Risk factors

Australian air pollution levels linked to coronary calcium scores

Ambient air pollution, even at the low levels common in Australia, is associated with coronary artery calcification in asymptomatic adults.

The findings, published in the European Heart Journal, suggest air pollution is a critical residual risk factor for coronary artery disease.

The study compared coronary calcium scores (CCS) in 606 adults from Tasmania, Victoria and Queensland with the annual average concentrations of fine particulate matter (PM2.5) and NO2 estimated at each participant’s residential address at the time of recruitment.

Participants had a mean age of 58 years, no cardiovascular symptoms and the vast majority had a low risk of experiencing a cardiac event in the next five years.

Despite very low levels of air pollution overall, the study found the concentrations of both PM2.5 and NO2 were positively correlated with CCS in a dose-response manner.

“These associations were independent of traditional cardiovascular risk factors and only slightly altered after adjusting for renal function, education, and socioeconomic factors,” the study said.

“Our findings were consistent with those from a number of previous studies that linked exposure to air pollution with an increase in, and progression of, intima media thickness – a marker of generalised atherosclerosis.”

The study said given the median levels of PM2.5 and NO2 were lower than Australian national standards and WHO guidelines, there was probably no threshold below which exposures can be considered safe at the population level.

Their findings support other evidence that the effects of chronic exposure to air pollution go beyond the triggering of acute adverse events, and can instead influence the development of atherosclerosis and increase the risk of CAD in a low-risk population.

The study, co-authored by cardiologists including Professor Thomas Marwick and Professor Kazuaki Negishi, said the findings ultimately had implications for both public policy and clinical research.

“Although we need to keep improving air quality, reducing nationwide (or worldwide) air pollution to such a low level is extremely challenging.”

“It is therefore critically important for future clinical research to investigate any possible intervention to reduce adverse effects induced by exposure to air pollution—which currently remains unknown.”

They noted their earlier research which had suggested possible protective effects of beta-blockers on heart failure readmissions triggered by acute exposure to air pollution.

“Future research into any medical therapies to mitigate or reverse the progression of atherosclerosis induced by exposure to air pollution among people at risks are therefore needed.”

Professor Negishi told the limbic despite the evidence and scientific statements from organisations such as the American Heart Association, there was some reluctance to accept the relationship between air quality and cardiovascular risk.

“If we could improve our air quality more, we could expect less cardiovascular episodes. So the continuous effort from government as well as people and industry to improve air quality is important for our health.”

He said COVID-19 had demonstrated that air quality globally could be improved significantly.

“Interestingly, we’ve seen some signal of a decrease in acute coronary syndromes. So this is controversial but if we stopped our economic activities we might be able to achieve air quality improvement.”

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