'So-called PM 3.0' needs to worry about PM2.5: Congress’ dig over Delhi air quality

Delhi’s air quality deteriorated sharply on November 2, 2026. The AQI was 312 at 9 a.m. This was the first time the city entered the “very poor” category that season. AQI is a combined measure used to describe how polluted the air is and how concerning it may be for health.

The Central Pollution Control Board classifies AQI from zero to 500. Zero to 50 is “good,” while 301 to 400 is “very poor.” Therefore, a reading of 312 was not merely a moderate rise. It signalled a serious pollution episode. It also crossed the level at which Delhi’s pollution-response plan is activated.

When AQI enters the “very poor” range, GRAP Stage 2 applies in Delhi. The Commission for Air Quality Management decides whether to invoke it using changing air-quality conditions and meteorological forecasts. The episode drew criticism from Congress leader Jairam Ramesh, who said PM2.5 was choking the capital.

PM2.5 means particulate matter with a diameter of 2.5 micrometres or less. These particles are much finer than PM10, which refers to particulate matter up to 10 micrometres in diameter. The labels describe particle size, not a single substance. PM2.5 can include different materials carried in polluted air.

The distinction matters because smaller particles can remain suspended in the atmosphere and reach deeper into the respiratory system. Larger PM10 particles are also harmful, but PM2.5 is generally treated as the more serious health concern. The article specifically calls PM2.5 “the real killer” for public health.

Congress leader Jairam Ramesh criticised the National Clean Air Programme for focusing heavily on PM10. He argued that PM2.5 deserves stronger standards and enforcement. The article says PM2.5 is choking Delhi and other parts of northern India, making its measurement and control especially important.

A PM2.5 particle measures 2.5 micrometres or less in diameter. A micrometre is one-millionth of a metre, so these particles are extremely small. Their size allows them to stay airborne and makes them different from larger particulate matter such as PM10.

The article says India’s PM2.5 safety standards are four times the World Health Organization’s safety levels when measured as a 24-hour average. It also says the gap is eight times when the comparison uses an annual average. These figures describe how much higher the reported Indian standards are than the WHO guidelines.

Jairam Ramesh argued that PM2.5 standards need urgent revision and strict enforcement. The comparison matters because standards shape how pollution is judged and controlled. If limits are set higher than health-based guidance, air can comply with domestic rules while remaining far above WHO-recommended levels.

PM2.5 is considered especially dangerous because its particles are so small. Unlike many larger particles, they can travel deep into the lungs. Some can pass from the lungs into the bloodstream. This allows pollution to affect organs beyond the airways and increases the risk of serious health damage.

Established health research links long-term exposure to fine particles with respiratory and cardiovascular disease. Short-term exposure can also worsen asthma and other breathing problems. These health mechanisms explain why particle size matters, even though larger PM10 particles can also harm people. The article itself does not detail these biological pathways.

Its central warning is that PM2.5, rather than only PM10, must guide clean-air policy. Jairam Ramesh said PM2.5 was choking Delhi and northern India. He urged urgent revision and strict enforcement of PM2.5 standards because current limits are reported as much higher than WHO safety levels.

Delhi and northern India can experience severe pollution episodes when pollutants accumulate faster than the atmosphere removes them. This is especially likely during seasons with calm winds, shallow atmospheric mixing, or temperature inversions. These conditions can keep polluted air close to the ground instead of allowing it to disperse. This explanation uses established atmospheric science; the article itself does not list the causes.

For example, weak winds reduce the sideways movement of pollution. A temperature inversion can place warmer air above cooler surface air and act like a lid. Limited vertical mixing then allows PM2.5 and other pollutants to build up near where people live and breathe. Regional pollution can add to local emissions.

The article reports that PM2.5 is choking Delhi and other parts of northern India. On November 2, Delhi’s AQI reached 312. The episode shows why pollution control must respond to both emissions and weather forecasts, which CAQM uses when considering GRAP measures.

GRAP Stage 2 is Delhi’s response when the AQI enters the “very poor” category. That category covers readings from 301 to 400. Stage 2 is intended to trigger stricter action to curb air pollution as conditions worsen. The article does not list each individual measure included in the stage.

The Commission for Air Quality Management, or CAQM, decides whether to invoke Stage 2. It considers dynamic air-quality data and meteorological forecasts rather than relying only on a single fixed reading. This allows the response to reflect changing pollution levels and expected weather conditions.

On November 2, Delhi recorded an AQI of 312 at 9 a.m., placing it in the relevant range. The article says Stage 2 includes strict measures to curb air pollution. It does not say when those measures would end, but continued monitoring and forecasts guide the authority’s decision.

PM2.5 comes from many sources. Established air-pollution science includes vehicle and fuel combustion, industry, power generation, construction activity, and fires. Some PM2.5 is emitted directly. Some forms when gases react in the atmosphere. The article does not identify particular sources, so these details come from established knowledge.

Weather determines whether those emissions spread or concentrate. Stronger winds generally move pollution away and dilute it. Calm winds allow it to accumulate. Strong atmospheric mixing lifts and disperses pollutants, while stable air limits vertical movement. A temperature inversion can trap cooler polluted air near the ground beneath warmer air.

These processes help explain why Delhi can face intense episodes even as conditions change quickly. The article reports an AQI of 312 and says CAQM uses dynamic air-quality and meteorological forecasts. Better control therefore requires both reducing emissions and responding to weather conditions that can trap PM2.5.