Air pollution in China is linked to lower birth weights, as evidenced by a new study published in Environmental Health Perspectives.

In response to international scrutiny preceding the 2008 Olympic games, the Chinese government restricted automobile use, closed factories and imposed a moratorium on construction projects in an effort to reduce air pollution. University of Rochester researchers followed 80,000 women who were pregnant in Beijing in 2008 to track fetal growth and development.

The good news: the presence of certain air pollutants in Beijing decreased up to 60% during the Olympics, and babies born in 2008 were an average of 8 ounces heavier than those born in 2007.

The bad news: the restrictions were only temporary, and have since been rescinded. The birth weight of babies born in 2009 dropped back down to 2007 levels as air pollution rebounded.

Low birth weight is associated with a variety of conditions; babies born weighing less than 5 pounds, 8 ounces are at a higher risk of inhibited growth and cognitive development than babies born at a healthy weight.

Researchers believe that fetuses are especially vulnerable to air pollution during the later stages of pregnancy, a period of development for the central nervous, cardiovascular, and skeletal systems.

“While Beijing’s pollution is particularly noteworthy, many of the world’s other cities face similar air quality problems,” said study co-author Dr. Junfeng Zhang. “This study shows that pollution controls i even short-term ones i can have positive public health benefits.”