Neutralization of Ricin Toxin on Surfaces using Low Concentration Hydrogen Peroxide Vapor
Citation:
Richter, W., M. Sunderman, J. Wood, J. Taylor, H. Ledbetter, Z. Willenberg, AND B. Weston. Neutralization of Ricin Toxin on Surfaces using Low Concentration Hydrogen Peroxide Vapor. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-23/096, 2023.
Impact/Purpose:
Ricin is a highly toxic protein capable of inhibiting protein synthesis within cells and is produced from the beans of the Ricinus communis (castor bean) plant. Previous studies have shown that ricin toxin can persist for more than 28 days when deposited onto building materials, dried, and held at 20°C. Numerous bioterrorism incidents using ricin toxin have occurred since the 1978 assassination of Georgi Markov using a pellet of ricin toxin disguised in the tip of an umbrella. In 2013, several letters that contained ricin toxin were sent to various locations, including the White House and the office of the New York City mayor. In 2018, ricin was detected in mail sent to the Pentagon. In 2020, ricin was discovered in a package sent to former President Donald Trump. These contaminated letters and packages had the potential to also contaminate the corresponding mail-sorting facilities, equipment, and the associated buildings, creating an exposure risk for those working in the area. A few studies have examined the decontamination efficacy of liquid disinfectants against ricin toxin. However, implementing liquid-based disinfectants in large complex buildings can be challenging in terms of both distribution as well as material degradation from the potentially harsh liquid disinfectants. Fumigants (gases) offer ease of distribution within large complex spaces; however, few studies have examined the effects of these types of decontamination methods against ricin toxin on building relevant surfaces. One such study examined the effects of vapor phase hydrogen peroxide and found that when a pure or crude form of ricin was exposed to 400 ppm vapor phase hydrogen peroxide for 14 hours, greater than 99% reduction was achieved. Achieving 400 parts per million (ppm) or greater within a large building can be challenging, requiring methods such as tarping to subdivide a space into smaller areas. One potential solution to simplify implementation is the potential use of low concentration hydrogen peroxide vapor (LCHPV), which has recently been studied for the inactivation of an Ebola surrogate virus, as well as for the inactivation of anthrax simulant spores. The LCHPV can be simply generated using off-the-shelf aqueous solutions of hydrogen peroxide disseminated with low-cost humidifiers. This study examined the use of LCHPV against a crude preparation of ricin toxin applied to common building materials (pine wood, ceramic tile, acrylonitrile butadiene styrene (ABS) plastic, and industrial carpet) to provide efficacy data assessing the suitability of LCHPV as a decontaminant for ricin toxin.
Description:
Ricin is a highly toxic protein that is produced from the castor bean plant. Incidents with using ricin as a terrorist weapon have become more commonplace in recent years. This study examined a technique (Low Concentration Hydrogen Peroxide Vapor; LCHPV) to decontaminate materials that have been contaminated with crude ricin. LCHPV is a "low-tech" decontamination approach that can be generated simply by using off-the-shelf humidifiers and aqueous solutions of hydrogen peroxide that can be bought at the drug store. The materials evaluated were pine wood, ceramic tile, carpet, and ABS plastic. The ricin toxin was quantified using a cytotoxicity assay. Decontamination efficacy was determined as the percent reduction, based on the mass of ricin toxin recovered from test coupons compared to the mass of toxin recovered from the positive controls. For the majority of test conditions, the use of LCHPV was shown to be an effective decontamination method against crude preparations of ricin toxin on the materials evaluated. Greater than 90% reduction was achieved using both 25 and 50 ppm hydrogen peroxide vapor for all materials at exposure times of 96 and 48 hours respectively. The LCHPV can be generated using low-tech methods such as an off-the-shelf humidifier filled with hydrogen peroxide solution, and provides sufficient efficacy for situations where higher concentrations of hydrogen peroxide vapor may not be readily obtainable in the field.