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Summary of Decontamination Techniques for Materials Contaminated with Ricin
Citation:
Wood, J. Summary of Decontamination Techniques for Materials Contaminated with Ricin. U.S. Environmental Protection Agency, Washington, DC, EPA/600/S-24/011, 2024.
Impact/Purpose:
This report summarizes previous research conducted by EPA/ORD to evaluate decontamination options for materials contaminated with ricin. This report summarizes the efficacy of several decontamination techniques to neutralize both crude and pure ricin on a number of different surfaces and materials. The decontamination techniques and their efficacy summarized in this report include natural attenuation/climate control, hydrogen peroxide vapor, chlorine dioxide gas, and several liquid decontaminants such as dilute bleach, peracetic acid, and a few off the shelf cleaners.
Description:
This technical summary report provides a review of the U.S. EPA Office of Research and Development’s (ORD) laboratory studies that evaluated the efficacy of decontamination techniques to neutralize ricin on a variety of different surfaces. The tests referenced in this summary report were conducted with either a vendor-provided pure ricin, a crude form of ricin produced in the laboratory from castor beans (which is more representative of what would be used in an actual incident), or both. Efficacy results for a decontaminant are reported as the percent reduction of ricin toxicity and calculated based on the ricin recovered from test material coupons (after decontamination) relative to the ricin recovered from positive controls (coupon materials inoculated with ricin but not exposed to the decontaminant). In the referenced studies, the cytotoxicity assay 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) was used to quantify ricin and utilizes Vero cells and ricin reference standards. The decontamination techniques and their efficacy for neutralizing ricin summarized in this report include natural attenuation or climate control, liquid decontaminants and cleaners (such as chlorine bleach, peracetic acid, and aqueous hydrogen peroxide), hydrogen peroxide vapor (HPV), and chlorine dioxide (ClO2) gas. For the tests in which both the crude and pure forms of ricin were used, the crude form was generally neutralized at a lower efficacy than the pure form. For incidents when the ricin is suspected of being dispersed throughout an area, and/or if the location of the ricin contamination is unknown, volumetric decontamination approaches may be better suited. In these cases, and if time is not a factor, decontamination via attenuation at elevated temperatures or LCHPV may be easy-to-implement options. With respect to the liquid decontaminants, the peracetic acid and the one in four bleach dilution were the most effective.