Study Explores Possible Mechanism to Explain Air Pollution-CVD Link

Potentially providing a mechanism to explain the established association between exposure to air pollution and cardiovascular disease, a new study shows that young, healthy, nonsmoking adults show evidence of endothelial injury and systemic inflammation at times of the year when they’re breathing elevated levels of particulate matter.

“Certainly in these young, healthy individuals, the initial vascular injury that we’re observing is likely to be very minor. It’s not resulting in clinical symptoms,” lead author C. Arden Pope III, PhD (Brigham Young University, Provo, UT), told TCTMD. “But the overall evidence suggests that repeated, prolonged exposure will contribute to the progression of vascular disease, and then—[in those with] more advanced disease—that even short-term exposures will increase the risk of life-threatening events like heart attacks and strokes.”

The findings require replication, but they are consistent with prior epidemiological studies showing that over long periods of time, people exposed to more air pollution are at risk for dying prematurely from cardiovascular disease, Pope said.

Importantly, he added, “the results suggest that exposure is a concern for all of us who are exposed and not just those who have existing [respiratory or cardiovascular] disease.”

Signs of Trouble in the Blood

The association between air pollution and cardiovascular disease first became apparent about 20 years ago, according to Pope, who said he was initially “quite skeptical” of the link. Further research convinced him otherwise, and he eventually was a co-author on the American Heart Association’s scientific statement about air pollution and cardiovascular disease, which was first published in 2004 then updated in 2010.

“It’s become quite evident that air pollution contributes to cardiovascular disease,” Pope said, adding that a search for potential mechanisms has been ongoing.

In the current study, published online October 25, 2016, ahead of print in Circulation Research, Pope and colleagues explored that issue by measuring levels of various biomarkers in the blood of young, healthy adults at times of the year with fluctuating levels of fine particulate matter air pollution (PM2.5).

The study included three groups of 24 people living in the city of Provo who had their blood drawn during three consecutive winter/spring periods: January to March 2013, January to March 2014, and December 2014 to April 2015. Provo is located in the Utah Valley; the area has predictable periods during which snow cover, a relatively high barometric pressure, and stagnant atmospheric conditions combine to trap air pollution, resulting in higher levels of exposure to the residents.

The researchers found that when particulate-matter air pollution was elevated, levels of endothelial microparticles indicative of endothelial damage and immune cells were also raised. In addition, circulating levels of proangiogenic growth factors were lower and levels of antiangiogenic and proinflammatory cytokines and endothelial adhesion molecules were higher, signifying a boost in systemic inflammation. 

An intervention that included fish oil supplementation failed to mitigate the effects of exposure, Pope said.

Next Steps

Pope said that there are many avenues for future research in this area, starting with replication of these findings by other groups, particularly in areas of the world with much higher levels of air pollution.

He also said he would like to see more research into potential interventions to dampen the adverse effects of exposure to air pollution. Although supplementation with omega-3 fatty acids did not have an impact in the current study, Pope said it is possible the approach would work in a larger study or with higher doses. He pointed to prior studies showing that fish oil reduces the impact of air pollution on cardiac autonomic function.

Other potential areas that can be explored, he said, are the effects of statin therapy and the relationships in older, more diseased populations.

Finally, air pollution appears to be just a tiny part of what goes into determining cardiovascular health.

“We found that air pollution exposure explained only a small amount of the variability in endothelial microparticles and markers of inflammation, suggesting that exposure to air pollution is one of multiple factors that influences cardiovascular health,” the authors write.

TCTMD’s L.A. McKeown contributed to the reporting on this story.