ZHU Tong | Health Effects of Global Air Pollution on Human Reproduction


On December 22, 2021, on the first anniversary of the establishment of the Peking University Institute for Global Health and Development (PKU-iGHD), the “2021 Peking University Global Health and Development Forum: Human Health and Medical Innovation in the Era of Low Carbon Economy”was successfully held. Prof. ZHU Tong, Dean of PKU College of Environmental Sciences and Engineering, Academician of the Chinese Academy of Sciences, delivered a keynote speech at Global Health and Low-Carbon Economic Transition.

We all know that air pollution causes human life. Every year, about 6.67 million premature deaths are attributable to air pollution. Health effects on adults of air pollution are well documented, according to the paper research there is increasing evidence that even before the births in utero exposure to air pollution could lead to an increase in death in the very young or the before the births of our next generation.


This figure on the right shows the aging distribution of the deaths attributed to the air pollution. We see two peaks. One is in aging population, the other one is neonate or just during early stage of our reproduction. That is an alarm to us to pay attention to control the air pollution. There are many literatures have been published regarding how the air pollution influence our human health with the underlying mechanism like the oxidative stress, influencing our autonomous system, nerve system, and also influencing our blood. And the WHO-UN establish this exposure response curve to estimate the risk of such a result. There's also evidence that the low birthweight infant or preterm birth infant are actually emerging more and more under the influence by air pollution. There are numbers that 15.6% of all low birth weight or 65.7% of all preterm births are attributable to the air pollution.

This is a one important stage we need to pay attention to. But throughout the whole reproduction process, air pollution is causing harms to this one. To the early stage, it could lower the sperm quality, ovarian dysfunction, and during the time, it also leads to the fertilization failure. Throughout the year, in the embryo stage, it could cost maternal embryonic defects, and then lead to the birth defects like neural tube defects. Even throughout the gestation, the mother will suffer from gestational hypertension caused by air pollution. And then we are going to see that the pregnancy loss most in the stillbirths and miscarriage. We have to mention about the preterm and the low birth weight of birth outcome. In finally, it has come to the declining fertility rate.

There's increased number of the study linking the pregnancy loss and air pollution, like the one that mentioned in the US, PM2.5 and the spontaneous abortion, and also in China, PM2.5 and the early miscarriage. We would like to see how this air pollution leads to this effect. We choose two regions to see how the air pollution is causing global pregnancy loss. One is with high pregnancy loss rate and with a moderate number, which is Africa, and another one is moderate rate but with high, large number, which is South Asia. From this map, we can see it's unequally distribution of this, and the PM2.5 or air pollution is also unequally distributed in the Asia, China, India or African countries. This is an indication how we should look at inequity on the global. From our study, we have summarized about 42,000 cases from about 33 African countries. Based on this case, we use so-called self-match design and found that with increase of PM2.5, the increased ratio of the pregnancy loss most in the miscarriage and stillbirths. Then we move to South Asia, including India, Bangladesh, and Pakistan. We see that high number of the pregnancy loss are associated with PM2.5. We even calculate that if India standard could meet its PM2.5, it can award about 7% pregnancy loss.

Well, there are many details, especially distribution of the study. We use the same design as we have done with the Africa one, use the same self-compared to case-control study and with just the gestation stage and we found, per 10 microgram increase, the increase of about 1.03% of the odds ratio associated with miscarriage and the stillbirths. When we look at the different region in Southern India, Pakistan, Northern India, and a different age, like 35 plus and 30 to 34 and a different area where living in the rural and urban area. We found those who live in the rural area, with age 35 years old have the highest rates. This gave us another unequal distribution of the risk associated with pregnancy loss.

This is a more detailed distribution to indicate that, in India, we see this Indo-Gangetic Plain has the highest rates or numbers associated with pregnancy loss attributed to the air pollution and at the other region are less and which is very much comparable to the level of PM2.5.

I will come to the quick conclusion. First, in-utero exposure is a very important factor to increase the risk of pregnancy loss, and this is very important for our understanding about the human population profile in the future, if the exposure to PM2.5 exists. The harmful effect is not only limited in developing countries, and it is a globally effect. It is unequally distributed in the countries which suffer higher PM2.5 and in the countries which has less public service to help to reduce this.

Finally, adverse effects of PM2.5 on human health bring a heavy disease burden in South Asia having a very high population and also a very high PM2.5 loading, and which is also under very fast developing stage. In the future, if we don't pay attention to reduce the PM2.5 concentration, this trend is going to maintain. Bringing the topic to what we are discussing today about the low carbon in the future. We believe the carbon neutrality in the countries, especially in the countries suffered most from the air pollution, carbon neutrality can bring co-benefits not only reducing the health effect from climate change, but most importantly, from air pollution, which is urgent and needed in current stage for climate change and air pollution.

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