As a famed investigative reporter, Chai Jing worked on many hard-hitting features about China’s environmental woes. But since becoming pregnant in 2013 — and discovering her baby was carrying a tumour in her womb — the country's runaway pollution has become personal, prompting her to ponder solutions to China’s trouble in the air.

Chai's baby survived following surgery performed last year, but Chai was left shattered and unable to enjoy the feeling of motherhood. She decided to quit her job at China’s state broadcaster, CCTV, to take care of her daughter.

Chai continued reporting, however, and her new independent documentary about China’s smog problem — a topic close to Chinese hearts and a giant political headache for the country's decision makers — has exploded on Chinese social media.

The nearly two-hour documentary, titled ‘Under the Dome’ went viral shortly after its release on Saturday. By Sunday morning, ‘#Chai Jing’s smog investigation’ was the top trending topic on China’s Twitter equivalent, Sina Weibo, and had already generated more than 30 million views on various Chinese video sharing platforms.

Packed with sobering pollution data and compelling personal anecdotes, the self-funded production has turned a spotlight on smog.

“This is my personal grudge with the smog. I need to know where it comes from and I need to figure out everything connected to it,” Chai tells viewers, adding that her daughter had to be “locked up like a prisoner” at home for half a year in 2014 due to the air pollution.

The documentary sees a softly-spoken Chai addressing a live audience in a style similar to a TED talk, with regular interludes for animations and footage of smoke-belching factories and thick lines of traffic in China's major cities.

As part of the investigation, Chai took field trips to polluting factories and even London and Los Angeles to revisit moments in smog history that have claimed thousands of lives.

What emerges from the documentary is a hard critical look at China’s over-reliance on dirty fossil fuels, its bloated heavy industries and its lax enforcement of environmental statutes.

Sixty percent of Chinese smog comes from the burning of coal and gasoline, the documentary notes, citing reports published by Chinese research institutions.

Today China is the world's largest consumer of coal, which accounts for 70% of the country's total energy consumption. Worse still, according to Chai's documentary, China washes less than half its coal, limiting the country's ability to reduce pollution and enhance fuel efficiency.

Despite Beijing's pledge to crack down on polluting industries — regularly endorsed by President Xi Jinping — resistance to environmental reform is likely to linger.

At one moment in the documentary, when Chai asks a Chinese environment official why the government cannot simply shut polluting steel plants, he offers an amazed rebuttal: “Are you joking? A steel plant with a yearly capacity of 10 million tons usually employs 100,000 workers, there is no way you could close steel plants in Hebei province.”

The documentary also highlights reluctance on the part of oil majors in China to impose more environmentally friendly gasoline standards. In most Western countries, gasoline standards are usually set by environmental authorities, but in China such powers rest with huge state-owned oil companies such as China National Petroleum Company (CNPC) and Sinopec.

The Chinese phrase for smog, (雾霾 pronounced Wu Mai) consists of two characters, fog and haze, and has only become more widely used in recent years, largely as a result of growing public demand for better air quality and a drumbeat of media reports detailing health risks.

Public discussion of the issue gained traction in January of 2013, when one key pollution indicator, (PM2.5, measuring fine particulates of less than 2.5 units in the air), went off the charts. PM2.5 is seen as particularly dangerous to public health as it can penetrate human lungs. The highest reading that month was close to 1000, nearly 40 times what the World Health Organization (WHO) deems safe for human beings.

While the documentary itself is not groundbreaking, it is the most comprehensive Chinese TV reporting on smog to date. Its release comes on the heels of a recent leadership reshuffle at China’s environment ministry, with the reform-minded former president of the elite Tsinghua University, Chen Jining, parachuted into the agency's top post.

Chen said on Sunday that he had already watched the documentary and sent a text message to Chai to thank her for raising public attention towards environmental issues, according to Chinese media reports.

In less than a week's time, at the annual sessions of the National People's Congress (NPC), pollution will be one of the hottest topics discussed.

Towards the end of the documentary, Chai strikes a defiant tone:

One day, tens of thousands of ordinary folks will say no. They will say they are not satisfied, they don’t want to wait and they don’t want to evade responsibility. I have to stand up and do something, and I will do it right now, right here, in the very moment where I am. I am the change.

She then casts her eye towards a rotating planet earth in the background (01:43:56 in the documentary) and makes an appeal as a mother: