A middle-aged client with a 30-year history of smoking was diagnosed with lung cancer. A health history revealed previous exposure to air pollution, asbestos, and radiation. Which of the following most likely had the greatest impact on development of the lung cancer?

Radiation
Cigarette smoke
Asbestos
Air pollution

The correct answer is- cigarette smoke

Explanation:

Cigarette contains tobacco and tobacco contains 7000 chemical out of which 250 are harmful and 69 are cancer-causing. People who smoke cigarettes are at 15-30 times higher risk of getting lung cancer than a person who does not smoke a cigarette.  

So as a middle-aged client has a 30-year history of smoking therefore smoking is most likely had the greatest impact on the development of lung cancer. Therefore the correct answer is cigarette smoke.