Air quality 'affects birth weight'

Exposure to air pollution during pregnancy can lead to a reduction in the birth weight of children, a new study has revealed. While previous studies have suggested that air pollution may be damaging during pregnancy, this has yet to be proven conclusively. However, the new study, which took place in New York, has found that lower air quality can result in lighter babies.

David Savitz from the Alpert Medical School of Brown University in Providence, Rhode Island, led the study that looked at the birth weight of over 250,000 babies. All of the babies were born in hospitals in New York City during the period of 2008 to 2010. 

Data taken from the New York City Community Air Survey was used to estimate the levels of air pollution that each of the mothers had been exposed to during their pregnancy, based upon where they lived. Nitrogen dioxide and particulate matter measuring less than 2.5 micrometres in diameter (PM2.5) were the main pollution types focused on.

It was found that for every ten microgram per cubic metre increase in PM2.5 that the women were exposed to during their pregnancies, the birth weight of the babies dropped by around 48 grams. Birth weight was also reduced by around 18 grams for every ten parts per billion increase in nitrogen dioxide that the pregnant women were exposed to. The findings were published in the 'American Journal of Epidemiology'. 

National air quality standards are set by the Environmental Protection Agency (EPA), which state that air pollution should not exceed 53 parts per billion of nitrogen dioxide and 15 micrograms of PM2.5 per cubic metre. The study found that the average pollution levels that the women were exposed to generally fell within those levels, however, the air quality did vary quite dramatically throughout the study.

The researchers noted in the study that although there appears to be a correlation between increase in air pollution and decrease in birth weight, it is not conclusively proven that the two are entirely related.