This is the VOA Special English Health Report.

Scientific evidence has been building about the dangers to people who do not smoke from those who do. Now the top doctor in the United States says the evidence cannot be argued: secondhand tobacco smoke is a serious public health risk.

Recently Surgeon General Richard Carmona released the government's largest report ever on secondhand smoke. For example, it says nonsmokers increase their risk of lung cancer by up to thirty percent if they live with a smoker.

Doctor Carmona noted the added dangers faced by children who have to breathe secondhand smoke. These children are at increased risk for sudden infant death syndrome , severe breathing problems and ear infections. The report says smoking by parents also slows lung growth in their children.

Children are especially at risk from the poisonous chemicals in tobacco smoke because their bodies are still developing.

Smoking during pregnancy can lead to babies with low birth weight. And low birth weight can lead to many health problems.

The surgeon general says there is no safe level of secondhand smoke. Effects in the blood can be seen after even a short time in a smoky room.

Scientists have estimated that secondhand smoke kills about fifty thousand adults in the United States each year. Most of these nonsmokers die from heart disease, the others from lung cancer. Also, an estimated four hundred thirty newborn babies die from sudden infant death syndrome as a result of secondhand smoke.

Scientists have identified more than fifty cancer-causing substances in secondhand smoke. Tobacco smoke also damages blood passages. And it reduces the ability of the heart to correct abnormal heartbeats .

The report says separating smokers from nonsmokers or trying to clean the air in buildings is not enough protection. Doctor Carmona noted the progress in establishing smoke-free public places in the United States. Blood tests show that Americans are being exposed to secondhand smoke in fewer numbers and at lower levels since the late nineteen eighties.

But the surgeon general says almost half of all nonsmokers in the United States are still breathing tobacco smoke at home, work or both.

The first surgeon general's report warning about the dangers of cigarettes came out in nineteen sixty-four.

And that's the VOA Special English Health Report for this week, written by Caty Weaver. Transcripts and archives are at voaspecialenglish.com. I'm Shep O'Neal.

sudden infant death syndrome :婴儿猝死综合症

heartbeat : 心跳

smoke-free public place : 无烟区