While nationwide air pollution fell thanks to a tough winter crackdown in smog-prone northern regions, concentrations of small, breathable particles known as PM2.5 surged 20 percent in the Yangtze delta in eastern China, which includes Shanghai as well as the highly industrialised province of Jiangsu.
A 3.9-percent increase in PM2.5 in the Pearl river delta near Hong Kong also raised fears that polluting heavy industrial output had moved to eastern and southern regions as a result of a crackdown in the north, which forced thousands of factories to curb production.
Speaking at a press briefing on Tuesday, Liu Bingjiang, head of the air quality department at China's Ministry of Environmental Protection (MEP), said changes in industrial output could have been responsible for the spike, noting that steel output data for 2017 indicated a shifting "production structure and layout" for industry.
"We will analyse more closely to see to what extent the rising PM2.5 is due to increasing industrial emissions," he added. "I am sure the Yangtze delta governments understand very well what their tasks are."
The top steel producing province of Hebei, which surrounds the capital Beijing, has been at the heart of a campaign to improve northern China's air quality, and saw output fall 1 percent to 191.2 million tonnes last year, despite a 5.7-percent nationwide production increase.
Over the same period, Jiangsu, the country's second biggest steel producer, saw steel production rise 4.64 percent to 104.3 million tonnes in 2017. It also saw nonferrous metals output surge 32.2 percent year-on-year, according to official data.
But it also suggested that unfavourable weather conditions were partially to blame, with the wind that helped cut smog in northern regions responsible for delivering pollution to the eastern coast.
Liu said at the Tuesday briefing that favourable weather was responsible for 30 percent of the improvements in air quality in northern China, but it was "irresponsible" to blame smog on wind - or on other regions.
"The (local) government should do its own job well and not focus on blaming other people," he said. "Otherwise they will miss the best chance to improve their own air quality."
Liu also said China was preparing to introduce even tougher air quality targets to cover the 2018-2020 period, without giving specific figures.
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)