Tobacco Documents Online

The 'No Thres iold' Argument 1. The 'no threshold' argument claims that no level of a cancer causing substance (carcinogen) is safe, however low. 2. This concept was lent credence by the US Delaney Amendment (1959) which legislated that no dose of a carcinogen is safe, however small. 3. There is, nevertheless, much debate about whether there are safe levels of exposure to carcinogens. 4. Most substances deemed to be carcinogens have been indicted by animal tests at very high doses. Whether they can cause human cancer at much lower doses is speculation. 5. Environmental tobacco smoke (ETS) contains traces of some such substances. It is therefore alleged that ETS can cause lung cancer by virtue of the substances it is claimed to contain. 6. But the vast majority of the substances known to be present in ETS are present in our environment from other sources. 7. Carcinogens exist everywhere in the human environment. Earth is a garden of carcinogens. Food is full of them. There are carcinogens in cabbages, strawberries, lettuces, mushrooms, apples, plums, peanuts, celery, carrots, pepper, potatoes, bread, beer, coffee, and orange juice (to mention a few). Cooking produces even more. 8. Our bodies cope - most of us survive in a healthy condition for a long time. This suggests that any insult to the body by low doses of carcinogens may be effectively repaired or neutralised by our natural defences. 9. A 1993 International Conference concluded that threshold doses are likely to exist, and condemned the Delaney Amendment as making no scientific sense. Ln F" Ln 10. They affirmed that legislative decisions should not be supported by pseudo- ~ scientific arguments or false and non-relevant data. N rn ~ 0, September 1993

The 'No Threshold' Argument Cancer causing substances (carcinogens) exist everywhere - in the food we eat, the water we drink, the very air we breathe - they are ubiquitous and unavoidable. But most have only been shown to be carcinogens in high-dose animal experiments: whether they cause cancer in humans at low doses is speculation. Because ETS is claimed to contain traces of such substances, and because it is assumed sometimes that there is no safe level of exposure to carcinogens, it has been suggested that inhaling someone else's tobacco smoke may cause lung cancer in nonsmokers (the 'no threshold' argument). The notion that there is no safe level of exposure to any carcinogen was promoted primarily by legislation not science. In 1959, during debates on the "Food, Drug and Cosmetic Act" in the USA, Congressman Delaney introduced an amendment - known as the Delaney Amendment - which postulated the notion that any molecule of a carcinogenic. substance can cause cancer. "No dose is safe" Delaney maintained, the corollary being that however miniscule the dose, if the population exposed is large enough, then some people must get cancer. This argument is akin to the fanciful idea that if there are enough monkeys with word processors, eventually one is bound to bash out a Shakespearian sonnet. Some doctors say that too much sun can give people skin cancer. But can we get cancer from a single sunbeam? In practice botfi notions are improbable. There is debate about whether there are safe levels of exposure to carcinogens, particularly in the' light of new insights into the mechanisms of chemical carcinogenesis. The vast majority of the chemicals present in tobacco smoke are also present in our outdoor and indoor environments, the food we eat, and the water we drink. In particular, food is a rich source of carcinogens; cooking food creates thousands more. Professor Ames recently pointed out that "99.99% of the chemicals we ingest are natural" (1992 Quarterly Projections No 7/8, 20). Even things as innocent as strawberries or as commonplace as cabbages are full of carcinogens. There are over a thousand chemicals reported in a cup of coffee; more than half that have been tested are claimed to be carcinogens. Further, the body produces additional carcinogens during metabolism of food. Because most of us survive in a healthy condition for a long time, it appears that injury to the body, if any, caused by low dose exposure to such chemicals may be effectively repaired or neutralised by efficient natural defences. As Dr Lazarides, Secretary of the Society for the Promotion of Nutritional Therapy stated (The Times, 4 March 1993): "All ourfoods are loaded with natural toxins but our bodies cope with them ". A Conference on Low Doses Of Carcinogens was held under the auspices of the International Center for Scientific Ecology (Paris 1993) at which many professors of science argued against the notion of a no safe dose level. They are to petition to have the Delaney Amendment reconsidered, as they believe it makes no scientific sense. Tap water would be proscribed if the Delaney Amendment were applied. Even ordinary salt, one of 'the other most common and necessary chemical compounds on Earth, falls foul of the Delaney Amendment, having now been shown to be carcinogenic at sufficient dose. So what should we take with a pinch of salt? As Paracelsus put it over four hundred years ago: "the dose alone makes the poison ". September 1993