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EPA Requirements for Liquid Propylene Glycol

Liquid propylene glycol is one of the two main types of antifreeze for engine cooling systems. It is also the most widely used aircraft deicing agent in the United States. Propylene glycol is much less toxic than ethylene glycol, the other dominant type of antifreeze. Most U.S. Environmental Protection Agency (EPA) regulation of propylene glycol occurs when the product is manufactured and when it is recovered following airplane deicing and anti-icing operations.

  1. Propylene glycol manufacturing

    • When propylene glycol is manufactured, wastewater associated with its manufacturing is regulated pursuant to different subparts of effluent limitations guidelines for organic chemicals, plastics, and synthetic fibers (OCPSF). Propylene glycol manufacturers are also regulated under the Clean Air Act with New Source Performance Standards for the Synthetic Organic Chemical Manufacturing Industry (SOCMI). Unlike ethylene glycol, which is classified as a hazardous air pollutant (HAP), propylene glycol is not classified as a HAP, so it does not fall under the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) and reporting requirements specific to that legislation.

    Deicing effluent limitations

    • According to an August 2000 EPA report about aircraft deicing operations, propylene glycol discharges are regulated by the EPA under the Clean Water Act of 1972, the Water Quality Act of 1987, and the resulting National Pollutant Discharge Elimination System Permit Application Regulations for Storm Water Discharges (NPDES). This permitting procedure limits the variety of propylene glycol capture systems that can be used at airports. Discharges of airport deicing operations are regulated under the EPA's storm water program.

    FDA propylene glycol

    • The federal Food and Drug Administration lists propylene glycol as generally recognized as safe (GRAS) except for use in or on cat food. Because propylene glycol is listed as GRAS, it is subject to many fewer government regulations in general and EPA requirements in particular. The Dow corporation technical data sheet for propylene glycol notes that it is used in the food, cosmetics, pharmaceutical, fragrance, and personal care industries, both as an ingredient and as a low temperature heat transfer agent in the dairy, brewing and ice cream industries, as well as in food storage.

    EPA general findings

    • In general, propylene glycol tested negative in a battery of EPA tests. In a 2006 EPA report titled "Reregistration Eligibility Decision for Propylene Glycol and Dipropylene Glycol," the agency found propylene glycol negative for carcogenicity up to agency testing limit doses. This finding updates the 1991 EPA Integrated Risk Information System (IRIS) carcinogenic assessment for propylene glycol, which at the time had not undergone a human carcinogenic potential evaluation. The 2006 study also found propylene glycol negative for mutagenicity and genotoxic potential.

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