As China’s air pollution increases, so does sadness

China landscape in smog
© iStock/Hung_Chung_Chih

China has been struggling to tackle high pollution levels that are crippling its major cities, now according to MIT, China’s air pollution may be contributing to low levels of happiness.

A recent study by researchers at Chinese Hong Kong University has found that air pollution in the country causes an average of 1.1 million premature deaths each year and costs its economy $38 billion (~€33.47 billion). Now researchers at Massachusetts Institute of Technology (MIT), USA, have discovered that air pollution in China’s cities may be contributing to low levels of happiness amongst the country’s urban population.

Tackling air pollution

Despite an annual economic growth rate of 8%, China’s urban population are not experiencing high satisfaction levels as would be expected.

Alongside inadequate public services, soaring house prices, and concerns over food safety, air pollution, caused by the country’s industrialisation, coal burning, and increasing use of cars, has had a significant impact on quality of life in urban areas.

Research has previously shown that air pollution is damaging to health, cognitive performance, labour productivity, and educational outcomes. But according to researchers, severe air pollution also has a broader impact on people’s social lives and behaviour.

To avoid high levels of air pollution, for example, individuals may move to cleaner cities or green buildings, buy protective equipment such as face masks and air purifiers, and spend less time outdoors.

The emotional cost of pollution

Xiaonan Zhang of Tsinghua University in Beijing, China, explains: “Pollution also has an emotional cost.”

“People are unhappy, and that means they may make irrational decisions.”

On polluted days, people have been shown to be more likely to engage in impulsive and risky behaviour that they may later regret, possibly as a result of short-term depression and anxiety.

“So, we wanted to explore a broader range of effects of air pollution on people’s daily lives in highly polluted Chinese cities.” adds Zhang.

Measuring happiness

The researchers used information on urban levels of ultrafine particulate matter, PM 2.5 concentration, from the daily air quality readings released by China’s Ministry of Environmental Protection.

Airborne particulate matter has become the primary air pollutant in Chinese cities in recent years, and PM 2.5 particles, which measure less than 2.5 microns in diameter, are particularly dangerous to people’s lungs.

And to measure daily happiness levels for each city, the team applied a machine-learning algorithm to analyse the 210 million geotagged tweets from China’s largest microblogging platform, Sina Weibo.

“Social media gives a real-time measure of people’s happiness levels and also provides a huge amount of data, across a lot of different cities.” Zheng says.

The tweets cover a period from March to November 2014. For each tweet, the researchers applied the machine-trained sentiment analysis algorithm to measure the sentiment of the post. They then calculated the median value for that city and day, the so-called expressed happiness index, ranging from 0 to 100, with 0 indicating a very negative mood, and 100 a very positive one.

Finally, the researchers merged this index with the daily PM2.5 concentration and weather data.

So, what did the research actually find?

There was a significantly negative correlation between pollution and happiness levels. What’s more, women were more sensitive to higher pollution levels than men, as were those on higher incomes.

Individuals from the very cleanest and very dirtiest cities were the most severely affected by pollution levels.

The researchers explain that this may be because those people who are particularly concerned about their health and air quality tend to move to clean cities, while those in very dirty cities are more aware of the damage to their health from long-term exposure to pollutants.

Zheng now hopes to continue her research into the impact of pollution on people’s behaviour, and to investigate how China’s politicians will respond to the increasing public demand for cleaner air.

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