The halocarbons, both halogenated compounds and halogenated solvents, are widespread pollutants found in air, water, soil, and sediment; they are recalcitrant molecules resistant to mineralization because the carbon-halogen bond is so stable. The stability and chemical inertness of many halogenated compounds is part of their appeal in many industrial processes, however it also makes them slow to degrade once they are released into the environment. In general, the more halogens there are on a molecule, the slower the degradation process. The focus for bioremediation of halocarbons is to exploit ability of organisms that have the natural capacity to mineralize these toxic contaminants into benign molecules.
Halogenated organic solvents have a wide range of uses including metal processing, electronics, dry cleaning and paint, paper and textile manufacturing. They thus have the potential to contaminate almost every aspect of the environment, particularly water and soil. Since halogenated solvents are generally denser than water they tend to sink and accumulate in groundwater sources (they are also known as DNAPLs or dense nonaqueous phase liquids.) Acute overexposure to halogenated solvents has serious health consequences for humans, including possible nervous system damage, heart failure, and increased rates of cancer. At lower doses halogenated solvents are considered potential carcinogens for humans and have been shown to cause cancer in laboratory animals. (Prince, 1998)
