The risk of lung cancer among Japanese people who are exposed to secondhand smoke is 1.3 times higher than for those who are not, the National Cancer Center Japan (NCC) reported.
Based on its study, the NCC upgraded its evaluation of the risks of lung cancer imposed by secondhand smoke from "nearly certain" to "certain" -- the same level as the risk of developing all types of cancer from drinking and smoking, as well as the risk of liver cancer caused by hepatitis viruses.
Of 426 research papers on the relationship between secondhand smoke and lung cancer among Japanese, the NCC analyzed data combined from nine papers published between 1984 and 2013, such as a study on the development of lung cancer among female non-smokers and the smoking patterns of their husbands. The analysis showed that the risk of developing lung cancer was 1.3 times higher among those who were exposed to secondhand smoke at home than residents of non-smoking homes -- the same conclusions drawn by analyses conducted overseas.
Secondhand smoke, which people inhale from tobacco being smoked by others, is known to cause illnesses of the circulatory organs and respiratory systems, as well as affect babies, resulting in sudden infant death syndrome.
Kota Katanoda, the head of the cancer registry statistics office at the NCC, points out the need to establish a ban on indoor smoking in Japan. A total of 49 countries impose a complete ban on indoor smoking in public places.
Studies have found that habitual smoking increases the risk of many types of cancer including in the lungs and esophagus, with 40 percent of deaths among men and 5 percent of deaths among women believed to be caused by smoking. However, the link between secondhand smoke and lung cancer had not been statistically verified, though the risk of lung cancer had been shown to increase with secondhand smoke in most studies.
The NCC provides science-based cancer prevention measures on its website and pamphlets. In regard to involuntary smoking, the center will change its wording from "avoid secondhand smoke as much as possible" to "avoid secondhand smoke."