Environmental groups are pushing the Government to expand this year's 12-month trial of liquefied petroleum gas (LPG) to more than just a handful of Hong Kong's 18,000 taxis. Greenpeace spokesman Anne Dingwall said the key environmental issue for the Government this year was air quality and traffic pollution and the trial needed to be broadened. 'It's important they take a more serious look at emission controls,' she said. The taxis are running on LPG instead of diesel, one of the main air pollutants. 'This small programme in place with taxis converting to LPG fuel is not going to make any major difference to air quality. It does not address the fact that it's killing hundreds of people a year,' Ms Dingwall said. 'The Government is moving at a snail's pace.' Officials should be considering the broader impact of vehicle emissions contributing to global warming, and should investigate more clean fuels and electric cars, she said. Friends of the Earth said there was no need for the trial to go on for a year, and urged the Government to cut it to four months. It should be extended to include minibuses and light goods vans, campaigner Edwin Lau Che-feng, said. The air pollution index was also inadequate, as it recorded air quality six to seven storeys above ground. 'It does not reflect how someone is actually feeling as they stand in the street in Causeway Bay, Wan Chai or Central,' he said. In December last year, Hong Kong's Air Pollution Index hit the 'unhealthy' range - when outdoor exercise is discouraged and asthmatics and the elderly are urged to stay indoors. For almost half the year, the index hovered in the 'moderate' range - 50 to 100 micrograms of suspended respirable polluting particles per cubic metre and other pollutants such as sulphur and nitrogen dioxide - most of it caused by diesel fuel. Air quality was one of three environmental issues on which the Citizens Party intended to campaign this year, said leader Christine Loh Kung-wai. The party was monitoring air on roads in Causeway Bay, Tuen Mun, Tsim Sha Tsui, Sha Tin and Yuen Long. The results would be available in a month, she said. If the taxi trial is unsuccessful, it could take eight years before diesel taxis are replaced, the Environmental Protection Department has warned.