Outdoor air pollution tied to premature births

By ANNA CHEN | March 9, 2017


PUBLIC DOMAIN Scientists have identified the decline in outdoor air quality as a risk factor for preterm births.

Air pollution has been a critical global issue for decades. Harmful emissions contribute to environmentally damaging natural phenomena like acid rain, changes in the pH level of oceans, rises in sea levels and more.

However nature and wildlife are not the only victims of pollution. According to the World Health Organization (WHO) the risk of stroke, heart disease, lung cancer and chronic and acute respiratory diseases including asthma has increased with the decline of air quality, especially in cities.

In a recent study by the University of York, outdoor pollution has been linked to millions of premature births (less than 37 weeks of gestation) annually.

Published in the journal Environment International and led by a team of researchers from The Stockholm Environment Institute (SEI), the study shows that 2.7 million premature births, about 18 percent of all premature births globally, are associated with exposure to fine particulate matter (PM2.5) outdoors.

There are many factors that can cause premature births, including the mother’s age, potential illnesses, income level  and other physiological and social factors. With this new study scientists have for the first time quantified the global impact of air pollution on premature births by combining data about air pollution in different countries with knowledge about how different levels of air pollution can be associated with premature birth rates.

According to the WHO’s latest urban air quality database, more than 80 percent of people living in urban areas are exposed to air pollution levels that exceed WHO recommended health limits. In developing countries 98 percent of cities with over 100,000 residents do not meet WHO air quality guidelines.

Although awareness of air pollution levels and the associated health impacts have increased throughout the years, air pollution continues to heavily impact human health.

“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,” Chris Malley, researcher at the SEI, said.

It is also important to note that premature births associated with air pollution exposure not only harm the possibility of the infants’ survival, but also may have life-long health effects on its survivors. These premature births have been tied to increased risks for long-term physical and neurological disabilities.

The greatest number of PM2.5-associated premature births occur in South and East Asia, which together contribute to approximately 75 percent of the total worldwide.

By itself India accounts for about one million of the 2.7 million total, and another 500,000 are from China. Western sub-Saharan Africa and the Middle East area also had high numbers, but most of the air pollution in those regions is associated with desert dust instead of industrial emissions.

Unfortunately there are many confounding factors that contribute to uncertainties in these estimates. Since they were based on studies in the United States and Europe and then generalized to fit global numbers, these results do not account for different sources of harmful particulate matter that may be present in developing countries but not in first-world countries.

For example, diesel vehicles, pollution emitted when agricultural residues are burned in fields and high levels of smoke and indoor pollution resulting from cooking with biomass fuels are not taken into account in the 2.7 million global estimate. Because of this, scientists believe that the number of premature births due to air pollution could be much greater than this study suggests.

Although the exact number may be an estimate, scientists are certain that pollution in the air we breathe has significant impacts on millions of premature births per year.

This new knowledge has important implications concerning mitigation methods for premature births as well as infant mortality and physical and mental disabilities. It stresses the importance of air pollution control on the health of not only the current but also of future generations.

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