"Let the sunshine, let the sunshine in...." my wife Ana blurted into a song this week, as she gazed eastwards through the window of our apartment in downtown Beijing.

The old tune from the Broadway show "Hair" seemed apt. This is the fourth consecutive morning that we woke up staring at a gray haze.

It's another bad-air day in Beijing. You can barely see. You can barely breathe. But you can feel -- and even taste -- the grit floating in the air.

The World Health Organization has set healthy level of Air Quality Index at 25 micrograms, while Beijing considers a 300 reading as "Bad" and 500 as "Hazardous." Last weekend, however, it breached 700!

"I'm getting itchy," complained my daughter Michelle, 22, visiting us from New York. "I could feel it at the back of my throat."

Longtime expatriate residents in the Chinese capital jokingly call it the "Beijing tickle," a nagging cough that takes a long time to shrug off.

Air pollution is a major problem in China because of the country's rapid pace of industrialization, reliance on coal power, explosive growth in car ownership and the sometimes disregard for environmental laws.

It is now paying the price of rapid development.

In 2007, China overtook the United States as the world's biggest emitter of greenhouse gases, according to China's Ministry of Commerce. It is also the No. 1 source of carbon emission worldwide, state-run China Daily reported recently.

Added to this, the World Bank says 20 of the 30 most polluted cities in the world are in China.

Health is the big casualty.

Almost 400,000 premature deaths are recorded in China each year, with the majority related to pollution, according to the World Bank's "Cost of Pollution in China," a report based on official Chinese figures.

A growing number of individuals and institutions are looking to find last-gasp solutions.

The government has already shut down high-polluting factories, built new subway lines, and allocated state subsidies to reduce the cost of public transport.

Beijing bans vehicles from the road one day a week to reduce heavy traffic and vehicle emissions.

It also imports natural gas from other provinces to rely less on coal for heating and cooking.

As part of a long-term solution, Chinese researchers are producing prototypes of solar and electric cars to replace gas-fueled vehicles.

So far, these measures have not produced consistently blue skies and clean air.

Green activists complain that even though government regulations have improved, laws are often ignored.

One of Beijing's big problems has been the city's geography, as it is surrounded by mountains shaped like a horseshoe.