Clean Air Healthy Heart

Kai Zhang of ABC Environment reports:

A SUDDEN REDUCTION OF air pollution might improve adverse cardiovascular effects in healthy adults, according to a study that tracked pollutants and compared levels to blood markers before, during and after Beijing's 2008 Olympic games.

This is the first major study to examine the biological link between short-term air pollution reductions and cardiovascular diseases in young adults who have no health problems. The study suggests that even healthy people can benefit from a temporary decline in air pollution.

Beijing is a megacity well known for its extreme levels of air pollution. To improve air quality for the 2008 Olympic games, vehicle use was restricted and numerous industrial factories in the city and nearby provinces were closed.

The changes led to a 60 per cent drop in air pollution emissions. At the same time, the levels of two heart markers linked with cardiovascular disease improved in young, healthy adults, the study shows.

When factory work and traffic returned to normal after the games, air pollution emissions rose rapidly and the levels of the heart health markers returned to previous levels.

A few human studies have examined the impacts of reduced air pollution on cardiovascular diseases. This study went further by trying to identify underlying mechanisms. In addition, the researchers looked at young, healthy adults while most of the previous studies focused on either the elderly or children.

Air pollution is a mix of small particles - called particulate matter - and gases - such as ozone and nitrogen dioxide. Vehicles, power plants, industrial factories and natural sources release the pollutants into the air.

Billions of people around the world live in areas with very high levels of air pollution. The worst air quality plagues the large megacities where populations exceed 10 million people.

Breathing air pollution can increase the risk for cardiovascular diseases, such as heart attacks and high blood pressure. Exposure to fine particulate matter - particles less than 2.5 micrometer in diameter (PM2.5) - is especially dangerous.

However, the underlying connections between air pollution and heart diseases are not well understood. The Chinese government's tight controls on emissions from factories and vehicles for the Beijing Olympics offered a rare chance to look at how air pollution might affect predictive markers for heart disease.

For the five-month study from June to November, the researchers recruited 125 resident doctors with an average age of 24 from a centrally located hospital. Half were male, and all were healthy with no history of diabetes or cardiovascular disease.

Air pollution emissions were also measured at similar times. Levels of most air pollutants during the games decreased up to 60 per cent compared to their pre-game levels, depending on the type of pollutants. For example PM2.5 dropped 27 per cent, nitrogen dioxide 43 per cent and sulphur dioxide 60 per cent. After the games when pollution controls were removed, emissions rose to higher levels than were measured before the games started.

This study suggests that even young healthy people can benefit from short-term air pollution reduction and supports efforts to quantify and understand the benefits and costs of air pollution control measures.