An odor-free, nontoxic and colorless gas, propane is a hydrocarbon (C3H8), a byproduct derived from oil refining and natural gas refining, according to the National Propane Gas Association. Used by millions in various environs—industry, farming, households—propane is considered an alternative clean fuel under the Clean Air Act (1990). Propane is frequently found in hair care products and cosmetics as a replacement for chlorofluorocarbons (also called CFC propellants) in aerosol cans.
Typically stored at low pressures, propellants are the gases responsible for spraying hairspray out of a canister. In the past, chlorofluorocarbon gasses (CFCs) were used, but these were found to contribute to the diminution of the ozone layer in the atmosphere. Because hydrocarbons—propane, methylpropane and butane—do not contain ozone-depleting chlorine or bromine atoms, they are used as substitutes for CFCs. To achieve a specific amount of pressure in a canister, mixtures of propane and butane are used. According to Cosmeticsinfo.org, the common propellant Butane 40 constitutes a blend of propane and butane with a vapor pressure of 40 pounds per square inch.
Hydrocarbon propellants such as propane and butane were widely used until the 1980s; however, scientists discovered that hydrocarbons contribute to air pollution. California and other states enacted legislation that limited the amount of these gases in hairsprays and other applications, and the use of propane propellants decreased.
In 1987, an international agreement known as the Montreal Protocol gradually eliminated the use of CFCs, which led to the adoption of long-term substitutes such as hydrofluorocarbons (HFCs). According to Science Daily, hydrofluorocarbon, a derivative of parent hydrocarbon, has been found to be a highly potent warming agent as of 2009. In comparison to CO2, HFCs currently account for less than one percent to climate change. By the year 2050, however, scientists expect the relative contribution to climate change by HFCs to increase to seven to 12 percent.
According to the Food and Drug Administration (FDA), propane, butane and isobutane has been listed under direct food substances as “Generally Recognized As Safe” (GRAS). Additionally, the Cosmetic Ingredient Review Expert (CIR) Panel has deemed these hydrocarbons as safe for cosmetics under best practices regarding usage and concentration.
Because propane, butane and isobutane are used primarily as propellants, the CIR has been more concerned with inhalation versus dermal toxicity. Several tests have been performed on the anesthetic impact of these hydrocarbons. Typically, exposure to propane propellants is usually brief (no longer than 10 seconds) and at a low level. Therefore, these studies are not believed to be relevant to their use in personal hair care products, reports Cosmeticsinfo.org.