Public tip-offs regarding environmental issues, especially relating to airborne pollution, are on the rise, a report shows, indicating public awareness of the problem has grown.

The number of environmental tips received on official hotline 12369 rose by 26 percent in 2013 over 2012's total, according to information released by the Environmental Protection Ministry on Friday.

More than 70 percent of the tips concerned airborne pollution, 1 percent more than the year before.

Airborne pollution has become the hottest environmental topic among the public, comprising more than half the tips starting in 2011, according to the ministry's environmental emergency and accident investigation center.

Data from five provinces - Hebei, Shandong, Jiangsu, Henan and Guangdong - accounted for almost half the 1,960 tips received by China's 31 provinces, municipalities and autonomous regions.

"This distribution corresponds with the areas that have the highest regional gross domestic product, densest population and greatest impact of pollution on local residents," said Ma Jun, director of an NGO called the Institute of Public and Environmental Affairs.

He said both growing awareness of environmental protection and news reports about illegal discharge issues are behind the results.

As much as 16 percent of the tips came from Hebei province, which was 80 percent more than in 2012.

The five cities with the greatest number of tips were all from Hebei province, and four of them - Baoding, Shijiazhuang, Tangshan and Langfang - were regulars on a list of the top-10 cities with the worst air quality, which the Environmental Protection Ministry started reporting on a monthly basis starting in January 2013.

"The sharp increase in the number of people calling in tips may also indicate weak official management of local industries' illegal environmental behaviors," Ma said.

"Normally, day-to-day supervision should work as the major channel to solve environmental problems."

But Hebei officials saw things differently.

"To help combat pollution more effectively, the provincial government set up a system in 2013 to reward residents who report environmental illegal behaviors, which was a very important reason for the rapid growth in the number of tips," said Wang Hongliang, an official from the provincial environmental protection bureau.

Wang said more than 10,000 environmental volunteers were recruited to supervise enterprises within the province, and the financial award in Shijiazhuang, the provincial capital, for example, could reach as high as 10,000 yuan ($1,599).

Environmental officials said they have responded to all the received tips by halting production, fining companies and closing down factories.

The Environmental Protection Ministry's hotline was set up in 2009. But detailed monthly information on the tips only started to be released on the ministry's official website in 2013.

Zheng Jinran contributed to this story.

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