These are mainly due to various chemical substances from industry which get into public water supply. Usually they contain solvents, detergents, heavy metals, dyes, pigments, sulphides, organic substances etc.
These chemicals may affect directly, by contact, to produce severe skin diseases, allergies or eczemoid reaction or chemical burns. Some toxins produce acute effects while others produce chronic effects. Sometimes, the chemicals are ingested by workers if they do not wash their hands before taking food. various toxic chemicals, and their effects on health. One may come in contact with them through other means besides water.