Why UC Davis’ monkey colony has researchers warning expectant moms about wildfire smoke
Researchers at the University of California, Davis, said Thursday they are concerned about the risk that wildfire smoke poses to newly pregnant women after documenting an increased number of miscarriages among a colony of monkeys that were breeding as fumes from the Camp Fire blanketed their outdoor habitat in 2018.
The researchers, who published a paper on their findings online Aug. 25 in the journal Reproductive Toxicology, said they advise pregnant women to try to avoid prolonged time outdoors when the air quality index registers as unhealthy for sensitive groups or worse. That would be starting at the orange tier, which is unhealthy for sensitive groups, and going up. Outdoor activities are fine when the AQI is good (green) or moderate (yellow), indicating lower levels of pollutants.
“Pregnant women should be cautious, particularly in the first trimester,” said Dr. Bryn Willson, an obstetrician and gynecologist who was the lead author on the study. “The same way we would counsel our patients with asthma or chronic obstructive pulmonary disease to be careful during this time, that’s how I would counsel pregnant women during the wildfires, which, unfortunately, are happening more often these days.”
As wildfires have increased in frequency, researchers have stepped up their analyses of how the accompanying smoke is affecting human health. They have pointed to links between the fine particulate matter, or PM 2.5, in the smoke and cardiovascular conditions, for instance, and a recent study in Reno found a link between smoke days and increased occurrence of COVID-19.
The UC Davis paper also noted that a study examining over 800,000 pregnancies during the 2003 wildfires in Southern California found that neonatal birth weight had dropped for all women, regardless of which trimester they were exposed.
While researchers have found such associations, they say they have not yet found the why, or the causal link, in many cases between air pollution and health issues that are being observed.
PM 2.5 is about 1/30th the size of a human hair, researchers told The Sacramento Bee, and that makes it so tiny that when people breathe, they follow that intake wind all the way down to the smallest air sacs in lungs. The particles may lodge in lung tissues, researchers have found, but they also can move to other parts of the body as oxygenated blood flows to other organs.
In the study, Willson was able to observe a colony of Rhesus macaques at the California National Primate Research Center in Davis in November 2018. That month, the Camp Fire was consuming tens of thousands of acres in Northern California, including the town of Paradise.
The fire spewed smoke that drifted 100 miles or more away and hung over Davis and much of the Sacramento Valley for days. The Rhesus macaques lived in outdoor corrals, Willson said, and it was their mating season.
This is the type of research you could never do with humans, Willson said, but primates have a number of similarities with humans and can offer invaluable insights for human gestation. Willson’s team randomly selected 66 female animals of reproductive age from the primate center’s colony and followed their pregnancy outcomes.
Fortunately for Willson and her team, UC Davis researchers have been monitoring breeding patterns on this colony of monkeys over many years, so this study’s data on births was compared with results from the prior nine years.
Of the 66 Rhesus macaques selected for study, 45 became pregnant while levels of smoke pollution were high and 20 conceived after air quality had returned to normal levels in December, according to the researchers’ paper. One did not become pregnant.
The 20 animals that conceived in December all had live births, Willson said, but of the 45 that were exposed to wildfire smoke early in their pregnancies, 37 had live births. That was a live birth rate of 82%, compared with rates of 86% to 93% in the prior nine years when air quality had been normal.
“We saw that the primates that were exposed early on in their pregnancies were the ones that went on to miscarry,” Willson said. “It makes us a little more cautious about that window of time, not only for primates but also for pregnant women who...are trying to conceive.”
Willson was a resident in obstetrics and gynecology at UC Davis Health when she undertook the study with Kent Pinkerton, a professor in the UC Davis Center for Health and Environment; Bill Lasley, a professor emeritus at the Center for Health and Environment and School of Veterinary Medicine; and other UC Davis researchers.
In the paper published Aug. 25, Willson noted that environmental risks such as outdoor air pollution have been described as the fifth fifth leading risk factor contributing to global mortality.
This story was originally published September 3, 2021 at 10:07 AM with the headline "Why UC Davis’ monkey colony has researchers warning expectant moms about wildfire smoke."
