As we approach autumn and winter, the predominantly southerly winds of the summer months will be replaced by northerlies. This will bring a drop in temperature and humidity as the moist ocean winds are replaced by those coming across the landmass of China. Over the next few months, our practices will also change, as environmental and seasonal variation bring with them differing ailments and medical conditions. There will be an increase in asthma and airway allergy associated with an increase in particulate matter in the air. The increase in particulates is associated with lower humidity, which enhances circulation of allergens and fomites. The allergens, whether naturally occurring, such as house dust mite and cat hair, or man made, will result in an increase in allergic respiratory symptoms. In addition, the seasonal variations of upper respiratory viral infections will produce an increase in attendance due to infective illnesses and symptoms.

It is also likely that over the coming months, as the wind shifts bring an increase in pollutants and the associated reduction in visibility, the issue of air pollution will again hit the headlines of our newspapers. I have lived and practiced in Hong Kong for most of my career. It is noticeable that poor air quality has been an issue, even throughout the summer months, over the last few years. Visibility has declined significantly. The U.S. Environmental Protection Agency identified reduced visibility as the best indicator of all environmental effects of air pollution. A large evidence base has demonstrated no safe threshold of pollutants. Seasonal environmental factors will influence exposure risk, as with allergens and viral illness. However, in absolute terms the health risks associated with pollution are increasing every year and 100% of the population are exposed to that risk.

Hong Kong has a great tradition of public health. In recent years evidence demonstrating the association between pollution and ill health has been published in Hong Kong. In 1990, legislation was introduced which resulted in a relatively modest change in fuel quality. Research in Hong Kong at that time was able to demonstrate major improvements in air quality and health benefits as a result of that intervention. It is ironic and somewhat tragic that 16 years later, there has been a further significant deterioration in air quality. A recent review was published by the community medicine departments at the Hong Kong and Chinese universities in addition to the university for science and technology.¹ The review used models based on the local and international evidence. The paper is available at www.civic-exchange.org and should be read by anyone with an interest in population health.

In the review, photographic evidence taken on different days was linked to hourly concentrations of the four major criteria pollutants. The evidence is disturbing. 43% of days in Hong Kong are badly polluted and only 2% of days have good air quality as defined by current international guidelines. Analysis using well validated models suggests that improving visibility in Hong Kong from an average day to that of a good day would result in a reduction of 1,600 unnecessary deaths and equivalent to 60,000 hospital days saving in health care expenditure. Total economic losses are estimated at $20 billion per year. It is notoriously difficult to measure the intangible losses due to pollution. In my personal practice, air pollution is the single most common reason that my patients give for leaving Hong Kong. The individuals who chose to leave are fortunate in that they have the option to determine their own exposure risks. For the majority of people in Hong Kong and the cities of China, exposure to air pollution is inevitable and unavoidable. It is simply a question of the quantity and degree. For every one kilometre loss in visibility, there is an increase in mortality between 0.36% and 0.55%. These risks are significant and increasing.

As Family Medicine practitioners our expertise is health, we have a duty of care not only to the patients in our consultation room but also to their family and to the greater community. As doctors, we have an obligation to educate and promote health and wellness as a positive concept. Ultimately, the solution to the air pollution problem will be found in economic and political intervention. We must use our personal and professional influence. There is now an urgent need for swift and decisive political and legislative action to control air quality.