Air pollution affects unborn girls more than boys

Air pollution seems to affect unborn girls more than boys, resulting in more pre-term girls than boys being born when pregnant woman are exposed to extreme air particulate pollution, researchers have found.

In addition to the infant mortality effect, air pollution results in earlier births, more of which are girls, Amir Jina, an environmental economist and Assistant Professor at the Harris School of Public Policy, University of Chicago, said from his yet-to-be-published study on the impact of particulate matter on infant mortality and fertility in developing countries.

“We however need to find out whether this is happening through pollution effects on the foetus itself by air pollution passing through the mother’s blood stream through the placenta to the baby, or if it is something happening to the mother,” he told indiaclimatedialogue.net.

In pregnant women, exposure to carbon monoxide, the major pollutant from vehicles and from wood and kerosene stoves, reduces the availability of oxygen to be transported to the foetus. Carbon monoxide also readily crosses the placenta and binds to foetal haemoglobin more readily than to maternal haemoglobin and is cleared from foetal blood more slowly than from maternal blood, leading to concentrations that may be 10% to 15% higher in the foetus’s blood than in the mother’s, according to several earlier studies.

However, particulate matter — from construction dust, motor vehicle exhaust and biomass fuel burning — cannot cross the placenta.

“Air pollution related infant death, on the other hand, claims more boys,” Jina, a founder of the Climate Impact Lab, said.

“When pregnant women are exposed to highly polluted air, it produces clots in the arteries and in some of the critical blood vessels including the placenta. As the placenta provides oxygen and nutrients to the growing baby during pregnancy, clots can deprive the baby of the flow of nutrients and oxygen and depending on the extent of the clot, they can either abort or have a premature birth,” said Sola Olopade, professor of medicine at the University of Chicago. “When pollution-driven clots are not severe enough but still compromised, babies are born full term but weighed 148 grams less than babies born to mothers who breathed cleaner air.”

More at risk

“Unborn babies exposed to air pollution can have learning and memory development issues,” Olopade said. “They are also at greater risk for chronic diseases such as asthma and cardiovascular disease later in life.”

In his study, Jina has measured the economic burden to individual lives and society in developing countries like India and others when an unborn baby, particularly a girl, survives pollution but is born with health complications that plague them throughout life owing to the pre-birth exposure.

Researching household air pollution impact on unborn babies, Olopade found that 70% exposure to pollutants was from indoor cooking smoke and 30% from outside pollutants, mainly vehicular exhaust.

The impact was very different when mothers cooked with dirty firewood or kerosene and when they cooked using ethanol, a clean biofuel.

Women who cooked with ethanol were more likely to be able to take their pregnancy to full term, significantly more than women who continued cooking with firewood or kerosene. They also had fewer miscarriages, according to Olopade. “We also observed women in the ethanol group had much lower blood pressure closer to delivery, relative to those using polluting cooking fuel. Both groups had normal blood pressure throughout early pregnancy,” he said.