A recent remark by Delhi Chief Minister Rekha Gupta — suggesting that the Air Quality Index (AQI) can be treated “like a temperature” and that watering or misting at pollution hotspots can meaningfully lower AQI readings — has gone viral and triggered a political and scientific debate. The comment drew sharp reactions from opponents and environmental observers, who argue the comparison is misleading. This article unpacks what AQI actually measures, whether local watering can change readings, and what experts say.
What is AQI — a quick explainer
AQI (Air Quality Index) is a composite number that translates concentrations of key pollutants — typically PM2.5, PM10, NO₂, SO₂, O₃, and CO — into a standard scale to indicate health risk levels. Each pollutant is converted into a sub-index based on measured concentrations and health-based thresholds. The highest sub-index at a monitoring site becomes the site’s AQI. AQI is not a direct physical property like temperature; it is calculated from multiple pollutant readings.
Why the “AQI is like temperature” comparison is misleading
Temperature is a single meteorological variable, while AQI is a composite index influenced by emissions, weather patterns, and atmospheric chemistry. Treating AQI as a uniform, easily manipulated number ignores the complex behavior of particulate matter across an urban region. Local spraying may momentarily affect a reading near one monitor, but it cannot shift pollution levels city-wide.
Can watering or misting legitimately reduce AQI readings?
Spraying water on roads or near monitoring equipment may temporarily reduce coarse dust by settling it. However, the effect is usually short-lived and hyper-local. Some studies show that increased humidity may also interfere with sensor behavior or contribute to fine-particle formation. Therefore, water spraying is not considered a scientifically reliable method for improving AQI in a broader area.
Concerns about “gaming” monitoring sites
Some reports suggest that sudden dips in AQI readings can coincide with misting around specific monitoring stations. While not always intentional, these incidents highlight the importance of transparent monitoring practices. Abrupt humidity spikes or changes in PM levels can distort the public’s understanding of overall air conditions.
What experts recommend for real AQI improvement
Experts emphasize systemic action: reducing vehicle emissions, improving industrial standards, managing construction dust, and addressing biomass burning. International health guidelines also stress long-term strategies over cosmetic interventions. Water spraying, while useful for dust control at micro-locations, does not replace structural pollution-management policies.
FAQs
1. What does AQI stand for?
AQI stands for Air Quality Index. It is a health-oriented number derived from concentrations of major pollutants monitored in the air.
2. Is AQI a temperature?
No. AQI is a composite index based on pollutant levels, while temperature is a single atmospheric measurement. They are unrelated.
3. Can watering roads permanently reduce AQI?
No. Watering can temporarily suppress local dust, but it does not address actual emissions and therefore cannot permanently reduce AQI.
4. Do sensors get affected by humidity?
Some sensors, especially low-cost optical ones, may show altered readings during sudden increases in humidity. This can create misleading short-term data.
5. How is AQI calculated?
AQI is calculated using sub-indices generated for each pollutant. The highest sub-index becomes the AQI for that location.
6. Who sets AQI standards in India?
India’s AQI standards are defined by the Central Pollution Control Board (CPCB), which sets pollutant breakpoints and monitoring guidelines.
7. Does a low AQI at one station mean the whole city is clean?
No. AQI varies across different parts of a city. A single station cannot represent overall air quality.
8. Are there independent ways to verify AQI?
Yes. Third-party networks, satellite observations, and independent sensors provide supplementary measurements to cross-check official data.
9. What truly lowers AQI long-term?
Reducing emissions at the source — from vehicles, industries, construction, biomass burning, and other major contributors — is the only long-term solution.
10. Should the public trust AQI alerts?
Generally, yes. Official AQI data is standardized, but sudden or unexplained changes warrant clarity and transparency from authorities.
11. Can officials legally tamper with AQI data?
Tampering with public environmental data violates accountability norms. This is why audits, public transparency, and independent checks are essential.
Conclusion
Rekha Gupta’s claim that AQI can be treated like temperature oversimplifies a complex scientific measurement. AQI reflects pollutant concentrations and health impacts, not weather conditions. While water spraying can have minor local effects, it cannot replace genuine, long-term emission-control strategies. For credible updates, accurate reporting, and responsible environmental coverage, follow trusted platforms like Toofan Express.
Report by Toofan Express