WASHINGTON, July 19 (Xinhua) -- Rapid urbanization in China is not contributing to air pollution, but actually may have brought health benefits for the hundreds of millions of people who have moved into cities, preventing an estimated 450,000 premature deaths over the last three decades, a new study said Wednesday.
That's because after migrating into the city, many Chinese switched from crop residue, firewood and low-quality coal to cleaner fuel types such as electricity and natural gas, which considerably lessened regional emissions and cut their exposure to harmful particles less than 2.5 micrometers in size, known as PM2.5, according to the study published by the U.S. journal Science Advances.
"In the past, it was generally thought that population migration into cities would lead to the accumulation of pollutants and the affected persons in a small space, increasing the exposure in regional, high-density population areas, thereby raising health risks," Professor Shu Tao at Peking University, who led the study, told Xinhua.
"This understanding ignores the the positive impact of energy structure changes on health," Tao said.
For the study, Tao's team investigated the influence of rural to urban migration on pollutant emissions from direct residential and transportation energy consumption sources and population exposure since 1980, when urbanization began to accelerate following the initiation of the Chinese economic reform and opening policy.
The researchers were able to track migration using the unique registration system of citizens in China, known as hukou, and adjusted for migrants living in cities who are "unregistered" and have limited access to urban energy infrastructure, social welfare and other city services.
They found that as a result of increased migration, the national average PM2.5 exposure concentration in 2010 was reduced by 3.9 ug/m3, which corresponded to an annual reduction of 36,000 premature deaths.
Overall, 450,000 premature deaths were avoided between 1980 and 2010, indicating "a health benefit from the three decades of migration," the study said.
Despite the net benefit on a national level, pollution levels associated with migration are still on the rise in megacities such as Beijing and Shanghai, which are experiencing massive immigrations that increase local emissions, it noted.
When looking into the future, the researchers predicted the country's urbanization rate will increase up to 70 percent by 2030 and corresponding pollutant exposure levels may drop by up to 8.8 ug/m3, doubling the current benefits on air quality and health.
