Steven Branstetter, assistant professor of biobehavioral health at Pennsylvania State University, said 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.
"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," Branstetter said in a statement.
Branstetter and colleague Joshua Muscat, a professor of public health sciences, examined data on 1,945 smoking adult participants from the National Health and Nutrition Examination Survey who had provided urine samples for analysis of NNAL.
The researchers found about 32 percent of the participants they examined smoked their first cigarette of the day within 5 minutes of waking; 31 percent smoked within 6-30 minutes of waking; 18 percent smoked within 31-60 minutes of waking; and 19 percent smoked more than one hour after waking.
In addition, the researchers found the NNAL level in the participants' blood correlated with the participants' age, the age they started smoking, their gender, and whether or not another smoker lived in their home, among other factors.
The findings were published in the journal Cancer, Epidemiology, Biomarkers and Prevention.