疾病控制There are two main causes of cancer: heredity and environment
We can do nothing to change our heredity, that is, the basic physical characteristics that were passed on to us by our parents
However, we can do a GREat deal to control our environment, which may account for 80-90 %of all cancers
Environmental pollution can be divided into two kinds: personal and impersonal
Personal pollution may be defined roughly as unhealthy habits such as smoking, drinking, and eating the wrong foods
Clearly, with enough will power we can control this personal environment
Impersonal pollution, on the other hand, refers to those things which are beyond our individual control
One example would be industrial pollution, which is very hard to control because of the expense involved
It would be expens