Bromine is used in flame retardants, pesticides, lighter fuel, antiknocking agents, and for water purification. The organic form of this element is used as flame retardants commercially and in pesticides. These chemicals have led to an increase in the depletion of the stratospheric ozone layer. Some countries use bromine to treat drinking water, similar to chlorination. Bromine is also present as impurities emitted from cooling towers.