Hong Kong has never met the air quality targets it adopted 25 years ago, according to an Audit Commission report released on Wednesday that reviewed the government’s efforts to improve air quality. The commission’s report found the concentration of two pollutants – nitrogen dioxide (NO2) and the PM10 particles – at roadside had “persistently and significantly exceeded the targets set by the Environmental Protection Department in 1987”. The air quality targets list the concentration levels of seven harmful air pollutants, including sulphur dioxide, NO2, and PM10 particles (those with a diameter of 10 micrometres or less). The roadside annual average concentration levels of NO2 and PM10 exceeded the targets by 53 per cent and 11 per cent respectively, and both exceeded the World Health Organisation standards by 205 per cent, the report said. The unsatisfactory results came despite adopting, since 1997, 16 major emission control measures, including the replacement diesel fuelled vehicles with those powered by liquefied petroleum gas, the requirement that newly registered cars be greener models and the introduction of emission caps on power plants. The commission also noted that the Environmental Protection Department had failed to achieve a performance target that the air pollution index not exceed the “very high” health risk level of 100 on any day of the year. However, the number of days with an API level over 100 showed an upward trend over the past five years, rising by 136 per cent from 74 days in 2007 to 175 last year. And while the ambient air pollution was partly caused by the regional pollution in the Pearl River Delta, the report said roadside pollution – mainly caused by vehicle emissions – could be reduced by vigorous efforts by the government. The report urged the government to give air quality improvement measures a higher priority to improve roadside pollution and to work closely with the Guangdong provincial government to improve regional air quality. The roadside API levels exceeded 100 in Causeway Bay, Central and Mong Kok on Wednesday.