Epidemiology became widely recognized with the discovery of tobacco smoking as a cause of lung cancer in the early
1950s. Subsequent decades have seen major discoveries relating to other causes of noncommunicable disease such as
asbestos, ionizing radiation, and dietary factors. These epidemiologic successes have in some cases led to successful
preventive interventions without the need for major social or political change. For example, occupational carcinogens can,
with some difficulty, be controlled through regulatory measures, and exposures to known occupational carcinogens have
been reduced in industrialized countries in recent decades. Another example is the successful World Health Organization
campaign against smallpox.27 More recently, some countries have passed legislation to restrict advertising of tobacco and
smoking in public places and have adopted health promotion programs aimed at changes in lifestyle.