Are smokers more susceptible to lung cancer than non-smokers?

Most people would agree that smokers are more susceptible to lung cancer than non-smokers. However, I would  have to disagree. A few years ago, I went to a pre-medical program and saw a cadaver whose lungs had spots on them. I automatically assumed he had been a smoker. To my surprise, he had not smoked a day in his life. He had worked in a factory all his life and the exhaust fumes from the factory had damaged his lungs. This is how he contracted lung cancer. This sparked my interest. Are smokers more susceptible to lung cancer than non-smokers? Research suggests that, "Lung cancer in non smokers is as real a threat as it is in smokers. What makes it worse is that while you, as a non-smoker, might make sure your life is healthy and without any vices, but being around smokers can cause much deadly damage to you, as it does to smokers"(Medical Health Tests). According to Harvard Medical School, "Lung cancer runs in families, but so does smoking, so it doesn’t jump out as an inherited, genetic condition. Family history was a stronger risk factor among never-smokers than among smokers, suggesting perhaps that never-smokers’ lung cancer may indeed have a significant inherited component". As you can see, lung cancer is just as prevalent in non-smokers as it is smokers. Genetics is also a big part of it. So, as a non-smoker should I be as concerned about lung cancer? The answer is yes.

References:
"Lung cancer: Not just for smokers." The Harvard Medical School Family Health
     Guide. Web. 29 Oct. 2013. <http://www.health.harvard.edu/
     fhg/updates/Lung-cancer-not-just-for-smokers.shtml>. 
 Nic. "Causes, Symptoms, Types & Risks of Lung Cancer In Non Smokers." Medical
     Health Tests. 14 Mar. 2013. Web. 29 Oct. 2013.
     <http://www.medicalhealthtests.com/articles/732/health-articles/
     lung-cancer-in-non-smokers.html>. 


Rachael S.W.