The study may help explain recent research suggesting that children are more susceptible than adults to illnesses caused by breathing polluted air, researchers say. Chronic coughing, bronchitis and asthma are among health problems worsened by dirty air.
"We believe this work is important because it supports observations by others about children being affected by particulate air pollution," said Dr. William D. Bennett, research associate professor of medicine at the UNC-CH School of Medicine's Center for Environmental Medicine and Lung Biology.
"Certainly it doesn't tell the whole story of why children tend to get sick this way, but it is likely a key part of the story. Other factors, for example, are that children are outside more often and exercise more than adults."
A report on the findings will appear in the September issue of Inhalation Toxicology. Dr. Kirby L. Zeman, research associate at the center, was co-author.
Bennett and Zeman asked 16 healthy children between ages 7 and 14, 11 adolescents up to age 18 and 12 adults between ages 19 and 35 to inhale tiny amounts of harmless carnauba wax particles while resting. Using sophisticated laser technology, researchers then measured how much of the particles remained in volunteers' lungs.
They found that while older adolescents and adults inhaled and retained more particles because of their larger lungs, younger volunteers retained about 35 percent more simulated "pollution" per unit of lung surface area.
"These results may prove useful in determining age-relative risks associated with inhaling air pollutants," Bennett said. "We now plan to extend our studies to exercising volunteers. That's because we also found children seemed to be much more sensitive to changes in the volume of air breathed in terms of the amount of particles they retain."
The UNC-CH scientists also will compare mouth versus nose breathing since people switch from breathing nasally to breathing orally at some point during vigorous exercise. They want to know whether children switch earlier and whether that causes them to trap more polluted air in their lungs.
Among strengths of the new study was that for the first time, researchers were able to ensure through an electronic technique called respiratory inductance plethysmography that volunteers' breathing during tests was the same as it was at rest before testing, Bennett said.
"This technique helps us avoid unintentional changes in breathing patterns caused by people breathing through a mouthpiece for the first time," he said.
A device known as a light scattering photometer attached to the mouthpiece measured particle concentrations during breathing. Non-toxic carnauba wax particles are a food additive derived from a Brazilian palm known as "the tree of life." Besides coating candy and pills, it is used as a car finish and leather preservative.
The research was supported through a cooperative agreement between the UNC-CH Center for Environmental Medicine and Lung Biology and the Environmental Protection Agency.
By David Williamson
Note: Bennett can be reached at (919) 966-6229 (w) or 967-1469 (h), Zeman at 966-6368.