Nearly three-quarters of environmental pollution complaints filed in 2013 via a tip-off hotline were about air, the Ministry of Environmental Protection (MEP) said in a circular Friday.

The ministry accepted nearly 2,000 complaints in 2013 via the hotline 12369, up more than a quarter compared with the previous year, according to the ministry. Of the complaints, about 80 percent were verified.

Hebei Province in China's north received more than 310 tip-offs, the most from the public regarding pollution. It was followed by Shandong Province with 205 tip-offs, Jiangsu Province with 190, Henan Province with nearly 140 and Guangdong Province with more than 110.

According to the ministry's tally, the chemical industry received the most complaints of any sector, or nearly a quarter of the total. Metal smelting and processing accounted for 17 percent of the total complaints and non-metal mineral product processing accounted for 11 percent of the complaints.

In 2009, the MEP opened hotline 12369 in an effort to give people a direct way to inform the ministry about environmental pollution.

The hotline takes calls about emergency environmental issues, cross-provincial pollution and other environmental issues that should be directly dealt with by the ministry.