以往,人们对香烟的危害多注意到化学物质。近年来,科学家们发现香烟中有一种新的放射性危险因素。DiFranza认为,一个每天吸一包半香烟的人,一年其肺脏所接受的放射剂量等于他的皮肤接触了约300次胸部X线照射。他指出,吸烟者肺癌的半数是由放射性物质引起的。由此可见香烟中放射性的危害性。香烟中放射性物质主要来源于磷肥、周围的土 In the past, people were more aware of the dangers of cigarettes chemicals. In recent years, scientists have found a new radioactive risk factor in cigarettes. According to DiFranza, a person who smokes a pack of semi-cigarettes a day receives about 300 chest X-rays from his lungs once a year. He pointed out that half of smokers with lung cancer is caused by radioactive material. This shows the dangers of radioactive cigarettes. Radioactive material in cigarettes comes mainly from phosphate fertilizer, the soil around