01 Oct

The Cancer Stick: Carcinogens in Cigarette Smoke

While almost everybody knows that cigarette smoke contains chemicals that are bad for a person’s health, very few people actually know what these chemicals are and what they do to the human body.

The smoke from tobacco cigarettes contains approximately 5000 identified chemicals and has been described as a “toxic and carcinogenic mixture” [1]. The relationship between cigarette smoking and lung cancer was established as long ago as 1950 [2, 3], and in the United States smoking contributes to more than 90% of all deaths from lung cancer in men and to about 80% of all deaths from lung cancer in women [4, 5]. Although lung cancer is the fifth most common form of cancer in Australia – after prostate, colorectal, breast and melanoma – it is the most common cause of cancer death, accounting for almost 20% of all cancer deaths [6]. Cigarette smoking is also causally related to cancer of the larynx, oesophagus, oral cavity, pancreas, renal pelvis and urinary bladder, and it is linked to cancer of the cervix [4, 5, 7]. A report by the United States Surgeon General in 1989 found that cigarette smoking was responsible for 81.8% of all deaths from chronic obstructive pulmonary disease, 21.5% of deaths from coronary heart disease and 18.0% of deaths from stroke [4].

The finding that cigarette smoke caused a number of cancers led to intensive research in to its chemical composition and to the identification of the toxic and carcinogenic agents in it. One result of this was the gradual identification of smoke constituents. In 1959, it was reported that about 600 compounds had been found in cigarette smoke [8], a figure that increased to 1000 in 1968 [9]. In 1988, one researcher listed 3794 cigarette smoke constituents [10], and in 1996 it was reported that a whopping 4800 compounds had been identified in tobacco smoke [11].

The first carcinogenic compound in cigarette smoke – benzopyrene – was identified in 1954 [12]. Subsequent research brought this figure to 69 by the year 2000 [13]. All 69 of these chemicals are carcinogenic to animals, while 11 of them are proven carcinogens in humans: arsenic, benzene, beryllium, cadmium, chromium, ethylene oxide, nickel, polonium-210, vinyl chloride, 2-naphthylamine and 4-aminobiphenyl [13]. It should be remembered that the lack of scientific evidence that many of the 69 chemicals cause cancer in people does not mean that they do not; it only means that there is insufficient scientific evidence. The fact that they are carcinogenic to laboratory animals is alarming and warrants concern.

Many people would be shocked to learn what some of the 11 proven human carcinogens are commonly used for. Arsenic, for example, is used as a wood preservative and insecticide. Benzene, which is derived from crude oil, is commonly used in the manufacture of industrial chemicals and as a petrol additive. Cadmium is used in car batteries. Most of the others are commonly used in the manufacture of industrial chemicals and products.

The tobacco cigarette has been described as “probably the most significant source of toxic chemical exposure and chemically mediated disease in humans” [1]. Not only does it cause numerous cancers as discussed above, but it also causes various cardiovascular and pulmonary diseases. The World Heath Organization estimates that approximately 5.4 million premature deaths each year can be attributed to cigarette smoking [14], a figure that will rise to an estimated 10 million by 2025 [15]. This is a horrendous loss of human life, especially given that it is entirely preventable.

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[4] United States Department of Health and Human Services (1989) Reducing the Health Consequences of Smoking: 25 Years of Progress, United States Department of Health and Human Services, Washington DC.
[5] Shopland D R (1995) “Effect of smoking on the incidence and mortality of lung cancer” in Johnson B E & Johnson D H (editors) (1995) Lung Cancer, John W & Sons, New York, 1-14.
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[13] Hoffmann D, Hoffmann I & El-Bayoumy K (2001) The less harmful cigarette: A controversial issue, Chemical Research in Toxicology, Volume 14, Number 7, 767-790.
[14] World Health Organization (2008) World Health Organization Report on the Global Tobacco Epidemic: The MPOWER Package, World Health Organization, Geneva.
[15] Hatsukami D K, Stead L F & Gupta P C (2008) Tobacco addiction, Lancet, Volume 371, 2027-2038.