The AP recently reported that both Boston and the state of Massachusetts are considering raising the minimum legal cigarette-purchasing age from 18 to 21, a policy change which has the potential to delay, not only legal access, but when young adults start smoking. According to the article, “[N]early 60 representatives and senators have signed on to a bill that would make it illegal to sell tobacco to people under 21, with penalties ranging from $100 to $300 for repeat violations.”

If the policy is instituted and does have the effect of delaying a young person’s contact with cigarettes—which is unfortunately not a forgone conclusions since adults in Massachusetts would still be able to legally provide tobacco products to under-aged users—the public health consequences could be significant.

In 1993, in a paper published in Epidemiology, Kurt T. Hegmann et al. analyzed the relationship between the age of smoking initiation and lung cancer risk. The researchers studied 282 patients diagnosed with lung cancer in Utah between 1989 and 1991.  After controlling for age, sex, and amount of tobacco exposure, they found that “men who began to smoke before age 20 had a substantially higher risk of developing lung cancer” than those who started smoking later on.  For women, starting to smoke before age 25 was associated with a much higher risk of lung cancer.”

A later (2002) paper by John K. Wiencke and Karl T. Kelsey in Environmental Health Perspectives offers an explanation for why such an increased risk exists among those who start smoking in their teens, even after controlling for tobacco exposure.  Adolescence, they write, “which is known to be the period of greatest development for the lung, may constitute a ‘critical period’ in which tobacco carcinogens can induce fields of genetic alterations that make the early smoker more susceptible to the damaging effects of continued smoking.”

Wiencke and Kelsey caution that their hypothesis—that “[g]rowth and development of the lungs during adolescence may set up a critical period of susceptibility to tobacco-related DNA damage”—had not yet been proven, but point to research indicating that early smoking initiation is correlated with a variety of genetic mutations associated with lung cancer. Smoking cigarettes during this developmentally sensitive lung development period has also been shown to dramatically alter the growth of lung volume.  “The linear phase of growth in lung volume is approximately 1 year shorter in males who smoke compared with those who never smoked and 2-3 years shorter in female smokers,” observed the authors.

The difference between starting smoking at 18 and 21, then, may be more than just a few more years of tobacco exposure.