Lung cancer in smokers is caused mainly by
- A. the carcinogenic chemicals in tar
- B. the heat of the smoke
- C. nicotine acting on the brain
- D. the loss of surfactant from the alveoli
Explanation
Tar contains carcinogens such as benzopyrene that mutate the genes controlling cell division in the bronchial epithelium, and years of exposure eventually produce an uncontrolled tumour. Nicotine is highly addictive but is not itself the main carcinogen, which is why a nicotine patch is far safer than a cigarette. The risk rises with the number of cigarettes and the number of years smoked.
Related questions
Carbon monoxide is dangerous because it
The component of cigarette smoke responsible for addiction and for raising heart rate and blood pressure is
In emphysema the patient becomes breathless because
The persistent cough of chronic bronchitis in a smoker develops because
Passive smoking is a health hazard because