Good Tobacco

"It's a very, very expensive process to dig up [contaminated] soil and incinerate it," says plant biologist Neil Bruce, "So we're trying to develop methods by which we can remove those explosives from soil using plants and microorganisms."

Now, researchers lead by Bruce at England's University of York say genetically modified tobacco plants may prove to be a cheaper way to clean up polluted firing ranges, munitions dumps, and even post war zones.

Toxin-eating bacteria image: Neil Bruce

Transgenic tobacco plants capable of treating TNT contamination function slightly differently from plants designed to treat RDX. The tobacco plants used to treat TNT basically transform TNT's molecular structure into a nontoxic form, while the plants that can dissolve RDX gradually pull nitrogen groups — molecular units of nitrogen and oxygen — from the explosive until it eventually falls apart. The plants then use the nitrogen groups as food to grow.

Bruce says creating plants that can breakdown RDX is particularly important because it can spread through soil and groundwater much more quickly than TNT, which can mean multimillion dollar clean up efforts.

Using plants to clean up contamination is not a new idea. In fact the military is using a variety of wetland plants, fungi, and poplars, to clean up sites polluted with heavy metals, PCBs, chlorinated solvents, and petroleum products, among other things. U.S. Army Environmental Center spokesman Robert DiMichele says that in certain circumstances it's a "process that has worked extremely well," and has proved less expensive.

Transgenic tobacco plant image: Neil Bruce

However, none of the military sites use genetically modified plants and as Bruce points out, "Traditional plants are unable to degrade explosives. They may take them up, but once the plant dies, the toxin just literally goes back into the soil again."

The Spoils of War?

The research naturally raises questions about whether the technology could be applied to other types of plants in different climates where tobacco will not grow and whether it would work in post-war zones. While the technique is the same one used to genetically modify other crops, like corn for example, Bruce says designing various plants capable of degrading explosives in different climates is still in the future. In his research, tobacco served only as a model, they do not have the skills, or what Bruce calls the scientific "tool box," to apply it to all plants and climates yet.

Furthermore, DiMichele says it's not appropriate for places like Iraq where there are more immediate needs. He says in Iraq, the "primary concern has been to clean up the unexploded bombs."

Bruce's colleague, University of Washington forester Stuart Strand, says the best place for the tobacco plants would be on active firing ranges, where it's obviously too dangerous to have cleanup crews working, and where the transgenic tobacco plants could provide "continuous treatment." But he says there is a lot more research that needs to be done before there is an established "beneficial effect outside the training range."

"One of the main concerns of genetically modified plants is the problem of gene transfer," says Bruce. "What happens if the genes get out into the environment, and what effect would it have on native species?"

Bruce doubts there would be any severe consequences because so many of the contaminated sites where the transgenic tobacco could be planted are so toxic that the plants could only have a beneficial effect. Still he says, "We've probably got another four or five years worth of science and trial within greenhouses," says Bruce.