Chengdu's Air Quality: A Pollution Problem?

Chengdu, a major city in Western China, has been facing issues with air pollution. The city's topography, characterised by still air and limited wind, coupled with a growing number of vehicles and factories, has led to the accumulation of pollutants. This has resulted in Chengdu being ranked among the top cities in respiratory mortality and lung cancer deaths related to fine particulate matter (PM2.5). While there have been efforts to improve air quality, such as reducing coal reliance and implementing cleaner mobility solutions, the city still experiences seasonal variations in pollution levels, with winter months typically recording higher pollutant emissions.

Chengdu's air quality index is currently unhealthy

Chengdu, a major city in Western China, currently has an unhealthy air quality index rating. The city's air pollution is caused by a variety of factors, including vehicle emissions, factory effluence, and coal burning. With a population of over 16 million people, the number of cars, motorbikes, trucks, lorries, and buses on the road has significantly increased in recent years, contributing to the poor air quality.

The topography of Chengdu, located on the western edge of the Sichuan Basin, also plays a role in the city's air pollution. The area experiences little wind from the Mongolian Plateau or the Indian Ocean, allowing polluted air to accumulate in the basin without dispersing. This still air, combined with the high humidity levels, traps the smoke and haze generated by vehicles, further degrading the air quality.

Data from Nanjing University underscores the severity of the issue, revealing that Chengdu was among the top three cities in terms of respiratory mortality related to fine particulate matter (PM2.5) and lung cancer deaths in 2013. The high levels of PM2.5 and O3 pollution in Chengdu have been linked to hundreds of deaths, with 351 attributed to PM2.5 and 328 to O3 in January and July 2017. The economic losses caused by these pollutants were also significant, amounting to 0.0974% and 0.0910% of Chengdu's gross regional product (GDP) in the same period.

While Chengdu has implemented policies that have led to reductions in air pollution and greenhouse gas emissions, the city's air quality remains a concern for its residents. The current unhealthy air quality index rating serves as a reminder that more action is needed to protect the health and well-being of those living in Chengdu.

PM2.5 and O3 are common pollutants in Chengdu

Chengdu, a major central city in Western China, has been facing air pollution issues common to cities undergoing rapid development. PM2.5 and O3 are among the common pollutants in Chengdu, and they can easily affect human health.

PM2.5, or fine particulate matter, is known to be one of the most important species causing air pollution in China. These airborne particles have an aerodynamic diameter of less than 2.5 µm and can have multiple direct and indirect effects on human health, visibility, ecosystems, and the Earth's climate. In Chengdu, the daily average concentration of PM2.5 is adopted as a measure of air quality. According to data from 2019, the city's worst readings of PM2.5 pollution occurred in December, January, and February, with readings well above the recommended threshold of 15 μg·m−3 as per the World Health Organization's Global Air Quality Guidelines (AQG 2021). The sources of PM2.5 in Chengdu include combustion sources, vehicular emissions, dust, and secondary aerosols, with the latter being the highest contributor.

O3, or ozone, is another pollutant of concern in Chengdu. While O3 levels tend to be lower in the summer and winter, they can still have a significant impact on air quality. The maximum eight-hour moving average concentration of O3 is used as a measure, and the daily threshold is set at 60 μg·m−3 by the World Health Organization.

The southeast area of Chengdu, dominated by residential and industrial sectors, is particularly affected by high emissions. The unique topography of the Sichuan Basin, where Chengdu is located, also contributes to the accumulation of pollutants. The basin is surrounded by mountains, which hinder the diffusion and removal of pollutants, while higher humidity levels and lower wind speeds allow smoke and haze to linger in the city.

To address the air pollution issues caused by PM2.5 and O3, Chengdu has been implementing pollution reduction policies. These policies have shown some success, as mass concentrations of PM2.5 have significantly decreased year by year from 2016 to 2020. However, there is still a need to prioritize key pollutants and sources in future policies to further improve the air quality in Chengdu.

The primary sources of Chengdu's air pollution

Chengdu, a major city in Western China, is facing air pollution issues common to rapidly developing cities. The primary sources of Chengdu's air pollution are vehicular emissions, factory effluence, and coal burning. With a population of 16.3 million, the city has witnessed a surge in the number of vehicles, including cars, motorbikes, trucks, lorries, and buses. The increased vehicle density, coupled with the city's geographical location in the Sichuan basin, which reduces wind flow and increases humidity, allows vehicle emissions to accumulate. This accumulation results in elevated levels of nitrogen dioxide and sulfur dioxide, which are harmful to human health.

Vehicular emissions are a significant contributor to Chengdu's air pollution, particularly from personal cars, motorbikes, and heavy-duty vehicles. The number of vehicles in the city has been increasing rapidly, with an estimated monthly rise of 20,000 vehicles in 2011. This surge in vehicle density has led to higher levels of nitrogen dioxide and sulfur dioxide in the atmosphere, which are released from vehicle engines and the incomplete combustion of fossil fuels.

Factory emissions also play a role in Chengdu's air pollution. The city serves as a business, financial, and transportation hub for southwest China, and industrial activities contribute to the release of pollutants. The southeast area of Chengdu is particularly affected by emissions from residential and industrial sectors.

Additionally, coal burning is another source of air pollution in Chengdu. The combustion of coal contributes to the presence of harmful compounds and particulate matter in the air, such as nitrogen dioxide and sulfur dioxide. These pollutants have detrimental effects on human health, including triggering asthma attacks and causing damage to the lungs and heart.

Furthermore, seasonal variations impact Chengdu's air quality. According to studies, air pollution levels tend to be higher in winter than in summer, with PM2.5 being the primary pollutant during the colder months. The Multi-resolution Emissions Inventory of the Chinese Model (MEIC v1.3) in 2017 confirmed that Chengdu's pollutant emissions are generally higher in winter.

Chengdu's air pollution and its impact on public health

Chengdu, a major central city in Western China, has been facing issues with air pollution, which has had a significant impact on public health. The city's geographical location in the Sichuan Basin contributes to the problem, as it experiences less wind and higher humidity levels, allowing pollutants to accumulate. The primary sources of air pollution in Chengdu are vehicle emissions, factory effluence, and coal burning. The number of vehicles on the roads has been increasing, leading to higher levels of fumes and emissions, particularly in high-traffic areas.

The air quality in Chengdu has been monitored through various indices, such as the Air Quality Index (AQI) and the Real-time Air Quality Index. These indices measure different pollutants, including PM2.5 (fine particulate matter), PM10 (respirable particulate matter), NO2 (nitrogen dioxide), SO2 (sulfur dioxide), CO (carbon monoxide), and O3 (ozone). The data shows that Chengdu's air quality is generally worse in the winter months, with higher readings of PM2.5 and O3 pollutants. For example, in January and July 2017, PM2.5 pollution accounted for 351 deaths, while O3 pollution accounted for 328 deaths. The economic losses caused by these pollutants were also significant, with health-related costs impacting the city's gross regional product.

The impact of air pollution on public health in Chengdu has been a growing concern. According to a study by Nanjing University, Chengdu was among the top three cities in China for respiratory mortality related to fine particulate matter (PM2.5) and lung cancer deaths in 2013. The high levels of air pollution have led to increased awareness among the public, with masks and air purifiers becoming popular purchases. Efforts to improve air quality in Chengdu have been made, and a five-year plan implemented from 2013 to 2017 resulted in significant reductions in air pollution and greenhouse gas emissions. This improvement was largely due to a decrease in the city's reliance on coal, with a shift towards hydropower, solar, wind, and natural gas energy sources.

Despite these efforts, Chengdu continues to experience periods of poor air quality, particularly during the winter months. The limited research available on the regional emissions and health effects of air pollution in Chengdu indicates a need for further study to fully understand the impact on public health. The development of additional air quality control strategies is crucial to mitigate the detrimental effects of air pollution on the health and well-being of Chengdu's residents.

Efforts to improve Chengdu's air quality

Chengdu, like many cities in China, faces air pollution issues typical of cities undergoing rapid development, including large-scale rural-urban migration and the associated increase in vehicles. The city's geographical location in the Sichuan basin also means less wind and higher humidity, allowing vehicle emissions to accumulate.

Chengdu has made significant efforts to improve its air quality. Between 2013 and 2018, the city undertook a range of measures to tackle air pollution, and the air quality is reported to be slowly getting better. In 2024, Chengdu achieved an 18% reduction in PM2.5 concentrations from the previous year, meeting the national standard for the first time. This remarkable improvement can be attributed to several initiatives:

• Controlling emissions from mobile sources: Chengdu accelerated the electrification of public-sector vehicles, tightened regulations on fuel-powered vehicles, and promoted new-energy heavy-duty commercial vehicles.
• Strict industrial pollution controls: The city supported ultra-low emission upgrades in the cement, petrochemical, and steel sectors.
• Construction sector dust mitigation: Chengdu established over 1,300 "green benchmark" sites to minimize dust emissions from construction activities.

These comprehensive measures have not only improved Chengdu's air quality but also provided a model for other urban areas to follow. Chengdu's successful experience in air pollution control has offered valuable insights for other cities striving for cleaner air.

Moving forward, Chengdu and other cities in China should continue to optimize industrial structures, strengthen transportation emission controls, and further tighten air quality standards. By doing so, they can foster sustainable economic growth, enhance public health, and pave the way for a cleaner and more sustainable future.

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