The Huai River is fed by tributaries high in China’s Tongbai Mountains and Dabie Mountains, and meanders 660 miles across Henan and Anhui provinces before it flows into Lake Hongze in Jiangsu province.

Historically, the river provided water for farmers’ crops on either side, with livelihoods growing up around it. On each bank today, people have a similar quality of life.

But those who live north of the river have a lower life expectancy – up to three years less – than those on its southern banks. The reason? Exposure to higher levels of pollution caused by burning free coal for winter fuel.

So discovered Professor Guojun He and his colleagues when they looked at the health impact of China’s Huai River Policy, which, since the 1950s, has been giving free or subsidized coal to residents living north of the river.

The study showed particulate pollution to be 46% higher just north of the river, leading to a reduction of average life expectancy of 3.1 years.

Pollution is a global health problem. Some 4.5 billion people worldwide are exposed to concentrations of airborne particulate matter (PM), at twice the level the World Health Organization considers safe, He’s report states.

More than 3.7 billion life years could be saved in China alone, he says, if the whole country complied with its own Class 1 standards for PM 10 (particulate matter 10 micrometres or less in diameter).

Here, the assistant professor of Economics, Environment and Sustainability, and Social Science at the Hong Kong University of Science and Technology (HKUST), whose work has been used to develop the air quality life index (AQLI), talks us through his research into China’s air quality and explains why pollution is one of the greatest environmental risks facing humanity.

Joining the red dots.
Image: PNAS

How was your research able to establish a link between pollution and life expectancy for the first time?

People have known air pollution is bad for health for a long time. But it’s quite challenging to quantify those health impacts, particularly in the long run. People migrate and, depending on their socio-economic status, they might be exposed to different levels of pollution. It's usually difficult to control all the factors that are correlated with air pollution.

So the study of the Huai River offers a unique setting to investigate this issue. The government drew a line saying, “OK, above this line, we are going to provide winter heating”, which brings a lot of coal. Below that line, there's no such system. Of course, it was intended as a benefit, but the unintended consequences were that northern China faces much higher levels of pollution. So after decades of exposure, we can use this very interesting setting to look at the impact of long-term exposure to air pollution on health.

Life expectancy on either side of the Huai River.
Image: PNAS

What’s happening in our bodies when we breathe in polluted air?

People are concerned with fine particulate matter, PM 2.5. Because the particles are so small, they can penetrate into your lungs and blood system. They can flow through your body and into the heart and brain. For example, if someone has pre-existing respiratory or cardiovascular diseases, PM 2.5 can trigger heart attack or stroke, among other things.

Your body has an inflammatory response to the particulate matter, which is what happens when something from outside your body goes into your system. And then the body tries to prevent it from doing harm, and that causes inflammation.

But it's not just physical: when the smoke particles go into your heart and even your brain, they’re also damaging your cognitive skills. So it's much more comprehensive than just inflammation. There were studies last year showing that pollution affects cognitive skills and productivity, but it’s not yet known how.

The World Health Organization's director general has described air pollution as a silent public health emergency. Do you agree?

Yes, but to some extent, I think they underestimate the potential harms of air pollution. But in general, I totally agree.

Methodologically speaking, the WHO and a lot of international organizations rely on estimates from what we call associational studies – looking at the association between air pollution and health. A lot of new studies which explore the so-called natural experiments and causal experiments are finding the impacts are larger than the associational studies.

“The potential harms of air pollution have been underestimated” – Professor Guojun He
Image: Handout/Guojunhe.com

How have we got to this situation?

It’s a complicated question, but I’ll try my best! The basic reason is when poor countries start to industrialize, because of the relative lags in environmental standards, they attract a lot of manufacturing, some of which is heavily polluting. But when people are poor, the willingness to pay for clean air is quite low. So both governments and the general public are not that concerned about air pollution until income gets to a certain level that people start to think, “OK, we want a better environment, we don't want those diseases”.

In economics, air pollution is often referred to as an “externality”, in which firms make production choices, but they don’t take into account the external cost imposed on the population. In such cases, if the government didn't do anything, then we would have observed a lot of bystanders harmed by those pollutants. It's like when someone is smoking, the bystanders are affected as well, but they’re not one of the transaction parties – the buyers or sellers.

You also researched the air in Beijing being cleaned up for the 2008 Olympic Games – what was the impact on mortality rates?

The international community had a lot of concerns around the air pollution in China, so they required Beijing to improve it. During a really short period of time, slightly more than a year, a lot of regulations were implemented, which resulted in a very dramatic improvement. The air quality during the Games was about 30% better than the previous year.

Those kind of improvements were almost unprecedented in history. So we had a study trying to look at whether the improvement in air quality during the Games affected people's health. And we found a huge improvement in population health, even in the short term. The number of people dying from cardio and respiratory diseases dropped immediately when the air became cleaner. And we compared cities that were affected by the regulations to those cities that weren’t. When the air quality improved, fewer people died from those diseases.

The estimated effect of implied Olympic regulations on monthly mortality rate

Image: Journal of Environmental Economics and Management

What’s the air quality in Beijing and other cities like now?

After the Games, from 2010 to 2013, the air quality in China deteriorated again. But in 2013, the government initiated the so-called war against pollution. Over the past five years, the air quality in northern Chinese cities, which were very polluted, on average has improved by more than 35%. So if you compare Beijing right now with five years ago, you can almost say the current air quality is even better than the level during the Olympic Games. It shows strong enforcement and better regulation can improve air pollution.

How has China achieved this?

It’s a rather comprehensive plan. It first looked at the sources of air pollution rain: cars, factories, and straw burning on farms. So, for example, they moved a lot of factories outside that core area and shut down and retired a lot of polluting plants. The government provides subsidies for farmers to recycle straw, so they don't have to burn it.

Who in society is most affected by air pollution?

If we look at the acute impacts, babies and elderly people are the most affected, because their bodies are most vulnerable to air pollution. But in the long run – so, many years rather than a few days or months – everyone is affected.

But in terms of exposure inequality, that's becoming an emerging issue in China, and maybe also in other developing countries. Richer people can afford to buy defensive equipment, at home and in the office, but poor people cannot. Richer people now spend 80% of their time indoors where air quality is much better than outdoors. But poor people don't have the capacity or the money to buy that equipment, so their exposure level is much higher. So the development of that defensive technology enlarges the environmental inequality between the poor and the rich.

Across different economies, how can we close the gap in terms of inequality over air pollution?

I have been thinking about that, too. Of course, we all care about air quality and the environment, but people also care about income and growth. I think the ideal way is to have a standard catered to the development stages of different countries.

So on the one hand, we say there should be an optimal level of regulation. We do not want regulation to be so stringent that it kills jobs. We also do not want it to be so loose that a lot of people are really affected by pollution. We need a more coordinated discussion.

Are you optimistic that, globally, we can reduce emissions to meet the World Health Organization guidelines on pollution?

In the long run, I think it's feasible, looking at current trends and the determination and consensus people have about air pollution. But we should also acknowledge the cost of reducing pollution is high, particularly for developing countries, which rely heavily on manufacturing.

Governments and academics should work together to find the cheapest way to do that. What China is doing – suspending production, relocating and shutting down firms – is quite expensive. But we should be able to figure out a low-cost way to achieve the targets. Right now, though, we lack scientific evidence on how to do this.

In every country, it’s ultimately the government’s responsibility to regulate polluting industries. There are now a lot of NGOs trying to publish pollution and emissions data online, which gives information to the public and puts pressure on the regulators to react. So we’re going to need collaboration between governments, NGOs and the general public to work on this issue.