The air quality in 338 Chinese cities showed improvements in the first half of this year, said the Ministry of Environmental Protection on July 17.

Beijing, Tianjin and 11 main cities in north China’s Hebei Province, an industrial zone troubled by air pollution, saw cleaner skies with about 57.4 percent of the January-June period having “good air quality”, 11 percentage points higher than the first half of 2015, said Luo Yi, head of the ministry’s environment monitoring division.

In Beijing, the rate was 58.8 percent, an year-on-year increase of 10.2 percentage points, while the density of PM2.5, fine particulate matter causing smog, stood at 64 micrograms on average, down 17.9 percent year on year.

However, six out of the 10 cities with the worst air quality were still in Hebei.

The top 10 cities with the cleanest air were mostly along the southeast coast, except Lhasa in Tibet.

The 25 cities along the Yangtze River Delta recorded 72.9 percent of days with good air quality, an year-on-year increase of 3.8 percentage points, while the ratio in nine cities along the Pearl River Delta was 94.7 percent, an increase of 4.1 points.

Meanwhile, according to Luo, the country’s surface water quality remained stable.

The Yangtze and Pearl rivers fell in the clean category while the Yellow River was slightly polluted. Tianjin’s Haihe River was heavily polluted.

Five of the 106 lakes under monitoring were at a moderate level of eutrophication and 15 were at a light level, which roused concerns of pollution, Luo said.