From: Robina Suwol
Date: 15 Oct 2002
Remote Name: 220.127.116.11
Monkeys have lasting problems after exposure as babies, a UC Davis study
By Edie Lau -- Bee Science Writer - (Published October 14, 2002)
Ending a marathon season of hot, stagnant, dirty air, we breathe easier -- or so we think. For the most vulnerable among us, breathing may never be easy after exposure to the Valley's most troublesome air pollutant, ozone.
Research with infant monkeys at the University of California, Davis, suggests that the lungs of young primates are permanently changed by inhaling
high concentrations of ozone. Even giving them pristine air doesn't reverse the damage.
Although the monkeys breathed levels of ozone markedly higher than are reached in the Sacramento region -- amounts akin to the pollution of Mexico City -- and monkeys aren't people, the scientists said their findings have unmistakable implications for Californians.
"I would certainly keep little kids in" on bad-air days, said Laurel Gershwin, an immunologist on the UC Davis research team. "If they're anything like the baby monkeys, we don't want them breathing high levels of air pollutants."
As with infant monkeys, much of the lung growth in baby humans occurs after birth. That development continues to adulthood, with the first few years considered the most critical.
Focusing on that period, the UC Davis team exposed baby rhesus macaques to .5 ppm concentrations of ozone off and on for six months. Some of the monkeys also were exposed to dust mites, a common allergen.
The scientists found that repeated exposure to dust mites caused allergic reactions similar to asthma, and that the reactions were exacerbated by ozone exposure.
Ozone in the stratosphere high above Earth protects the planet from ultraviolet radiation. Closer to the ground, ozone is an invisible component of smog. Heat accelerates the formation of ozone from tailpipe emissions, making high ozone levels typically a summertime phenomenon.
The scientists noted striking changes in the lungs of monkeys that breathed high ozone: the number of lung branches was fewer; mucous cells were more abundant and produced mucus in prodigious amounts; the basement membrane around the airways was thicker, reducing lung elasticity; the airways, when constricted, tightened more than usual; and even neurons in the brain were hypersensitive to irritants.
The animals were exposed from the time they were 1 month until they were 6 months old -- comparable to 3-year-old humans, said the research team leader, Charles Plopper.
Next, the scientists wanted to know whether giving monkeys clean air would correct their problems. So for the next six months, filtered air was piped into the animals' enclosures -- air cleaner than a person could hope to encounter in Sacramento at any time of the year.
The researchers still are evaluating their data, so their findings have not yet been published, but they say the general results are unambiguous: "They didn't get better," Lisa Miller, an immunologist on the team, said of the monkeys.
Plopper, a professor of anatomy, physiology and cell biology, said that while the growth rate of the exposed monkeys' lungs was not affected -- they were comparable in size to the lungs of monkeys not exposed to ozone -- the organization of the lungs remained abnormal. "It goes ahead and grows, but doesn't repair (itself)," he said.
The scientists fear that such a system would be incapable of coping with future assaults. "It's like having a damaged joint," Plopper said. "You could walk on it, but when you have to run away from fire, you can't." The damage might even shorten the life span.
"Decrease in lung reserves is directly related to longevity," said Edward Schelegle, a physiologist on the team. " ... After about age 25, as you age, you lose lung function. As a result, those people who have less to start off with will have less to give up in the long term."
Such news is especially alarming coming on the heels of a singularly bad air-pollution season. On 28 days this summer, the air-quality index topped 100 in the Sacramento region, meaning that ozone concentrations were harmful to sensitive groups, or worse.
The worst day was Aug. 14, when the index reached 209 in the El Dorado County town of Cool. Anything over 200 is considered very unhealthy for everybody.
"That was a precedent-setting number," said Kerry Shearer, spokesman for the Sacramento Metropolitan Air Quality Management District. "It was a pretty ugly summer."
To put it into perspective, the highest ozone reading in the area all summer was .16 ppm, which is one-third the level the researchers used in the monkey study.
But ozone concentrations need not be as high as those in the study to be harmful. Researchers at the University of Southern California have tracked the health and lung function of 6,000 children for nearly 10 years. Those who live in the smoggiest parts of the Los Angeles basin clearly do worse than those in communities with cleaner air, such as Lompoc and Santa Barbara, said James Gauderman, an associate professor of preventive medicine.
Now, like the UC Davis researchers, the USC scientists want to know whether the effects of smog are reversible. In following a group of about 100 children who moved out of the area -- some as far away as Seattle -- the researchers found that getting away from dirty air seems to make a difference.
"If they moved to a cleaner community, their lung function improved, and if they moved to a more polluted community, it seemed to get worse in terms of the growth of their lung function -- the growth rate was affected," Gauderman said.
Whether the children experienced the lung structure changes of the young monkeys isn't known because the children's lungs cannot be examined directly.
"It's a very interesting question whether that kind of restructuring is happening in the kids as well," Gauderman said. Developments in CT scans that can form three-dimensional pictures of organs may help answer that question in the future, he said.
At UC Davis, the research team hopes to focus next on treatment. A small pilot study using an experimental drug had remarkable results: asthmatic symptoms in three adult monkeys were completely reversed by the drug.
Unlike existing therapies, this one uses strands of synthetic DNA that mimic the DNA of certain bacteria. One hypothesis for the rise in allergies and asthma holds that the immune systems of people in industrial societies aren't sufficiently challenged by bacterial infections, resulting in an imbalance in the immune system that causes it to overreact to allergens.
The DNA treatment is thought to stimulate the immune system the same way that an invasion of bacteria would, and to suppress the allergic response.
Plopper cautioned that the results with the monkeys are preliminary and not peer-reviewed, but acknowledged being excited. "This opportunity to actually find something that might help is a big stimulus," he said.
About the Writer
The Bee's Edie Lau can be reached at (916) 321-1098 or firstname.lastname@example.org.