When it comes to cigarettes and your health, who are you going to believe, Philip Morris or the Harvard School of Public Health?
Yesterday, HSPH released its study (PDF) of nicotine in cigarettes based on data collected for a study (PDF) by the Massachusetts Department of Public Health, which was released last summer to great media fanfare. (I criticized press coverage of the Massachusetts report in Slate.)
The new HSPH study "confirms" the Massachusetts findings that the cigarette companies increased machine-measured levels of nicotine "in the smoke of their products" between 1997 and 2005. The HSPH study goes on to assert that nicotine yields grew 8.5 percent over those years and that the companies came by those gains by "increasing nicotine in the tobacco rod and by other design modifications," including varying the "filter ventilation" and slowing the "burn rate," which allows more puffs per cigarette. Furthermore, HSPH's analysis found that the increases in machine-measured levels of nicotine constituted a "statistically significant trend." In other words, the increases in nicotine yield over the researched period weren't random.
Given the anti-tobacco bias of the press—and who can blame them?—this week's reports largely endorse the HSPH findings. The Washington Post'sabysmal wire brief confused the amount of nicotine detected by a machine with the amount of nicotine inhaled by human smokers. Neither the Boston Globenor the New York Timesdug into the science to question whether the trend of higher levels of nicotine—if it is a trend—really makes cigarettes more dangerous.
A substantial body of scientific research shows that smokers excel at milking cigarettes for the nicotine dose they desire, irrespective of how many milligrams of nicotine the actual cigarette they end up smoking contains. The well-known behavior is called "compensatory smoking." University of Waterloo professor David Hammond wrote in a sidebar to my piece last summer, "humans adjust the intensity of their smoking in response to the cigarette design and emission level. Therefore, 'lower nicotine' yield cigarettes are smoked systematically more intensely."
If you search for the words "nicotine yield" in PubMed, you'll quickly find a half-dozen relevant scientific papers that support Hammond's position. In a recent paper from Germany (abstract), researchers confirmed earlier studies that show "at most a weak association between the machine-derived smoke yields and the uptake of smoke constituents by the smoker" by assaying urine samples from real-life smokers. The number of cigarettes consumed is a much stronger predictor of how much nicotine a smoker will take on board, the study concludes. The researchers write:
It is suggested that the evaluation of potentially reduced-exposure products should also include human biomarker studies in order to avoid erroneous conclusions from the smoking machine results.
Philip Morris USA quarrels with the Massachusetts and HSPH findings, stating in a press release yesterday that the nicotine yield of its Marlboro brand was unchanged from 1997 to 2006—1.86 milligrams per cigarette. Philip Morris' credibility is, shall we say, wanting, on the subject of tobacco, so I don't expect you to believe anything it says.
But I do expect you to listen. In a Sept. 25, 2006, letter to Massachusetts authorities and CC'd to 15 scientists and public-health officials, Philip Morris USA Vice President Kenneth F. Podraza discusses the "Kentucky Reference Cigarette 2R4F" that the company makes under government direction for research purposes. Podraza writes that the machine-measured nicotine yields of this reference cigarette from just one production run varied from about 0.78 milligrams per cigarette to 0.86 milligrams in 28 tests over a six-month period. Essentially, in invoking a research cigarette that his company tries to keep standard, Podraza argues that some variations in nicotine levels are to be expected. Then again, Podraza does work for a tobacco company. …
Whenever the press writes about nicotine yields, it invariably quotes some public-health advocate warning that even these incremental increases in nicotine automatically make cigarettes more addictive. But if that were true, wouldn't the press or somebody have saluted the tobacco industry for reducing the addictive potential of cigarettes whenever nicotine levels dropped? Indeed, between 1972 and 1983, the average measured nicotine (sales weighted) dropped from 1.39 milligrams per cigarette to 0.88 milligrams per cigarette. From 1989 to 1996, it dropped from 0.96 milligrams per cigarette to 0.88 milligrams per cigarette. (See this Federal Trade Commission PDF.) I don't recall hearing any cheering.