As a public health expert with a focus on epidemiology, I can tell you that the link between smoking and cancer is well-established. However, it's important to note that there is no specific number of cigarettes that guarantees the development of cancer, as the risk is influenced by a multitude of factors including genetics, duration of smoking, the number of cigarettes smoked, and the individual's overall health.

Cigarette smoke contains over 7,000 chemicals, with at least 70 known to be carcinogens. Even smoking a small number of cigarettes can increase the risk of developing cancer, particularly lung cancer, but also cancers of the mouth, throat, esophagus, bladder, kidney, pancreas, and cervix.

The risk increases significantly with the number of cigarettes smoked per day and the duration of the smoking habit. For instance, someone who smokes a pack a day (20 cigarettes) has a much higher risk than someone who smokes just one or two cigarettes a day. However, even the latter cannot be considered safe, as there is no safe level of smoking.

It's also crucial to consider the concept of cumulative exposure. The longer a person smokes and the more cigarettes they consume over their lifetime, the higher their risk of developing cancer.

In conclusion, while it's not possible to pinpoint an exact number of cigarettes that will cause cancer, it's clear that any amount of smoking increases the risk. The best way to reduce the risk is to quit smoking entirely.

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On average, respondents in this group considered that smoking can cause cancer only if one smokes at least 19.4 cigarettes per day (for an average reported consumption of 5.5 cigarettes per day), and that cancer risk becomes high for a smoking duration of 16.9 years or more (reported average duration: 16.7).read more >>