During the Middle Ages a superstitious society believed that black cats portended bad luck. But a program to rid society of black cats brought little improvement in hunger and misery. So, it was concluded that not just black cats, but all cats must be evil. A massive campaign soon rid Europe of all its evil cats. Rats and mice proliferated then, and a great plague descended on Europe.

I'd like to suggest that airborne exposures are industrial hygiene's black cats. The further they are reduced, the more workers become endangered by dermal exposures. The industrial hygiene profession argues endlessly over what represents a safe airborne exposure limit. If workers are sick, the universal response is to lower the airborne exposure limit. But the profession is misled by a myth that says lowering airborne exposures will better protect workers.