Air pollution affecting millions of births

Around this time last year, researchers in London reported that they had found particulate matter from air pollution in the placentas of women giving birth in the capital. They concluded that what pregnant women breathe in can sometimes end up in their developing baby. They didn’t look at the impact on the children in that study. But now University of California, San Francisco epidemiologist Rakesh Ghosh has taken things a step further and married up data from exposure to small particles of airborne pollution - termed PM2.5 - with the risk of a baby being born either too early, or weighing less than it should. He told Cameron Voisey what he found...

Rakesh - So the main finding of this study is that there are almost 6 million preterm babies and 2.8 million underweight babies born every year that are due to PM2.5 exposure during pregnancy. These are very small particles, less than 2.5 micrometres that can travel deep into the lungs and pass into the bloodstream.

Cameron - And how is it that these particules affect babies?

Rakesh - So there could be three possible ways that we can think of. One: by effecting the development of the placenta and the umbilical cord. The second could be these particles induce some kind of inflammation of the membranes and cause the baby to be born early. And the third possible pathway could be by causing oxidative damage to the DNA.

Cameron - And what are the problems associated with preterm birth?

Rakesh - Preterm birth is the most important cause of neonatal mortality, which is death in the first four weeks after birth. And those who go on to survive, it is often observed that these preterm babies develop long-term disability because their body, including the brain, was not fully mature when they were born.

Cameron - So what are the main sources of this particulate matter? What leads to this pollution being in the air?

Rakesh - In many of the countries, the main source, particularly the high-income countries, is traffic and industrial sources, for example, coal-fired power plants. In other countries, such as Sub-Saharan Africa and the Indian sub-continent a major source of PM2.5 is household air pollution. So in many of these places wood, dung, even coal are used as fuel for cooking. And my results show that huge amount of these 6 million that I was talking about is happening in these parts of the world where pollution levels are very high.

Cameron - So how did you actually carry out the study? What data did you use?

Rakesh - So first I started with compiling the evidence from the studies that have been conducted so far. And I primarily did this to examine critically whether the relationship between PM2.5 exposure and the adverse outcomes like preterm birth and low birth weight is causal. And once I was convinced that this association is causal, then I estimated along with the team, the magnitude of the risk at different levels of exposure.

Cameron - So looking forward, where would you say we go from here?

Rakesh - Outdoor air pollution, as we all know, is ubiquitous. It has to be acted upon by different authorities. For countries where indoor air pollution is a problem, I think a message should be part of the prenatal care. Do whatever you can to minimise exposure to indoor air pollution or household air pollution. It is high time to realise that air pollution is not just about premature deaths, but it is harming the babies and our future generations even before they are born.