ABSTRACT
In recent years, the word "natural" has become almost synonymous with everything that is good in life. Yet certain natural phenomena pose a constant threat to our molecular wellbeing. Even those parts of our environment which we know to be essential, such as sunlight and oxygen, create unwanted, destructive changes in our most important biological macromolecules. When these changes occur in DNA, swift action must be taken in order to repair the damage and so preserve the genetic constancy of the cell. Many naturally occurring chemicals can also modify DNA. When one adds to these the long list of man-made chemicals from our industrial society then it is easy to understand the current interest in human toxicology and self-preservation. The near-equivalence of DNA-damaging agents, mutagens and carcinogens is at the center of this concern.
