First Hard Proof of Secondhand Smoke Damage to Lungs Revealed

Martha Kerr
November 27, 2007 (Chicago) — Although it has been speculated about for years, investigators have now revealed the first real, hard evidence that secondhand smoke does, in fact, damage the lungs.
The findings of a study using long-time-scale, global, helium-3 diffusion magnetic resonance imaging (MRI) of nonsmokers with high and low secondhand-smoke exposure and of smokers were announced here yesterday during the Radiological Society of North America 93rd Annual Scientific Assembly.
The study involved 60 volunteers, all with normal spirometry measures, with forced expiratory volumes in 1 second ranging between 58% and 92%, and all without other symptoms of lung disease.
Of these, 23 participants were nonsmokers with low levels of secondhand-smoke exposure, defined as no family members who smoked and no exposure to smoke in the workplace; 22 were nonsmokers with high secondhand-smoke exposure; and 15 were past or current smokers. All had at least 10 years of exposure in their respective categories.
Lung structure was assessed using helium-3 diffusion MRI, with apparent diffusion coefficient (ADC) values calculated for each participant. The lower the ADC value, the better the lung function. Higher ADC values reflect enlargement of the alveoli.
Only 4% of those with low secondhand-smoke exposure had elevated ADC values, reported principal investigator Chengbo Wang, PhD, a magnetic resonance physicist in the Department of Radiology at The Children's Hospital of Philadelphia, Pennsylvania. Of those with high levels of secondhand-smoke exposure, 27% had elevated ADC values, whereas 67% of past and current smokers had high ADC values.
"Nonsmokers with high secondhand-smoke exposure were not as bad as the smokers but were much worse than those with low exposure," Dr. Wang pointed out.
"Helium-3 diffusion MRI detects changes [in lung structure] before symptoms are evident," he told Medscape Radiology. "These were all basically healthy people with normal lung function tests.
"We know that about half of smokers have normal lung function. They just don't seem to be sensitive to smoke," Dr. Wang noted.
"If we want to find proof [of secondhand smoke damage to the lung], we can see it now. This is a very solid finding," Dr. Wang said. "This is very exciting that we can see this difference."
The findings have important public health implications, he added. "We really need to prohibit smoking in public places."
The Philadelphia investigator said that helium-3 diffusion MRI could also be useful in evaluating the efficacy of inhalation therapy such as albuterol on the lung. "Before, we had to guess."
Dr. Wang cautioned that this is still an investigational technique, noting, "It is not yet FDA approved."
Katarzyna J. Macura, MD, assistant professor at the Russell H. Morgan Department of Radiology and Radiological Sciences at Johns Hopkins Medical Institution in Baltimore, Maryland, commented that Dr. Wang "is using a very sophisticated, very expensive technique. We first need more validation of this technology," she told Medscape Radiology. "For screening, we need to see that lung damage is occurring. This [study] appears to show that [damage]."
The scanner for Dr. Wang's study was provided by Siemans, AG, of Munich, Germany, but he developed the software himself. Dr. Wang and Dr. Macura have disclosed no relevant financial relationships.
Radiological Society of North America 93rd Annual Scientific Assembly: Abstract LL-CA2568-L12. Presented November 26, 2007.