The safety and toxicity information for propylene glycol has been under scrutiny by various health and research entities. In particular, the Organization for Economic Cooperation and Development SIAM reviewed its oral toxicity. No probable long-term damages were found in rats after fed as much as 5 percent of propylene glycol for 104 weeks in a study conducted. Because of the low toxicity, propylene glycol is deemed safe and classified under GRAS (“generally recognized as safe”) classification. It has been included in the United States Pharmacopeia and in the New and Non-official Remedies as an ingredient for medical and dental products since 1942.
However, another study conducted by the CIR Expert Panel recommended a concentration limit of 50 percent for propylene glycol and its polymers based on human irritation and sensitization tests. According to studies, diseased skin may develop irritation/sensitization reactions to propylene glycol. With normal skin tested under occlusive patches, it is suggested that it can be a potential skin irritant and is dependent on its strength.
Despite the findings by the CIR, prolonged skin contact with propylene glycol is non-irritating to the skin in minimal levels. When undiluted, it irritates the eye minimally and can cause transient conjunctivitis until it is removed. Propylene glycol vapor is generally deemed safe for upper respiratory tract in ordinary application though it may cause irritation in some subjects. Meanwhile, the National Toxicology Program’s (NTP) Center for the Evaluation of Risk to Human reproduction (CEHRER) Expert Panel in 2003 found out that propylene glycol poses no risk for reproductive or developmental toxicity to humans. There is also no evidence that it can be carcinogenic.
Proper Handling and Storage
Propylene glycol is stable unless exposed to extreme hot temperatures which will decompose the product. Because of its non-volatility and water solubility, air contamination is not possible during a spillage though it can cause slippage so extreme care is taken. Although it is biodegradable, propylene glycol is still not advisable to be dumped in any place and must be disposed in compliance with government standards.
Propylene glycol should be stored in aluminum, stainless steel, Plasite 3066-lined containers, 316 stainless steel, or opaque plastic containers. It should neither be stored in direct sunlight nor in elevated temperatures, and should avoid contact with oxidizing materials.
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