Well, when reading the material safety data sheet (MSDS) on an item, it is important to keep focused on the intent of that sheet. Many manufacturers use them as a way of trying to escape liability - hence the horror warnings - but that route has not been found viable in court cases as of Jan 3, 2007 (my retirement date - all bets are off subsequent to that time as I no longer have a reason to keep up with the regulations and laws).
However, there are many very hazardous materials that (when properly used) can be rubbed up against quite safely. That's why all of that boiling point, flash point and other numeric data is included in Section 2 of the forms. Similarly, there are supposed to be instructions in Section 4 (I think - my memory ain't what it once was) as to how to safely use the stuff.
Regardless of all of this, there are a few items that might surprise you when you learn all of the details about them. And, those details are often not that hard to discern once you start looking.
For example, we clarinet players regularly rub up against a substance (grenadilla wood) that has been shown to cause cancers when left in prolonged contact with human skin. This isn't too widely known, and the hazard is deemed quite small (being about as likely to cause cancerous growth as common salt), but the problem does exist.
Conversely, some of the substances in everyday use in the home are actually wrath of God materials. Take automotive wheel cleaner for a good example. Some brands of this stuff use hydrofluoric acid as the active cleaning agent, yet you would be hard pressed to figure it out from reading the label on the cans. Only on the MSDS is it clearly articulated, and few bother to read the MSDS. Hydrofluoric acid, even in dilute solutions, eats through the skin and then attacks the bone structure within the body, not something that you would expect from a semi-household product.
We deal with hazardous materials by either isolating them from our contact, or by isolating us from contact with them. The lead (a very small percentage, to be sure) that goes into musical instrument manufacturer is a strong nerve toxin, but in our horns it is bound up in alloys or in solder that should not come into contact with a weak acid (like saliva) that could coax it out in the form of a soluble salt.
The carbon dioxide heavy atmosphere that would exist if all of the gas from a typical soda fountain setup were liberated at once is kept bound up in a system of pressure lines and a B bottle that contain and confine it quite nicely.
The theatrical fog that started all of this conversation (which is really a liquid version of what is called a fume in metals - both are finely divided particles) in its aerosol can (itself a safety measure) is, when dispensed around the feet of the actors, quite safe to use. (It's the same as wading through 1' deep water - harmless as long as not inhaled.)
The problems generally arise when stuff is used in a fashion which was unintended by the producer of the stuff. One could argue that you would expect a heavier than air suspension of particles would cascade off of a stage and settle in the orchestra pit, and we know that it can happen from our personal experience, but the producers of the stuff very likely never thought about orchestra pits (or even musical theater) when they sent the stuff out. And, in any event, the can's warnings clearly state the intended use; the manufacturer would be off the hook here due to their warning, and the liability (which is what this is all about in the end) would devolve on the "end users", the theater that chose to use the stuff in a situation where the producer specified otherwise.
In such a case (looking at it from both a product and legal liability standpoint again), the production company (i.e., the theater or whoever was operating the production within the theater) would be in violation of several sections of §29 CFR 1910.1200, specifically those calling for proper use of the materials as listed on the MSDS and (under paragraph (g)) the training of those who are exposed to the stuff. (This would cover the actors, the stage crew, and the musicians in the orchestra pit.)
Penalties for violations for these sections would range from $1,000 (for a low end, other than serious violation) all the way up to circa $7,000 (for a first time, serious violation). Most likely, the penalty would fall in the $5,000 range.
None of this has any bearing on the product liability issue, though. OSHA fines the employer, while worker's compensation compensates (duh!) the worker. That fight, in a state-operated system full of loopholes and legal tricks, is much less promising. All you can do is to file your claim and see what happens. I always urge people who feel that their workplace is injuring them or making them sick to file under the process, because if you don't and later the problem becomes more severe, you are up the creek without a paddle.
There was one semi-theatrical case a few years back involving the stuff being used to blow a "bubble floor" in a dance club (the whole dance floor fills up with tiny bubbles in a foam, and the dancers somehow have a good time dancing in it all) where the propellant of choice for the foam making machines was propane. (They ran out of the pressurized nitrogen intended for the use, and substituted airbrush propellant cans (filled with propane) instead.)
As you might imagine, the propane-inflated foam and the cigarettes of the patrons did not mix very well.
All in all, none of this is as hazardous as working in a foundry or a steel mill or a wooden door factory, but still hazardous (and all the worse by being unexpected).