Aberdeen Proving Ground was once the premier army facility for chemical testing and research. In fact, the most robust trees are growing in the areas of highest concentration of chlorinated solvents. Nor are they polluting the atmosphere through transpiration through the leaves. In fact, studies show very little transpiration of solvents. Each tree removes 7 to 10 gallons of water a day, or 2,000 gallons of water per day in the stand.
Plants are also a cost-effective way of cleaning up hazardous waste.
As of January 2001 there were 40,000 toxic sites, including 1,700 on the Superfund National Priorities List. They are abandoned waste storage or treatment plants, and weapons manufacturing and mining facilities. They pose the greatest threat to public health and the environment. Dealing with hazardous waste is a challenge for this country. These include large companies, such as chemical manufacturers, businesses that produce hazardous waste like dry cleaners and auto repair shops.