The government yesterday took the power companies to task for last weekend's poor air quality, noting that the concentration of sulfur dioxide was 17.9 times the average level. The administration said 92 per cent of sulfur dioxide emissions in the city came from Hongkong Electric and CLP Power. Sulfur dioxide reduces lung function and increases disease and death rates. The Environmental Protection Department said the highest air pollution index reading on Sunday morning was 149 in Causeway Bay. It said it would not tolerate foul air, and detailed the measures it had taken to improve air quality. However, much of the effort had been impaired by the increase in emissions from the local power companies, it said. 'Power generation emits 92 per cent of the sulfur dioxide and half of the nitrogen oxide in Hong Kong. Between 1997 and 2004, the emission of sulfur dioxide by power generation increased by as much as 60 per cent.' The comments came as Guangdong Meteorological Bureau forecast that thick smog blanketing cities in the Peal River Delta would continue for the next few days and warned residents to avoid exercising outdoors. The haze descended on the delta on Saturday and worsened on Sunday with high air pollution indexes and low visibility recorded in Guangzhou, Shenzhen, Jiangmen, Maoming, Yunfu and Chaozhou . Guangzhou suffered the most severe pollution, with a reading of 161 on Sunday. A reading of more than 100 means air quality is rated 'polluted'.