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Association Between Tiny Air Particulates and Sudden Cardiac Arrests

In Singapore, small particles in air pollution may have resulted in sudden cardiac arrests in several people, as per research conducted by Duke-NUS Medical School collaborating with the National Environment Agency (NEA) as part of the Pan-Asian Resuscitation Outcomes Study (PAROS).

Association Between Tiny Air Particulates and Sudden Cardiac Arrests

Image Credit: Ralf Geithe/

As reported in the journal The Lancet Public Health, this outcome, which is dependant on data gathered between 2009 and 2018, settles the doubt caused by discrepancies in earlier studies as a result of the limitations in the quality and availability of environmental and disease data.

The study team, including members from NEA’s Environmental Health Institute and the Environmental Monitoring and Modeling Division of the Clean Environment Group, evaluated if there was a relationship between out-of-hospital cardiac arrests (OHCA) and the levels of small air pollution particles that are at least 25 times smaller compared to the width of a human hair.

This PM2.5 category of particulate matter is known from earlier research to considerably increase the hazard of respiratory, cardiovascular, and even ocular diseases.

We have produced clear evidence of a short-term association of PM2.5 with out-of-hospital cardiac arrest, which is a catastrophic event that often results in sudden death.

Joel Aik, Study Lead Investigator and Adjunct Assistant Professor, Pre-Hospital & Emergency Research Center, Duke-NUS Medical School

This study, which tracks a methodology that is the same as that utilized in studies mentioned by the World Health Organization to set air quality guidelines, founded its outcomes on data reported to PAROS on all cases of OHCA in Singapore between July 1st, 2009, and December 31st, 2018. The timing of such cases was compared with the daily air pollutant levels over the same time.

Statistical analysis found 492 out of 18,131 OHCA events that the scientists were able to attribute to an increase in PM2.5 concentrations either on the day of the cardiac arrest or up to two days before.

Also, the study determined a clear reduction in risk from three to five days following exposure to the pollutant, indicating a comparatively short-term effect.

The average PM2.5 concentration at the time of the study period was 18.44 μg/m3, and a reduction of just one microgram led to an 8% decrease in the number of OHCA events, while a decrease of 3 μg brought a 30% reduction.

These results make it clear that efforts to reduce the levels of air pollution particles in the 2.5 micrograms or lower range, and steps to protect against exposure to these particles, could play a part in reducing sudden cardiac arrests in Singapore’s population, while also reducing the burden on health services.

Joel Aik, Study Lead Investigator and Adjunct Assistant Professor, Pre-Hospital & Emergency Research Center, Duke-NUS Medical School

Aik is also an environmental epidemiologist with the NEA.

Aik stressed the significance of this study to many cities throughout the world where air pollution seems to be an everyday issue. Less common but extreme events, like haze and wildfires, can also result in abrupt and considerable increases in PM2.5 particles.

In spite of the consistency in study outcomes with those elsewhere, and a biologically plausible mechanism of the effect of PM2.5 on OHCA events, Aik warned that this was an observational study and does not indicate direct causation.

This study provides strong evidence for the impact of air quality on health and should stimulate policy and ground efforts to manage emissions from key sources that can lead to PM2.5 increases and prevent potential harm to public health. New policy interventions, such as phasing out internal combustion engine vehicles, can help to reduce the dangers.

Marcus Ong, Professor and Director, Health Services & Systems Research Program and PERC, Duke-NUS Medical School

Professor Ong, who is also a Chairman of PAROS and Senior Consultant at the Department of Emergency Medicine at Singapore General Hospital, added, “Individuals can also take simple but significant steps, such as wearing high efficiency air filtration masks during periods when the PM2.5 levels are elevated and not smoking.”

Journal Reference:

Wah, A. F., et al. (2022) Air quality and the risk of out-of-hospital cardiac arrest in Singapore (PAROS): a time series analysis. The Lancet Public Health.


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