The mainland's new environment minister, Chen Jining, pledged the government would go after all illegal polluters and ensure green laws clamped down with "iron teeth". But Chen admitted the challenge the nation faced was "unprecedented in human history". "We cannot rush for solutions, nor should we expect rapid improvement overnight," Chen told reporters at the National People's Congress session in Beijing, his first public appearance in the role. Chen said the nation had not yet unleashed the full potential of pollution-treatment technologies due to poor innovation. Less than a week into the country's annual legislative sessions, both President Xi Jinping and Premier Li Keqiang have made promises to tackle the pollution crisis, marked by choking smog, contaminated rivers and toxic soil. But Chen spent much of his time before the world media repeating existing policies and clean-up plans, with no new insights on solutions offered. Chen, 51, has a doctorate in environmental system science, and was previously president of Tsinghua University. His experience in environmental research and policy had raised public expectations he would bring more expertise to the role that his predecessor, Zhou Shengxian , who has retired. But Chen has no experience working in a government agency, having spent his career at Tsinghua. There was also no mention at the 75-minute press conference of Under The Dome , the documentary on air pollution by former CCTV presenter Chai Jing, which has gone viral on the mainland, racking up an estimated of 200 million views in less than a week. Chen personally endorsed the film before it was quietly pulled from most major Chinese video streaming sites on Friday. Some online commentators began to blame the government for the country's environmental problems, which appears to have set off the censorship. Chai's documentary blames the powerful energy companies and weak government enforcement for the smog that undermines public health. Some critics have argued a political system that puts no checks on government power was the deeper cause of pollution woes. Chen, however, said the mainland could push forward clean-up campaigns from the top leadership down to the grassroots.