Beating bad air quality: the best ways to defend your lungs from air pollution

Hong Kong has an air pollution problem. If the territory conformed to the World Health Organisation's (WHO) standards for clean air, only 10 per cent of the days here would pass muster.

According to the WHO, air pollution is "the world's single largest environmental risk". In October last year, the WHO's International Agency for Research on Cancer (IARC) classified air pollution as a group 1 carcinogen for the first time. This puts it in the same category as smoking cigarettes, with "sufficient evidence" that exposure causes lung cancer. The IARC also classified particulate matter (PM), a major component of the air pollution in Hong Kong, as carcinogenic.

Lung cancer is only one of many negative outcomes. Air pollution both causes and exacerbates ongoing irritations such as coughs, mucous build-up and inflamed airways. It also leads to more life-threatening situations such as cardiovascular disease and heart attacks. Vulnerable groups, including children, the elderly and people with existing heart and respiratory conditions, are most at risk. Some people are genetically predisposed to be more sensitive to pollutants. Those who spend a lot of time outdoors are also more likely to succumb to health problems. The more you delve into the subject, the more our pollution-tinged skies appear ominous.

"Air pollution is certainly the most important public health risk in Hong Kong," says Dr Tian Linwei, associate professor at the School of Public Health, at the University of Hong Kong. "If you look at environmental issues of air, water and solid waste, the quality of the air stands out as being well below standard. And the air quality is worsening. Even without any pollution data, we can simply see that the visibility is getting worse. The government says it is improving, and it is in some respects, for example, the PM 10 levels. However, overall it has deteriorated."

In public-health terms, air pollution is defined as having both a chronic, long-term effect and an acute, short-term effect. The acute effect day-by-day, month-by-month, eventually merges into the chronic effect.

"There are a lot of studies in Hong Kong that demonstrate the link between air pollution and hospital admissions, in other words an acute effect," says Tian. "Data about the long-term effect of pollution on health is not readily available as a population-based study requires a lot of resources and infrastructure. Globally, there have only been about five meaningful studies, in America and Europe. They have three consistent findings. First that air pollution shortens life expectancy. Second, that a high level of the smallest particles in air pollution is related to lung cancer risk. Third, these small particles are also related to cardiovascular disease and mortality. The higher the levels of particles in the pollution, the higher the risk."