Beijing. At first, after the film starts streaming, all you see is a chart of Beijing air pollution and all you hear is a woman's voice. Then you see the woman speaking, alone on a bare stage, in jeans and a white blouse, a thin microphone curving round her face. Her audience of young Chinese know her well. Her name is Chai Jing, a reporter for Chinese state television, whose memoirs sold a million copies.

She says her daughter was born with a benign tumor, thankfully cured, but after she brought her daughter home she became much more concerned with the crisis of air pollution in China.

The 100-minute documentary resulting from her year-long personal investigation is available with English subtitles on YouTube at Chai Jing: Under the Dome - Investigating China's Smog.

The film is fascinating on many levels: interview clips with scientists and officials, supported by vivid graphs, followed by images of pervasive pollution sickening an entire country. Charts show that China burns as much coal as the entire rest of the world, and lung cancer rates in China over the past 30 years have increased almost 500%. The former head of a large state-owned petrochemical company admits that the government commission to set fuel-quality and car-emissions standards is controlled by the oil industry. Images careen by the viewer - of dust and smoke, of highways choked with cars, of skylines obscured, and of a populace in face masks.

We hear from environmental scientists that if existing environmental laws were respected - without corrupt avoidance - the most dangerous components of air pollution in China could be reduced by some 60 percent.

This widespread belief, that the worst effects of air pollution are the result of corrupt, systemic disregard of law - by companies owned by the state and ultimately controlled by the Communist Party - is why air pollution, more than any other social ill, is such a powerful indictment of Chinese government and failure of rule of law. And, of course, in an age of cheap air-quality monitors and iPhone apps, air pollution cannot be concealed.

Chai Jing's film was released (over the Internet, for free viewing) on the first weekend of March, just days before the annual meeting of the National People's Congress. One environmental minister, intriguingly, released a positive comment, saying the film recalled the book "Silent Spring" by Rachel Carson, which helped launch the American environmental movement. This suggested that some factions in the Chinese government wanted to build public support for urgent environmental action against the lobbying pressure of vested industrial interests. Someone in government saw political usefulness to allowing wide dissemination of the film. By the middle of that same week, astoundingly, the film had been downloaded 200 million times.
But as the opening day of the NPC annual meeting grew closer, government censors (likely from very different precincts of the political spectrum than the environmental minister) became alarmed. The film was becoming a cultural phenomenon and might distract public attention from the official media script for the NPC meetings.

And so, about noon on Tuesday of the same week, the Central Propaganda Department in Beijing sent an urgent (and secret, but leaked) "Notice to News Work Units." It read in part:

"To prevent the dilution of the main topics of the annual meeting you must not amplify sensitive topics coming from the Internet and from society.

"Media and websites of all types must absolutely discontinue coverage of the documentary 'Under the Dome' and its creator ... resolutely block and delete speech that uses this as an opportunity to cast doubt on or attack the government."

Within a few hours, all traces of Chai Jing's film, and of any microblog discussion of the issues raised in the film, disappeared from the Internet sites available in China.

Two days later, the Premier of China opened the NPC annual meeting with a government work report that promised the 3,000 delegates that the government would "enforce existing environmental laws, and crack down on illegal emissions, and hold officials who allow illegal emissions accountable for their irresponsible conduct."

Premier Li called pollution "a blight on people's quality of life, and a trouble that weighs on their hearts."

The events of the first week of March - from the exhilarating viral spread of Chai Jing's film, to its sudden suppression, to the Premier's very public pledge to enforce the laws against polluters - showed the often enigmatic interplay between civic discussion and government response in today's China.

Toward the end of her film, Chai Jing asserts that "only when information is open is there a foundation for public debate."

For three days this March in China, 200 million Chinese showed they agreed with her.

Silent spring, indeed.

Stephen Harder is a resident of Rockport, living and working in China.