Lungs of adults who had grown up with secondhand smoke had more ` ` . '' ( lung tissue is naturally denser than air ) , and also calculated what percentage of their lungs was made up of these `` holes . '' Many ` ` holes '' -- less dense areas of lung -- are characteristic of emphysema . Even though smoke - filled lungs functioned fine , there 's risk for future health . About 10 million people in the United States have emphysema , chronic disease .
Lungs of adults who had grown up with secondhand smoke had more ` ` . '' Many ` ` holes '' -- less dense areas of lung -- are characteristic of emphysema . Even though smoke - filled lungs functioned fine , there 's risk for future health . About 10 million people in the United States have emphysema , chronic disease .