Public perceptions of increased risks and a lack of trust in government promises are behind many mass disturbances caused by environmental concerns, according to a report released on Tuesday.

Some environmental projects that have triggered heavy protests are not as dangerous as perceived by the public, with some having a very low risk, the report by non-governmental organization Friends of Nature said.

The annual report on China's environmental development for 2014 released by the environmental protection organization and Social Sciences Academic Press illustrates severe challenges.

It is the ninth year that the organization has released the report.

Zeng Fanxu, an associate professor at Tsinghua School of Journalism and Communication, said environmental risks in China are sometimes exaggerated through the spreading of information by the media, opinion leaders and some experts.

A lack of public trust in local governments also served to exaggerate the risks attached to some projects.

On Saturday, construction of a garbage incinerator in Hangzhou, Zhejiang province, sparked protests. Police vehicles were overturned and torched by demonstrators, and police officers were attacked.

Fifty-three people have been detained, police said on Monday.

It was not the first time that waste incineration plants have sparked protests over concerns about possible health and environmental hazards.

Work on an incineration plant in Beijing was suspended in 2011 after strong opposition from residents. In March, a protest against a paraxylene project in Maoming, Guangdong province, turned violent.

Environmental pollution was the main reason for large-scale mass disturbances, with half of the cases triggered by concerns about contamination, according to the Annual Report on China's Rule of Law for 2014.