Just how bad is air pollution for human health?



Evidence for air pollution being causally related to cardiovascular disease is as strong as that for high cholesterol or high blood pressure.

Tim Nawrot, Hasselt University professor of env i ronmental epidemiology and the 2021 Belgian Francqui Chair of the Faculty of Public Health, tells us.

How do you conduct research on pollution’s impact on human health?

We developed methods to measure pollutants inside the human body. We can measure carbon in urine or the placenta or other areas, as well as hormone-distributing chemicals. We also look at the impact of extreme meteorological conditions on health. But most of my research is on air pollution, where we focus on vulnerable groups, such as pregnant women and what exposure means for the foetus. It may cause fatal abnormalities, but more research is required.

So air pollution affects organs other than the lungs?

There’s been a tsunami of publications with very strong evidence of the impact of environmental pollution on human health. In the 1990s it was thought that air pollution affected only the lungs, but because the smallest particles can easily travel from the lower airways to the entire body, they sometimes exert an even greater effect on other organ systems. So cardiovascular disease effects are more pronounced than lung effects. In fact, the evidence linking air pollution and cardiovascular disease is as strong as high cholesterol or high blood pressure.

What’s the impact of pollution on the brain?

We did studies in children. When they live in areas with higher levels of air pollution, their attention and memory skills are reduced. On days with peaks of air pollution, there’s a temporal effect that reduces such skills. In the elderly we know the risk of dementia is higher for people living close to major roads. These particles enter the brain via the olfactory nerves, causing inflammatory responses that in turn cause detrimental health effects.

Has air pollution over the last, say, 50 years transformed humans?

That’s more of an evolutionary question and can only be measured over aeons. When the most polluted persons become incapable of reproducing themselves, then natural selection will ensue. But pollution today is much less than it was in the mid- 20th century, when you had widespread coal-burning for heating. Air quality has improved, but it’s not good enough, we still see health impacts, we have to stop burning fossil fuels. While the health effects of air pollution are mainly in vulnerable people such as the elderly, children with asthma, and pregnant women, the impact for society is huge because we’re all exposed, meaning that even relatively small impacts become important.

How do you see our future?

In some ways we’re on the right track. More efforts have been made to reduce pollution. It has decreased in the last ten years. CO2 itself isn’t a concern for human health because it’s not toxic to us, but of course it causes climate change and thus has enormous health and ecological consequences. We already know that heat waves cause a higher mortality rate. In Belgium, the lowest mortality occurs on days averaging 16 degrees, in Nordic countries 11 degrees, in Spain 27 degrees, so populations have adapted to temperature but we don’t know how long such adaptations take. Climate change policies will further ban fossil fuel burning, which will improve general air quality. I’m not totally negative, but there are so many feedback systems: ice melt not only increases sea level but the radiation it reflected is absorbed, increasing water temperature. So many other feedback systems will be more difficult to stop, I hope we’re not reacting too late. CO2 is still rising after all. We need to design our cities in accordance with climate adaptation, improving and introducing more green areas and taking it for granted that the air we breathe should comply with strict standards, such as those from the World Health Organization.

Lee Gillette

Article paru dans le Louvain[s] de mars - avril - mai 2021