In the first study to assess the global impact of second-hand smoke, WHO experts found that children are more heavily exposed to second-hand smoke than any other age-group, and around 165,000 of them a year die because of it.

"Two-thirds of these deaths occur in Africa and South Asia," the researchers, led by Annette Pruss-Ustun of the WHO in Geneva, wrote in their study.

Children's exposure to second-hand smoke is most likely to happen at home, and the double blow of infectious diseases and tobacco "seems to be a deadly combination for children in these regions", they said.

Commenting on the findings in the Lancet journal, Heather Wipfli and Jonathan Samet from the University of Southern California said policymakers try to motivate families to stop smoking in the home.

"In some countries, smoke-free homes are becoming the norm, but far from universally," they wrote.

The WHO researchers looked at data from 192 countries for their study. To get comprehensive data from all 192, they had to go back to 2004. They used mathematical modeling to estimate deaths.

Worldwide, 40 percent of children, 33 percent of non-smoking men and 35 percent non-smoking women were exposed to second-hand smoke in 2004, they found.

This exposure was estimated to have caused 379,000 deaths from heart disease, 165,000 from lower respiratory infections, 36,900 from asthma and 21,400 from lung cancer.

For the full impact of smoking, these deaths should be added to the estimated 5.1 million deaths a year attributable to active tobacco use, the researchers said.

While deaths due to passive smoking in children were skewed toward poor and middle-income countries, deaths in adults were spread across countries at all income levels.

In Europe's high-income countries, only 71 child deaths occurred, while 35,388 deaths were in adults. Yet in the countries assessed in Africa, an estimated 43,375 deaths due to passive smoking were in children compared with 9,514 in adults.

世界卫生组织的研究人员周五称，全球每100例死亡中就有1例是死于被动吸烟，每年全球约有60万人死于二手烟。

这一研究首次对二手烟的全球影响进行了评估。世界卫生组织的专家发现，儿童比其他年龄段的人更多的暴露于二手烟环境中，每年约有16.5万儿童因此丧命。

研究人员在报告中写道：“因吸入二手烟而导致的死亡有三分之二发生在非洲和南亚。”总部位于日内瓦的世界卫生组织的安妮特?普鲁丝-乌斯顿是这一研究的领头人。

他们称，儿童在家中暴露于二手烟的情况最多，传染病和烟草的双重侵害“对于这些地区的儿童似乎是一个致命的组合”。

来自南加州大学的希瑟?威普弗利和乔纳森?沙美对发表在《柳叶刀》杂志上的这一研究报告做了评论。他们说，决策者试图对家庭实施激励手段，阻止在家中吸烟的行为。

他们写道：“在一些国家，无烟家庭越来越常见，但离普及还相差得很远。”

为了进行这一研究，世界卫生组织的研究人员查看了来自192个国家的资料。他们还查看了2004年的资料，以得到192个国家的全面信息，并用数学模式来估算死亡人数。

他们发现，在2004年，世界范围内有40%的儿童、33%的不吸烟男性和35%的不吸烟女性暴露于二手烟环境下。

经过估算，这种二手烟环境已导致37.9万人死于心脏病，16.5万人死于下呼吸道感染，3.69万人死于哮喘病，2.14万人死于肺癌。

研究人员说，为了全面反映吸烟造成的影响，这些死亡人数也应该加入每年死于主动吸烟的约510万人。

尽管被动吸烟造成的儿童死亡多发生于中低收入的国家，吸二手烟而导致的成人死亡在各个收入水平的国家中却普遍存在。

在欧洲的高收入国家中，只发生了71例因被动吸烟而导致的儿童死亡，而二手烟导致的成人死亡却有3.5万例。但是在接受评估的非洲国家中，被动吸烟导致的死亡人口约有4.3万为儿童，9514人为成人。