"ideal"water temperature

I know USMS has this somewhere but.....I'm looking for an article, etc about what the water temperature should be for fitness swimming. Some of the ladies at my hospital-based health club are petitioning for the lap pool temp to go up to +84 degrees! It has been kept at 81-82 degrees which is ok. They want the water temp if they could up to 86 degrees! Can you direct me as to where I could find documentation that it isn't conducive to actively exercise in that warm of water? Also isn't there a higher cost for chemicals, etc? We fitness swimmers need help!:frustrated: Thanks.