Nanjing's Pollution Problem: A Critical Analysis

Nanjing, China, is facing a critical level of air pollution, with a recent air quality index (AQI) of 199. The main pollutant is O3, and the PM2.5 concentration is currently 1.4 times the World Health Organization's annual guideline value. This means that even healthy individuals may experience symptoms after short exposures to the polluted air.

Nanjing's air quality index (AQI)

On May 22, 2025, Nanjing's overall AQI was 72, indicating that the air quality was generally acceptable. However, sensitive groups may experience minor to moderate symptoms from long-term exposure. The individual pollutant indexes for this day were as follows: PM2.5 AQI of 72, PM10 AQI of 38, NO2 AQI of 3, SO2 AQI of 2, CO AQI of 4, and O3 AQI of N/A.

It is important to note that the World Health Organization (WHO) has specific guidelines for annual PM2.5 concentrations, and Nanjing's PM2.5 concentration is currently 1.4 times higher than this guideline value. This means that the air quality in Nanjing may still pose health risks, especially for sensitive groups and with prolonged exposure.

Real-time air quality data for Nanjing is available through various sources, such as online maps and plugins for web browsers. These tools provide up-to-date information on the city's AQI and help individuals make informed decisions about their outdoor activities. It is always advisable to stay informed about the local air quality and take necessary precautions to protect one's health.

Overall, while Nanjing's AQI may fluctuate and sensitive groups need to take extra precautions, the city's air quality is generally acceptable for most individuals to continue their normal outdoor activities.

PM2.5 concentration

PM2.5 refers to fine particulate matter that is 2.5 microns or less in diameter. It is a mixture of solid and liquid particles that are suspended in the air. These particles are so small that they can be inhaled and deposited in the lungs, which can lead to adverse health effects. Sources of PM2.5 include emissions from the combustion of gasoline, oil, diesel fuel, or wood, as well as industrial processes and motor vehicle exhaust.

In Nanjing, the PM2.5 concentration is currently 1.4 times the World Health Organization's annual PM2.5 guideline value. While I cannot find the exact concentration, a PM2.5 AQI of 72 is given. This is a measure of air quality, with a higher number indicating worse air quality.

The health risks associated with PM2.5 exposure include respiratory and cardiovascular issues. Short-term exposures of up to 24 hours have been linked to premature mortality, increased hospital admissions for heart or lung causes, acute and chronic bronchitis, asthma attacks, and restricted activity days. People with pre-existing breathing and heart problems, children, and the elderly may be especially sensitive to the effects of PM2.5 pollution.

To protect public health, air quality monitors measure PM2.5 concentrations, and this data is used by various agencies to ensure that PM2.5 levels are within safe limits. In indoor spaces, HEPA-grade filters and air purifiers can help manage PM2.5 levels.

Overall, while I cannot provide an exact concentration for PM2.5 in Nanjing, the AQI of 72 indicates that the air quality is poor, and the PM2.5 concentration exceeds the World Health Organization's guidelines, which can have negative implications for the health of the city's residents.

NO2 and SO2 levels

NO2 and SO2 are two of the major air pollutants in Nanjing, China. In 2019, the Nanjing government implemented stricter atmospheric control measures, but air pollution unexpectedly increased. A study that year used Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) to observe the vertical structures of the precursors of the city's air pollution, including NO2 and SO2. The study found that the concentration of NO2 was primarily within 200 metres of the surface, while SO2 extended to higher altitudes. The potential source contribution function (PSCF) was then used to analyse the source distributions in different atmospheric layers during different seasons.

The results of the 2019 study revealed that downtown Nanjing and the area to its north were the most important potential source areas for NO2 and SO2. Additionally, the results indicated that there were significant SO2 transports from the northwest and west orientations, while most NO2 transports were from the west and north. The study also found that the performance of Nanjing in terms of air quality was terrible compared to other cities in the Yangtze River Delta.

While specific figures for NO2 and SO2 levels in Nanjing are scarce, one source provides air quality data for the city as of May 22, 2025. According to this source, the air quality index for NO2 was 3, while the index for SO2 was 2. However, it is unclear what units these figures are in and how they compare to safe or acceptable levels.

SO2 emissions have various harmful effects on the environment and human health, and China significantly contributes to global SO2 emissions. SO2 emissions in China have been studied using network analysis, which can simultaneously analyse spatial and temporal relationships and is suitable for studying interrelationships in terms of graphic nodes and edges. This approach can help lay the foundation for policymaking to improve environmental conditions in the country.

Nanjing's pollution compared to China

Nanjing, China, has a history of poor air quality. The city's air pollution is measured by its Air Quality Index (AQI), which takes into account various pollutants, including PM2.5 (fine particulate matter), PM10 (respirable particulate matter), NO2 (nitrogen dioxide), SO2 (sulfur dioxide), CO (carbon monoxide), and O3 (ozone).

At the time of writing, Nanjing's overall AQI was 72, with the main pollutant being O3. While this is below 100, which indicates hazardous air quality, it is still well above the World Health Organization's annual PM2.5 guideline value by 40%. This highlights that even though Nanjing's air pollution may not be as severe as other cities in China, it still poses a potential health risk to residents and visitors.

Nanjing's air pollution is influenced by a range of factors, including industrial activities, vehicle emissions, and weather conditions. The city has implemented various measures to improve air quality, such as real-time air quality monitoring and the promotion of public transportation and renewable energy sources.

In comparison to other cities in China, Nanjing's air quality is generally considered to be better than some of the country's most polluted cities, such as Beijing and Shanghai. However, it is important to note that air pollution is a complex issue that can vary significantly from one city to another, depending on a multitude of factors.

Overall, while Nanjing's air pollution may not be as severe as some other cities in China, it still exceeds recommended health guidelines and requires continued efforts to improve and maintain air quality for the benefit of its residents and the environment.

Health recommendations

The air pollution in Nanjing is a health concern for residents and visitors. The PM2.5 concentration in Nanjing is 1.4 times higher than the World Health Organization's annual guideline value. The air quality index (AQI) is often in the "very unhealthy" range, with main pollutants including PM2.5, PM10, NO2, and O3.

• Monitor air quality updates and try to stay indoors when the air pollution levels are particularly high. Avoid outdoor activities, especially strenuous exercise, to minimize the risk of inhaling harmful pollutants.
• If you must go outside during periods of high air pollution, consider wearing a well-fitting and certified air mask or respirator. Look for masks that can filter out fine particulate matter, such as N95 or P100 respirators.
• Invest in an indoor air purifier for your home or office. This can help reduce the levels of indoor air pollutants and create a cleaner air environment, especially if you spend a significant amount of time indoors.
• Keep windows and doors closed during periods of high air pollution to prevent outdoor air from entering your home. Using air conditioning or air filtration systems can also help maintain better indoor air quality.
• Stay informed about the pollen count in Nanjing, especially if you have allergies or respiratory conditions. Take necessary precautions, such as taking allergy medication or using air purifiers with HEPA filters, to minimize the impact of pollen on your health.
• If you experience any unusual or persistent symptoms, such as respiratory problems, headaches, or eye irritation, seek medical advice. Air pollution can exacerbate existing health conditions, so it is important to prioritize your health and well-being.
• Stay hydrated and maintain a healthy diet rich in antioxidants. This can help strengthen your body's natural defenses and potentially reduce the impact of air pollution on your overall health.
• If you are a smoker, consider quitting smoking, as smoking can further irritate the respiratory system and increase your risk of developing health complications from air pollution.
• When planning outdoor activities or events, try to choose locations that are away from busy roads or industrial areas, as these areas typically have higher levels of air pollution. Opt for green spaces or less polluted environments when possible.
• Be mindful of vulnerable populations, such as children, the elderly, or individuals with pre-existing health conditions. They may be more susceptible to the effects of air pollution, so take extra precautions to protect their health and well-being.

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