Bioremediation is an approach to removing pollution from the environment that relies on the use of microorganisms to metabolize pollutants into nontoxic products. Sometimes these microorganisms have been genetically engineered for a specific application. For example, a bacterium called deinococcus radiodurans has been genetically engineered to digest ionic mercury compounds and toluene from nuclear waste sites. In such cases, bioremediation can often be accomplished by introducing a microorganism at the site of the pollution, thus avoiding the need for physical cleanup and transportation of the waste to a new location.