First off, I've been around here for a couple of years and this site is BY FAR the best place to get great info regarding pool care!
That being said, I've seen the recommendation regarding maximum safe FC levels used quite a bit - that being it is safe to swim in a pool once the FC level has dropped to below shock level. The question I have is: why? I'm curious as to whether there is evidence of harm to swimmers above that level or if it's merely a rule of thumb. I've heard of eczema sufferers whom benefit from 'bleach baths' where the FC level is, presumably, much higher than what is normally seen in a pool. So on the surface, there seems to be a bit of a conflict. So beyond the possibility of ruining a bathing suit sooner or the like, what's the harm?