Regardless of the cause of autism (and I agree that the studies do not show a statistically significant increase in autism in children taking vaccines with mercury in them vs. those who did not or any relationship vs. number of vaccines, amount of mercury exposure, etc.), anyone who is concerned with minimizing exposure to carcinogens and chemicals that can cause asthma and other ills should be aware that it is primarily the disinfection by-products (DPBs) that are the problem and, as stated in the earlier post, not the chlorine itself. Specifically, it is when chlorine combines with organic compounds (and with ammonia which can produce nitrogen trichloride if not shocked to breakpoint first) that causes the problem.

Using CYA in the pool will significantly reduce disinfecting chlorine levels and the rate of production of DPBs since that is dependent on the chlorine concentration (HOCl concentration, not FC). Also, an outdoor pool with even a small breeze will sweep away most of the volatile DPBs and sunlight *may* breakdown some of them as well. So, IMHO, the risk in an outdoor pool exposed to sunlight and wind is very, very small.

On the other hand, the risk in an indoor pool is much higher. Indoor pools don't use CYA (though perhaps they should use a little for the reasons cited above) so DPB production is much larger and ventiliation can be poor and there is no sunlight exposure. All of the studies showing problems with asthma and other ills in competitive swimmers and in children (who breath more air per body weight than adults) are with indoor pools, not outdoor pools.

Finally, if someone is still concerned, you can spend money on a non-chlorine shock of potassium monopersulfate (KMPS) which will oxidize the organics before chlorine gets a chance to and therefore reduces the amount of DPBs. If a weekly dose buys piece of mind, then it's worth it. Personally, I don't think it's needed in outdoor pools, but it won't hurt (except for the cost). It will increase sulfates in the water, but that's the only side effect.

Richard