Air pollution increases the chances of babies having a low birth weight, research has shown
Sooty air pollution in towns and cities increases the chances of women giving birth to small babies, research has shown.
A study involving millions of births around the world found that higher pollution levels raised the risk of low birth weight. Although small, the effect is said to be statistically significant. At national population scales it could have an important impact on child health, said the researchers.
Babies are underweight at birth if they tip the scales at less than 2,500 grams, or five pounds eight ounces. They face an increased risk of dying in infancy, as well as chronic poor health and impaired mental development.
The new study, the largest of its kind ever conducted, focused on tiny sooty carbon particles called PM10s and even smaller PM2.5s which are known to be linked to heart and lung problems and early death. They originate from a number of sources, including diesel exhausts and the chimneys of coal-fired power stations and factories.
Professor Tanja Pless-Mulloli, who led the UK arm of the study at the University of Newcastle, said: "As air pollution increases we can see that more babies are smaller at birth which in turn puts them at risk of poor health later in life.
"These microscopic particles, five times smaller than the width of a human hair, are part of the air we breathe every day. What we have shown definitively is that these levels are already having an effect on pregnant mothers."
The research, published in the journal Environmental Health Perspectives, examined the impact of a 10 microgram per cubic metre increase in average exposure to pollution particles over the course of a pregnancy.
For PM10s, this raised the chances of having a low birth weight baby by 0.03%, which was said to be statistically significant. In the case of PM2.5s, a much larger 10% risk increase was seen. The research also showed a continual trend of elevated low birth weight risk with higher levels of air pollution.
Prof Pless-Mulloli added: "Currently in some parts of London we see around 40 units of particulate air pollution and in Newcastle it is around 20 units but going back to the 1960s we saw around 700 units of air pollution. While much has been done to improve air quality, this study shows we can't be complacent as we've shown that clean air is really important for the health of our newborns."
The scientists collected data on more than three million births at 14 locations in the UK, North and South America, Asia and Australia.