The cumulative affect of air pollution from new infrastructure proposed for Tung Chung - including a HK$136.2 billion third runway - could be up to 50 per cent higher than a legal limit that may come into effect this year.
The proposed infrastructure also comprises a cross-border bridge connecting Hong Kong, Macau and Zhuhai, and all related roads and border facilities. A preliminary assessment, commissioned by the Airport Authority, says that such infrastructure could by 2030 together produce nitrogen dioxide about 50 per cent higher than the proposed new limit. Tung Chung, Sha Lo Wan and the airport island would be the most affected, it says.
Existing environmental legislation requires a developer to take the cumulative impact of all construction works in the region into account.
The runway alone would raise the level of nitrogen dioxide - a pollutant that can damage the respiratory system - above the newly proposed threshold of 200 micrograms per cubic metre per hour in some areas at Chek Lap Kok airport.
A spokesman for the Airport Authority said that necessary mitigation measures would be implemented to ensure the project complied with legal requirements on air quality.
The authority only said during its three-month public consultation that the proposed project complied with existing air quality objectives.
At a forum on aviation emissions last week, Alexis Lau Kai-hon, an environment professor at University of Science and Technology, said that the airport was responsible for 20 per cent of Tung Chung's nitrogen oxide emissions, but that the airport contributed less than 7 per cent of other pollutants - including nitrogen dioxide and carbon dioxide.
Friends of the Earth said that the Airport Authority had not considered the additional road traffic that would be brought by the third runway and the other projects. 'Officials previously claimed that the concentration of nitrogen dioxide in Tung Chung by 2030 would be even lower than the 2010 level,' said Thomas Choi Ka-man of the green group.
'Are they trying to mislead us?'
WWF - which has called for a halt to the project's consultation - said none of the consultancy reports commissioned by the authority had covered the amount of carbon emissions to be brought by the runway.
WWF earlier expected the project would create an extra 5.3 million tonnes of carbon emissions a year.
The Airport Authority has released eight of nine reports produced following demand for more information on the costly project. They cover topics including the runway's environmental impact and implications for airspace.
But WWF's climate head Dr William Yiu Yuen-ping said the reports still failed to provide the public with a full picture. 'The reports covered four construction options of the runway, but they did not include the one we are now being consulted on.'