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A new study investigates links between air pollution and perinatal outcomes. aire images/Getty Images
  • A new study links air pollution to almost 6 million premature births and almost 3 million underweight infants in 1 year.
  • The study indicates that indoor air pollution, mostly from cooking stoves, drives two-thirds of these perinatal issues.
  • While the authors found that the situation was worse in low- to middle-income countries, air pollution is a global health problem.

A new global burden of disease study and meta-analysis provides the most in-depth look yet at the effect of air pollution on premature births and underweight newborns.

Scientists from the University of California, San Francisco, and the University of Washington in Seattle authored the research. The study appears in PLOS Medicine.

It finds that air pollution was associated with almost 6 million premature births and almost 3 million underweight babies in 2019.

The authors believe this is also the first study to analyze perinatal outcomes due to the effects of both outdoor and indoor air pollution, which comes primarily from cooking stoves.

The authors find that indoor air pollution could be responsible for about two-thirds of premature and underweight newborns.

The World Health Organization (WHO) estimates that about 15 million preterm babies are born each year. Complications related to preterm births are the leading cause of death among children younger than 5, resulting in about 1 million deaths in 2015. Low birth weight also has associations with a greater risk of adulthood illness.

The current study looks at links between air pollution and several important perinatal health indicators, including preterm birth, gestational age at birth, birth weight, and low birth weight.

Previous research concluded that air containing less than 2.5 micrometers of particulates has associations with adverse perinatal outcomes.

“Particulate matter [PM] has been identified as the most toxic component based on a large number of epidemiological and toxicological studies,” said Cornell University’s Prof. K. Max Zhang in an email to Medical News Today. Dr. Zhang studies the effects of airborne particulate matter but was not involved in the study.

The lead author of the study Rakesh Ghosh, Ph.D. explained to MNT what prompted him to undertake the study:

“I will start with a more emotional than scientific reason for my interest. My very first work experience in the outskirts of Kolkata — the capital of West Bengal, an eastern Indian State — led me to this area of research. The images of the sick and malnourished babies in those villages live with me to this day.”

According to the WHO, 99% of the world’s population breathes air that falls short of the organization’s safety standards, with people living in low- and middle-income countries experiencing the greatest exposure. The WHO estimates that outdoor air pollution accounts for 4.2 million deaths each year.

The WHO also calculates that 3.8 million premature deaths occur annually due to indoor air pollution, such as smoke from cooking fires. Again, this primarily occurs in low- and middle-income countries.

Burning coal, dung, and wood in inefficient stoves and open hearths are the leading producers of health-damaging pollutants, such as airborne particulates. Single-wick kerosene lamps also contribute to the problem.

The new study found indoor air pollution most common in South Asia and sub-Saharan Africa, two areas with the highest preterm birth rates globally.

Dr. Zhang was not surprised by this finding, even though, he noted, “Only two out of a total of 180 studies included in the meta-analysis took place in Sub-Saharan Africa.” He explained:

“Africa, in general, has a much smaller number of air quality monitoring stations than any other continents, according to the 2020 World Air Quality Report. The lack of air quality data and health studies contributed to the uncertainties of the findings, but the health effects are very likely to be underestimated rather than overestimated. This is a vivid example of global health inequalities.”

The study’s authors say that significantly reducing air pollution in these two areas could lower the incidence of preterm birth and low birth weight by 78%.

Perinatal issues from air pollution are also common in more developed areas. The study mentions that it contributed to almost 12,000 preterm births in the United States in 2019.

“The air pollution-attributable burden is enormous, yet with sufficient effort, it could be largely mitigated,” Dr. Ghosh tells UCSF.

“We should make pregnant women aware that exposure to air pollution is unhealthy for the baby, just like drinking and smoking during pregnancy,” Dr. Ghosh told MNT. “This should be a key message as part of prenatal care, especially in places where household air pollution is prevalent.”

He also cited the value of wearing a mask. “Mothers who have [no choice but] to spend a certain amount of time in a closed, polluted environment should be provided and encouraged to wear N95 or N99 masks. Wherever possible, replace solid fuels with cleaner ones. There are national schemes in some South Asian countries to use LPG [liquified petroleum gas].”

Dr. Zhang also noted the efforts of the Global Alliance for Clean Cookstoves, which the U.S. Department of State partly sponsors.

Dr. Ghosh hopes that the study can lead to more effective approaches for reducing preterm births and low birth weights. He said:

“A comprehensive global burden assessment is the best scientific evidence a researcher can provide to the policymakers for action. The previous global burden assessment included outdoor PM2.5 air pollution only. Without considering household PM2.5 air pollution, we are only partially estimating the burden.”