I received a PM which I copy below so that this question and my response may be seen by everyone:
I suspect that being an indoor pool there is no Cyanuric Acid (CYA) in the water. You should ask to verify that, but if that's the case then the active chlorine level is much too strong and will oxidize your swimsuits, skin and hair about 30 times faster than in your own outdoor pool with CYA, assuming you have an FC that is around 10% of the CYA level. My wife experienced this difference every year where her swimsuits would degrade over just one winter season of use in an indoor pool (with 1-2 ppm FC and no CYA) while in our outdoor pool in the summer the swimsuits would last for 6-7 years or more. Also, her skin was flakier and hair frizzier from the indoor pool compared to our outdoor pool.Hi I'm from Toronto, Canada and I read your post on pool chlorine levels in swimming pools.
I thought I might ask your views, if you have time, on the effects of chlorine on habitual swimmers like myself.
I've read some material on apparently known effects on competitive swimmers.
For years I've been swimming 7 days a week at an indoor pool for about 40 minutes straight. I shower before and after. I talked to the lifeguard and he said generally the chlorine levels are about 3ppm.
It's never been a concern for me. I've never experienced chlorine as a problem. Do you have any views from a practical standpoint on the long term health risks, e..g, respiratory problems or cancer.
The rate of disinfection by-products is also dependent on the active chlorine level, especially for the very volatile and irritating nitrogen trichloride most associated with "bad pool smell". Have you noticed a bad smell at the indoor pool or does it just smell like a faint whiff of "clean bleach". If you don't smell nitrogen trichloride, then your respiratory risk may be low and the pool may be properly managed with supplemental oxidation systems, most likely UV. Ask to see what else they are doing -- using UV or ozone and also how much water dilution they do regularly (% of pool volume and how often).
The cancer risk is low, though possibly somewhat higher than it should be unless supplemental oxidation systems are being used or unless the bather load is low. With high bather load and without supplemental oxidation system or coagulation/filtration systems to remove organics from the water, then one can get more chlorinated disinfection by-products. Also, if the fill water has high bromide content, then this is worse with regard to the amount of potential cancer-causing chemicals since the brominated THMs are the ones of concern -- chloroform is not. Even so, the risk is still rather low. See this post for a summary of epidemiological studies on chlorinated water.