Decontamination of soil contaminated at the surface with Bacillus anthracis spores using dry thermal treatment.

In the event of a large, aerosol release of Bacillus anthracis spores in a major metropolitan area, soils and other outdoor materials may become contaminated with the biological agent. A study was conducted to assess the in-situ remediation of soil using a dry thermal treatment approach to inactivate a B. anthracis spore surrogate inoculated into soil samples. The study was conducted in two phases, using loam, clay and sand-based soils, as well as biological indicators and spore-inoculated stainless-steel coupons. Initial experiments were performed in an environmental test chamber with temperatures controlled between 80 and 110 °C, with and without added humidity, and with contact times ranging from 4 h to 7 weeks. Tests were then scaled up to assess the thermal inactivation of spores in small soil columns, in which a heating plate set to 141 °C was applied to the soil surface. These column tests were conducted to assess time requirements to inactivate spores as a function of soil depth and soil type. Results from the initial phase of testing showed that increasing the temperature and relative humidity reduced the time requirements to achieve samples in which no surrogate spores were detected. For the test at 80 °C with no added humidity, 49 days were required to achieve soil samples with no spores detected in clay and loam. At 110 °C, 24 h were required to achieve samples in which no spores were detected. In the column tests, no spores were detected at the 2.5 cm depth at four days and at the 5.1 cm depth at 21 days, for two of the three soils. The experiments described in the study demonstrate the feasibility of using dry thermal techniques to decontaminate soils that have been surficially contaminated with B. anthracis spores.

Low-concentration hydrogen peroxide decontamination for Bacillus spore contamination in buildings.

Remediation and recovery efforts after a release of Bacillus anthracis (anthrax) spores may be difficult and costly. In addition, response and recovery technologies may be focused on critical resources, leaving the small business or homeowner without remediation options. This study evaluates the efficacy of relatively low levels of hydrogen peroxide vapor (HPV) delivered from off-the-shelf equipment for the inactivation of Bacillus spores within an indoor environment. Decontamination evaluations were conducted in a house using both Bacillus atrophaeus var. globigii (Bg; as surrogates for B. anthracis ) inoculated on the carpet and galvanized metal as coupons and Geobacillus stearothermophilus (Gs) as biological indicators on steel. The total decontamination time ranged from 4 to 7 days. Using the longer exposure times, low concentrations of HPV (average levels below 20 parts per million) effectively inactivated Bg and Gs spores on the materials tested. The HPV was generated with commercial humidifiers and household-strength hydrogen peroxide solutions. The presence of home furnishings did not have a significant impact on HPV efficacy. This simple, inexpensive, and effective decontamination method could have significant utility for remediation following a B. anthracis spore release, such as following a terrorist attack.