Smoky summer days in Davis have led researchers to find for the first time evidence that being exposed in infancy to high levels of fine-particle pollution harms the development of the immune system’s ability to fight disease.
The study also found that exposure negatively impacts the development of normal lung function, according to immunologist Lisa Miller, the head of the respiratory diseases group and associate director of research at the California National Primate Center.
On some days in June and July 2008, smoke from wildfires grew thick “like fog in the wintertime,” Miller said. Levels of PM2.5 — inhalable particles smaller than 2.5 microns — climbed to 50 to 60 micrograms per cubic meter, far beyond the federal standard of 35 micrograms per cubic meter.
That smoke rolled into Davis during the season when many rhesus macaque monkeys are born in the outdoor corrals at the Primate Center, located west of the city.
Backed by a $268,029 Air Resources Board grant, the researchers have since studied 50 monkeys who were 1 to 3 months old during that smoky period and another 50 born a year later, when particle pollution levels were below the federal standard.
Blood samples from the animals were treated with a component of bacteria, mimicking the bacterial response in a tissue culture dish.
Those from the animals exposed to smoke responded “in a much-reduced fashion” compared to the control group, said Miller, an associate professor in the School of Veterinary Medicine.
“What that says is that when one of those animals encounters that pathogen, under normal circumstances, the immune system won’t respond as robustly,” she said.
The animals’ immune systems functioned — just not as well. And so far, those early effects of the smoke exposure have persisted.
“Perhaps what we’re looking at is individuals who recover very slowly,” she said. “Some people respond to a virus and get well in 24 hours, others may take weeks to recover.”
Miller’s co-investigator, Ed Schelegle, a professor of anatomy, physiology and cell biology at the vet school, measured reactivity, or how sensitive lungs are to a stimulus, and compliance, or how well lungs stretch.
He found that a subset of the exposed monkeys had very reactive lungs, like those of an asthmatic, and some very stiff lungs. Those most impacted were female.
Preliminary evidence also suggests that females exposed to smoke are gaining weight more quickly. “We think we might have some evidence of metabolic syndrome developing in these animals,” Miller said.
It’s “not a stretch to think that the effects we’re seeing in animals that were exposed as infants” would be similar in humans, she said.
“It begs the question whether the kids in this area ought to be monitored in some fashion, but no one has done that at this point in time,” she said. “Perhaps after we publish this study, that will happen.”
Many studies have linked exposure to PM2.5, which also can be found in smog, to a variety of human health problems and even death, especially in people with heart disease.
Adults with sensitive lung issues are warned to be wary of poor air, because it can aggravate conditions like asthma.
The study’s findings show the danger may be more serious for infants and children because “it’s not a temporary response — it’s something that stays with them for the rest of their lives,” Miller said.
“Ultimately, these kids could develop more severe lung disease, like chronic obstructive pulmonary disease, which a significant disorder in this country.”
The researchers plan to submit their paper for publication soon. They hope to find biomarkers that would enable doctors to know from a blood sample whether a child is more susceptible disease later in life, Miller said.
— Reach Cory Golden at [email protected] or 530-747-8046. Follow him on Twitter at @cory_golden