Cigarettes look deceptively simple, consisting of paper tubes containing chopped up tobacco leaf, usually with a filter at the mouth end.
In fact, they are highly engineered products, designed to deliver a steady dose of nicotine.
Cigarette tobacco is blended from two main leaf varieties: yellowish ‘bright’, also known as Virginia where it was originallygrown, contains 2.5-3% nicotine; and ‘burley’ tobacco which has higher nicotine content (3.5-4%).
US blends also contain up to 10% of imported ‘oriental’ tobacco which is aromatic but relatively low (less than 2%) in nicotine.
In addition to the leaf blend, cigarettes contain ‘fillers’ which are made from the stems and other bits of tobacco, which would otherwise be waste products. These aremixed with water and various flavorings and additives. The ratio of filler varies among brands.
For example, high filler content makes a less dense cigarette with a slightly lower tar delivery. Additives are used to make tobacco products more acceptable to the consumer.
They include humectants (moisturizers) to prolong shelf life; sugars to make the smoke seem milder and easier to inhale; andflavorings such as chocolate and vanilla. While some of these may appear to be quite harmless in their natural form they may be toxic in combination with other substances.
Also when the 600 permitted additives are burned, new products of combustion are formed and these may be toxic.
The nicotine and tar delivery can also be modified by the type of paper used in the cigarette. Using more porous paperwill let more air into the cigarette, diluting the smoke and (in theory) reducing the amount of tar and nicotine reaching the smoker’s lungs.
Filters are made of cellulose acetate and trap some of the tar and smoke particles from the inhaled smoke. Filters also cool the smoke slightly, making it easier to inhale. They were added to cigarettes in the 1950s, in response to the first reports thatsmoking was hazardous to health. Tobacco companies claimed that their filtered brands had lower tar than others and encouraged consumers to believe that they were safer.
Tobacco smoke is made up of “sidestream smoke” from the burning tip of the cigarette and “mainstream smoke” from the filter or mouth end.
Tobacco smoke contains thousands of different chemicals which are released into the air asparticles and gases.
Many toxins are present in higher concentrations in sidestream smoke than in mainstream smoke and, typically, nearly 85% of the smoke in a room results from sidestream smoke.
The particulate phase includes nicotine, “tar” (itself composed of many chemicals), benzene and benzo(a)pyrene. The gas phase includes carbon monoxide, ammonia, dimethylnitrosamine, formaldehyde,hydrogen cyanide and acrolein. Some of these have marked irritant properties and some 60, including benzo(a)pyrene and dimethylnitrosamine, have been shown to cause cancer.
One study has established the link between smoking and lung cancer at the cellular level. It found that a substance in the tar of cigarettes, benzo(a)pyrene diol epoxide (BPDE), damages DNA in a key tumour suppresser gene.
What isCigarette Tar?
“Tar”, also known as total particulate matter, is inhaled when the smoker draws on a lighted cigarette. In its condensate form, tar is the sticky brown substance (filled with chemicals) which can stain smokers’ fingers and teeth yellow-brown. All cigarettes produce tar but the brands differ in amounts.
The average tar yield of cigarettes has declined from about 30mg per cigarettein the period 1955 to 61 to 11mg today. There have also been reductions in nicotine (from an average of about 2mg in 1955, 61 to about 0.9mg by 1996). Until January 1992, information about tar yields of cigarettes was given in a general fashion on cigarette packets and advertisements as a result of a voluntary agreement between the tobacco industry and the Government.
Due to labeling (Safety)...