A novel UC Davis study with possible implications for human health has found that exposure to wildfire smoke makes young rhesus monkeys more vulnerable to disease.
The research, conducted by UC Davis and the California Air Resources Board, found that rhesus macaque monkeys born at the university’s Primate Research Center in the summer of 2008 – an unusually intense fire season – had depressed immune systems compared with those born a year later.
The study is timely given scientists’ predictions that climate change will increase the frequency and intensity of wildfires.
Researchers measured the effects of fine particulate matter, known as PM 2.5. That matter lodges deep in the lungs and its presence has been linked to health risks, including asthma and cardiovascular disease.
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During late June 2008, PM 2.5 levels spiked at ARB measuring stations in Davis and Woodland, not far from the primate research center, said Lisa Miller, professor of veterinary medicine at UC Davis and a researcher at the primate center. Smoke had drifted into the Central Valley from more than 2,000 fires ignited by lightning strikes. More than 1.2 million acres burned.
“In 2008, monitoring locations had readings of 75 micrograms per cubic meter for a 24-hour period,” said Miller. “That is extremely high.”
The current national standard for safety is less than half that amount. Additionally, wildfire smoke also causes higher ozone levels, which are linked to asthma, lower birth weights and heart problems.
The effect of that particulate matter was measured on 50 monkeys – 25 that were born in 2008 and 25 in the mostly quiet fire season of 2009. Use of the primates is seen as a crucial model for establishing the effects of toxins and environmental effects on humans.
The young monkeys, which live outdoors at the primate center, were between 1 and 3 months old when they were examined. Researchers took blood samples and did lung function studies. “The idea behind this is that if we detected any changes in the animals this information might translate as a biomarker that can be used for kids,” said Miller, whose specialty is childhood respiratory diseases.
The outcome proved surprising, Miller said. Conventional medical wisdom says that smoke and other irritants cause immune systems to kick into high gear. This study, however, found the opposite.
“When we took blood samples and put them in a tissue culture dish and treated that culture with a mimic of an infectious organism, we found that the blood from animals exposed to wildfire smoke responded in a reduced manner when compared to the control group from 2009,” said Miller. “That means the ability of the animals to respond to a real pathogen was reduced.”
“It was a surprise – and somewhat disturbing,” said Miller. “You certainly don’t want to be walking around with a suppressed immune system.”
Exposure to fine particulate matter on growing lung tissues is a concern for scientists, Miller said, because exposure leads to adverse health effects later in life. For humans the development of the lung is a lengthy process – it takes 18 years for the lung to fully mature, Miller said.
The results also were cause for concern at the Air Resources Board, which would like to see further study on the effects of wildfire smoke. “We’ve known for some time about PM 2.5’s effect on lung function – so the results were not particularly surprising,” said Deborah Drechsler, an air pollution specialist with the agency.
Drechsler said this initial study will have to be confirmed with further studies, and that the data must be taken with certain caveats – such as the fact that other toxins were present in the air and that the monkeys spent all of their time outdoors.
At the U.S. Forest Service, the effect of wildfire smoke on human health is a serious area of study, said Andrzej Bytnerowicz, a Forest Service ecologist. He said the agency, in a collaboration with the University of California, Merced, is planning to research the effects of wildfire smoke on people who live in the Central Valley.
The issue has become more pressing at the agency because of the wild card that is climate change. Since the 1970s, California wildfires have become more severe. A recent Scripps Institute report on climate change found that the average large fire in the 1970s burned for about a week. In the 2000s, big fires burned for an average of five weeks.
“With changing climate there is a higher potential for catastrophic fires,” Bytnerowicz said. “And this year may be a really bad one with the almost lack of snow in the Sierra Nevada. These conditions will be predisposing for potential fires.”
The agency is looking to use more prescribed blazes as a way to prevent catastrophic fires by reducing the amount of fuel available, he said. However, prescribed fires also add particulate matter to the region’s air.
“We do not know yet if that would prevent us from using prescribed fires as a tool,” Bytnerowicz said.