Conference Proceedings
Section V: TECH PANEL: Homeland Defense Beyond 2000

Transcript...

Dr. Ellen Raber, Lawrence Livermore National Laboratory
Decontamination Technologies

As a follow-up to my earlier talk at this Symposium, I would like to discuss the status of decontamination technologies. I will talk about requirements for the civilian sector, some emerging technologies, and in particular, where the Department of Energy (DOE) laboratories are going with respect to new decontamination technologies.

The requirements for decontamination in the civilian sector are demanding and somewhat different from decontamination requirements from a military perspective. The military needs decontamination technologies that essentially allow them to continue with a battle. For the civilian sector, the situation is different.

Let me begin by mentioning what I consider to be the overall objectives of a decontamination system for civilian applications. The ideal system would be a single decontamination method that works for both chemical warfare (CW) and biological warfare (BW) agents. That is the direction that the DOE laboratories are currently going, and I'll give you some examples in a moment. It would also be helpful to have a method that's relatively noncorrosive, which is not the case right now for standard military decontamination aimed at CW agents. Another goal is to have something that is nonhazardous or that breaks down in the environment to nonhazardous components. Short decontamination times, on the order of several hours, is enough for the civilian sector, whereas the military sector requires even faster action. Another requirement is to have a material that can sustain contact with surfaces, such as ceilings and walls. In decontaminating a building, we need to have enough contact time to ensure that we actually destroy the agent, especially in a BW scenario. We would all like something that's relatively inexpensive and readily available. A pre-mixed formulation with a long shelf life, greater than a year, is highly desirable so that first-line responders can keep it on hand. Easy application with minimal logistics and minimal training are important, along with easy deployment by a variety of dispersal mechanisms.

So the ideal is to have one system that is noncorrosive, nonhazardous, fast-acting, inexpensive, available, and easily deployed. But now recall the three types of scenarios that I discussed in my earlier talk: an outdoor scenario, a semi-enclosed scenario, and an indoor scenario. A contaminated building would require one type of dispersal system, whereas wide-area distribution in an outdoor setting would require a helicopter or perhaps an agricultural-type dispersal system. That means we need something that has varied capability to address the different types of possible scenarios.

A wide-distribution decontamination method for outdoors is very different than the kind of system that might be required in a subway system with walls, ceilings, tracks, soil, concrete, and other materials to decontaminate. For example, one might want to avoid causing problems to the subway cars themselves, and especially to the engines, because of possible damage and repair costs. On the other hand, you might very well have to deal with different absorption/adsorption phenomena on subway surfaces, like painted walls or concrete floors that would need to be considered in a decontamination strategy. In an indoor or enclosed scenario, a principal focus might be the ventilation systems where some kind of aerosol or gas-based system would be required to decontaminate effectively.

I mentioned before that doing nothing can sometimes be the best approach to take. Several years ago, we did some experiments with the British in Porton Downs, Great Britain, to see how long various agents stay around. We conducted GC-MS analyses as a function of time to determine the amount of actual agent remaining in soils and/or gasket materials. For the G series of agents, we found that basically everything was gone (below the detection limits) within three days for two different soil types and on the gasket material we tested. VX was gone in the soil after three days, although it could still be detected at a low level on the rubber gasket material after six days. Thus, I want to re-emphasize that the specific materials involved in different scenarios are an important consideration when ensuring that a decontamination approach works effectively.

The list of current, available decontamination technologies is fairly long. For BW agents, plain soap and water is quite effective in many cases. Hydrogen peroxide, ammonia, ethyl alcohol, and isopropyl alcohol are also used. The list includes phenol, sodium hypochlorite, and a variety of gases, but they are all very toxic. Ethylene oxide and para-formaldehyde are used by the CDC to decontaminate their laboratories. Then there are the energy sources, some of which are not readily used these days even though they are known to be quite effective for biological sterilization. Heat is an obvious example of an energy source along with ultraviolet (UV) light. Unfortunately, UV has some drawbacks in that the agent must be in the line of sight of the UV light. UV is ineffective if the BW agent is hidden in a crack or behind a wall, so shadowing effects are a problem. X rays and gamma rays are also very effective, but they are less developed for operational use.

For CW agents, water is sometimes effective because many of the CW agents, like Sarin and Soman, hydrolyze readily. Soap and water, and household bleach are also very effective. In fact, household bleach is one of the few reagents that works for both BW and CW agents. DS2 and calcium hypochlorite are the Army's standards for CW agents. However, DS2 eats away the paint as well, so it's not the most environmentally acceptable approach. There's a Canadian system that basically uses calcium hypochlorite and a German system that is based on the chemical Fichlor. These are being tested in the United States. Today, we have essentially no gases that can be used for CW decontamination. If we were faced today with an incident in which a CW agent were put into a ventilation system, we really do not have an effective way to decontaminate the agent.

So, what are we doing to improve the present situation? The answer is that we are trying to come up with decontaminating materials that are not only more environmentally acceptable but also can be used for both CW and BW agents. We want to provide reagent systems that are easily deployable by a variety of dispersal mechanisms. In my earlier presentation, I provided you with some information on establishing cleanup levels. Those cleanup levels will be met by the decontamination technologies that I will be discussing next. I'll also say something about verification and sampling methods that are needed to provide for effective decontamination.

A variety of new CBW decontamination systems are being developed right now. Several different groups of investigators are looking at UV, and x rays are also being evaluated for BW decontamination. I'll show you an example of a plasma source that is being developed by Los Alamos National Laboratory. The Army is working on several enzymatic methods, including designing bacteria to degrade stockpiled CW munitions. Although it could become an effective approach, the Army has only been successful so far with G agents and mustard, but not the V agents.

Hydrolysis methods, catalytic methods, and oxidants can all be used. Two commercial companies are working on reactive nanoparticles. The dispersants that can be used are water-based foam systems, vapor or aerosol systems, inorganic gels, and water-based sprays. We'd like something that first-line responders could use in a man-portable system, similar to a garden sprayer or electric paint sprayer, and that also could be easily adapted for spraying by an airplane, crop duster, or the like.

The first system I'm going to discuss is being developed right now at Lawrence Livermore National Laboratory. It is a gel-based system that can be delivered in a hand-held device, such as an ordinary electric paint sprayer. The system uses peroxymonosulfate, which has the trade name of Oxone. Although it has been effective for both CW and BW agents, our most difficult BW decontamination challenge was Bacillus globigii (BG) spores. If you can kill the spores, then you've solved a major part of the problem.

Our silica-based gel is a mixture that is three to five times more viscous than water. Because it is a thixotropic fluid, it will spray when a shear is applied. But when the material hits a ceiling or wall, it doesn't move very much so coverage is quite effective. This system requires about a 30-minute contact time to be successful. The silica particles are amorphous, so there are no inhalation concerns. We've also analyzed the residue using both the EPA's GC-MS volatile and semi-volatile methods, and we found no environmentally toxic byproducts.

Like some of the other systems I'm going to show you in a moment, we tested our peroxymonosulfate/gel system on various CBW surrogate agents as well as in a variety of laboratory and field tests using real agents. The particular field tests shown here were conducted in the Czech Republic last year. We compared the Livermore system with the effectiveness of two foreign systems using the G agents and V agents on concrete. Our system was more successful than the Army's standard HTH system, which I previously mentioned. We also looked at the effectiveness of our system on BG spores. When we compared the results for peroxymonosulfate in the gel, versus the gel as a blank without the active ingredient, a 30-minute contact time was found to be sufficient. After about an hour, the material dries to a white powder and can be vacuumed up. More recent BW-related tests at Dugway were also successful, and laboratory studies conducted by the Army at Edgewood showed this material to be highly effective.

A foam-based system, which is also environmentally acceptable, is being developed by Mark Tucker at Sandia National Labs. It has been successful in tests using real agents under laboratory conditions. Foam has many useful applications, just as gel does, but its effectiveness depends on the particular scenario. For example, foam would be an excellent choice if the objective were to decontaminate a tank or other large piece of equipment. The Sandia foam is nontoxic and noncorrosive, and it is also a rapid decontamination system for CW agents, taking about 30 minutes. The decontamination time for anthrax is about the same. This aqueous-based foam system has a high expansion ratio and good stability, which minimizes the amount of water that needs to be used. Sandia is looking for commercial partners to develop their system.

Los Alamos is looking at two systems. The first is a gaseous decontamination system that's being developed by Robert Currier. As I suggested before, gaseous systems are especially useful in air ducts, cracks, porous materials, and ventilation systems in general. The Los Alamos system is based on ozone and has been tested principally on BG spores. After using 9000 parts per million of ozone, they found essentially no surviving spores after about 70 minutes. They are planning to look at the effectiveness of this system for all the CW and BW agents. They need to study the impact of environmental factors as well because increased humidity seems to have a detrimental effect, causing the ozone to oxidize. They need to assess possible damage in high-value facilities because ozone can sometimes be quite corrosive. And finally, they need to look at CW agent permeation into the materials prior to decontamination and any toxicity associated with the reaction products of ozone.

The second method under development at Los Alamos is a cold plasma decontamination system being developed by Hans Herman. It has been tested on CW agents, on surrogates, and on actual VX at Edgewood. This reactive, meta-stable, cold ozone system is basically produced right on the spot. Although the system would not be suitable to decontaminate an entire room or wide area, it could be useful for cleaning cracks and small areas. It would also be extremely useful for high-value electronics. Experiments have shown that this approach does not impact computer disks or integrated circuits, and that those devices still work following decontamination with this method. Los Alamos won an R&D 100 award for their system just last year.

The good news is that several methods with excellent potential are under development at the DOE labs. However, it still comes down to the question of how well these kinds of systems work in real time in the field. We easily achieve 99.999 percent decontamination in the laboratory, and we've achieved the same results in field testing as well. But in an actual scenario, such as a room, or a subway where you have cracks, ventilation systems, and the underside of vehicles to contend with, you really have to employ a sampling strategy that's going to be effective in evaluating success.

LLNL is currently looking at a strategy that was developed by the US Geological Survey, called hot-spot sampling. I think this strategy will take us one step closer to success. Basically, it's a method that allows us to answer some important questions with confidence once the decontamination has been completed. You first determine what kind of grid spacing is needed to hit a hot-spot with a specified confidence, such as 95 or 99 percent confidence. Then for a given grid spacing, you are able to determine the probability of hitting a hot-spot of a specified size. Finally, you can determine the probability that a hot-spot exists when you didn't find any on the sampling grid.

Ultimately, the entire matter really centers on public confidence in the decontamination and sampling verification method that we use. As I mentioned previously, one thing that I'm concerned about is that to do effective decontamination in the field, especially in a BW scenario, we must have the ability to know how well we are actually doing in real time. I think it is rather naive to simply assume that a particular decontamination system is going to work in the field as well as it did under laboratory conditions. In a BW scenario, especially if spores are present, we now have to wait two to four days while culturing is done to see what is actually still present and alive, and what has been successfully killed. What we really need is a way to determine viability in the field and gain the necessary real-time feedback to effectively decontaminate as well as potentially eliminate hoaxes. This is an important area that needs further consideration and discussion.

I want to leave you with few final conclusions that are a combination of my last talk and this one.  Effective decontamination involves site-specific parameters and requirements. It's not enough, and I don't think that anyone here would propose, to simply spray bleach over a stadium from an airplane, and then consider the job done.  The decontamination systems now under development appear to offer clear advantages over the existing systems today. However, technologies and methods for effective sampling and verification are still limited for BW cleanup. Health-risk assessments for specific agents, and for generic scenarios, still need to be done. A risk-based decision process, like the one I presented in my earlier talk, needs to be able to point out options at specific sites.  Finally, regulatory and stakeholder requirements have to be part of the entire process, even down to selection of the final decontamination method that is used.