Around the world, breathing a variety of air pollutants – in some cases for a single day – increases the chance that people will suffer heart attacks, according to a new analysis published Tuesday.
For the first time, scientists analyzed previous studies from five continents to verify and quantify the links between air pollution and heart health. They found that short-term exposure – less than seven days – to all major air pollutants except ozone was associated with an increase in heart attacks.
The team reported in the Journal of the American Medical Assn. that the magnitude of the risk “is relatively small” compared to other factors, such as smoking, high blood pressure and diabetes. But they stressed that so many people worldwide are breathing fine particulates, carbon monoxide, sulfur dioxide and other contaminants that the numbers of people at risk are substantial.
“Thus an improvement in air quality could have a significant effect on public health,” wrote the authors, led by Dr. Hazrije Mustafic of the Paris Cardiovascular Research Center at University Paris Descartes.
Published on Valentine’s Day, the new study shows that the human heart is perhaps the most vulnerable part of the body when it comes to air pollution.
Dr. Jesus Araujo, an assistant professor of medicine and director of environmental cardiology at UCLA, said there is now “more than enough evidence” from human, animal and cellular studies that air pollution kills.
One of the most important findings of the new research is that it confirms that heart attacks increase even when exposures to worsening air quality are short in duration.
“We don’t have to be exposed for weeks or months or years,” Araujo said.
Air in most urban areas is made up of an array of contaminants, some gases, some microscopic particles, all containing a variety of chemical ingredients. In recent years, most of the attention has focused on fine particulates – microscopic pieces of soot from diesel engines and other sources. Studies conducted in numerous cities have shown that whenever fine particles increase, deaths and hospitalizations from cardiovascular and respiratory diseases increase, too.
In the new analysis, the researchers examined more than 100 studies from around the world and included 34 that met certain standards, then combined them to calculate the risk of heart attacks associated with fine particles, coarse particles, ozone, nitrogen dioxide, carbon monoxide and sulfur dioxide. Most are pollutants related to the combustion of fossil fuels, emitted by vehicles or industry.
“One strength of our study is the comprehensive nature of our search that spanned multiple databases and was not restricted to particular publication language or a single pollutant,” wrote the authors, who are from several institutions in France as well as the Mayo Clinic in Minnesota.
Araujo said it is “quite significant” that the authors combined the results of several dozen studies and found that heart attacks increased with all of the air pollutants except ozone.
“What this study is showing us is that the gaseous pollutants are important, too. It shows that not only particulate pollution is associated with deaths but also the other major gaseous pollutants,” said Araujo, who did not participate in the new study.
Jean Ospital, health officer of the agency responsible for cleaning up the Los Angeles basin's air, said Tuesday that although the link between air pollution and heart attacks has been documented by individual studies for years, the new analysis is global and gives it “more statistical power and a larger sample size.”
“The studies are overall consistent,” said Ospital, who has been health officer at the South Coast Air Quality Management District since 2000. “There are a number of investigators looking at alternative explanations, but it always seems to come out that air pollutants are associated with premature deaths. And as the testing becomes more sophisticated, we find more effects at lower levels.”