Smoke rises from a chimneys of a steel mill on a hazy day in Fengnan district of Tangshan, Hebei province February 18, 2014.[Photo/Agencies]

Hebei has achieved its target of lowering airborne PM2.5 levels by more than 20 percent two years ahead of schedule, according to the province's Environmental Protection Bureau.

The average concentration of PM 2.5 in the province last year was 28.7 percent lower than it was in 2013, when the State Council ordered in a "National Action Plan for the Prevention and Control of Air Pollution" that it should fall by 25 percent in the Beijing-Tianjin-Hebei region by 2017.

PM 2.5 refers to airborne particulate matter with a diameter of 2.5 micrometers or less that is hazardous to human health.

The average concentration of PM2.5 in the province last year was 77 micrograms per cubic meter, which is a 18.9 percent year-on-year decrease — the largest drop in the region.

Hebei is notorious for its bad air quality, with seven of its cities consistently ranking among the top 10 most polluted nationwide, out of the 74 cities that are monitored.

A package of measures has been rolled out to improve matters, which includes reducing coal consumption, banning highly-polluting vehicles and planting trees in the province.

Zhang Qingwei, governor of Hebei, said the province spent 24 billion yuan ($ 2.7 billion) in preventing and controlling air pollution from 2011 to 2015.

For the 13th Five-Year (2016-2020) period, PM 2.5 concentration is expected to fall by a further 40 percent from its 2013 levels, and the current highly-polluted cities will no longer rank among the top 10 most polluted in the nation, Zhang said.