shuumai, my asthma is permanent, but was caused by me swimming in different pool just once, one that I was due to do a triathlon in a month later. I never took part in that or anything since. swim, run and cycle slower now, as well as run and cycle shorter distances. Only thing I do more is swim further, but slower than before, may be a good thing, well I have to try and find a possitive somewhere.
my normal pools, are fine, one is virtually chlorine free, the other has normal regulation levels, but is cold, and again no problems.