The number of days with the air pollution index exceeding 100 has dropped from 87 in 2004 to 49 last year, the Environmental Protection Department says.

Between 1997 and 2004, nitrogen oxide emissions were cut 16%, respirable suspended particulates cut 28% and volatile organic compounds cut 23%.

Despite the progress, some days with high indices are still unavoidable, the department said.

The air pollution index hit 149 at Causeway Bay on February 12, while the nitrogen dioxide and sulphur dioxide concentrations were 5.3 times and 17.9 times the average.

The elderly and people with heart and respiratory diseases should check the indices and follow health advice.

The department said while recent calm weather caused pollutant accumulation, cutting emissions is the only solution.

With the implementation of a comprehensive programme to cut vehicle emissions, particulates and nitrogen oxides in the urban areas have fallen 80% and 40%, while the number of smoky vehicles has dropped 80%.

However, the department said much of the effort has been vitiated by the surge in emissions from power companies. The emission of sulphur dioxide grew 47% between 1997 and 2004.

It said power companies must substantially reduce emissions to achieve a sustained improvement in air quality.

At high levels, sulphur dioxide reduces lung function and increases morbidity and mortality rates. Reacting with other pollutants in the air, it forms very fine sulphur particles, the department warned. Analysis shows that up to 30% of the very fine particles in the air are sulphate. It is a major component of smog.

Power generation emits 92% of the sulphur dioxide and half of the nitrogen oxides in Hong Kong. Between 1997 and 2004, the emission of sulphur dioxide by power generation grew 60%.

Close surveillance

The department has put power plants under close surveillance. China Light & Power's plants were inspected six times last year. The department has informed the power companies of the 2010 emission caps.

The Government has been working with Guangdong authorities to reduce emissions in Pearl River Delta Region.

On September 28 the Chief Executive and the Governor of Guangdong Province reiterated both sides would implement the delta regional air quality management plan progressively.

Since November 30, the monitoring network jointly established under the plan has been commissioned and the delta regional air quality index is published daily.

This year major tasks under the plan include:

* completion of phase one construction of the liquefied natural gas trunk pipeline in Guangdong, commissioning of a number of LNG power plants in phases, and installation of more flue gas desulphurisation systems to oil-fired and coal-fired power plants;

* Guangdong authorities will advance the implementation of National III motor vehicle emission standards (on a par with Euro III ones) while Hong Kong will implement Euro IV motor vehicle emission standards in line with the EU;

* the data collected by the regional air quality monitoring network will be analysed by the environmental protection authorities of the two governments, and a report will be issued on a half-year basis;

* environmental protection authorities will strengthen technical exchange and joint studies, especially on continuous emissions monitoring of stationary pollution sources and commissioning studies on regional air pollution on a need basis; and,