China is expected to unveil an ambitious plan to tackle pollution soon, but in the meantime, residents of the capital have no choice but to struggle to catch their breath.

Smog hanging over Beijing was off-the-charts bad this week, as officials at the U.S. Embassy there reported it had exceeded the standard air quality scale.

Embassy officials, who have been independently monitoring air quality in the Chinese capital, said that pollution levels were "beyond index." That means the air quality index was well beyond the threshold of what would typically be considered "hazardous."

The standard air quality chart tops out at 500, but the U.S. embassy said it climbed to a staggering 595 in the Chinese capital last week.

In contrast, the worst air quality level recorded in Toronto last year was just 59.

It was so bad in Beijing last week, that the entire cross-section of the 22 million people who call the Beijing metropolitan area home, including otherwise healthy adults, were quietly advised to avoid going outdoors at all.

Health experts say breathing polluted air, with its potent combination of

sulfur dioxide, carbon monoxide, and volatile organic compounds, can affect respiratory functions and worsen problems for those with asthma or allergies.

But there's really no escaping Beijing's dirty air, as it is being constantly recharged by particulate pollution from the city's numerous coal-fired power stations and the 4.8 million vehicles on its roads. When temperatures rise and the wind disappears, as it did last week, the result is a cloying blanket of thick smog.

As a result, the Beijing weather bureau said visibility in parts of the city was reduced to just 200 metres.

Reporting from the Chinese capital, CTV's Asian Bureau Chief Ben O'Hara-Byrne said the country is expected to reveal its environmental plan as part of its next 5-year economic blueprint.

"It will likely include measures to reduce pollution including new taxes and big money for green technology development," O'Hara Byrne said.

While Beijing took several steps to clean its air in the run-up to the 2008 Olympics -- including limiting new car licences and expanding the public transit network -- its challenges, unlike its smog-shrouded skyline, remain clear as day.

As it stands, more than two-thirds of China's electricity demands are met by coal-fired plants. And considering the continued pace of growth in the Asian giant, it continues to build more. Already, China accounts for almost one-quarter of the world's Co2 emissions.

With files from CTV's Asian Bureau Chief Ben O'Hara Byrne