Tobacco smoke - sometimes referred to as second-hand smoke, or 'Environmental Tobacco Smoke' (ETS) - is defined by the Environmental Health Centre website as 'a mixture of particles that are emitted from the burning end of a cigarette, pipe, or cigar, and smoke exhaled by the smoker'. These particles can be any of over 4000 chemical compounds, 200 of which are known poisons and 43 are known to cause cancer in humans or animals¹. Many of these 4000 chemicals are strong irritants. Tobacco smoke is primarily composed of a dozen gases. There are large amounts of carbon monoxide, but nicotine (an addictive drug), benzene, formaldehyde and tar are also present. A list of deleterious components of tobacco smoke can be found in Toxic Tobacco Smoke, but a few of the more dangerous ones are: Acetone; Ammonia; Arsenic; Benzene; Cadmium; Cyanide; Formaldehyde; Lead; Mercury; Nickel; Phenol; Styrene; Toluene. If you are interested in the actual levels of toxicity of these compounds, the Risk Assessment Information System website provides you with all the necessary information.

Tobacco smoke has been classified by the Environmental Protection Agency as a class 'A' carcinogen. This rating is only placed on substances that are known to cause cancer in humans. This rating places cigarettes in the same category as a number of other chemicals including benzene and asbestos. Exposure to tobacco smoke is known as passive smoking. This is extremely dangerous, as none of the chemical compounds are able to be filtered out.

Differences Between the Different Types of Tobacco

There are a number of components that are present irrespective of the type of tobacco being smoked, though the quantity and presence of others does alter according to the tobacco. These have been outlined above. Most of the compounds present in tobacco smoke are formed during the burning of the tobacco, and are a mere by-product of the combustion process of various chemical compounds (precursors) present in the tobacco. As such, the chemical composition of the smoke depends on two factors - the chemicals in the tobacco and the conditions under which combustion occurs.

The chemical composition of tobacco is affected by the manufacturing processes of the tobacco company. The way in which the tobacco is grown, cultivated, disinfected and cured all affect the final tobacco. Companies also add a number of chemicals to add flavour to the tobacco and to dampen it. The combustion process is also as varied. It depends on the temperature of the combustion, the length of cigarette and stub, the presence of a filter and the type of filter, as well as the strength and degree of inhalation.

Cigars

Like cigarettes, cigar smoke contains over 4000 chemical compounds, with more than 50 of them being carcinogenic. Unfortunately, smoking a single cigar in an unventilated room produces the equivalent of 42 cigarettes. Cigar smoke, compared to cigarette smoke, contains 20 times the amount of ammonia, ten times the amount of cadmium and 90 times the amount of nitrosamines. The majority of nitrosamines are mutagens, which alter the genetic content of cells, and a number of them are organ specific carcinogens. The average cigar releases three times the amount of carcinogenic material and 30 times the amount of carbon monoxide compared to a normal cigarette. The smoke from cigars is slightly alkaline, as opposed to cigarette smoke which is slightly acidic. This means that the smoke can be more effectively absorbed into the blood stream through the mucosal linings of the nose and mouth.

Pipes

It is difficult to find any information on the actual content of pipe smoke. It does have the advantage over other forms of tobacco smoking of having a lower combustion temperature², and the fact that not all the tobacco is burned. However, it must be stressed that despite this, there is still the presence of a number of dangerous chemical compounds. Pipe smokers are more likely to develop cancer of the mouth than cigarette smokers - mainly because they do not inhale the smoke to the same degree.

Light Cigarettes?

Although it would make sense for 'light' and 'ultra-light' cigarettes to have less of a health impact than 'full-strength' cigarettes, it does not appear to be the case. The ISO³ cigarette test measures the levels of tar, nicotine and carbon dioxide yields from cigarettes, and the results from this enable a cigarette to be labelled as 'light' or 'ultra-light'. However, it is not felt by the whole of the scientific community that these tests are meaningful. 'Light' cigarette filters contain small holes which are intended to maximise the amount of air mixed with the tobacco smoke, thereby reducing the measured readings of tar, nicotine and carbon monoxide. As these holes are covered by the smoker, the amount of air mixing is further reduced, increasing the concentration of chemicals further. Scientists feel that this 'skews' the results in favour of the cigarette⁴.

In the January 2000 edition of Journal of the National Cancer Institute, a study was published, which suggested that smokers contract twice the amount of tar and nicotine from 'low-tar' cigarettes than was previously believed. It was also suggested that 'low-tar' cigarettes carry a greater health risk than high tar cigarettes. The reasoning behind this is that the smoke from high tar cigarettes is too irritating to inhale very deeply. With the low-tar cigarette, the smoker can inhale deeper, resulting in more carcinogens and toxins entering the peripheral lung area. This has been attributed to the increase of the previously rare lung cancer - adenocarcinoma.

For these reasons, it is difficult to distinguish between the different types of tobacco smoke. The amount of toxins you inhale depends on how much you smoke, and will increase if you:

• Inhale deeply
• Take more puffs
• Hold the smoke in your lungs longer
• Smoke the cigarette right down to the filter
• Cover the vent holes that are near the filter

As such, this entry will have to generalise to a certain degree. It is not in dispute though that different tobacco contains the same dangerous chemicals, only the quantities present.

Short Term Effects of Tobacco Smoke?

When nicotine is inhaled, it reaches the brain faster than it would if it were to enter the body intravenously. According to the Oregon Graduate Institute of Science and Technology, nicotine can exist in both an acid and base form (similar to cocaine). The addition of ammonia (from the smoke) converts the nicotine from the acidic to the basic form. This form of nicotine vaporises more easily into a gas, meaning that it can deposit directly on the lung tissue and diffuse quickly throughout the body. This technique is known as 'free-basing' and heightens the effect of the drug. Its use enables the nicotine to reach the brain in just eight seconds from taking a drag on the cigarette.

Smokers become physically and mentally addicted to nicotine, as they associate smoking with many social activities. It is a difficult habit to break, and giving up smoking is a very difficult thing to do.

Short-term effects of nicotine in cigarette smoke include sweating and throat irritation. It also affects the mood of the smoker - it can stimulate, depress or relax, depending very much on the smoker themselves. Smoking can also cause vomiting to occur in new smokers.

Long Term Effects of Tobacco Smoke?

Nicotine produces effects on the lungs, and tar exposes the user to the risk of emphysema, which is a common disease among cigarette smokers. It is ten times more likely to occur in smokers than in non-smokers. Smoking causes most cases of emphysema, and 16,700 Americans died in 2000 from bronchitis⁵.

Tar exposes the user to the risk of bronchial disorders (infections of the tubes to the lungs). For example, chronic bronchitis is a common disease among cigarette smokers. Again, it is ten times more likely to occur in smokers than in non-smokers. Smoking causes most cases of chronic bronchitis, and 1,167 Americans died in 2000 from bronchitis.

Nicotine produces effects on the heart. The carbon monoxide in the smoke increases the chance of cardiovascular⁶ diseases, including coronary heart disease and strokes. The risk of congestive heart failure is also increased by the effects of nicotine. 170,000 Americans die each year from smoking-related heart diseases.

Nicotine produces effects on the stomach, neurotransmitters⁷, and sympathetic and parasympathetic nervous systems⁸.

43 of the poisons in a cigarette are known to cause cancer. Tar exposes the user to the risk of lung cancer, which is the most serious effect of smoking. Cancers of the mouth, lips, pharynx, larynx, oesophagus, pancreas, uterine cervix, kidney and bladder are also associated with cigarette, cigar and pipe smoking. Smoking is directly responsible for 87% of lung cancer cases (resulting in 3,000 annual non-smoker deaths). 30% of US cancer deaths (130,000 per year) are linked to smoking.

Smoking has also been linked to conditions and disorders, including slower healing of wounds, infertility, and peptic ulcer disease.

It is believed that a mother who smokes has an increased risk of giving birth prematurely. This may cause the baby to have underdeveloped lungs and air passages. If smoke is present in the air after birth, these airways may decrease in diameter. This will increase any breathing difficulties, possibly causing bronchitis or pneumonia. This will further reduce the baby's health.

It is believed that a mother who smokes will produce a smaller baby. Smaller babies are more likely to need special care and stay longer in hospital. Some may die either at birth or within the first year.

Through research it has been shown that children born to smokers are prone to asthma, increased frequency of colds, coughs and middle-ear infections. There are approximately 150,000 to 300,000 cases of lower respiratory tract infections in children less than 18 months of age in America. This results in 7,500 to 15,000 annual hospitalisations, which are believed to be caused by passive smoking.

Women who smoke generally have earlier menopause. If women smoke cigarettes and also take oral contraceptives they are more prone to cardiovascular and cerebrovascular⁹ diseases than other smokers. This is especially true for women over 30 years old.

Each year smoking kills more Americans than alcohol, cocaine, crack, heroin, murder, suicide, car accidents, fires and AIDS combined. In total, cigarette disease victims die more than twenty years before the life expectancy of non-smokers.

Thus, about 430,700 Americans die annually (including those affected indirectly, such as premature babies due to prenatal maternal smoking and some victims of passive smoking).

How Does Tobacco Smoke Affect Babies?

Pre-Natal Effects

When a pregnant mother smokes, the nicotine and carbon monoxide from the cigarette smoke penetrate through to the placenta. This prevents the foetus from getting the nutrients and oxygen needed to grow. Smoking may decrease the immunity of the foetus, which can lead to infection. Smoking may even lead to learning difficulties in later life.

The lack of nutrients, coupled with the lack of oxygen increases the risk of having a spontaneous abortion (miscarriage), a stillborn or premature infant, or an infant with low birth weight. If the baby is premature, there is also the possibility that the lungs are not fully developed.

Smoking accounts for 20-30% of low birth weight babies, 14% of premature births and 10% of all infant deaths.

Postnatal Effects

Babies are more likely to die of Cot Death¹⁰ than any other cause: the Foundation for the Study of Infant Deaths states that:

Cot death is the leading cause of death in babies over one month old - more deaths than from meningitis, leukaemia, other forms of cancer, household and road traffic accidents.

Babies who are exposed to tobacco smoke are at an increased risk of cot death: 30% of the cases of cot death could be related to smoking. A baby who is exposed to the smoke of 20 or more cigarettes a day is eight times more likely to be a victim of cot death.

Further Information

• The British Medical Association have produced a Tobacco Fact File, which presents all sorts of key facts and data about tobacco. It is an invaluable source of excellent information.

• Factsheets are available online from the Lung and Asthma Information Agency (please note, these factsheets are presented in PDF format. You may need to download additional software to view them).

• The Cot Death society has more information on believed causes of sudden infant death.