Cigarette smoking is the primary cause of lung cancer throughout the world.

The risk of developing lung cancer is related to the total dose of smoke to which you have been exposed during your lifetime. This can be estimated in several ways including: the number of cigarettes smoked per day, the depth of smoke inhalation, the number of pack-years, and the age at which smoking began.

These measures of exposure correlate well with the risk of getting lung cancer, but they are subjective measures and rely on the truthfulness and accuracy of the information smokers report about themselves. Recently, a novel method of more accurately determining smoke cumulative smoke exposure was reported in the American Journal of Epidemiology.

Toe nail samples were collected from 210 men with lung cancer. Nicotine levels within the toenails were analyzed and compared with toenail samples from 630 controls who were matched for age and other factors. The nicotine levels in the toenails of the men with lung cancer averaged 0.95 ng/mg compared with 0.25 ng/mg among controls. This showed a strong relationship between the dose of cigarettes and the response by their bodies.

The men with the highest levels of toenail nicotine had a 10 times higher risk of lung cancer than those with the lowest levels. Toenail nicotine levels were a stronger predictor of lung cancer than the men’s smoking history alone.