Fluoride is added to drinking water and toothpaste to prevent tooth decay.Chlorine is added to water to kill bacteria. Chlorine is also an extremely toxic gas. It is a respiratory irritant in small concentrations and fatal in large concentrations.Bromine is used in flame retardants. When the substance burns starves the fire of oxygen causing it to go out. Potassium bromide is used as an anticonvulsant.
Iodine is used as an antiseptic to clean wounds and is needed by the thyroid gland in trace amounts.
Iodine is used as an antiseptic to clean wounds and is needed by the thyroid gland in trace amounts.