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 performed, 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.

Professor Tanja Pless-Mulloli, who led the UK arm of the study at Newcastle University, 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.”

In the UK, Newcastle University researchers used records from the city going back over 50 years. Allowing for socio-economic status and occupation, they were able to correlate the amount of particles in the outdoor air to the birth weight of children. Low birth weight is defined as less than 2,500 grams or 5lbs 8oz.

Professor Pless-Mulloli added: “The particles which are affecting pregnant mothers mainly come from the burning of fossil fuels. In the past the culprit may have been coal fires, now it is primarily vehicle fumes.

“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 1960’s 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 international study was led by co-principal investigator Tracey J. Woodruff, PhD, MPH, Professor of Obstetrics and Gynecology and Reproductive Sciences at the University of California, San Francisco along with Jennifer Parker, PhD, of the National Center for Health Statistics, Centers for Disease Control, USA.
 
In the study the researchers noted that nations with tighter regulations on particulate air pollution have lower levels of these air pollutants.

Particulate matter (PM) found in air pollution is measured in size (microns) and weight (micrograms per cubic meter). In the European Union, England and Wales the limit is 25 µg/m3 of particles measuring less than 2.5 microns, and regulatory agencies in Europe are currently debating whether to lower it.

In the United States and Scotland, regulations require that there be no more than 12.0 µg/m3 of particles measuring less than 2.5 microns annually.

The researchers observed that particulate air pollution in Beijing, China recently measured over 700 µg/m3.

“We would like policy makers to use the results of  this study to inform decisions on whether the permitted levels of air pollution should be changed,” said Professor Pless-Mulloli. “We would urge countries considering reviewing their air pollution standards to include estimates of the growth of newborns as a measure of air quality standards.”

Judith Rankin, Professor of Maternal and Perinatal Epidemiology at Newcastle University added: “This should not deter mothers-to-be from taking exercise outdoors as the benefits of keeping active in pregnancy are well known. This is not something that individuals can address but that policy makers need to be considering.”

Reacting to the study Frank Kelly, Professor of Environmental Health at King’s College London said: “The study by Dadvand and colleagues removes any doubt that poor air quality, in the form of particulate pollution, has detrimental effects on the unborn child. Increasing numbers of studies had suggested this to be the case but, to date, the evidence had been insufficient to infer a causal association.  This study moves the field forward and clarifies the work now required to identify the nature and sources of the particulate pollution responsible to inform policies which remove these from the air.”

Reference: Maternal Exposure to Particulate Air Pollution and Term Birth Weight: A Multi-Country Evaluation of Effect and Heterogeneity. Payam Dadvand,Jennifer Parker, Michelle L. Bell, Matteo Bonzini, Michael Brauer, Lyndsey A. Darrow, Ulrike Gehring, Svetlana V. Glinianaia, Nelson Gouveia, Eun-hee Ha, Jong Han Leem, Edith H. van den Hooven, Bin Jalaludin, Bill M. Jesdale,  Johanna Lepeule, Rachel Morello-Frosch, Geoffrey G. Morgan, Angela Cecilia Pesatori, Frank H. Pierik, Tanja Pless-Mulloli, David Q. Rich, Sheela Sathyanarayana, Juhee Seo, Rémy Slama, Matthew Strickland, Lillian Tamburic, Daniel Wartenberg, Mark J Nieuwenhuijsen, Tracey J. Woodruff

published on: 6 February 2013