Even low levels of air pollution may be bad for your heart: Study

Short term exposure to low levels of air pollution is associated with a higher risk of sudden heart problems, especially among older people, according to a study.

Researchers from the University of Sydney in Australia found that over 90 per cent cases of out-of-hospital cardiac arrest (OHCA) occurred at PM2.5 levels lower than the World Health Organization (WHO) guideline, a daily-average of 25 microgrammes per cubic metre. The study, published in The Lancet Planetary Health journal, shows an association between OHCA and exposure to gaseous pollutants such as those from coal burning or mining, bushfires and motor vehicles.

The study of data from Japan, chosen for its superior monitoring, population density and relative air quality, is believed to be by far the largest of its kind, the researchers said. It provides comprehensive evidence of the relationship between PM2.5 and cardiac arrests, using a sample three times larger than all previous research combined, and demonstrating the impacts on groups such as the elderly, they said. Previous research into air pollution and acute cardiac events had been inconsistent, especially at air concentrations that met or bettered the WHO guidelines, said Kazuaki Negishi from the University of Sydney School of Medicine.

"OHCA 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. The researchers analysed almost a quarter of a million cases of OHCA, and found a clear link with acute air pollution levels. The 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, they said.

"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," Negishi said. The elderly where generally at the risk of cardiovascular impacts, he said. "If you're young and healthy, there should be no immediate risk of devastating consequence," said Negishi. However, he noted these findings are only in relation to the short-term, and that the effects can last for up to five years.