According to a new study published in the journal Environmental Health Perspectives, there is a small — but steady — link between local air pollution levels and lower infant birth weight.
While there is some speculation as to the exact nature of the link between air pollution and low infant birth weight, experts theorize that air pollution “can affect the attachment of the fetus to the placenta” and “stress the mother’s body, which could affect fetal growth.” And, as the study found, the more the air pollution, the lower birth weights tended to be:

The researchers found that for every 10-microgram increase of pollution particles per cubic meter of air, average birth weights decreased by 8.9 grams, roughly one-third of an ounce, and infants were 3 percent more likely to be a low birth weight. An infant is considered low birth weight if he or she weighs less than 5 pounds, 8 ounces.
Low birth weight is a known risk factor for infant mortality as well as heart, breathing and behavior problems later in life.

Pollution levels at study sites ranged from approximately 10 to 70 micrograms per cubic meter of air. “These are definitely exposures that people would have in many places around the world,” said Tracey Woodruff, a reproductive health scientist in the division of Maternal-Fetal Medicine at the University of California, San Francisco Medical Center, who worked on the study.“This study increases our confidence that the impact of air pollution on birth weight is real.”

Air pollution has increasingly come under scrutiny as a major contributor to poor public health, particularly after shocking images of Beijing’s catastrophic air contamination levels became worldwide news. For the first time ever, air pollution is now considered a bigger killer than high cholesterol.
But the problem isn’t limited to China or other developing nations just now mastering the use of mechanical industry. In Utah — one of the five most polluted states in America — doctors have urged Gov. Gary Herbert (R) to declare a public health emergency over what they perceive to be dangerous levels of air pollution, regardless of the significant environmental advances made under the auspices of the Clean Air Act.