The most populous nation in the world is now also the largest emitter of carbon dioxide, the Netherlands Environmental Assessment Agency said in a recent study.

Air pollution in China is a major problem, caused in large part by the nation's immense thirst for coal-powered energy and the skyrocketing use of cars.

With 1.3 billion people, China emits less CO2 per capita than the United States, but the government admits emissions are continuing to climb as the country continues its fast-paced industrial development.

The government is also trying to slow the rate of population growth, but a decades-old law that permits only one child per couple has been controversial.

Planet in Peril