Secondhand smoke can cause lung damage and emphysema is an oft repeated refrain. But doctors lacked a way to prove this as previous detection methods simply weren’t sufficiently sensitive. Now, for the first time, researchers say they have discovered a way to prove that long-term exposure to secondhand smoke can cause structural damage in the lungs, indicative of emphysema. Research also suggests that modified magnetic resonance imaging (MRI) technique used to detect the lung damage may be able to spot emphysema long before symptoms occur. The results of the study—conducted by researchers at the University of Virginia School of Medicine in Charlottesville and The Children’s Hospital of Philadelphia in Pennsylvania—were presented at the annual meeting of the Radiological Society of North America (RSNA).
In recent years, secondhand smoke has emerged as a public health threat, and the toxic substance has been classified as a carcinogen by the Environmental Protection Agency and linked to heart disease, lung cancer, and a number of respiratory ailments, including asthma and chronic bronchitis. Children are particularly susceptible to the harmful effects of secondhand smoke. According to the American Lung Association, 35 percent of American children live in homes where regular smoking occurs.
For the RSNA study, researchers used a global helium-3 diffusion MRI to study the lungs of 13 current or former smokers and 45 people who had never smoked. Helium-3 diffusion MRI differs from conventional MRI in that helium gas is polarized with a laser, the patient inhales the specially prepared helium gas, and the scanner collects images showing how the gas distributes in the tiny air sacs—alveoli—in the lung, allowing for microscopic detection. Helium-3 diffusion offers more detailed images of the lungs than previous techniques and allows radiologists and physicists to detect changes deep in the small airways and sacs in the lungs, which can break down, become enlarged, and develop holes after prolonged exposure to cigarette smoke—early signs of emphysema. As a result, helium travels much further in people with enlarged air sacs than in people with healthy alveoli. Using helium MRI, researchers were able to detect microscopic changes suggestive of emphysema in smokers and people exposed to secondhand smoke.
Of the nonsmokers, 22 had heavy exposure to secondhand smoke, meaning they lived with a smoker or worked in a bar for at least a decade. None of the individuals participating in the study had symptoms of lung disease. The modified MRI detected signs of early lung damage in 67 percent of smokers and 27 percent of nonsmokers with heavy exposure to secondhand smoke. Conversely, only four-percent of nonsmokers who had never smoked and had fewer than 10 years of exposure appeared to have signs of early lung damage.
Since legislation to limit public exposure to secondhand smoke is still being considered in many states, it is hoped that this research can be used to add momentum to the drive to pass such legislation.
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