Who doesn't know about Cancer !! 
The disease , which killed millions of people in last decades. 
lets have some idea on cancer and the way how does it spreads. Cancer is the group of disease which starts for uncontrolled cell division , caused by the genetic change. Some factors can change your gene to product new cells. These are radiation, chemicals like asbestos, radon, azo dyes, and the UV light the most important and concerned reason. Some drugs like immunosuppressants can create the cancer also. But to day is the concern is the air. Which contains a lots of carcinogens that can be the reason of  lung cancer. 
A quote, 
?Air pollution levels in most US cities used to be much higher than they are now, but scientific research and effective policies to reduce pollution levels have made the air safer and continue to be important to protect public health. High levels of air pollution in other parts of the world may present more significant health hazards." (Simon, WHO)
Some chemicals, like arsenic, benzene, beryllium, asbestos, vinyl chloride are known human carcinogens. 
Now come to the gas, CO ( carbon monoxide) also a cause of cancer that can create a lung cancer as well. 
But the most important one is the radon. Which were emphasized in various articles as the main reason of cancer. 
So what can we do? Can we clean the air by using air fresheners or just doing tree plantation. Yes this can be the best idea. but before that we have some responsibilities like raising awareness. See a simple issue, smoking in public area can make the non-smokers to passive smokers. This can lead a man to cancer if he has a sensitive lung or other lung diseases.