On the other hand, this chromosomal region does not increase the risk of lung cancer among non-smokers (Lips et al., 2010). Furthermore, cigarettes per day may not fully account for the exposure to carcinogens in cigarette smoke. An intriguing study demonstrated that smokers with the risk variants in the chromosome 15 region ingested more toxins even after controlling for the number of cigarettes smoked (Le Marchand et al., 2008). This implies that the smokers with the risk variants are inhaling more intensely and increasing their exposure to nicotine and other carcinogens in cigarette smoke. Thus the measurement of cigarettes per day is an imprecise measure of the risk of smoking related to lung cancer and COPD.
