydrolic oil, etc and don,t disolve into nothing.
Nitrile Is Recommended for:
General purpose sealing.
Petroleum oils and fluids.
Cold Water.
Silicone greases and oils
Di-ester base lubricants (MIL-L-7808).
Ethylene glycol base fluids (Hydrolubes)
Neoprene.
http://www.science-education.org/classroom_activities/chlorine_compound/neoprene.html
I wouldn't spray it on any latex comdoms though.
MSDS sheets are the catch all CYA tool. Government requires the manufacture of the product to provide them, government doesn't say what goes into them. If Acme Rocket Fuel Co. wants to say it is safe to drink it's product they can. Similar to warning labels. "DO NOT IRON CHOTHES WHILE WEARING THEM", back to that uncommon common sense.
Pure air is about the only substance I can think of that you can't get too much of, rub it all over, inhale it swallow it, no problem. Even pure water, if too much is ingested can dilute and alter the body electrolite balance.
I wouldn't want to see a MSDS on a Big Mac.
Here is an MSDS for no stick cooking spray.
http://www2.itap.purdue.edu/MSDS/docs/2811.pdf
I say this from 30+ years of experience. Last time I checked I was still breathing and had a pulse so I guess common sense has served me well.