Why do some smokers get cancer, and others don’t. There are likely many factors such as genetics, exposure to environmental pollutants, immune system strength, and others. A new study by Penn State found that the sooner a person smokes a cigarette upon waking in the morning, the more likely he or she is to acquire lung or oral cancer.

“We found that smokers who consume cigarettes immediately after waking have higher levels of NNAL — a metabolite of the tobacco-specific carcinogen NNK — in their blood than smokers who refrain from smoking a half hour or more after waking, regardless of how many cigarettes they smoke per day,” said Steven Branstetter, assistant professor of biobehavioral health.

According to Branstetter, other research has shown that NNK (4-(methylnitrosamino)-1-[3-pyridyl]-1-butanone) induces lung tumors in several rodent species. Levels of NNAL (4-(methylnitrosamnino)-1-(3-pyridyl)-1-butanol) in the blood can therefore predict lung cancer risk in rodents as well as in humans. In addition, NNAL levels are stable in smokers over time, and a single measurement can accurately reflect an individual’s exposure.