Nearly a decade of data collected in Singapore suggests that elevated concentrations of tiny particles in the air can actually trigger cardiac arrests, making the need to reduce air pollution levels around the world even more urgent.
The researchers looked for tiny particles in the air at least 25 times smaller than the width of a human hair, known as PM2.5 particles (because they are 2.5 micrometers in diameter). Their small size means they can be inhaled easily and have been linked to a number of health problems, including autoimmune diseases.
Pollution levels in Singapore were tracked across more than 18,000 reported cases of out-of-hospital cardiac arrest between July 2010 and December 2018. Through statistical analysis, 492 of the cases could be attributed to increased PM2.5 concentrations.
“We have provided clear evidence of a short-term association of PM2.5 with out-of-hospital cardiac arrest, which is a catastrophic event that often leads to sudden death,” says epidemiologist Joel Aik, from Duke-NUS Medical School at the University Nationals of Singapore.
The tiny particles in the air responsible for some health problems
This is an observational study, which means we can only speculate on the relationship between pollution levels and cardiac arrests. Additionally, air pollution measurements taken at air quality stations cannot be assumed to reflect individual exposure, they note Science Alert.
However, the data are sufficient to indicate that there is an association that deserves further exploration. The data showed that daily concentrations of the tiny particles in the air averaged 18.44 micrograms per cubic meter.
Testing hypothetical reductions in air pollution, the researchers found that a drop of 1 microgram per cubic meter correlated with an 8% reduction in heart attack events, while a drop of 3 micrograms per cubic meter saw a reduction of 30% Hypothetically, these reductions translate into 39 and 149 fewer heart attacks, respectively.
There was also a clear decrease in the risk of having a heart attack 3-5 days after exposure to higher levels of pollution, suggesting that the effects are short-term. Researchers say cleaning up the city’s air could save lives and reduce pressure on hospitals.
Reasons to reduce air pollution
“These results clearly show that efforts to reduce levels of air pollution particles in the range of 2.5 micrograms or less, as well as protective measures against exposure to these particles, could have a role in reducing sudden cardiac arrests in population in Singapore, while reducing the burden on health services,” says Aik.
Sudden heart attacks have a typical survival rate of about 10%, much lower than the chances of surviving a heart attack in the hospital. So it is no exaggeration to say that reducing the number of these cases saves lives. We can add it to the long list of reasons why we should clean our air.
Although this link has been seen before in cities such as New York and Melbourne, Australia, the results have been inconsistent with data collected in other places such as Denmark. These inconsistencies tend to occur at pollution concentrations below the World Health Organization’s guideline values for air quality, but research shows that there is no “safe” level of exposure for heart health.
What is clear is that most people breathe poor quality air, which is believed to be responsible for millions of premature deaths in both urban and rural areas each year.
Political interventions are needed
The team behind the new study wants more to be done to control air quality in places like Singapore. With everything from traffic congestion to wildfires, there are plenty of places where progress can be made, including indoors.
“This study provides strong evidence for the impact of air quality on health and should stimulate policy and on-the-ground efforts to manage emissions from key sources that can lead to increases in PM2.5 and prevent potential harm to public health,” it says Marcus Ong, a clinician at Duke–NUS Medical School.
“New policy interventions, such as phasing out internal combustion engine vehicles, can help reduce the dangers,” he added.
The research was published in The Lancet Public Health.