Tobacco

Tobacco comes from the leaves of the tobacco plant (Nicotiana tabacum and Nicotiana rustica), which contain nicotine. Nicotine is a stimulant drug. Stimulant drugs act on the central nervous system to speed up the messages traveling between the brain and the body.

The leaf of the tobacco plant is dried, cured and aged before having other ingredients added to manufacture a range of tobacco-based products. For example, cigarettes (including some herbal cigarettes), cigars, pipe tobacco, chewing tobacco, and wet and dry snuff.

What's in cigarette smoke?

There are more than 4000 chemicals in tobacco smoke. Many of these chemicals are poisonous and at least 43 of them are carcinogenic (cause cancer). The three major chemicals in tobacco smoke are:

• Nicotine - the chemical on which smokers become dependent
• Tar - which is released when a cigarette burns
• Carbon monoxide (CO) a colorless, odorless and very toxic gas that is taken up more readily by the lungs than oxygen. Smokers typically have high levels of CO in the blood.

Effects of tobacco smoke

Tar in cigarettes coat the lungs and can cause lung and throat cancer in smokers. It is also responsible for the yellow–brown staining on smokers' fingers and teeth.

Carbon monoxide in cigarettes robs the muscles, brain and blood of oxygen, making the whole body—especially the heart—work harder. Over time this causes airways to narrow and blood pressure to rise, and can lead to heart attack and stroke. High levels of CO, together with nicotine, increase the risk of heart disease, hardening of the arteries and other circulatory problems. A first-time smoker will often feel dizzy and sick.

"Light" or "low tar" cigarettes

Research has shown that there is little difference between the amount of chemicals inhaled by people who smoke "light" or "low tar" cigarettes and those who smoke regular cigarettes. People who smoke "light" cigarettes have the same risk of developing smoking-related diseases as people who smoke regular cigarettes.

Immediate effects

Soon after smoking tobacco, the following effects may be experienced:

• initial stimulation, then reduction in brain and nervous system activity
• enhanced alertness and concentration
• mild euphoria
• feelings of relaxation
• increased blood pressure and heart rate
• decreased blood flow to body extremities like the fingers and toes
• dizziness, nausea, watery eyes and acid in the stomach
• decreased appetite, taste and smell.

Overdose

Although rare, it is possible to overdose on the nicotine in tobacco.

Very large doses of nicotine can result in an increase in the unpleasant effects, including feelings of faintness and confusion, and a rapid decrease in blood pressure and breathing rate.

In some cases, it can lead to convulsions and death from respiratory failure. Sixty milligrams of nicotine taken orally can be fatal for an adult.

Long-term effects

It is estimated that more than 140 000 hospital episodes and 19 000 deaths in Australia can be attributed to tobacco use every year. The principal diagnoses are cancer, heart disease and chronic obstructive pulmonary disease.

Passive smoking

Passive smoking can cause a number of health problems including heart disease, lung cancer and irritation of the eyes and nose. It involves breathing in tobacco smoke from other people's cigarettes: smoke that has been exhaled or smoke from the end of a lit cigarette.

50 Australians die every day from smoking, compared to 10 who die from alcohol-related conditions and four who die as a result of road accidents.
Tolerance and dependence

People who use tobacco tend to develop a tolerance to the effects of the nicotine in the tobacco very quickly. This means they need to smoke more and more in order to get the same effect.

With repeated use of tobacco, the risk of dependence on nicotine is high. Dependence on nicotine can be physiological, psychological or both.
People who are physically dependent on nicotine find their body has become used to functioning with the nicotine present and may experience withdrawal symptoms when they reduce their nicotine intake.

People who are psychologically dependent on nicotine may find they feel an urge to smoke when they are in specific surroundings, such as at the pub, or in particular situations such as during their lunch break or socializing with friends.

Research has shown that smoking is often associated with different roles and meanings for smokers, including:

• Social roles - such as enjoyment of the company of friends, the drinking of coffee or alcohol, and promoting social confidence and feelings of independence (particularly for young women)
• Emotional roles - caring for the self, such as helping to deal with stress and anxiety, weight control and providing "companionship"
• Temporal roles - such as connecting the flow of events or time in the smoker's day, providing a break from work or activities and relieving boredom.

This may be why smoking is sometimes referred to as the most difficult drug to give up.

Withdrawal

If a person who is dependent on the nicotine in tobacco suddenly stops using it or reduces the amount they use, they will experience withdrawal symptoms because their body has to readjust to functioning without the drug.

Most of these symptoms will disappear within days or weeks of quitting smoking, but cravings may persist for years after stopping using tobacco.

Symptoms include: 

• cravings
• irritability, agitation, depression and anxiety
• insomnia and disturbed sleeping patterns
• increased appetite and weight gain
• restlessness and loss of concentration
• headaches
• coughing and sore throat
• body aches and pains
• stomach and bowel upsets.

• For more information on the risks of tobacco-related harm, contact the alcohol and drug information service in your state or territory.