Scientists and professionals around the world have been making continuous efforts to identify new benchmarks for clean air so as to enable Governments to draw up plans and measures to improve air quality to achieve optimal health for their people.

Hong Kong has been monitoring closely these international developments, the most notable being the recent report that a working group of the World Health Organisation has proposed a draft new WHO air quality guidelines for release in late 2006. Up to now, no country has adopted these draft new guidelines as their domestic air-quality standards or objectives.

In a consultation document published in April 2006 on options for further improving air quality, the UK Government considers it not practical to fully achieve the proposed new WHO air quality guidelines in the UK until 2020. For some air pollutants, such as particulates, the timeframe being considered in the UK is 2050.

Many groups reviewing ways to boost air quality

Recent research suggests that particulate matters smaller than 2.5 microns, or PM2.5, have more direct effects on health than the scientists have previously thought. Also, very low concentration levels of pollutants may be correlated to health impacts. Thus, the need for introducing new standards for PM2.5 and tightening the air-quality standards are under examination by a number of countries including the United States, the European Union and the WHO.

The US Environmental Protection Agency is planning to finalise the proposed PM2.5 standards later in 2006 and the proposed ozone standard by the end of 2007. The EU has issued a draft directive in September 2005 on ambient air quality, which included a proposed PM2.5 annual average standard set to be achieved by 2015. The proposal is still being examined within EU and will not be finalised until 2007.

From a purely scientific perspective it would be perfectly correct to propose that the level of air pollution should be as low as possible to achieve optimal health. Therefore the proposed new WHO air-quality guidelines are extremely stringent such that many advanced countries are not able to meet such levels in the next few decades.

Interim targets recommended

In view of that, the WHO working group has recommended interim targets to enable countries of the world to progressively improve the air quality. Furthermore, the WHO working group cautions that the actual air-quality standards in each country will have to vary according to country-specific situations and approaches which should balance the risks to health, technological feasibility, and other socio-economic considerations. It advises that individual governments should consider their own local circumstances carefully when using the new WHO air quality guidelines.

The new WHO air quality guidelines will have knock-on effects on a wide range of policy areas including energy, transportation, economic development, urban planning and conservation. People's current way of life will inevitably have to change. There will be additional costs for the community and the business sector. In addition, some technologies needed, such as zero-emission clean-coal technology, are still at a developing stage.

Time needed to reach WHO targets

The achievement of the proposed new WHO air quality guidelines will thus necessarily take a long time. For Hong Kong, being one of the most populated cities in the world and geographically located at the Pearl River's estuary, presents additional challenges.

Air pollution knows no boundaries. Given the pervasive influence of the regional factor on the local air quality, local emission reduction efforts and measures alone are not enough if Hong Kong is to meet the new WHO guidelines.

For Hong Kong, the new guidelines are not met even at our background air-quality monitoring station at Tap Mun, a place with no industries, no vehicles and far away from our urban areas. The achievement of the proposed new WHO guidelines will hence require joint efforts with the Mainland.

We are now examining the WHO draft guidelines carefully in anticipation of their official release later this year. We will need to evaluate the need and justifications for revising Hong Kong's air-quality objectives  according to the principles suggested by WHO and taking into account local factors and considerations as well as practicability. We will also engage the community and the business sector before deciding on the way forward.

While the proposed new WHO guidelines are long-term objectives, the Government is fully committed to taking immediate actions to control air pollution. We need to work closely and amicably with the Guangdong Government so that together we will achieve the 2010 emission-reduction targets and that we can see significant improvement of the air quality in both Hong Kong and the Pearl River Delta Region.

Secretary for the Environment, Transport & Works Dr Sarah Liao's remarks were published in several local newspapers.