Emissions of four major pollutants in China have dropped year on year during the first half of 2014, China's environmental watchdog said on September 24.

The chemical oxygen demand index, a measure of water pollution, decreased by 2.26 percent, while the volume of sulfur dioxide emissions, a main indicator for measuring air pollution, totaled 10.37 million tons, a year-on-year drop of 1.87 percent, the Ministry of Environmental Protection said in a statement.

Ammonia nitrogen emissions totaled 1.23 million tons in the first six months of this year, a decrease of 2.67 percent, and nitrogen oxide emissions were cut by 5.82 percent from the levels of the same period last year, the statement said.