A worldwide study has shown that pregnant mothers exposed to air pollution emitted by vehicles and coal power plants, are significantly more likely to have smaller babies.
The study, the largest of its kind ever undertaken, analysed data from more than three million births in nine nations at 14 sites in the UK, Europe, North America, South America, Asia and Australia.
Publishing today in the journal Environmental Health Perspectives, the researchers found the higher the level of pollution, the greater the rate of low birth weight.
Low birth weight is associated with serious health consequences, including increased risk of perinatal death, as well as ill health and chronic health problems in later life.
According to professor Tanja Pless-Mulloli, who led the UK arm of the study at Newcastle University, ''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.''