New study confirms ‘no safe level’ of air pollution protects against cardiac arrest

A new study published in the high-impact journal, Lancet Planetary Health, found a correlation between human exposure to particle matter known as PM_2.5 and cardiac arrest. Researchers in Sydney confirmed that even low-level exposure of air pollution set by the World Health Organization as safe posed a risk of cardiac arrest in 65 year olds and older.

Scientists from the University of Sydney suggested tighter regulations and cleaner energy are required to protect human health.

“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,” Kazuaki Negishi, report author and professor from the University of Sydney School of Medicine, said.

The study analyzed “air quality in Japan against 249,372 cases of out-of-hospital cardiac arrests” (OHCA) to determine that “there has been increasing evidence of an association with the more acute air pollution, or fine particulate matter such as PM_2.5.”

“Out-of-hospital cardiac arrest is a major medical emergency—with less than one in 10 people worldwide surviving these events—and there has been increasing evidence of an association with the more acute air pollution, or fine particulate matter such as PM2.5,” Negishi said. “We analyzed almost a quarter of a million cases of out-of-hospital cardiac arrests and found a clear link with acute air pollution levels.”

Professor Kazuaki Negishi said previous studies into air pollution and acute cardiac arrest were “inconsistent” when air concentrations either met or bettered the World Health Organization (WHO) guidelines, The University of Sydney reported.

“Inconsistencies in previous data were addressed through the size and robustness of this study, which found that more than 90 percent of OHCAs occurred at PM_2.5 levels lower than the WHO guideline (and Australian standard level), a daily average of 25 micrograms per cubic metre (µg/m³). As well, 98 percent of OHCAs happened at levels lower than the Japanese or American daily standard level of 35 µg/m³.”

The study found a 1 to 4 percent increased risk of cardiac arrest associated with every 10 µg/m³ increase in PM_2.5. 

The two main sources of PM_2.5  worldwide are traffic caused by motor vehicles and bushfires. While PM_2.5 cannot be seen, its fine particle matter can travel further into the body and stay for a while, therefore making it the most dangerous air pollution to the human body.

While the study didn’t identify a safe level for exposure to PM2.5, but it determined that current standards must be re-evaluated.

“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 lung cancer—must be taken into account in health care responses,” said Negishi said.