That's the term being used to describe the invisible yet toxic brew of gases and particles clinging to smokers' hair and clothing, not to mention cushions and carpeting, that lingers long after second-hand smoke has cleared from a room. The residue includes heavy metals, carcinogens and even radioactive materials that young children can get on their hands and ingest, especially if they're crawling or playing on the floor。

Doctors from MassGeneral Hospital for Children in Boston coined the term "third-hand smoke" to describe these chemicals in a new study that focused on the risks they pose to infants and children. The study was published in the latest issue of the journal Pediatrics。

"Everyone knows that second-hand smoke is bad, but they don't know about this," said Dr. Jonathan P. Winickoff, the lead author of the study and an assistant professor of pediatrics at Harvard Medical School。

"When their kids are out of the house, they might smoke. Or they smoke in the car. Or they strap the kid in the car seat in the back and crack the window and smoke, and they think it's okay because the second-hand smoke isn't getting to their kids. We needed a term to describe these tobacco toxins that aren't visible."

The study reported on attitudes toward smoking in 1,500 households across the United States. It found that the vast majority of both smokers and nonsmokers were aware that second-hand smoke is harmful to children. Some 95 percent of nonsmokers and 84 percent of smokers agreed with the statement that "inhaling smoke from a parent's cigarette can harm the health of infants and children"。

But far fewer of those surveyed were aware of the risks of third-hand smoke. Since the term is so new, the researchers asked people if they agreed with the statement that "breathing air in a room today where people smoked yesterday can harm the health of infants and children"。

Only 65 percent of nonsmokers and 43 percent of smokers agreed with that statement, which researchers interpreted as acknowledgement of the risks of third-hand smoke。

吸烟的父母常常会开窗或打开电扇，以此为他们的孩子净化空气，不过专家们最近发现了另一种与香烟有关的对儿童健康的威胁，而且更难对付——三手烟。

所谓“三手烟”是指房间内的“二手烟”清除许久之后，仍残留在坐垫、地毯甚或吸烟者头发和衣物上看不见的气体和颗粒的有毒混合物。残留物包含重金属、致癌物，甚至辐射物质，它们很容易沾在婴幼儿的手上并被吃到嘴里，尤其是当小孩子在地板上爬或玩耍时。

在一项针对这些化学物质对婴幼儿危害的新的研究中，波士顿大众婴幼儿专科医院的医生们创造了“三手烟”这个词来形容它们。研究结果发表于最近一期的《小儿科》医学期刊上。

研究报告的第一作者，哈弗大学医学院的小儿科助理教授乔纳森·温尼考夫说：“每个人都知道二手烟有害，但他们却不知道三手烟的存在。”

“许多父母认为，只要孩子们在屋外，他们就可以吸烟。或者在车上时，把孩子放在后座上，打开车窗，也可以吸烟。他们认为这样就没有问题了，因为毕竟小孩子没吸到二手烟。而我们需要一个术语来描述这些看不见的香烟毒素。”

该研究报告了全美1500个家庭对待吸烟的态度，发现绝大多数受访者(烟民与非烟民)都明白二手烟损害儿童健康。大约95%的不吸烟者和84%的吸烟者都同意“婴幼儿吸入父母的二手烟可能致病”的论断。

但受访者中却很少有人知道三手烟的危害。因为这个名称过于新颖，所以调查者换了种说法，提问人们是否同意“昨天有人抽过烟的屋子里的空气会对婴幼儿产生危害”的论断。

只有65%的非烟民和43%的烟民认同该说法。研究者以此作为公众承认三手烟危害的证据。