Environmental protection departments nationwide received more than 618,000 tips related to pollution from the public last year, an increase of 135 percent over 2016, with air pollution still topping the complaints.

More than 60 percent of the complaints were lodged through the environment protection telephone hotline 12369, and most were made from provinces in east and central China, with Jiangsu province reporting the most－about 93,000.

The rest were made through the official reporting WeChat account and website, the Ministry of Environmental Protection said in a statement on Tuesday.

Tips from WeChat account for 20 percent of the total. Five provinces in central and eastern regions－Guangdong, Henan, Shandong, Jiangsu and Hebei－contributed about 50 percent to the total.

In addition, WeChat reports from Henan, Anhui and Sichuan provinces all increased more than 200 percent over the previous year, according to the statement.

Of all the complaints, about 56 percent were related to air quality, while noise and water accounted for 34 percent and 10 percent respectively, according to the ministry.

Odor, dust and waste gas pollution were the main reasons for air pollution complaints－about 70 percent. The majority of noise pollution complaints came from construction and industrial noise.

The construction industry was the subject of the majority of complaints－about 31 percent of the total, followed by the hotel and catering industry, and chemical production, the ministry said.

The waste disposal industry received only 3 percent of the total complaints, but it received the most repeated reports of all industries, especially in Guangdong province and Shanghai.

The ministry said more than 580,000 cases have been concluded. The average processing time was 22 days, and among them 70 percent of the cases last year were found to be valid tips.

Guo Yongqi, president of an environmental nongovernmental organization in Shandong province, said he and other volunteers make complaints through WeChat or the website if the case is not extremely complicated.

"Reporting through WeChat is simple and all the details we report will be saved there for further reference. We can also check how the case is being processed," said Guo.

"The environment bureaus give us feedback in several days, but usually without detailed information. There were several times that we did not receive feedback from environmental departments in small counties. I hope the inspection of the reporting system can be strengthened," he added.