History of the Aerosol
The first use for an aerosol package arose during World War II, but the idea of using low-pressure liquefied gas to atomize droplets of liquid in the air was developed in 1924. Canisters filled with insecticide and propellants were used to protect U.S. servicemen from insects carrying diseases such as malaria. Shortly after the war, Robert Abplanalp, founder of Precision Valve Corporation (PVC), invented the first mass-produced aerosol valve. The patent was filed in September 1949 and was issued on March 17, 1953. From that invention, the aerosol industry quickly developed in the United States and around the world.
How an Aerosol Works
The aerosol package is a self-contained dispensing system with three main elements:
Active Ingredients (soap or disinfectant, etc.)
Inert or Inactive ingredients (water)
The propellant is a gaseous compound which pushes the product out of the container and produces a spray or foam. In most cases, the propellant also acts as a solvent to keep the product at the proper strength. In the United States, the most common propellants are naturally occurring hydrocarbons. A few products, about 10% of today’s aerosols, use compressed gases like carbon dioxide and nitrous oxide as propellants.
The final element is the container, which is usually a steel or aluminum can. The leak-proof can protects the product from contamination and evaporation.
All of these pieces work together based on simple scientific principles. An aerosol package is an air-tight, pressurized container. Pressing the actuator button opens the valve. Since the pressure outside the can is less that the pressure inside, the propellant expands, pushing the product up the dip tube and out through the valve. This system allows the product to be applied in a variety of ways; in a fine mist, a metered spray delivering just the right amount, foam, or even a long distance spray.
Let’s Set the Record Straight on Aerosols!
Q. What are aerosols, anyway?
A. Aerosols are very fine particles of liquid or solid substances suspended in air. Fog, for example, is a normal aerosol. In aerosol packaging, the substance to be sprayed is propelled through a valve as a fine mist or foam. This provides a safe, efficient means of dispensing thousands of consumer products such as shaving cream, hair spray, paint and antiperspirants.
Q. How long have aerosols been around?
A. Sixty-five years ago, U.S. Department of Agriculture scientists developed the principle of pressurized insect spray. This gave birth to the container used by American troops to fight malaria by killing mosquitoes in the South Pacific during World War II. Today’s lightweight low-pressure can is a direct descendant of those ponderous, high-pressure canisters. Refinements to containers, valves, propellants and formulas have broadened the range of aerosol products and widened consumer acceptance. Aerosol-related jobs now employ over 50,000 Americans.
Q. What is the ozone layer?
A. In the stratosphere, some 12-20 miles above the Earth, ozone (an unstable and very reactive form of oxygen) forms a protective layer that blocks most of the sun’s ultra-violet rays.
Q. What causes ozone depletion?
A. In addition to natural phenomena such as earthquakes, among the man-made products believed to contribute to ozone damage are chlorofluorocarbons (CFCs) used mainly in refrigerators and air conditioners. CFCs contain chlorine which attacks ozone in the upper atmosphere.
Q. Do aerosols contain chlorofluorocarbons?
A. Since 1978, no aerosols made or sold in the U.S. have contained CFCs except for a tiny fraction (less than 2%) specifically approved by the government for essential medical and other unique uses, such as inhalers for asthma sufferers. Not only are CFCs absent from the propellant used in aerosols, but there are no CFCs in the products packed in aerosol packages, such as hair spray, deodorants, antiperspirants or other personal care items, nor are they in spray paint, household, food or automotive products. The industry is in full compliance with rules established by the EPA, the FDA, and the Consumer Products Safety Commission.
Q. Then why the confusion?
A. Aerosol manufacturers in Europe and other parts of the world initially did not follow the lead of the U.S. industry in substituting alternative propellants for CFCs. The fact that aerosols made in underdeveloped countries may contain CFCs has caused confusion in press reports and in the public mind about the stratospheric ozone/aerosol link. However, American consumers can be confident that aerosols made in the U.S. will not damage the ozone layer. Other countries have also changed from ozone-depleting propellants to non-depleting forms because those countries signed the Montreal Protocol. The Montreal Protocol, of which the U.S.A. was a signatory, may arguably be the most effective international environmental agreement ever written. All nations of the world signed the agreement and the phase-out of CFCs and ozone-depleting substances (ODS) is 90% complete worldwide.
Q. What about the problem with urban smog, also known as ambient ozone?
A. As urban areas struggle to meet federal air quality standards, regulators are attempting to identify any products that emit volatile organic compounds (VOCs) which in turn contribute to lower level ozone. Unlike upper level ozone, which protects us, this lower level or tropospheric ozone is a major component of smog. The smog problem is particularly acute in California and that state has identified a variety of consumer products which emit VOCs as among those sources and are now being regulated.
Q. So aerosols do contain VOCs?
A. Yes, but so do fingernail polish, perfume and mouthwash, as well as pump hair sprays, roll-ons, and stick deodorants. Restrictions on these products are hardly the answer to air pollution. The solution to the smog problem, for example, lies on the freeways and in the power plants…not in the medicine cabinet or the bedroom!
Q. What propellants are used in aerosol containers today?
A. Depending on the end use, either liquefied or compresses gases are used to dispense the product from the aerosol container in the most efficient manner. Neither type is a chlorofluorocarbon. Liquefied propellants, such as isobutene, normal butane or pentane, are natural organic products which do not deplete the ozone layer, taint the soil or pollute the water supply. They do not contribute to global warming. As used in aerosol cans, their contribution to lower level ozone formation is negligible.
Compressed gas, such as carbon dioxide (the same gas which puts the “fizz” in soda pop) is used in products designed to deliver a coarse spray at close range…in household disinfectants, or example. Nitrogen, as used in contact lens cleaners and nitrous oxide, as used in whipped toppings, are also used as propellants.
Q. If the contribution of aerosols to air pollution is minimal, then why are they suspect?
A. Aerosols, still remembered from the pre-1978 chlorofluorocarbon/ozone controversy, offer a convenient target. Perhaps because of their “high tech” characteristics, they don’t seem to fit the profile of a “natural” product. Rather than switching to non-aerosol containers, well-meaning consumers who are concerned about air quality would be far better advised to simply maintain the family car properly!
Q. But aren’t alternative packages better for the environment?
A. Once again, myth prevails over reality. For example, pump sprays are generally perceived as being environmentally superior. Actually, the ingredients in the pump container which replace the aerosol propellant, contain many more reactive VOCs than the aerosol package. The aerosol steel can is fully recyclable; pumps and roll-ons are not.
Q. But after all, do we really need aerosols?
A. The aerosol container is a unique package. It is convenient, effective and efficient. It offers consumers a controlled “clean hands’ way to deliver personal care, spray paint, household and automotive products. It is hermetically sealed and its contents are always free of bacterial contamination.
It would be tragic indeed if aerosols were to be replaced with less effective alternatives, with absolutely no resulting improvement in air quality. Evidently the American consumer agrees, in that 3.7 billion aerosol units were produced in the USA in 2005. Western Europe, which also does not use CFCs as propellant, produced over 5 billion aerosol units in 2005.
Safety and Disposal
Like most household or personal care products, aerosols are not hazardous when handled and disposed of properly. Reading and following the instructions printed on the label will ensure proper and safe use. The label instructions are there for your protection.
The best way to dispose of an empty aerosol container is to recycle it. Aerosol cans are made of steel and aluminum and can be recycled like any other empty steel cans. A growing number of communities accept empty aerosol cans together with other metal containers. Check with your local recycling coordinator, however, before putting any material in your recycling bin. Be sure the can is empty before placing the container in the trash with your other solid waste if recycling is not available.