Epidemiology is the study and control of diseases within a human population. Long-term epidemiological studies have linked diet to heart disease, smoking to lung cancer, and identified all known environmental poisons and occupational diseases. By labeling certain habits or substances as dangerous, we can diminish our chances of illness by consciously avoiding exposure to them. Using computers, researchers can now gather and analyze human population data at an unprecedented rate.

Unfortunately, animal experimentation often impedes the ready acceptance of epidemiological evidence. Cigarette smoke, alcohol, asbestos, arsenic and benzene are just a few of the harmful substances that, according to animal tests, are safe for humans to ingest. However, epidemiological research has conclusively proven all of them to be hazardous to humans.