Emissions of the key pollutant sulfur dioxide fell marginally in China during the first half of the year but water quality worsened, the State Environmental Protection Agency (SEPA) said on Tuesday. Total emissions of sulfur dioxide came to 12.6 million metric tons, down 0.88% year-on-year, AP reported. Meanwhile, chemical oxygen demand, a water pollution index, rose 0.24% over the same period. SEPA said rapid economic growth and weak enforcement of environmental regulations were responsible for the "grim" situation. Meanwhile, Beijing's four-day trial car ban was hailed as a success by officials, with state media reporting that conditions were "fairly good" despite a constant gray haze. A total of 1.3 million cars were banned from the roads each day as the city seeks ways to minimize air pollution ahead of next year's Olympics.