Research published on bmj.com today revealed that high levels of pollution could increase the risk of having a heart attack for up to six hours after exposure, however, the risk diminishes after a six hour time frame.

Researchers speculate that the heart attack would have happened regardless and was merely pulled forward by a few hours. They base their assumption on the transient nature of the increased risk known as a short-term displacement (or “harvesting”) effect of pollution.

Although research has proven that high pollution levels are linked to premature death from heart disease, according to the authors, the association with an increased risk of heart attack is less clear.

Krishnan Bhaskaran, an epidemiologist from the London School of Hygiene and Tropical Medicine, and his team conducted a study in which they evaluated 79,288 heart attack cases from 2003 to 2006 and hourly exposure to pollution levels.

By using the UK National Air Quality Archive they investigated the levels of specific pollutants in the atmosphere, including pollutant particles (PM10), carbon monoxide (CO), nitrogen dioxide (NO2), sulphur dioxide (SO2) and ozone.

Bhaskaran stated that higher levels of PM10 and NO2 are well-known markers of traffic related pollution.

Seeing that there was no net increase in heart attack risk over a broader timescale, the authors argue that there may be:

“limited potential for reducing the overall burden of myocardial infarction through reductions in pollution alone, but that should not undermine calls for action on air pollution, which has well established associations with broader health outcomes including overall, respiratory and cardiovascular mortality.”

Professor Richard Edwards and Dr Simon Hales from the University of Otago in New Zealand say in an accompanying editorial that:

“despite the strengths of the study, it is possible that a true effect was missed because of imprecise measurements and inadequate statistical power. Given other evidence that exposure to air pollution increases overall mortality and morbidity, the case for stringent controls on pollutant levels remains strong.”

Written by Petra Rattue