The Hong Kong Asthma Society has joined other groups in criticising the government's proposed adoption of the World Health Organisation's minimum air-quality targets. Society chairman Alfred Tam Yat-cheung said lax targets for reducing fine particles - known as PM2.5 and PM10 - were particularly unacceptable because they were the key pollutants affecting asthma patients. In March, the government proposed adopting the WHO's least stringent emission-control level for PM2.5, and the second-loosest target for PM10. Dr Tam, a paediatrician, said Hong Kong would lag behind the EU and Australia, which had adopted far more stringent targets. 'The government, of course, has its political and economic considerations, but if public health is the first and foremost concern, I see no reason why it should not take the ultimate WHO target,' he said. More fine particles in the air provide more surfaces for viruses to attach to, he said, increasing infection risks and breathing problems. Ten per cent of children in the city suffered from asthma, up from 4 per cent 15 years ago, he added. Dr Tam urged the government to install a review mechanism for targets, which he said should be used 'constantly' as the environment changed. 'Don't leave it until 20 years later, like we have done,' he said. Three hundred people have signed the society's petition calling for tighter air-quality targets. The petition will be submitted to the government this week. In June 2007, the government commissioned a study to review and update the city's air-quality objectives - which had not changed since 1987 - with reference to WHO guidelines issued in 2006. In revealing its findings in March, officials said compliance with the WHO guidelines could cut hospital admissions caused by air pollution and increase the average Hongkonger's lifespan by about nine hours. Nineteen first-phase measures, including increasing the use of natural gas, were identified as helping to meet the new objectives. The draft report will be released next month.