As water becomes more and more polluted, there are two options: develop increasingly complex and expensive methods of cleaning the water; or risk environmental degradation and associated consequences to human health of drinking polluted water.

Toxic chemicals can be eliminated, at different rates, from the subterranean environment. Chemical and physical processes are important for some pollutants but microbial breakdown is the principal means of degradation.

A better understanding of how toxic chemicals break down would help in the design of less toxic and more readily degradable alternative industrial and agricultural chemicals.

The nature and biological basis of the toxicity of a limited number of pollutants are known. Contamination by hormones from birth control pills have been implicated in an apparent drop in male fertility.