At Significantly Higher Risk 
• Cigarette smokers. 
• The male to female ratio remains 4 to 1. Peak incidence occurs between ages 50 and 60, with less than a 1
  percent incidence under the age of 30 and about a 10 percent incidence in people over 70.
• Workers exposed to industrial substances such as asbestos, nickel, chromium compounds and chloromethyl
  ether, especially those who smoke.

At Slightly Higher Risk 
• Patients with previous or pre-existing lung disease.
• Former smokers. 
• People exposed to second-hand smoke over many years.
• People exposed to radon.