Thursday, January 24, 2008

Secondhand Smoke: the “no threshold” Scare

A major argument for smoking bans is the claim “there is no safe level”—no threshold—below which tobacco smoke is not dangerous. The ban advocates/activists invoke the well-known link of smoking and lung cancer and assert that, therefore, even secondhand smoke must also be carcinogenic. They claim the air from smoking can never be made clean enough to eliminate the health risk and thus smoking must be banned altogether. But the “no threshold” hypothesis about cancer has never been shown to be true for ANY chemical, much less secondhand smoke. The idea that if something is carcinogenic at high doses it must also be proportionately so at small doses simply does not fit the real world. At least ten elements (including iron and oxygen) are carcinogens at high doses but essential to human life in small doses. And some carcinogens, such as selenium and Vitamin A, are proven anti-carcinogens at low doses. These facts contradict the “no-threshold” idea. Thresholds are a law of nature; the mere title of one treatise says it all: “Environmental Carcinogenesis—The Threshold Principle: A Law of Nature." The authors, Claus and Bolander, state that the no-threshold concept about any dose being dangerous ignores “all the fundamental principles of cell biology.”

Dr. Elizabeth Miller, former president of the American Association for Research on Cancer, has stated: “Chemical carcinogenesis is a strongly dose-dependent phenomenon.” This is opposite to the claim by smoking ban advocates—including the surgeon general—that it is not dose dependent, that any dose is a health hazard.

The no-threshold concept, when applied to secondhand smoke, “incorporates unsound assumptions that are not valid,” says an article by Drs. Huber (pulmonary specialist), Brockie (cardiologist), and Mahajan (a hospital director of internal medicine and professor of medicine.)

Furthermore, thresholds are known to exist for mainstream tobacco smoke in total as well as for each of the individual carcinogens known to be in it. It is preposterous to claim, as the surgeon general has done, that secondhand smoke—which is more than 100,000 times more dilute than mainstream smoke—has no threshold, even though mainstream smoke does. This turns the dose-response principle of epidemiology on its head and means secondhand smoke can be more dangerous than actual smoking! Ridiculous!

The surgeon general should know that thresholds for all carcinogens in—or even assumed to be in—secondhand smoke have been identified. They have been calculated by the American Conference of Government Industrial Hygienists. Below these thresholds, the chemicals are considered safe. To reach the threshold for the carcinogen with the lowest threshold (hydroquinone) would require 1,250 cigarettes to be smoked in a sealed, unventilated room 20 by 22 feet within one hour. This would mean 30 people in that room each smoking slightly more than 2 PACKS of cigarettes per hour. And remember this is in a sealed room, where no one would enter or leave in that hour and where there would be no mechanical ventilation. Open a door or window or add mechanical ventilation, and the number of cigarettes needed to reach the threshold would be even higher. Of course, nobody—much less everyone in a room—will ever smoke 2 packs of cigarettes per hour. Thus it is essentially impossible for secondhand smoke to be a cancer risk despite the pathetic claims of the surgeon general and other smoking ban activist/advocates.

Notice that I began the last paragraph by speaking of all the carcinogens known “or even assumed” to be in secondhand smoke. This is because most of the carcinogens have never actually been found in secondhand smoke. If they exist there at all, they are in quantities too small to be measurable. They are simply assumed to be there because they are known to exist in the smoke from which secondhand smoke is derived. So calculations of their presence in secondhand smoke are based on their proportions in the parent smoke. But they may not exist at all in secondhand smoke because of physical, chemical and behavioral differences from the parent smoke. Secondhand smoke has extremely low concentrations of volatiles. Mainstream smoke is highly concentrated, and its higher gas phase concentrations favor larger respirable particles that condense and retain more volatile compounds. Evaporation is faster from secondhand smoke particles; within fractions of a second, they becomes 50 to 100 times smaller than their mainstream counterparts. Secondhand smoke quickly undergoes a variety of other changes: oxidation, polymerizations, photochemical transformations, and other changes. All these changes take place extremely quickly. So suddenly secondhand smoke is a very different collection of chemicals than the smoke from which it was derived, and carcinogens assumed to be there may, in fact, be absent. But even if present, they are in quantities far below the threshold levels. And secondhand smoke is “so highly diluted,” say Huber/Brockie/Mahajan, “that it is not even appropriate to call it smoke, in the conventional sense. Indeed, the term 'environmental tobacco smoke' is a misnomer.”

For more on secondhand smoke and other issues, see “Free Essays” on my website