As someone with some health & safety training, I'd like to share a couple of points.
Incidental airborne exposure to most chemicals we use in our hobby poses no more risk than incidental exposures to secondhand smoke, car exhaust, household chemicals. Doesn't mean that we should go ahead and not worry about it. Just be practical.
However, if you were to start feeling nauseous, then that is an indication that you ARE being overexposed and you should get some fresh air. (duh, like that doesn't make sense...
Exposures to soldering fumes can be dangerous over the long run especially if it is lead based. Definitely use a fan to vent away the fumes. Exposures to metal dust will mainly cause irritation of the lungs but shouldn't result in permanent damage.
Skin contact with solvents such as motor spray, nitro fuels, etc. should be minimized to prevent the occurence of rashes known as dermatitis. But if you only do it a couple of times a week, then we can agree that the risk is pretty low.
Now if you do this 8 hours/day for 40 hours/week, then it makes sense that additional precautions is needed to reduce exposures as much as possible.
I almost want to say use "Common Sense" but that phrase doesn't mean the same thing to everyone. Be practical and use protection when you can to minimize. As a racer, I don't go overboard worrying but I do take practical precautions so that I know I will around to enjoy this hobby for a long long time.
P.S. Socal Raceway does have a strong constant Paragon odor, but nothing that we should worry about. Heck, the workers are there full time and they seem pretty normal...