Hong Kong's pollution levels were once again at the forefront of media attention last month. The 10^th Hong Kong Standard Chartered Marathon was held on the 12 February 2006, attracting nearly 40,000 runners to this popular event. The event had a promising start and attracted the greatest number of runners since its introduction. This seemed to reflect the changing health awareness of a population which had so recently gone through SARS.

However, as the race progressed, the recorded air pollution levels that day sent over 20 runners to the hospital, including one person who died after collapsing during the race.

The General Air Pollution Index (API) recorded by the Hong Kong Environmental Protection Department that day was on average >100 (API levels ranges from 0-500), which was classified as a significant high level. According to the Department's guidelines, no immediate response action was needed to be suggested to the general public.¹ This was despite the fact that at this level, people with existing heart or respiratory illnesses will notice a mild aggravation of their health while some healthy individuals may also notice some discomfort as well.

This was not the first time that Hong Kong's pollution levels have attracted media attention. Thick smog was of concern back in 2002 and also as recently as 2004. Experts estimate that some 80% of this pollution drifts in from southern China's heavily industrialized neighbouring Pearl River Delta. In fact, China has been said by the World Health Organisation to rank seventh in the world's 10 most polluted cities.

Only last month, a recording of a High General API level (51-100) was seen for 64% of that time, while roadside stations recorded this level for 86% of the month. This should warrant concern especially for us who are in the health care profession.

In a city such as Hong Kong, pollution is made worst by the hot and humid weather that is the norm at this time of the year. It is well known that ground-level ozone is the major part of air pollution in most cities. This should not however, be confused with the ozone layer which is miles above in the atmosphere and which protects the earth from the sun's harmful radiation.

This ground-level ozone is created when engine and fuel gases, which have been released into the air, interact with sunlight. These levels are increased during times where the air is still and the sun is bright and the atmosphere humid.

Exercise or strenuous activities would render us more susceptible to health damage by these pollutants. It is often during these times that we would breathe mostly through our mouth, bypassing our nasal passage, which is our body's first defence against pollutants in the air.

It is not only through exercising vigorously that we are at risk of health damage from pollutants. There is also a concern regarding the possible cumulative effects of chronic exposure.

In one study conducted last year in America, it was shown that the cumulative effects on health due to continual exposure to environmental pollutants could be serious even at levels below the US national ambient air quality. It is suggested that different pollutants may require different cumulative periods on average to impact on health but they share a similar functional form in respect of their impact.²

The short-term exposure to fine particles (particulate matter < or =2.5 micron in aerodynamic diameter) has also been shown to increase the risk for hospital admission for cardiovascular and respiratory diseases.³

The long-term consequences of cumulative exposure could possibly include adverse effects on lung growth, chronic bronchitis, lung cancer and the possible development of asthma and atherosclerosis. These morbidities would ultimately lead to a shorter life expectancy.⁴

Not only are adults affected by air pollution, neonates seem to be affected as well. Studies in areas with relatively high levels of air pollution have found positive associations between exposure to ambient levels of air pollution and several birth outcomes. Exposure during the first trimester of pregnancies to relatively low levels of some air pollutants may be associated with a reduction in birth weights of term-born infants.⁵ It has also been shown that exposure of expectant mothers to combustion-related urban air pollution may alter the structure of babies' chromosomes while in-utero.⁶

Air pollutions affect us not only physically but also our health related quality of life.⁷

In the world air pollution is not limited only to outdoors but also exists indoors. There is a growing amount of evidence that indoor air pollution plays a significant role in health issues as well. This is particularly so because people generally spend a majority of their time indoors.

Common indoor pollutants are environmental tobacco smoke, particulate matter, nitrogen dioxide, carbon monoxide, volatile organic compounds and biological allergens. One and a half to 2 million deaths per year worldwide could be attributed to indoor air pollution. Today, indoor pollution is ranked tenth among the preventable risk factors contributing to the global health burden.⁸ Hence the morbidity and mortality is related to sources of both indoor and outdoor pollution causing or interacting with respiratory infections and other acute and chronic health conditions, e.g. asthma.⁹

In all, it would seem that air pollution is a major health concern to all of us across society. As health professionals, we have the privilege to be in an influential position in helping to decrease the health burden in the society thus caused.

Family physicians are in a unique position to be able to educate and influence our patient's behaviour. This can be seen clearly with smoking interventions, which were initiated by Family Physicians. Russell et al (1979) found that the advice given as a part of a routine consultation (and supplemented with leaflet and warning at follow-up) persuaded about 5% of smokers to give up smoking. This might not sound a lot but it is significant in terms of absolute numbers.¹⁰

Here is some general advice that Family Physicians can give to further help our patients to improve their health in spite of the level of indoor or outdoor pollution in existence.

At Home- try to recycle paper, plastic, glass bottles, cardboard and aluminum cans. This helps to conserve energy and reduces production emissions. Paint with a brush, not a spray can. Have leaky air conditioning and refrigeration systems repaired. Cut back on air conditioning and heating if possible. Have air conditioning systems checked in the spring.

If our patients drive, we can educate them on the need for regular engine tune-ups and car maintenance checks. Avoid revving or idling engines for more than 30 seconds. Fill gas tanks during cooler evening hours to cut down on evaporation and avoid spillage.

Advise all patients, even our "healthy" patients to be aware of the latest API levels for that day. This is not difficult as it is now widely broadcasted along with the weather. Alert them to be aware of high risk weather conditions, such as hot, sunny humid days and limit outdoor activity to the early morning hours or wait until after sunset. This is important as sunshine increases the hazardous ozone levels.

As Family Physicians, our role does not need to be limited to only educating a patient about their cholesterol level, or tobacco smoking habit. We have a further role in helping facilitate our patients to be active participants in tackling the bigger health issues of our society such as air pollution. This I believe is one of the many faces of a Family Doctor, educating and facilitating change in the health of our patients.

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