Spot Check Raises Doubts on Accuracy of AQI Data
Concerns are mounting regarding the accuracy of air quality data, as inconsistencies and questionable practices observed at monitoring stations across Delhi raise doubts about the reliability of official Air Quality Index (AQI) figures. As the city grapples with thick smog, and residents report respiratory problems, a recent ground check conducted by the Times of India (TOI) has exposed discrepancies that could be influencing the readings.
One concerning observation was the practice of repeatedly dousing the area around the monitoring unit with water using high-pressure hoses at Anand Vihar, a known pollution hotspot. While officials on-site claimed this was routine dust suppression, experts warn that such measures can distort AQI readings. Similarly, the location of certain monitoring stations raises questions. For instance, the Dilshad Garden station, which reported a relatively better AQI compared to other areas, is situated deep within a forested patch of a medical institute, shielded from city dust and traffic. The Mandir Marg station is also located within a green belt and is largely inaccessible, while the ITO monitor sits next to a regularly sprinkled area.
Further fueling the skepticism, readings from two stations in Lodhi Road, merely blocks apart, differed by as much as 80 points at the same time. These discrepancies highlight potential issues with the representativeness and credibility of the capital's air quality network.
In response to these concerns, Delhi's environment minister, Manjinder Singh Sirsa, defended the data, stating that sprinkling is a natural and necessary method of dust suppression employed throughout the city, including around monitoring stations. He asserted that these measures are successfully controlling pollution. However, experts caution that excessive sprinkling near stations is unethical and can mislead both the public and policymakers. According to M P George, former additional director of the Delhi Pollution Control Committee, these stations are designed to capture air quality over a two to three-kilometer radius and are approved by all relevant agencies.
Concerns about AQI accuracy aren't limited to specific locations or practices. Some experts point out that low-cost AQI monitors may not be well-calibrated, leading to variations in readings even when placed next to each other. Furthermore, many sensors have a significant error rate, and the AQI calculation considers factors like temperature and humidity, which can cause inaccurate spikes. Google Maps, which recently introduced an air quality overlay, draws data from satellites and ground-based stations. However, satellite data may not capture local pollution nuances, and the platform's data may not always update in real-time, showing averages rather than immediate changes. Different countries also use different AQI systems, which can lead to variations in reported air quality.
These inconsistencies highlight the importance of understanding how air quality data is collected, processed, and presented. Air quality maps may use different air quality indexes, detection methods, and data processing techniques. A study comparing PurpleAir and Airbeam 3 monitors with government-reported values revealed that PurpleAir devices generally reported lower AQI values than EPA AirNow, while Airbeam 3 readings were not significantly different. This suggests that sensor type and location can heavily impact the accuracy of reported AQI values.
While official AQI data provides a general overview of air quality, it's crucial to recognize its limitations. For more accurate and localized data, personal air quality monitors may be a better option. In the face of growing concerns, a thorough review of monitoring practices and data validation methods is essential to ensure the public receives reliable information about the air they breathe.
