Decontamination [Bio Agents]

Contamination is the introduction of an infectious or chemical agent on a body surface, food or water, or other inanimate objects.

Decontamination involves either disinfection or sterilization to reduce microorganisms and chemical agents to an acceptable level on contaminated surfaces.

Disinfection is the selective reduction of undesirable microbes to a level below that required for transmission.

Sterilization is the killing of all organisms.

Decontamination methods have always played an important role in the control of infectious diseases. However, we are often unable use the most efficient means of rendering microbes harmless (e.g., toxic chemical sterilization), as these methods may injure people and damage materials which are to be decontaminated.

Biological and chemical agents can be decontaminated by mechanical, chemical and physical methods:

Mechanical decontamination involves measures to remove but not necessarily neutralize an agent. An example is the fi ltering of drinking water to remove certain water-borne pathogens; in a biowarfare context, mechanical contamination would be the use of an air fi lter to remove aerosolized anthrax spores, or water to wash agent from the skin.
Chemical decontamination renders biological and chemical agents harmless through liquid, gas or aerosol disinfectants. Some disinfectants are harmful to humans, animals, the environment, and materials.
Physical decontamination measures (heat, radiation) can be employed for decontamination of objects.

For civilian emergency first aid, skin (dermal) exposure to a suspected biological or chemical agent should be immediately treated by a bleach solution [see: Decontamination Solutions] or soap and water decontamination.

Careful washing with soap and water removes nearly all the agent from the skin surface.
The use of a strong household bleach solution, or other disinfectants, for use directly on the skin should be limited to major contamination.
Harsh or caustic disinfectants can predispose a casualty to superinfection by reducing normal skin flora.
In the absence of gross biological or chemical agent contamination, disinfectants will confer little additional benefi t. Grossly contaminated skin surfaces should be washed with a 0.5% household bleach solution with a contact time of 10 to 15 minutes.
The solution is then applied with a cloth or swab. The solution should be made fresh daily with the pH in the alkaline range.
Chlorine solutions must NOT be used in (1) open body cavity wounds, as it may lead to the formation of adhesions, or (2) brain and spinal cord injuries. However, this solution may be instilled into non-cavity wounds and then removed through rinsing with sterile water or saline solution.
Contain the contaminated rinse solution in order to avoid further contamination. Within about 5 minutes, this contaminated solution will be neutralized and non-hazardous. Subsequent irrigation with saline or other surgical solutions should be performed. Prevent the chlorine solution from being sprayed into the eyes to avoid injury.
For decontamination of fabric, clothing or equipment, a 5% hypochlorite solution should be used. For decontamination of equipment, a contact time of 30 minutes prior to normal cleaning is required. This is corrosive to most metals and injurious to most fabrics, so rinse thoroughly and oil metal surfaces after completion.

Biological and some chemical agents can be rendered harmless with heat. To render biological agents completely harmless, sterilize with dry heat for two hours at 160 degrees centigrade.

Solar ultraviolet (UV) radiation has a disinfectant effect, often in combination with drying. This is effective in certain environmental conditions but hard to standardize for practical usage for decontamination purposes.

The health hazards posed by environmental contamination by biological agents differ from those posed by persistent or volatile chemical agents. Suspended biological agents would be eventually inactivated by solar ultraviolet light, desiccation, and oxidation. Little, if any, environmental residues would occur. Possible exceptions include the immediate area surrounding the area of release.

Biological agents deposited on the soil would be subject to degradation by environmental factors, and competing soil microflora.

Environmental decontamination of terrain is costly and diffi cult and should be left to properly trained emergency response personnel. If it is necessary to decontaminate these surfaces, chlorine-calcium or lye should be used. Otherwise, rely on the natural processes that, especially outdoors, lead to the decontamination of biological agents via drying and solar UV radiation.

Interior spaces should be decontaminated with gases or liquids in aerosol form (e.g., formaldehyde). This is usually combined with surface disinfectants to ensure complete decontamination.