Secondhand Smoke. Secondhand smoke (SHS) is a mixture of 2 forms of smoke that come from burning tobacco: Sidestream smoke ( 支流煙 ) – smoke from the lighted end of a cigarette, pipe, or cigar Mainstream smoke ( 主流煙 ) – the smoke exhaled by a smoker.
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Sidestream smoke (支流煙) – smoke from the lighted end of a cigarette, pipe, or cigar
Mainstream smoke (主流煙) – the smoke exhaled by a smoker
Sidestream smoke has come from burning tobacco:higher concentrations of cancer-causing agents (carcinogens，致癌物) than mainstream smoke. And, it has smaller particles than mainstream smoke, which make their way into the lungs and the body’s cells more easily.
Secondhand smoke is classified as a “known human carcinogen” (人類已知致癌物)(cancer-causing agent) by the US Environmental Protection Agency (EPA), the US National Toxicology Program, and the International Agency for Research on Cancer (IARC), a branch of the World Health Organization.
IARC reported in 2009 that parents who smoked before and during pregnancy (妊娠) were more likely to have a child with hepatoblastoma. This rare cancer is thought to start while the child is still in the uterus. Compared with non-smoking parents, the risk was about twice as high if only one parent smoked, but nearly 5 times higher when both parents smoked.
Both mainstream and SHS have about 20 chemicals that, in high concentrations, cause breast cancer in rodents (齧齒類). And we know that in humans, chemicals from tobacco smoke reach breast tissue and are found in breast milk (母乳).
One reason the link between SHS and breast cancer risk in human studies is uncertain is because breast cancer risk has not been shown to be increased in active smokers. One possible explanation for this is that tobacco smoke might have different effects on breast cancer risk in smokers and in those who are exposed to SHS.
Findings on smoking, secondhand smoke, and health human studies is uncertain is because breast cancer risk has not been shown to be increased in active smokers. One possible explanation for this is that tobacco smoke might have different effects on breast cancer risk in smokers and in those who are exposed to SHS.
SHS kills children and adults who don’t smoke.
SHS causes disease in children and in adults who don’t smoke.
Exposure to SHS while pregnant increases the chance that a woman will have a spontaneous abortion (自發流產), stillborn birth (死胎), low birth-weight baby, and other pregnancy and delivery problems.
SHS causes lung cancer in people who have never smoked. Even brief exposure can damage cells in ways that set the cancer process in motion.
Chemicals in tobacco smoke damage sperm ( circulation in a harmful way. Over time it can cause heart disease, strokes (精子) which might reduce fertility (生殖力) and harm fetal development (胎兒發育). SHS is known to damage sperm in animals, but more studies are needed to find out its effects in humans.
There is no safe level of exposure to SHS. Any exposure is harmful.