The chemicals evaporate out of the water and are inhaled. They can also spread through the house and be inhaled by others. The toxic chemicals are inhaled in high concentrations.
Chlorine is the greatest cripple and killer of the modern times.
While it prevented epidemics of one disease, it was creating another. Two decades ago, after the start of chlorinating our drinking water in 1904. The present epidemic of the heart trouble, cancer and senility began. A long established public health practice for the disinfection of drinking water. On one hand, chlorination has freed civilization form the constant dangers of waterborne epidemics.