The greater the air pollution, the smaller the baby, study finds
Pregnant women increase the risk of having a low-birth-weight baby when they breathe in air pollution from vehicles, heating and coal power plants, an international study has concluded.
The research, the most extensive of its kind on the link between air pollution and fetal development, found that the higher the pollution, the greater the rate of children born with a low weight. It was published in the US journal Environmental Health Perspectives.
The study also found that for every 10-microgram increase in the average exposure of a pregnant woman to PM10 particles, their babies were 8.9 grams lighter at birth, adjusted for such variables as socio-economic status. PM10 refers to the amount of particles 10 microns or less in diameter in a cubic metre of air.
Scientists analysed data from more than three million births in nine nations in North America, South America, Europe, Asia and Australia. Most of the data was collected from the mid-1990s to the late 2000s, with some obtained earlier.
Low birth weight - below 2.5 kilograms - is linked to serious problems, including a higher risk of complications or death in the weeks right after birth, as well as chronic health problems later in life, says lead author Payam Dadvand, of the Centre for Research in Environmental Epidemiology in Barcelona.
Co-lead investigator Tracey Woodruff said the pollution was ubiquitous.
"What's significant is that these are air pollution levels to which practically everyone in the world is commonly exposed," said Woodruff, a professor of obstetrics and gynaecology and reproductive sciences at UC San Francisco. "These microscopic particles, which are smaller than the width of a human hair, are in the air that we all breathe."
But she noted that nations with tighter air pollution restrictions had lower levels of the pollutants. "In the US, we have shown that the benefits to health and well-being from reducing air pollution are far greater than the costs," Woodruff said. "This is a lesson that all nations can learn from."
An epidemiological study of some of the children included in the data is investigating if these pregnancy exposures can have an impact in their later years.