BEIJING: China saw levels of two common air pollutants improve modestly in the first half of 2015, environmental group Greenpeace East Asia said on Wednesday.

Average levels of PM2.5 - particulate matter with a diameter of 2.5 micrometers that can penetrate deep into the lungs - fell 16 percent in the first six months from a year ago, the group said, adding that sulphur dioxide levels also fell 18 percent.

"The fall in coal consumption is the principal reason for recent improvements in air quality," said the group's climate and environmental campaigner, Dong Liansai, in a statement.

Beijing, the capital, was ranked as the region with the third-worst levels of PM2.5, behind neighbouring Hebei province and central Henan province, slipping from the fourth place in the first quarter. Shanghai was ranked as having the 11th-worst levels, versus a 14th place in the first quarter.

Greenpeace East Asia's calculations were based on data provided by China's environment ministry from monitoring stations in 189 cities across the country.

Last week, the ministry said nearly 75 percent of China's big cities had failed to meet air quality standards in June, an improvement over the same month last year. Beijing saw PM2.5 levels rise 11 percent last month.

Amid growing public disquiet about smog and other environmental risks, China has declared a war on pollution, vowing to abandon a decades-old growth-at-all-costs economic model that has spoilt much of its water, skies and soil.

China has sought to improve transparency and compel polluters to provide comprehensive and real-time emissions data, but doubts have arisen in the past about the accuracy of Chinese air pollution indices.

In April, China's vice minister for environmental protection announced a two-year inspection campaign to root out fake air quality data and accused some local governments of manipulating the information to meet national standards.

Greenpeace East Asia did not provide comparisons for other pollutants, such as carbon monoxide, nitrogen dioxide, and ozone, or for levels of particulate matter over 10 micrometers in diameter, known as PM10.