Expectant mothers breathing polluted air resulted in premature birth of over one million babies in India in 2010, highest in the world and twice the numbers for China, a study claimed today.
The study found that in 2010, about 2.7 million preterm births globally were associated with outdoor exposure to fine particulate matter and largest contribution to global PM2.5 associated premature births was from South and East Asia, which together contributed about 75 per cent of the total.
Noting that a pregnant woman's exposure can vary greatly depending on where she lives, the study said that in a city in China or India, for instance, the woman might inhale "more than 10 times" as much pollution as she would in rural England or France.
When a baby is born preterm (at less than 37 weeks of gestation), there is an increased risk of death or long-term physical and neurological disabilities.
There are many risk factors for preterm birth - from the mother's age, to illness, to poverty and other social factors and recent research has suggested that exposure to air pollution could also be a risk factor.
"In 2010, about 2.7 million preterm births globally - or 18 per cent of all pre-term births - were associated with outdoor exposure to fine particulate matter," said the study led by a team from The Stockholm Environment Institute at the University of York, that was published in the journal Environment International.
"The largest contribution to global PM2.5-associated preterm births was from South Asia and East Asia, which together contributed about 75 per cent of the global total.
"India alone accounted for about 1 million of the total 2.7 million global estimate, and China for about another 500,000," the study.
The study said that in 2010, an estimated 14.9 million births were preterm - about 4-5 per cent of the total in some European countries, but up to 15-18 per cent in some African and South Asian countries and the human and economic costs are "enormous".
"The large contribution of South and East Asia to global PM2.5-associated preterm births was mainly due to PM2.5 associated preterm births in India at 1.1 million (0.3–1.8 million) and China at 0.5 million (0.1–0.7 million) respectively," the study said. (MORE) The study estimated 2.7–3.4 million preterm births may be
associated with PM2.5 exposure in 2010 globally.
Results of the study suggested that addressing major sources of fine particulate matter (PM2.5) - from diesel vehicles, to agricultural waste-burning, could save babies' lives and improve health outcomes.
"For some countries, maternal exposure was to relatively moderate ambient PM2.5 concentrations - Democratic Republic of the Congo and Ethiopia) while in others the PM2.5 concentrations were among the highest calculated for any country - Pakistan, Bangladesh, Iran, Egypt, Yemen, Nepal, Niger, Mali, Iraq, India and China," it said.
A study for the first time quantifies the global impact by combining data about air pollution in different countries with knowledge about how exposure to different levels of air pollution is associated with preterm birth rates.
"This study highlights that air pollution may not just harm people who are breathing the air directly - it may also seriously affect a baby in its mother's womb.
"Preterm births associated with this exposure not only contribute to infant mortality, but can have lifelong health effects in survivors," said Chris Malley, lead author and a researcher in SEI's York Centre at the University of York.
Malley noted that while many other health impacts of air pollution have been documented - most notably through the Global Burden of Disease studies - the focus has been mainly on premature deaths from heart disease, respiratory problems and others.
"This study adds an important new consideration in measuring the health burden of air pollution and the benefits of mitigation measures," he said.
"There is uncertainty in these estimates because the concentration-response function we used is based mainly on studies in the United States and Europe.
"Not only don't we know whether the relationship is the same at much higher concentrations, such as those found in some Indian or Chinese cities, but the prevalence of other risk factors also varies considerably," Malley said.
Expectant mothers in many places are also exposed to high levels of indoor pollution from cooking smoke and resolving these uncertainties will require more studies in these countries and regions, he said.
"Knowing that reducing outdoor air pollution could help reduce preterm births provides a compelling new reason to invest in mitigation measures," said Johan C I Kuylenstierna, co-author of the study and SEI's Policy Director.