Air quality refers to the measure of pollutants present in the air, which determines its suitability for living organisms and the environment. Good atmospheric purity is essential for maintaining public health and ecological balance. Poor air quality can lead to respiratory and cardiovascular diseases in humans, harm wildlife, and contribute to habitat issues like acid rain and climate change. Therefore, ensuring clean air is crucial for sustainable development and well-being.1
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What is the Air Quality Index (AQI)?
The air quality index (AQI) is a standardized tool used to communicate the quality of air and its potential health effects to the public. It measures key air pollutants such as particulate matter (PM2.5 and PM10), ozone, carbon monoxide (CO), sulfur dioxide (SO2), and nitrogen dioxide (NO2).
The AQI scale, ranging from 0 to 500, categorizes air quality into six levels of health concern, with values indicating increasing risk to people. It uses specific concentration breakpoints for each harmful substance to calculate an overall AQI value by offering a composite atmospheric condition indicator for daily public use.2
The AQI uses a color-coded system to represent air cleanliness levels. The scale ranges from green (good) to maroon (hazardous), with each color corresponding to a specific AQI range. Green indicates atmospheric health is satisfactory with little or no risk.
Yellow and orange signal moderate to diseased air for sensitive groups. Red, purple, and maroon represent increasingly unhealthy levels, with maroon indicating hazardous air composition, posing serious health risks for all individuals. The color-coded system helps people take necessary precautions based on real-time data.3
A recent study in Atmospheric Environment highlighted Hong Kong's AQ Health Index (AQHI) as an example of environmental air state risk communication.4 The AQHI has been used for nearly a decade to assess short-term health risks related to pollutant exposure.
While it focused on immediate health impacts like hospitalization risks, updates to the World Health Organization's Air Quality Guidelines (AQGs) suggested incorporating long-term health risks. Despite rising ozone levels, overall health risks in regions like Hong Kong have decreased due to reduced NO2 and PM.
Why is it Important to Understand Air Quality Index (AQI)?
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How is Air Quality Measured?
Ambient air condition is measured using monitoring stations that detect various pollutants, including PM2.5, PM10, ozone, CO, SO2, and NO2.
These stations collect real-time data, which is then analyzed to calculate the AQI based on the density of these polluting agents. The resulting AQI value is used to communicate the overall quality of the environment.5
Various methods are used for measuring atmospheric quality, including passive sampling devices, optical particle counters, electrochemical sensors, and meteorological stations.
Passive sampling devices gather pollutants over extended periods for later analysis, making them cost-effective for long-term assessments. Optical particle counters detect particulate matter by measuring light scattering.
While electrochemical sensors detect gases like NO2 and CO2, they are highly sensitive but require frequent calibration. Meteorological stations provide fundamental data on wind speed, temperature, and humidity, aiding in pollutant dispersion predictions.5
Air quality monitoring is managed by specific agencies in different countries. In the United States (US), the Environmental Protection Agency (EPA) oversees air quality standards, while in China, the Ministry of Ecology and Environment (MEE) monitors air pollution levels.7,8 In India, the Central Pollution Control Board (CPCB) and state agencies ensure air quality management.9
The United Kingdom (UK) relies on the Department for Environment, Food & Rural Affairs (DEFRA) for air quality monitoring, while Canada's Environment and Climate Change Canada (ECCC) controls air quality tracking.
Similarly, the Department of Climate Change, Energy, the Environment and Water (DCCEEW) oversees air quality standards in Australia.6 These agencies play crucial roles in mitigating environmental and health impacts caused by air pollution.
Pollution Control and Mitigation
Air pollution is controlled using various strategies to reduce emissions from vehicles, industries, and energy sources.
Emissions regulations are enacted to limit pollutants like PM, SO2, NO2, and volatile organic compounds (VOCs) from various sources, including vehicles and industrial facilities. By enforcing emission limits, automotive standards promote cleaner alternatives, such as electric vehicles (EVs) or low-emission vehicles.10
Industrial controls focus on shifting energy sources, regulating industrial emissions, and adopting cleaner technologies to minimize pollution.
A recent study in Nature Sustainability highlighted China's adoption of electric arc furnaces in steel production as an example of successful air pollution control efforts.11
These innovations have significantly reduced air pollution, showcasing the country's commitment to improving atmospheric hygiene while advancing industrial capabilities. Industries' shift toward renewable energy and natural gas further helps reduce pollution.
Transportation policies are crucial in reducing air pollution. These include free public transportation programs, congestion charges, and encouraging public transit over private cars.
Incentive and supportive policies, like subsidies for cleaner household fuels and renewable energy sources, are designed to reduce pollution on both domestic and industrial levels.
Punitive policies, such as tolls and fees for high-emission vehicles entering pollution-prone areas, aim to discourage high-pollution vehicles and further reduce traffic-related emissions. These strategies, implemented individually or in combination, significantly reduce air pollution across various regions.12
A study of six cities (Accra, Barranquilla, Beijing, Jakarta, Kampala, and New York City) highlights successful pollution control strategies. These cities have used various measures, such as adopting cleaner fuels, implementing vehicular emissions testing, and offering financial incentives for residents to switch from coal to cleaner energy.
Key strategies included engaging multiple stakeholders to foster collaboration, utilizing health data to inform and guide effective policies, and adopting technological advancements to enhance air quality monitoring systems. Each city provides insights into how coordinated efforts can significantly reduce air pollution and improve community health.13
Conclusion
Understanding air quality measurements is important to identify harmful pollutants and protect public well-being.
Monitoring the AQI allows timely action to minimize exposure, such as reducing outdoor activities, particularly in high-pollution zones. It also enables long-term planning to mitigate health risks by advocating for cleaner technologies and policies.
Regularly checking local AQI helps make informed decisions, safeguards overall health, and enhances community awareness about pollution control measures.
Continue Reading: How are Sensors Used in Air Pollution Monitoring?
References and Further Reading
1. Diener, A., & Mudu, P. (2021). How can vegetation protect us from air pollution? A critical review on green spaces' mitigation abilities for air-borne particles from a public health perspective - with implications for urban planning. Science of The Total Environment, 796, 148605. DOI: 10.1016/j.scitotenv.2021.148605, https://www.sciencedirect.com/science/article/pii/S0048969721036779
2. Rajan, D., & V Rohini. (2024). Exploring Advances in Machine Learning and Deep Learning for Anticipating Air Quality Index and Forecasting Ambient Air Pollutants: A Comprehensive Review with Trend Analysis. IEEE, DOI: 10.1109/icccnt61001.2024.10725099, https://ieeexplore.ieee.org/abstract/document/10725099
3. Horn, S. A., & Dasgupta, P. K. (2024). The Air Quality Index (AQI) is a tutorial review's historical and analytical perspective. Talanta, 267, 125260. DOI:10.1016/j.talanta.2023.125260, https://www.sciencedirect.com/science/article/abs/pii/S0039914023010111
4. Tang, K. T. J., et al. (2024). Update of Air Quality Health Index (AQHI) and harmonization of health protection and climate mitigation. Atmospheric Environment, 326, 120473. DOI: 10.1016/j.atmosenv.2024.120473, https://www.sciencedirect.com/science/article/abs/pii/S1352231024001481
5.Seesaard, T., Kamjornkittikoon, K., & Wongchoosuk, C. (2024). A comprehensive review of advancements in sensors for air pollution applications. Science of The Total Environment, 951, 175696. DOI: 10.1016/j.scitotenv.2024.175696, https://www.sciencedirect.com/science/article/abs/pii/S0048969724058522
6.Tewari, S., Pandey, N., & Dong, J. (2024). Air Quality Legislation in Australia and Canada—A Review. Challenges, 15:4, 43. DOI: 10.3390/challe15040043, https://www.mdpi.com/2078-1547/15/4/43
7. Robert. B., (2024). Public Health Relevance of US EPA Air Quality Index Activity Recommendations. Jamanetwork.com. https://jamanetwork.com/journals/jamanetworkopen/article-abstract/2817296
8. Lyu, Y., & Yang, L. (2024). Environmental monitoring and enforcement in China: an economic perspective review. China Economic Journal, 17:1, 3–25. DOI: 10.1080/17538963.2023.2300863, https://www.tandfonline.com/doi/abs/10.1080/17538963.2023.2300863
9. Ravi Prakash Srivastava, Kumar, S., & Tiwari, A. (2024). Continuous emission monitoring systems (CEMS) in India: Performance evaluation, policy gaps and financial implications for effective air pollution control. Journal of Environmental Management, 359, 120584–120584. DOI: 10.1016/j.jenvman.2024.120584, https://www.sciencedirect.com/science/article/abs/pii/S030147972400570X
10. Jonidi Jafari, A., Charkhloo, E., & Pasalari, H. (2021). Urban air pollution control policies and strategies: a systematic review. Journal of Environmental Health Science and Engineering, 19:2, 1911–1940. DOI: 10.1007/s40201-021-00744-4, https://link.springer.com/article/10.1007/s40201-021-00744-4
11. Qian, H., Xu, S., Cao, J., Ren, F., Wei, W., Meng, J., & Wu, L. (2021). Air pollution reduction and climate co-benefits in China’s industries. Nature Sustainability. https://doi.org/10.1038/s41893-020-00669-0, https://www.nature.com/articles/s41893-020-00669-0
12. Dey, S., & Mehta, N. (2020). Automobile pollution control using catalysis. Resources, Environment and Sustainability, 2, 100006. DOI: 10.1016/j.resenv.2020.100006, https://www.sciencedirect.com/science/article/pii/S2666916120300062
13. Six Cities Successfully Reduce Toxic Air Pollution By As Much As 50%. (2023). Vital Strategies. https://www.vitalstrategies.org/mega-cities-successfully-reduce-toxic-air-pollution-by-as-much-as-50/
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