Pregnant women exposed to air pollution from road traffic are more likely to give birth to babies that are underweight or smaller than they should be, a study conducted in the UK warns.
However, when it comes to traffic-related noise, the study of more than half a million infants, published in The BMJ, found no conclusive effect on babies' health.
Cutting the average concentration of fine particle pollution emitted by London's road traffic by just 10 per cent could prevent around 90 babies a year (three per cent of cases) being born with low birth weight.
The findings led by researchers at Imperial College London could be applicable to other cities in the UK and across Europe with comparable levels of road traffic pollution, highlighting the need for environmental health policies to improve air quality in urban areas.
Previous studies have shown a link between air pollution, pregnancy complications and childhood illness, but studies of noise pollution in pregnancy have provided conflicting results.
The latest study looked at the link between exposure to air and noise pollution from road traffic during pregnancy and the effect on measures of birth weight both low birth weight (less than 2,500 grammes) and being born small for gestational age.
The study focused on records of more than half a million (540,365) babies born in the Greater London area between 2006 and 2010, along with the mother's home address location.
Researchers estimated average monthly concentrations of pollutants related to road traffic, including nitrogen dioxide (NO2), and fine particulate matter (PM2.5) from traffic exhaust and non-exhaust sources, such as brakes or tyre wear, as well as larger particulate matter (PM10).
Average day and night-time road traffic noise levels were also estimated.
They found higher levels of these air pollutants, particularly PM2.5, were associated with two per cent to six per cent increased odds of low birth weight and one per cent to three per cent increased odds of being small for gestational age.
"Our study has shown that a small but significant proportion of babies born underweight in London are directly attributable to exposure to air pollution, particularly to small particles produced by road traffic," said Mireille Toledano from Imperial.
"Babies born with low birth weight or who are small for their gestational age, are at increased risk of dying within their first month, as well as diseases in later life, such as cardiovascular disease," said Toledano.
"Any policies aimed at reducing road traffic pollution in urban environments could therefore help to reduce the health impact on unborn babies and their life-long disease risk," she said.
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