Eastern China’s Jiangsu province will step up its war on pollution and focus on “high-quality development” following a spike in smog early this year, the China Daily reported, citing the provincial governor.

The province of Jiangsu is a major part of the Yangtze river delta manufacturing hub. Concentrations of breathable smog particles known as PM2.5 soared 20 percent in the region in January.

Jiangsu’s major heavy industrial center, Xuzhou, was also ranked China’s smoggiest city in December 2017, after a winter campaign to cut emissions in northern China led to a significant drop in PM2.5 concentrations in traditional smog zones.

Governor Wu Zhenglong promised “stricter strategies with higher standards” to control emissions, China Daily said.

Despite the January spike, average PM2.5 concentrations in the province still fell from 73 micrograms to 49 micrograms last year, the report added.

Late last month, an environment ministry official urged regions in the Yangtze delta and elsewhere to take responsibility for their air quality problems.

The Energy Policy Institute at the University of Chicago (EPIC), said in a report this week that China was winning its war on pollution after cutting average PM2.5 concentrations by 32 percent in just four years.

“The available evidence from our monitoring data indicate that pollution has decreased nearly across the board,” said Michael Greenstone, director of EPIC. “We estimate that just 4 percent of the 900 million residents covered by the monitor network saw pollution rise in their prefecture between 2013 and 2017,” he added.