This is Sarah Long. And this is Bob Doughty with SCIENCE IN THE NEWS, a VOA Special English program about recent developments in science

Today, we tell about the health effects of smoking tobacco products. We also offer advice about how to stop smoking.

For many years, scientists have warned that smoking tobacco is bad for your health. Yet people around the world continue to smoke. The World Health Organization estimates that almost five-million people around the world die each year from the effects of smoking. That number is increasing. W-H-O officials say tobacco use will kill more than eight-million people a year by two-thousand-twenty if nothing is done to control the problem.

In the United States, more than forty-six-million adults currently smoke. American health experts say tobacco use is the leading preventable cause of death in the United States. This year, an estimated four-hundred-forty-thousand Americans will die of diseases linked to smoking.

Smoking tobacco is the leading cause of lung disease. Smoking also has been linked to heart disease, stroke and many kinds of cancer. The American Cancer Society says smoking is responsible for about eighty-seven percent of all lung cancers in the United States. The group adds that smoking is a major cause of cancers of the mouth, esophagus, kidney, bladder and pancreas. Scientists have identified more than forty chemicals in tobacco smoke that cause cancer in humans and animals. Smokeless tobacco and cigars also have been linked to cancer.

American government health experts say smoking affects not only the smoker. Women who smoke cigarettes during pregnancy are more likely to have babies with health problems. Pregnant women who smoke are at risk of having a baby who weighs less than normal. Low birth weight babies have an increased risk of early death and may suffer from a number of health disorders.

Experts say tobacco smoke also affects the health of people who do not smoke. Smokers may harm the health of family members and people at work when they breathe out smoke from cigarettes. This is called "second-hand smoke." Tobacco smoke causes an estimated three-thousand non-smoking Americans to die of lung cancer each year. Tobacco smoke also causes lung infections in as many as three-hundred-thousand American children each year.

The American Cancer Society says there is no safe way to smoke. It says smoking begins to cause damage immediately. All cigarettes can damage the body. Smoking even a small number of cigarettes is dangerous.

Nicotine is the major substance in cigarettes that gives pleasure to smokers. Nicotine is a poison. The American Cancer Society says nicotine can kill a person when taken in large amounts. It does this by stopping the muscles used for breathing.

The body grows to depend on nicotine. When a former smoker smokes a cigarette, the nicotine reaction may start again, forcing the person to keep smoking.

Studies have found that nicotine can be as powerful as alcohol or the illegal drug cocaine. So experts say it is better not to start smoking and become dependent on nicotine than it is to smoke with the idea of stopping later.

Most people who smoke have heard about the harmful effects of cigarettes. Some of them decide to smoke fewer cigarettes. However, most smokers find that is difficult. Experts say menthol cigarettes are no safer than other tobacco products. Menthol cigarettes produce a cool feeling in the smoker's throat. People who use menthol cigarettes can hold the smoke inside their lungs longer than smokers of other cigarettes. As a result, experts say menthol cigarettes may be even more dangerous.

Other smokers believe that cigarettes with low tar levels are safer. Tar is a substance produced when tobacco leaves are burned. It is known to cause cancer.

In two-thousand-one, the National Cancer Institute released a report about low tar cigarettes. It found that people who smoke these cigarettes do not reduce their risk of getting smoking-related diseases. In fact, some people who use low tar or low nicotine cigarettes often smoke more. The report found no evidence that changes in cigarette design and production during the past fifty years have improved public health.

It is not easy to stop smoking permanently. However, doctors say you probably will live longer if you do stop smoking. You will feel better and look better. You also will protect the health of family members and others who breathe your smoke.

The American Cancer Society says the sooner smokers stop smoking, the more they can reduce their chances of getting cancer and other diseases. It says blood pressure returns to normal twenty minutes after smoking the last cigarette.

Carbon monoxide gas levels in the blood return to normal after eight hours. After one day, the chance of heart attack decreases. After one year, the risk of heart disease for a non-smoker is half that of a smoker.

Experts say there are several products designed to help end a smoker's dependency on cigarettes. There are several kinds of nicotine replacement products that provide small amounts of the substance. These can help people stop smoking.

For example, smokers can place small, specially treated pieces of material on their skin. They can chew or swallow other products that contain nicotine. Or they can breathe small amounts of nicotine through their nose or mouth.

A drug to fight depression has proved effective for many smokers. Depression is the mental condition that causes extreme sadness and hopelessness. The anti-depressant drug is called Zyban. It does not contain nicotine. The drug works by increasing levels of the chemical dopamine in the brain. Dopamine produces feelings of pleasure. Studies have shown that Zyban reduces the urge to smoke for some people.

There is strong evidence that people who have suffered from depression are much more likely than other people to smoke. The same is true for people who have brain disorders such as schizophrenia. Doctors say these people can think better and feel better when they are smoking. It also is much harder for them to stop smoking than it is for other people.

We have some other ideas to help you stop smoking. The American Cancer Society says there is not just one right way to stop. It says one method or a combination of methods may be successful. They include attending self-help programs or following directions in a book. The group says any way to stop smoking that is legal, moral and effective is worth trying.

To stop smoking, you should carefully plan your actions for at least one week. Try to stay away from people and situations that might trouble you. Do not go to public places where people are smoking. If you drink alcohol, you probably will need to stop drinking temporarily. Many people lose their inner strength when they drink alcohol.

Many experts say it is best to stop smoking completely. Even one cigarette can make you a smoker again. In the first week or two without cigarettes, you probably will feel terrible. You may be angry all the time or you may feel sad. You may have a headache or your stomach may feel sick. Do not lose hope. If you stay away from tobacco, those feelings will go away in a few weeks. Tell yourself that you will be happier as a non-smoker. Tell yourself that nicotine should not control your life.

Move around as much as possible. Go for a quick walk or a run at least two times a day. Walking or running will make you breathe deeply. This will help clear the nicotine from your body. Also, when you have the urge to smoke, you could chew gum or eat a piece of fruit or vegetable instead.

For a long time, you will continue to have periods when you really want a cigarette. Yet these times will come less often. One day, you will recognize that you have won the struggle against smoking.

This SCIENCE IN THE NEWS program was written and produced by George Grow. This is Sarah Long. And this is Bob Doughty. Join us again next week for more news about science in Special English on the Voice of America.