First-ever link found between prenatal exposure to ultrafine particles, pediatric asthma

Researchers said they have found evidence that children exposed to ultrafine particles from air pollution in utero were more likely to develop asthma than unexposed children.

It is the first study in the United States to identify the association, according to Rosalind J. Wright, MD, MPH, dean of translational biomedical research at Mount Sinai Health System, and colleagues.

Since ultrafine participles (UFPs) have “enhanced oxidative capacity” and the “ability to translocate systematically,” they may be more toxic than other pollutants, Wright and colleagues wrote in the American Journal of Respiratory and Critical Care Medicine. UFPs are those measuring 100 nm or less, according to the researchers.

“Childhood asthma remains a global epidemic that is likely to grow with the anticipated rise in particulate air pollution exposures due to effects of climate change,” Wright said in a press release.

The researchers noted that ultrafine particulate matter is not regulated, hindering the ability to estimate long-term exposures. They added that “studies linking UFPs with child health have focused on short-term exposure due to lack of adequate spatiotemporal modeling.”

Wright and colleagues estimated the link between daily average prenatal UFP exposure and asthma incidence among 376 children (192 of them girls) whose mothers lived in the Boston area. The researchers used Bayesian distributed lag interaction models (BDLIMs) to identify sensitive windows for exposure to UFPs and determine whether effect estimates differed by sex. All the mothers were at least 37 weeks pregnant and nearly 82% were either Black or Hispanic. The UFPs came primarily from local traffic; however, on windy days, UFPs from a nearby airport were recorded.

Wright and colleagues found that the median prenatal exposure to UFP was 27,842 counts/cm² (interquartile range = 24,033 counts/cm² to 32,302 counts/cm²). In addition, 18.4% of the children developed asthma by age 30 months. The cumulative OR for developing childhood asthma was 4.28 (95% CI, 1.41-15.7), “per doubling of UFP exposure level across pregnancy,” with similar effects among boys and girls, the researchers wrote.

Overall, there was a significant link between increased UFP exposure during 28 to 35 weeks gestation and increased odds for asthma in children, according to Wright and colleagues. BDLIMs showed that girls had the highest risk for developing asthma when exposed to higher UFPs during late pregnancy, while for boys “all windows of exposure were estimated to be equally important with risk elevated across the entire pregnancy.” All risks remained even after the data were adjusted for fine particles and nitrous dioxide, the researchers reported.

“This research is an important early step in building the evidence base that can lead to better monitoring of exposure to ultrafine particles in the United States and ultimately to regulation,” Wright said in a press release. “As we advance methods for measuring these tiny particles, we hope for replication of these findings, both within different geographic areas across the United States as well as globally.”