Eastern parts of Hong Kong recorded more hours of poor air quality last year compared to 2014, despite a continuing improvement of general air quality in the city. While there was a drop in several types of air pollutants, the level of ozone – one of the four major items measured by local air quality monitoring stations – remained high, according to the preliminary annual air quality data on last year released by the Environmental Protection Department. READ MORE: Serious pollution levels hit Hong Kong, especially in western New Territories Green groups were not happy with the drop in pollutants and said interdepartmental cooperation should be strengthened. According to the department, Eastern District had 213 hours when the air quality health index was high, very high or serious last year, a 31 per cent increase from the previous year. A higher level indicates a greater health risk to individuals from air pollution. Central and Western and Tai Po also experienced more hours of poor air quality, recording a 12 per cent and 7 per cent increase respectively. “In 2015, there were days when regional air pollution was high, yet the prevailing wind from the north was more easterly. Eastern parts of Hong Kong were therefore more affected by the air pollutants,” said Mok Wai-chuen, assistant director of environmental protection. Air pollution in the east, however, was still less severe than in the west. Tuen Mun, Tung Chung and Yuen Long topped the chart for air pollution, despite a general drop in the number of hours of poor air quality. Overall air quality was also better than in the previous year. There was a 13 per cent reduction in the total number of hours of high or above recordings at all general stations, and a 7 per cent drop at roadside stations. Air pollutants, including fine and respirable suspended particulates, sulphur dioxide and nitrogen dioxide, also dropped from the previous year. However, ozone, a major air pollutant which can lead to respiratory diseases, remained at a high level of 45 micrograms per cubic metre of air. Mok said the high level was due to an increase in ozone emissions in the Pearl River Delta. “If we want to solve the ozone problem, we need to work hand in hand with the mainland,” said Mok. The Hong Kong and Guangdong governments set emission reduction targets for 2015 and 2020 in November 2012. Both governments are now conducting an interim review of last year ‘s emissions and the 2020 targets. Patrick Fung Kin-wai, director of communications for Clean Air Network, an NGO focusing on air pollution, said it was hard for him to be happy with the latest air quality data. “From 1998 [till now], the level of roadside pollution has stayed at its original point,” said Fung. He took nitrogen dioxide, a pollutant mainly emitted by vehicles, as an example. The 1998 and 2015 levels were almost the same, close to 100 micrograms per cubic metre. Fung urged greater cross-departmental work, such as designating more busy areas as pedestrian zones, in a bid to improve air quality.