1, cigarettes contain a large number of carcinogens or toxic substances, at least 250 known. For example, we know that benzo(a)pyrene is a strong carcinogen. Smoking can cause lung cancer (and other cancers), as everyone on earth knows. 2. The lung cancer mortality rate for smokers is more than ten times that of nonsmokers, and about 90% of lung cancer deaths are related to smoking. These clichés persist, the growth in the number of smokers continues, and unfortunately so does the growth in the incidence of lung cancer. 3. Now let’s put it another way. Some studies have shown that cigarettes contain the radioactive substance polonium, which can also cause lung cancer. Although it is not a very important factor, some people have a much stronger fear of radioactive substances than carcinogens. 4.If you are afraid of nuclear radiation, please quit smoking. A doctor has calculated that the amount of pm2.5 inhaled in a month of living in a city with severe haze is equivalent to smoking only 5 cigarettes. If you are afraid of haze, please quit smoking.