As summer approaches, many of us are looking ahead to languid days by the pool. New research, alas, suggests many of them are laced with something other than water. Though we all suspect it's there, it's not easy to assess how much urine there is in a particular swimming pool. It is not an insignificant public health question. The scientists sampled 29 pools and hot tubs in british columbia and alberta, and found the artificial sweetener, called acesulfame potassium, in every one.