Makes sense in the case of bleach, which when combined with the ammonia containing body ingredients shed off in the shower, reacts to produce chloramine, which

Makes sense in the case of bleach, which when combined with the ammonia containing body ingredients shed off in the shower, reacts to produce chloramine, which hydrolyzes to produce hypochlorous acid, which is a strong oxidizing agent, and I assume said hydrolysis takes place in the lungs, meaning ample exposure to free radicals, which I assume can lead to cancer if inhaled often enough.