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Chemical Decontamination

The Department of Defense (DoD) was charged with enhancing the capability of federal, state, and local emergency responders in incidents involving nuclear, biological, and chemical terrorism. The U.S. Army Soldier and Biological Chemical Command (SBCCOM), Aberdeen Proving Ground, Maryland, was assigned the mission of developing an Improved Response Program (IRP) to identify problems and develop solutions to the tasks faced in responding to such incidents. Under this authorization, the SBCCOM Domestic Preparedness Office Chemical Team conducted a study to recommend methods for civilian mass casualty decontamination after a chemical terrorist incident.

Decontamination must be conducted as soon as possible to save lives. Firefighters should use resources that are immediately available and start decontamination as soon as possible. Since they can bring large amounts of water to bear, the most expedient approach is to use currently available equipment to provide an emergency low-pressure deluge. The following forms of water-based decontamination were considered:

• Water alone. Flushing or showering uses shear force and dilution to physically remove chemical agent from skin. Water alone is an excellent decontamination solution.
• Soap and water. By adding soap, a marginal improvement in results can be achieved by ionic degradation of the chemical agent. Soap aids in dissolving oily substances like mustard or blister agent. Liquid soaps are quicker to use than solids, and reduce the need for mechanical scrubbing; however, when scrubbing, potential victims should not abrade the skin.
  • A disadvantage of soap is the need to have an adequate supply on hand. Additionally, extra time may be spent employing it, and using soap may hydrate the skin, possibly increasing damage by blister agents.
• Bleach and water. Bleach (sodium hypochlorite) and water solutions remove, hydrolyze, and neutralize most chemical agents. However, this approach is not recommended in a mass decontamination situation where speed is the paramount consideration for the following reasons:
  • Commercial bleach must be diluted and applied with equipment not generally available to firefighters.
  • Skin contact time is excessive. Laboratory studies show that chemical agents and relatively nontoxic, aqueous decontaminants may need to be in contact for durations longer than expected shower durations for significant reaction to occur.- Laboratory studies suggest that bleach solutions at the 0.5% level may not be better than flushing with water alone.2, 3
  • Medically, bleach solutions are not recommended for use near eyes or mucous membranes, or for those with abdominal, thoracic, or neural wounds.

Decontamination by removing clothes and flushing or showering with water is the most expedient and the most practical method for mass casualty decontamination. Disrobing and showering meets all the purposes and principles of decontamination. Showering is recommended whenever liquid transfer from clothing to skin is suspected.5 Disrobing should occur prior to showering for chemical agents; however, the decision to disrobe should be made by the Incident Commander based upon the situation. Wetting down casualties as they start to disrobe speeds up the decontamination process and is recommended for decontaminating biological or radiological casualties. However, this process may:

• Force chemical agents through the clothing if water pressure is too high
• Decrease the potential efficacy of directly showering skin afforded by shear forces and dilution
• Relocate chemical agent within the actual showering area, thereby increasing the chance of contamination spread through personal contact and shower water runoff.

The MCDRT recommends that victims remove clothing at least down to their undergarments prior to showering. Victims should be encouraged to remove as much clothing as possible, proceeding from head to toe. Victims unwilling to disrobe should shower clothed before leaving the decontamination area. It is also recommended that emergency responders use a high volume of water delivered at a minimum of 60 pounds per square inch (psi) waterpressure (standard household shower pressures usually average between 60-90 psi) to ensure the showering process physically removes viscous agent. The actual showering time will be an incident-specific decision but may be as long as two to three minutes per individual under ideal situations. When large numbers of potential casualties are involved and queued for decontamination, showering time may be significantly shortened. This may also be dependent upon the volume of water available in the showering facilities.

In the course of deconning victims, first responders may inadvertently become contaminated. High-pressure, low-volume decontamination showers are recommended primarily for wet decontamination of emergency responders in Level A suits after a HAZMAT incident. This gross decontamination procedure forcibly removes the contaminant from the personal protective equipment (PPE) worn by the emergency responders while conserving water. Often a secondary wash, and possible a tertiary wash, and rinse station are used. However, for decontaminating potential victims, a consensus exists among the MCDRT medical experts that high pressure could force chemical agent through the victim's clothing onto the skin. Therefore, the Occupational Safety & Health Administration (OSHA) standard for a chemical accident (high-volume, low-pressure) is the recommended "default standard".