Another factor effecting the ozone concentration of the stratosphere may be the increasing use of pressurized aerosol spray cans. They are increasingly being used for products ranging from paint and pesticides to hairsprays and boot polish. In the UK, L 200 M a year is spent on aerosol cans. The cans operate through the use of gaseous propellants of the freon type, which are chlorofluorocarbon compounds such as trichlorofluoromethane.