Washington, Dec 17 : New satellite data has revealed the impact of the pollution control strategy that China took during the Olympics, which resulted in the levels of nitrogen dioxide (NO2) plunging nearly 50 percent in and around Beijing in August 2008.

The lowering down of the NO2 levels was a result of strict traffic restrictions instituted by Chinese government officials in preparation for the Olympic Games.

The measures included temporarily shutting down some factories and banishing many cars in a pre-Olympic sprint to clean up Beijing's air.

NASA researchers have since analyzed data from their Aura and Terra satellites that show how key pollutants responded to the Olympic restrictions.

According to atmospheric scientist Jacquelyn Witte and colleagues from NASA's Goddard Space Flight Center in Greenbelt, Maryland, the emission restrictions had an unmistakable impact.

During the two months when restrictions were in place, the levels of nitrogen dioxide (NO2) - a noxious gas resulting from fossil fuel combustion (primarily in cars, trucks, and power plants) - plunged nearly 50 percent.

Likewise, levels of carbon monoxide (CO) fell about 20 percent.

The steep decline in certain pollutants surprised the researchers. In a preliminary analysis of the data, the effect seemed to be minimal, explained Mark Schoeberl, project scientist for the Aura mission and a contributor to the study.

The reductions only became noticeable when the investigators focused tightly on the Beijing area.

Although satellites detected reductions in levels of SO2, a major byproduct of coal-fired power plants and a key ingredient of acid rain, the decline was more widespread due to a larger effort to reduce SO2 emissions across China, according to Kenneth Pickering, another Goddard scientist involved in the research.

Some scientists have questioned whether Beijing's highly publicized air quality restrictions actually had an impact. This new data shows clearly that they did.

"After the authorities lifted the traffic restrictions, the levels of these pollutants shot right back up," Witte noted. (ANI)