“We know that people with heart failure or people who are developing heart failure, their heart will undergo changes, and one of the changes is they become larger,” said Aung. “When they become larger, that means that the heart is under stress, so the only way to accommodate this increased pressure and volume is to become larger. If you don’t treat or reverse that change, in the long run the heart may fail.”
Aung said the study found that an increase in exposure to PM2.5 of 1µg/m3 was linked to an increase in the size of each ventricle of just under 1%. He stressed that the findings were of particular concern because most of the participants lived in areas with relatively low exposure to air pollution.
On average, the participants were exposed to average PM2.5 concentrations of 8-12µg per cubic metre, close to the WHO recommended limit of 10µg/m3, but well within the UK guidelines of 25µg/m3. Research last year found that in some polluted areas such as central London, average levels of PM2.5 were above 18µg/ m3, with even higher levels seen on bad pollution days.
Previous work has also shown that mice exposed to high concentrations of PM2.5 develop larger left ventricles, the authors note.
Chris Gale, professor of cardiovascular medicine at University of Leeds who was not involved in the study, said that since people travel for work and other purposes, the home addresses of the participants might not represent the main location where they encountered air pollution. What’s more, he said the study looks at a snapshot in time, rather than recruiting and following individuals over years.
Nonetheless, he said the study was important: “[It] offers a possible mechanistic clinical pathway between the detrimental effects of air pollution and cardiovascular disease,” he said.
Kevin McConway, emeritus professor of Applied Statistics at the Open University, welcomed the study. “I think the study provides pretty convincing evidence of a correlation between levels of two air pollutants – fine particulates in the air and nitrogen dioxide – and measurable changes in the heart,” he said.
But, he added, the study only shows a link, rather than showing that it is air pollution that is driving the heart changes. “In this study the researchers did adjust their results carefully to allow for possible effects of many factors to do with lifestyle,” he said. “Such statistical adjustments can never be perfect, though, so some doubt must remain about whether the heart changes are actually caused by the pollution.”
Aung said that while the government’s recent consultation on clear air is a step in the right direction, avoiding air pollution can be difficult and individuals should also improve their health through other measures including tackling issues such as obesity, high cholesterol or high blood pressure.
Katie Nield of environmental legal group ClientEarth said: “This study is particularly worrying as it shows the serious health effects of air pollution at levels well below the current legal limits. We need a new Clean Air Act with stricter, binding air quality standards that reflect the latest science and help protect people from the serious damage that air pollution does to their health.”
Comment