The world is experiencing a boom in megacities. According to the United Nations, there are currently around 30 urban areas in the world with populations greater than 10 million, mainly in Southeast Asia, Africa and the Middle East. The UN expects the number of these so-called megacities to increase over the next decade, especially in China and India. As these metropolises grow in size and number, scientists are scrambling to understand what impact they will have on the world as a whole, especially when it comes to air pollution.
In a study published last week in Scientists progress, a group of international researchers examined satellite data on air pollution from 2005 to 2018 in 46 projected future megacities in tropical regions of Asia, Africa and the Middle East. By examining month-by-month imagery of pollutants such as nitrogen dioxide, formaldehyde, ammonia and fine particulates, scientists observed that cities were becoming increasingly polluted.
“The bottom line, in a nutshell, is that most of these fast-growing cities actually show increases in almost all of these pollutants across the board,” says study author Karn Vohra, a geography researcher. at University College London. “What surprised us was the magnitude of these changes.”
[Related: Living in the same city doesn’t mean breathing the same air.]
In 40 of the 46 cities studied, the exposure of the urban population to air pollution increased 1.5 to 4 times between 2005 and 2018. Some of these results run counter to existing studies on the quality air, which focused on regional bands or national data. Examination of data at this scale clearly showed that certain trends in air pollutants were two to three times more pronounced in megacities than in surrounding areas. For example, says Vorha, recent studies have indicated a decrease in nitrogen dioxide pollution across Africa due to less reliance on burning biofuels. But in cities where most people live, this new study shows that pollution is getting worse.
“We continue to shift air pollution from region to region, rather than learning from past mistakes and ensuring that rapid industrialization and economic development do not harm public health. “, co-author of the study Eloise Marais, associate professor in physical geography at UCL, said in a press release.
Poor air quality can contribute to a plethora of health problems, from asthma to death. Throughout the timeline of their observations, the researchers were able to estimate the number of premature deaths caused by air pollution: 180,000 in 2018, a 62% increase from 2005. The highest increase rapid took place in Dhaka, Bangladesh, as well as a number of cities in India, including Mumbai, Bangalore, Kolkata, Hyderabad, Chennai, Surat, Pune and Ahmedabad.
“If…these trends persist, the situation will certainly get worse,” says Vohra. “Let’s say the air quality doesn’t change. Even so, the population of these cities is growing at a very rapid rate. Also in this case, premature mortality will increase.
[Related: Better vehicle emissions standards may have saved thousands of Americans.]
This does not mean that all hope is lost. Urban residents can help by relying more on public transit to keep cars off the road, Vohra notes.
On an even larger scale to protect residents, it’s crucial that policymakers and leaders in growing communities develop tough pollution measures (and actively monitor them) as the industry continues to infiltrate. Start a movement toward cleaner energy sources like wind and solar, and these cities will already be on the path to cleaner air.
“Many studies have predicted that these will be megacities, most people will live in the tropics and live in these cities,” Vohra said. “If we know something like this is going to happen, we should definitely implement strict anti-pollution measures immediately.”
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