Skip navigation

News Home

Bushfire smoke and sunset

The invisible threat to your heart

29 Jan 2020


Air pollution, even for short periods at relatively low concentrations, increases the risk of heart attacks according to a study of almost 250,000 cardiac arrests published by Nepean Hospital cardiologist, Professor Kazuaki Negishi in the international journal, The Lancet Planetary Health.

The study analysed data from Japan for short-term exposure to low concentrations of fine particulate matter (PM2.5) which is invisible to the naked eye and only about 3 percent the width of a human hair.

Major sources of PM2.5 include motor vehicles, coal burning/mining and bushfires.

“We analysed almost a quarter of a million cases of out-of-hospital cardiac arrests and found a clear link with acute air pollution levels,” says Professor Negishi, who is also Head of Medicine in the University of Sydney’s Nepean Clinical School and a member of the Charles Perkins Centre Nepean.

“Out-of-hospital cardiac arrest is a major medical emergency and there has been increasing evidence of an association with the more acute air pollution, or fine particulate matter, such as PM2.5.

“Our study supports recent evidence that there is no safe level of air pollution – finding an increased risk of cardiac arrest despite air quality generally meeting the standards,” he says.

Within 3 days of exposure to air pollution that was measured at or lower than the World Health Organisation (WHO) guidelines (a daily average of 25 micrograms per cubic metre), there was a significant increase in the risk of out-of-hospital cardiac arrest (OHCA). The risk was higher for those over 65 years old.

There are about 15,000 OHCAs annually in Australia. In a hypothetical situation, if there is a 10-unit increase in the daily average of PM2.5, it could lead to another 600 OHCAs resulting in 540 deaths (based on global 10 percent survival rate). The positive aspect of this is that if we are able to improve our air quality further, we can expect the potential health benefit.

During the recent Australian bushfires PM2.5 levels 20 times the WHO guidelines were recorded in Richmond, in North West Sydney. Because PM2.5 are very small particles they can travel deeper into the body and the effects on the heart can occur up to five to seven days after exposure. The study findings could help authorities predict the health impacts of air pollution and allocate resources more efficiently.

“Given the fact that there is a tendency towards worsening air pollution from increasing numbers of cars as well as disasters such as bushfires, the impacts on cardiovascular events, in addition to respiratory diseases and cancers must be taken into account in health care responses,” says Professor Negishi.

The study authors are also calling for regulatory standards and targets to incorporate the potential health gains from continual air quality improvement even in locations already meeting World Health Organisation standards.

NSW Health Advice about Air Pollution


This research is a collaboration between the University of Sydney, the University of Tasmania/Menzies Institute for Medical Research, Monash University, the University Centre for Rural Health in Australia and Gunma University in Japan.

Short-term exposure to ambient fine particulate matter and out-of-hospital cardiac arrest: a nationwide case-crossover study in Japan

Bing Zhao, MD; Fay H Johnston, MBBS; Farhad Salimi, PhD; Prof Masahiko Kurabayashi, MD; Prof Kazuaki Negishi, MD

Open Access Published: January, 2020 The Lancet Planetary Health DOI: