Air quality at Beijing Railway Station from December 17-22 (left to right), 2016 (XINHUA)

The air pollution problems that Beijing and many other cities in China are currently facing have been well-documented, both domestically and internationally. Environmental issues, including air pollution, is one of the key topics discussed at the Two Sessions of China's National People's Congress and Chinese People's Political Consultative Conference National Committee in Beijing.

Roy Harrison OBE of Birmingham University in the UK is an expert on air pollution; its sources, the atmospheric processes that create air pollution, and its health effects. Harrison is involved with a major UK-Chinese field study, "Air Pollution and Human Health," funded by the UK Natural Environment Research Council (NERC) and Medical Research Council (MRC), and the National Natural Science Foundation of China (NSFC). The consortium of UK universities are collaborating with Tsinghua and Peking Universities, as well as the Institute for Atmospheric Physics and the Guangzhou Institute for Geochemistry under the Chinese Academy of Sciences.

Harrison explains what the study involves, "It is a 50/50 Chinese-UK scientific study. It starts with studying the emissions, goes through the atmospheric processes, then there are some studies on exposure and the effects on health. I'm more involved at the emissions and atmospheric processing end of it. What we will generate is a high-quality numerical model which we can use to run tests. For example, if we could cut the emissions from certain types of road vehicles by 50 percent, what would the impact on air pollutant concentrations and people's health be?"

These results could help to inform policy decisions, as Harrison continues, "We are looking to generate a level of knowledge that will allow us to predict how mitigation strategies will improve air quality."

Meanwhile, the studies on the effects of pollution on health can help to improve our understanding of the dangers of smog.

"The health effects studies are designed to generate exposure response functions that measure exposure to pollutants in Beijing and then the health outcomes from those exposures. This will add to the body of knowledge about the health effects of breathing polluted air," Harrison explains.

The UK has of course experienced its fair share of air pollution problems. From the beginning of the industrial revolution in the eighteenth century, London and other major UK cities began to confront issues of poor air quality. In the early twentieth century, these clouds of smog were known as "pea soupers" due to their black-yellow colour that reminded some people of that particular soup.

The UK and London's most infamous air pollution event was the Great Smog of 1952. Cold weather in the capital resulted in people burning more coal to keep warm. Combined with low wind, these conditions created serious smog across London from Friday 5 December until Tuesday 9 December 1952.

Harrison says that the pollution London experienced in the mid-twentieth century was very different to the pollution that Beijing endures today.

"The 1950's air pollution in London was made up of low-level emissions from chimneys. People burned coal in fireplaces in their homes which created smoke and sulphur dioxide pollution," Harrison explains. "Beijing's problems are more complex. Local coal burning is not a major source of pollution in Beijing. A lot of the pollution comes from outside the city, particularly from Hebei province, and much of it is secondary pollutants: pollutants that are formed in the atmosphere through reactions with other pollutants. There are a lot of sulphates, nitrates and organic matter, all of which come from the oxidation of gases. There is also some contribution from road traffic emissions in Beijing, which wasn't such a big issue in 1950's London."

The terrible health effects of the 1952 Great Smog (around 12,000 people are estimated to have died prematurely from the five-day smog) spurred the UK Government into action. The Clean Air Act 1956 attempted to improve air quality in the UK's major cities. Can London's experience of battling air pollution over fifty years ago help Beijing fight smog today?

"I don't think the experience from the 50's and 60's helps us very much because the Clean Air Act effectively banned smoky fuels from cities and that is not really an issue for China. I think they need to look at the more recent experience of Western Europe," he illustrates.

Western European cities, including London, are still dealing with the problem of air pollution in 2017. The pollution is different from the pollution fifty years ago, and is also different from air pollution in China.

"If we look at the various pollutants, the one that is causing a lot of concern in London is nitrogen dioxide because the UK is in breach of European Union [EU] limit values. Concentrations of nitrogen dioxide in London are a little bit lower than in Beijing, but they are comparable," Harrison explains.

"Sulphur dioxide is at very low levels in London but is still at quite appreciable levels in Beijing, to the extent that it may be causing some effects on health in China, whereas in London I should think it is negligible. However, the pollutant causing the biggest public health issues [in both cities] is particulate matter [PM]. PM levels in Beijing are on average much worse than in London."

Harrison suggests that the health effects from PM pollution are serious: "Short-term effects, when air pollution levels are high for a day or so, include increases in deaths and hospital admissions. Obviously there are respiratory diseases such as the exacerbation of asthma or cases of chronic bronchitis, but also cardiovascular diseases such as heart disease. Strokes and heart attacks are more prevalent on high pollution days. In terms of overall public health impact, the biggest effect is the reduction of life expectancy. For people who are unwell or elderly, it is an additional stress factor and they may die younger. On average in London we estimate that there is a loss of life expectancy of somewhere around 6 months for breathing airborne particles, averaged across the whole population. Of course, it is more for some people and less for others."

The nature of the beast has changed and so too have the ways of dealing with air pollution. The EU sets regulations on air quality levels that member countries are required to meet.

Harrison believes that regulating emissions from industrial sources in China is key.

"What would have the biggest impact in China would be to reduce the emissions of sulphur dioxide and oxides of nitrogen because that would cut the sulphate and nitrate levels in the air. The major sources of oxides of nitrogen are heavy industry and road traffic. The biggest source of sulphur dioxide is industry and power stations; burning coal and oil. China needs to improve the controls on the industrial sources of those pollutants in order to deal effectively with the problem of smog."

The most pressing concern in London now is trying to limit nitrogen dioxide particles in the atmosphere, which come from the burning of diesel fuel in cars and heavy-duty vehicles. The UK government has proposed to ban vehicles which use older, dirtier diesel from town centres in order to address this problem. Harrison argues that this problem is not so significant in Beijing, where most cars use petrol, not diesel. However, there are heavy-duty vehicles like trucks and buses which do use diesel, which can be tackled through the uptake of new technologies.

Harrison elaborates, "Using natural gas as a fuel could be effective. Also, some of the technologies that try to remove the nitrogen oxides from exhaust fumes appear to be very effective. So if you legislated for those newer control technologies you could clean up the exhausts considerably. There is some evidence from London that the new buses that have got these technologies emit less oxides of nitrogen than diesel cars. There is a technology called Selective Catalytic Reduction [SCR] which removes nitrogen oxides quite effectively if it is applied well."

Therefore, Harrison argues that stricter controls on industry emissions and the uptake of new vehicle technologies could help to reduce air pollution in Beijing. So, can Beijing overcome its current smog problems and reach the standards of air quality seen in Western European cities?

"I think it is very achievable but it will take decades to do it," he says. "These are not things that can be achieved quickly. In the case of London, we still haven't resolved the problems and we've been tackling them since the 1950's. That is a very long time, so China can learn from our experience and it can take more radical action more quickly than in the UK but I suspect that it is still going to be 20 or 30 years before China can get air pollution concentrations down to those comparable with Western Europe."