Air pollution likely contributed to nearly six million premature births and almost three million underweight babies around the world in 2019, according to a study published on Wednesday.
Researchers at the University of California San Francisco (UCSF) and University of Washington in the US quantified the effects of indoor and outdoor pollution around the world using data from 204 countries.
The finding, published in the journal PLOS Medicine, is the most in-depth look yet at how small particulate matter (PM2.5) affects several key indicators of pregnancy, including gestational age at birth, reduction in birth weight, low birth weight, and preterm birth.
It is the first global burden of disease study of these indicators to include the effects of indoor air pollution, mostly from cook stoves, which accounted for two-thirds of the measured effects, the researchers said.
"Our findings suggest that about 2.8 million low birth weight and 5.9 million preterm birth infants, globally, could have been averted in 2019 if the mean PM2.5 exposure during the entire pregnancy was reduced to the theoretical minimum risk exposure level," the authors of the study noted.
"South Asia and sub-Saharan Africa combined could have decreased the 2019 low birth weight and preterm birth incidence by about 78 per cent," they added.
The researchers noted that preterm birth is the leading cause of neonatal mortality worldwide, affecting more than 15 million infants every year. Children with low birth weight or who are born premature have higher rates of major illness throughout their lives, they explained.
"The air pollution-attributable burden is enormous, yet with sufficient effort, it could be largely mitigated," said lead author Rakesh Ghosh, a public health specialist at UCSF.
The World Health Organization estimates that more than 90 per cent of the world’s population lives with polluted outdoor air, and half the global population is also exposed to indoor air pollution from burning coal, dung and wood inside the home.
The study concluded that the global incidence of preterm birth and low birth weight could be reduced by almost 78 per cent if air pollution were minimised in Southeast Asia and sub-Saharan Africa, where indoor pollution is common and preterm birth rates are the highest in the world.
However, it also found significant risks from ambient air pollution in more developed parts of the world. In the US, for example, outdoor air pollution is estimated to have contributed to almost 12,000 preterm births in 2019.
Previously, the same research team quantified the effects of air pollution on early life mortality, concluding that it contributed to the deaths of 500,000 newborns in 2019.
"With this new, global and more rigorously generated evidence, air pollution should now be considered a major driver of infant morbidity and mortality, not just of chronic adult diseases," Ghosh said.
"Our study suggests that taking measures to mitigate climate change and reduce air pollution levels will have significant health co-benefit for newborns," he added.