SHANGHAI (Reuters) - China's smog-prone province of Hebei, the country's biggest steel producing region, met a national air quality standard for the first time last month, its environment bureau said on Tuesday.
The heavily industrial province surrounds Beijing and has been on the frontline of a war on pollution since 2014 after toxic smog spread from Hebei to the national capital city.
Hebei has converted thousands of households to natural gas from coal, curbed pollution from vehicles and imposed new ultra-low emissions standards on its many steel mills, cement factories and power plants.
In May, Hebei's average concentration of lung-damaging small particles, known as PM2.5, stood at 33 micrograms per cubic metre, the Hebei Ecology and Environment Bureau said in a notice on Tuesday.
It was the first time that Hebei's monthly average fell below the interim standard of 35 micrograms since China began measuring PM2.5 in 2013, the bureau said.
The World Health Organization (WHO) recommends average PM2.5 rates of no more than 10 micrograms.
Hebei's overall air pollution index fell 6.6 percent in May compared to the same month last year.
While the province has had success in reducing PM2.5 rates and other air pollutants, concentrations of ground-level ozone - known as "sunburn for the lungs" - have continued to rise.
Ozone levels reached 196 micrograms per cubic metre in May, up 5.9 percent from the same month a year ago, the bureau said.
Ozone is caused by the interaction of sunlight with volatile organic compounds found in car exhaust fumes.
Air pollution in China generally eases in May as weather conditions improve and coal consumption falls.
From January to April, PM2.5 rates in Hebei actually rose year on year, raising fears that the war on pollution had stalled amid concerns about China's slowing economy.
(Reporting by David Stanway; editing by Darren Schuettler)