Environmental Decontamination

Contaminated areas

The release of a biological agent will create a contaminated area, the location and size of which will depend on the site of release, the mechanism of dispersal of the agent, local geographical and meteorological factors, and the properties of the particles used to disperse the agent. The duration of the infectious risk will depend on the time of release and the biological properties of the agent used. Contaminated areas should remain cordoned off until either the infectious risk has elapsed naturally, or until they have been fully decontaminated.

Environmental sampling

Specimens from the contaminated area may be useful to confirm the type and biological properties of the agent released, and to examine the extent of contamination. This information can be used to guide prophylactic treatment.

Organism specific decontamination procedures

Different organisms require different procedures for decontamination, as described in the table. Expert advice will be provided as necessary to determine the time after release for which the bioagent remains active and to advise on decontamination.

Procedures for decontamination

Organism	Procedure
Anthrax	Anthrax spores remain infectious for long periods, although once spores have settled the risk of infection is lower. Decontamination of small areas may be achieved with hypochlorite solution (5,000ppm available chlorine).
Smallpox	Variola virus is destroyed rapidly by sunlight, and therefore environmental decontamination is unlikely to be necessary. In situations where small areas have been grossly contaminated and cannot be avoided whilst the infectious risk persists, they may be cleaned with a hypochlorite solution (5,000ppm available chlorine).
Botulism	The toxin naturally loses activity over a few days and subsequent environmental decontamination is not necessary. In situations where small areas have been grossly contaminated and cannot be avoided whilst the toxin remains active, they should be cleaned with a hypochlorite solution (5,000ppm available chlorine).
Plague	The bacteria are killed rapidly by desiccation and exposure to sunlight , therefore environmental decontamination is not required. In situations where small areas have been grossly contaminated and cannot be avoided whilst the infectious risk persists, they may be cleaned with a hypochlorite solution (5,000ppm available chlorine).
Tularemia	The more pathogenic type A strains are unlikely to survive for long on environmental surfaces as they are killed by desiccation, exposure to sunlight and oxidation. In situations where small areas have been grossly contaminated they should be cleaned with hypochlorite solution (10,000ppm available chlorine). Chlorination used in UK mains water supplies (0.5-1 ppm available chlorine) kills 99-100% of the bacteria within five minutes at 10ºC. Boiling rapidly kills the bacteria.
Viral haemorrhagic fevers	Drying and exposure to sunlight will kill the organisms. Environmental decontamination is not recommended, except for highly localised contamination like vomitus or blood spillages in the laboratory or the ward. If such a situation rises, standard disinfectants like strong hypochlorite solution containing 5,000ppm of available chlorine should be used according to local policies.

Last reviewed: 15 March 2012