Adults who were exposed to large amounts of secondhand smoke during childhood have lungs that look different on CT scans from those of people who grew up in a smoke-free environment , a new study suggests . The harmful short-term effects of secondhand smoke are well known ; the long-term consequences are n't as clear . Specifically , their lungs have slightly more , and larger , emphysema-like `` holes '' than those with less smoke exposure , says Gina Lovasi , M.P.H. , Ph.D. , of Columbia University , and her colleagues . Although breathing tests showed that the smoke-exposed lungs were functioning just fine , Lovasi said the changes could signal an increased vulnerability to developing emphysema and other lung problems down the road . Health.com : Should smoking around kids be illegal ? Emphysema is a progressive lung disease characterized by shortness of breath , coughing , fatigue , and weight loss . About 24 million people in the United States have emphysema and/or chronic bronchitis , which together are known as chronic obstructive pulmonary disease ( COPD ) ; however about half of those people do n't realize they have COPD . The lung condition is the fourth-leading cause of death in the United States , and smoking is a major cause of COPD . Health.com : I 'm a nonsmoker , but I have emphysema due to a rare genetic condition . `` The interesting part about this is that we do n't know a lot about how the lungs change over time and whether they heal completely after being exposed to tobacco , '' says Lovasi , who is scheduled to present her findings on Tuesday at the American Thoracic Society 's 105th International Conference in San Diego . `` We can still see a difference even decades later . '' The harmful short-term effects of breathing other people 's cigarette smoke are well known , but the long-term consequences are n't as clear . To investigate , Lovasi and her team looked at CT scans of the lungs of 1,781 nonsmoking 45- to 84-year-olds taking part in the Multi-Ethnic Study of Atherosclerosis ( MESA ) trial . Health.com : 5 celebrities who had -- or are at risk of -- the lung disease COPD . About half of the study participants said that no one with whom they lived during childhood smoked cigarettes at home , 31 percent lived with one person who smoked at home , and 17 percent lived with two or more smokers . Lovasi and her team checked the lung CT scans for large areas where the density was similar to air ( lung tissue is naturally denser than air ) , and also calculated what percentage of their lungs was made up of these `` holes . '' Health.com : My smoker 's cough turned out to be emphysema . `` The lungs are supposed to have air in them , but it 's important that the air is interspersed with blood vessels so that we can get the oxygen out of the air , '' she says . `` Small holes can expand over time and merge to form larger holes . '' For people who had n't grown up with smokers , 17 percent of their lung tissue had this air-like density , while `` holes '' made up 20 percent of the lung area of people who had lived with at least two smokers during childhood . The more heavily smoke-exposed study participants also had more relatively large holes in their lungs . In comparison , `` someone with emphysema would typically have between 30 percent and 60 percent of the lungs classified as air-like ( or emphysema-like ) using the threshold we used for our study , '' says Lovasi . Health.com : 1 in 3 smokers would kick habit to protect pet . Lovasi says she and her colleagues will be following the MESA participants over time to see how their lungs change , and whether people with more early smoke exposure are indeed more vulnerable to lung problems later on . Enter to win a monthly Room Makeover Giveaway from MyHomeIdeas.com . Copyright Health Magazine 2009 .
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 .