China’s top environmental official warned yesterday that air and water quality are on the decline and soil erosion is continuing at a fast clip in the country. Nearly half of China’s river water supplies don’t meet safety standards, said Xie Zhenhua, director of the Environmental Protection Administration, which produces an annual state of the environment report. This year’s report found that 90 percent of grasslands, which cover about 40 percent of China, have been degraded, contributing to desertification. Xie said, “People have to get the sense that protecting the environment is directly linked to their own personal well-being.” Xie also used the occasion to criticize as “irresponsible” the decision by U.S. President Bush to withdraw from the Kyoto treaty on climate change.