Scientists in the US have produced strong evidence for the harmful effects of passive smoke inhalation.
Chengbo Wang and his colleagues at the children's hospital of Philadelphia made the discovery by using a new imaging technique called global helium-3 diffusion magnetic resonance imaging (MRI), to test the lungs of 60 volunteers aged between 41 and 79 years, including 15 current or former smokers and 45 lifelong non-smokers, half of whom had been exposed to high levels of passive smoking in the past (indicated by living with a smoker for more than 10 years). The subjects breathed in a small amount of a form of helium called helium-3, and the MRI scanner was used to monitor how the atoms moved around inside the subjects' airways, a measure called the ADC or apparent diffusion coefficient.
In healthy non-smokers the air spaces in the lungs are small and compact, which helps the blood to efficiently collect oxygen and shed carbon dioxide. This also means that the helium atoms don't tend to move very far. But smoking causes lung tissue to break down, which is known as emphysematous change, and makes the air spaces larger.
When these changes are present the helium atoms can move much greater distances, and this can be picked up by the scanner. Indeed the researchers found that almost one third of the non-smokers with high exposure to secondhand smoke had structural changes in their lungs similar to the smokers, suggesting that damage was present.
"To our knowledge, this is the first imaging study to find lung damage in non-smokers heavily exposed to secondhand smoke," said Wang. "We hope our work strengthens the efforts of legislators and policymakers to limit public exposure to secondhand smoke.