Propylene oxide has been identified as an intermediate of aldehyde production in the thermal degradation of Propylene Glycol (PG).
It is worth noticing that the US Food and Drug Administration has approved the use of propylene oxide fumigation in the process of pasteurization of almonds and pistachio nuts, for example.
The carcinogenicity of propylene oxide is not grounded on clinical studies but evoked, based on the classification of the molecule:
- in the group 2B (possible carcinogen to humans) of the International Agency for Research on Cancer (IARC) list. This list aggregates chemicals or mixtures with limited evidence of carcinogenicity in humans and less than sufficient evidence of carcinogenicity in experimental animals.
- in the group B2 (probable carcinogen) of the US Environmental Protection Agency list. The agency recognizes the substance as irritant upon acute exposure and with dilute solution. Upon inhalation, it produced inflammatory lesions. Long-term exposure revealed neurological effects on animals and caused tumors on rodents’ stomach when ingested.
- in the California Proposition 65 list, a proposition of the Safe Drinking Water and Toxic Enforcement Act of 1986 that protects California state’s drinking water sources from being contaminated with chemicals known to cause cancer, birth defects or other reproductive harm.