Answer:
Because the repository of genetic information in each living cell, its integrity and stability are essential to life. So there for a chemical entity subject to assault from the environment, and any resulting damage, if not repaired, will lead to mutation and possibly disease. Perhaps the best-known example of the link between environmental-induced DNA damage and disease is that of skin cancer, which can be caused by excessive exposure to UV radiation in the form of sunlight (and, to a lesser degree, tanning beds).
Explanation:
