Betapropiolactone

Beta-propiolactone (BPL) is commonly used to inactivate reagent viruses during production of vaccines, because it likely inactivates viral infectivity by modifying viral protein. BPL was used for the sterilization of blood plasma, vaccines, tissue grafts, surgical instruments, and enzymes, and as an antimicrobial agent. BPL is a colorless liquid with a sweet odor, unstable at room temperature but stable at 5°C in glass containers. BPL vapor has been experimented with ethylene oxide for effectiveness as a sterilizing agent for influenza virus, and COVID virus vaccines. Its use as a sterilant was at one time extended to many other products. The main metabolite of BPL is lactic acid, and its main hydrolysis product is hydracrylic acid, both of which are excreted rapidly. BPL does not absorb or distribute appreciably after oral, or inhalation exposures based on the fact that tissue types of tumors seen in cancer bioassays are those experiencing first contact. Oral/gastrointestinal exposures resulted in increased combined incidence of benign and malignant tumors of the forestomach, and inhalation exposures caused nasal cancers. Toxicity to kidney and liver has been reported in animal studies but only after intravenous administration. BPL is sometimes classified as a direct-acting alkylating agent capable of attaching to DNA and forming DNA adducts. Glutathione has been proposed as a natural scavenger of BPL, and its presence in the organism likely protect from BPL's genotoxicity, mutagenicity, and even carcinogenicity. This property probably accounts for its mutagenicity in a wide variety of in vitro and in vivo test systems (both somatic and germ cells). The NTP's 2011 Report on Carcinogens considers BPL to be a reasonably anticipated human carcinogen based on sufficient evidence of carcinogenicity from studies in experimental animals. Potential for BPL exposure of the general population is becoming increasingly limited, although it is currently an FDA approved indirect additive used in food contact substances.