From December 7, the world leaders and their advisers will be in Copenhagen attending the UN conference on climate change and global warming. Their aim is to agree on a new international deal to tackle climate change, which should come into force in 2013 and replace the Kyoto protocol. Images of rapidly melting glaciers and global reports of increasingly extreme weather conditions underline the urgency of the talks.

While there are very clear environmental reasons for being concerned about the predicted increase in temperatures of six degrees Celsius by the end of the century, there are also very clear health concerns. Scientific evidence indicates that climate change may increase the spread of vector-borne diseases such as malaria and dengue fever. The threat of rising sea levels would endanger the lives of many living in coastal regions; droughts and famine would also result from changing weather patterns.

Large scale population movement is predicted as people abandon inhospitable environments, with migration leading to massive health problems and potential political and civil unrest. The burden from the health impacts of climate change will fall disproportionately on poorer developing countries and on women, who, within these countries, make up a larger share of the agricultural workforce, have fewer income earning opportunities, and, because of their role as carers, are less mobile and thus more vulnerable to weather-related natural disasters.

Some experts suggest that slowing population growth would provide greater social resilience to the effects of climate change. Politicians in Copenhagen must henceforth consider public health and the broader context of social equity, given the potential impact on the basic elements of life for both present and future generations. They need to respond to the concerns of groups such as the International Climate and Health Group which has been actively campaigning to draw attention to the health threats of climate change, calling for the new treaty to set strong targets on emission reductions, to promote clean energy, and to mandate major funding for developing countries to cope with the climate crisis. The arguments are both humanitarian and economic.

The WHO has calculated that more than 2 million premature deaths each year can be attributed to the effects of urban outdoor air pollution and indoor air pollution (caused by the burning of solid fuels). Even relatively low concentrations of air pollutants have been related to a range of adverse health effects affecting respiratory and cardiovascular systems. Reducing greenhouse gases and common air pollutants would improve health and mitigate the impact of global warming. A European Commission impact assessment estimated that the annual public health savings resulting from a 20 percent reduction in carbon emissions (from 1990 levels) by 2020 would be $77 billion each year after 2020 in Europe alone.

Pollution and reducing carbon emissions are also important concerns for the people in Hong Kong. As Hong Kong records its hottest and coldest days of the seasons for many years, environmental health campaigners are increasingly concerned about the impact of our poor air quality on the population's health and prosperity. The Clean Air Network website provides local data telling us that air pollution causes three (avoidable) deaths a day or more than 1,100 per year in Hong Kong, and that the air in Hong Kong is three times more polluted than in New York and more than twice as polluted as London. By WHO standards, our air is only decently breathable 41 days a year (according to 2006 data). Here, as in developing countries, the impact is inequitable, falling disproportionately on vulnerable groups such as children and the elderly, reflecting the gravity of the challenge and the urgency to act.

The Hedley Environmental Index (http://hedleyindex.sph.hku.hk/home), developed by professor Tony Hedley, one of the public health experts on air pollution at the University of Hong Kong, monitors and publishes in real-time the economic costs of Hong Kong's poor air. In the first 11 months of this year there were an estimated 740 premature deaths, over 700 patients admitted to hospital with asthma, many of them children, nearly 60,000 hospital bed-days, and over 5.5 million doctor visits from the adverse health impacts of air pollution. The tangible costs are estimated at around HK$1.6 million but the intangible costs are far greater, potentially around HK$11 billion, and rising.

These figures speak for themselves: the air quality in Hong Kong has to improve and we look to our representatives in Copenhagen to seek to reach agreements that will take account of the health of the population both locally and globally.

The author is director of School of Public Health and Primary Care, Faculty of Medicine, the Chinese University of Hong Kong

(HK Edition 11/26/2009 page1)