PM10 and PM2.5: What the Air Quality Standards Mean for You

PM10 and PM2.5 are tiny particles in the air, 10 and 2.5 micrometres across or smaller. India's National Ambient Air Quality Standards, 2009 say the average concentration should not cross 100 µg/m³ for PM10 and 60 µg/m³ for PM2.5 over 24 hours, or 60 and 40 µg/m³ averaged over a year. These are limits for the air in an area, not for one chimney. They tell you whether the air you breathe meets the legal benchmark, and they can support a complaint, but they rarely prove on their own which source is to blame.

People usually meet these numbers on a phone app or a news ticker in November, with no explanation of what they mean legally. This guide explains the standards in plain words, how the 24-hour and annual figures work, how the AQI relates to them, where official data comes from, and how residents and RWAs can use the numbers in a complaint without overstating what they prove.

If you are dealing with a specific factory, plant or construction site that is making the air worse where you live, our industrial air pollution lawyers can help you turn the data into a complaint the board or the NGT has to deal with.

The essentials

What do PM10 and PM2.5 actually mean?

PM stands for particulate matter: solid particles and liquid droplets suspended in the air. PM10 is all the particles 10 micrometres across or smaller; PM2.5 is the finer part of that, 2.5 micrometres or smaller. Both are far thinner than a human hair, which is why you can breathe air that looks only slightly hazy and still be taking in a heavy dose.

The two sizes come from different places. Coarser PM10 is dominated by dust: unpaved roads, construction sites, stone crushers, open stockpiles, road dust stirred up by traffic. PM2.5 comes mostly from burning, whether in vehicle engines, industrial furnaces and boilers, diesel generators, brick kilns, garbage fires or crop residue, and from gases that react in the air to form particles. PM2.5 is part of PM10, so a PM10 reading always includes the PM2.5.

The size matters for health and for law. Coarse dust tends to settle within a shorter distance of its source, which makes it easier to tie to a nearby crusher or construction site. Fine particles stay in the air longer and travel further, so a high PM2.5 reading in your colony may have as much to do with the region as with the factory next door.

What are the PM10 and PM2.5 limits in India?

The National Ambient Air Quality Standards, 2009 set limits for twelve pollutants. For particulate matter, the limits are the same for industrial, residential, rural and other areas; there is a separate, stricter set for some other pollutants in ecologically sensitive areas.

µg/m³ means micrograms per cubic metre of air. A microgram is a millionth of a gram, so the quantities are tiny by weight; it is the number of particles and where they lodge in the body that matters.

How to read a PM reading without getting it wrong

The standards are averages. The 24-hour limit is compared with the average concentration over a full day; the annual limit with the average of readings over the year. A monitor that shows PM2.5 at 250 at 11 pm on a winter night is reporting a one-hour or even a fifteen-minute value. It tells you the air is bad at that moment; it does not by itself show a breach of the 24-hour standard, although on such nights the daily average usually ends up well above the limit too.

The notified standards also say that the 24-hour values should be met 98 percent of the time in a year, which allows exceedance on a small number of days but not on consecutive days. In much of north India, particularly in winter, the 24-hour limits are crossed on far more days than that, which is why most of these cities fail the standard by any measure.

Watch the units and the instrument. Some apps show AQI, not concentration, and the two numbers look alike. Some show readings from low-cost sensors, which can drift with humidity. Before you quote a number in a complaint, note where it came from, whether it is a concentration in µg/m³ or an index value, and over what period it was averaged.

How does the AQI relate to PM10 and PM2.5 standards?

The National Air Quality Index, published by the CPCB, converts concentrations of several pollutants into a single number and a colour band: Good, Satisfactory, Moderate, Poor, Very Poor and Severe. Each pollutant gets a sub-index, and the AQI shown is the worst of them. In north Indian winters that is almost always PM2.5 or PM10.

The bands are built around the standards. An AQI of 100, the top of the Satisfactory band, corresponds to the 24-hour standard for the pollutant concerned, so for PM10 that is 100 µg/m³ and for PM2.5 it is 60 µg/m³. Anything in the Moderate band or worse means the daily standard is being exceeded for that pollutant. That is a handy rule of thumb when you see only an AQI figure.

The AQI is a communication tool, not a separate legal limit. Boards, CAQM and the NGT may refer to AQI levels, and in Delhi NCR the Graded Response Action Plan is triggered by AQI bands, but when you argue that the air fails the law, it is the concentration standards of 2009 you are relying on.

Are the PM10 and PM2.5 standards legally binding?

The standards are notified under the Environment (Protection) Act, 1986 and form part of the Environment (Protection) Rules. They are the official measure of whether air quality in an area is acceptable. They do not, by themselves, create an offence for any particular person: no individual factory is prosecuted because the city's PM2.5 average is too high. What they do is set the target that the CPCB, State Boards, CAQM and city governments are meant to achieve, and the benchmark against which the NGT and the courts judge whether authorities are doing their job.

That matters because the right to life under Article 21 of the Constitution has long been read by the Supreme Court to include the right to a pollution-free environment. When air in an area persistently fails the standards and the authorities do little, residents can ask the NGT to direct them to act. Cities that consistently fail the standards have been identified as non-attainment cities under the National Clean Air Programme launched by the Environment Ministry in 2019, and have city action plans that the tribunal has monitored.

For businesses, the standards feed into decisions on consent conditions, siting, expansion and, in Delhi NCR, restrictions under GRAP. In industrial clusters rated critically polluted in CPCB's CEPI assessments, moratoriums on new or expanded units have been imposed at times.

Why a high PM reading does not, by itself, prove a factory is at fault

There are two different kinds of standard. Ambient standards, like the 2009 PM limits, measure the air people breathe. Emission standards measure what comes out of a particular source, such as a boiler stack or a furnace, usually in milligrams per normal cubic metre of flue gas, and they are set industry by industry in the schedules to the Environment (Protection) Rules and in each unit's consent order. There are also limits on fugitive emissions, the dust escaping from open handling and stockpiles.

A factory is in breach when its stack or fugitive emissions exceed its own standards or it ignores its consent conditions. A bad ambient reading near the factory is evidence that something is wrong in the area, and a strong reason to demand stack monitoring, but the board will want to link the pollution to the source. If there is a busy highway, a garbage dump and three other units nearby, the factory will point at all of them.

So use the ambient numbers as the opening of your case, not the whole of it. Pair them with what ties the pollution to the source: dust that is visibly the same as the unit's raw material, black smoke from its stack on video, readings that rise when the unit runs and fall when it stops, and the unit's own consent conditions. Our guide on complaining about factory smoke covers that side in detail.

Where can I get reliable PM10 and PM2.5 data for my area?

Official data comes from two kinds of station. Continuous ambient air quality monitoring stations record readings round the clock and feed them to public dashboards run by the CPCB and State Boards. Manual stations under the national air quality monitoring programme take samples on set days, which are then analysed in a laboratory. Both are run or supervised by the boards, which makes their data harder for anyone to dismiss.

The catch is coverage. Most stations are in cities, often some distance from the industrial area or village where the problem is. A station two kilometres upwind of a cluster of rolling mills will not show what the families downwind are breathing. You can ask the board, by letter or RTI, for the readings from the nearest station for specific dates, for any monitoring it has done near a particular unit, and for its stack monitoring results for that unit.

Where there is no nearby station, a complaint can reasonably ask the board to carry out ambient monitoring at the site, or ask the NGT to direct a joint committee to do so. Monitoring done by a laboratory recognised under the Environment (Protection) Act carries the most weight. Our note on expert and laboratory evidence in the NGT explains why the source of a reading matters so much.

How to use air quality data in a pollution complaint

These steps are for residents or RWAs who believe a particular source is making local air worse. They work alongside the usual complaint process, not instead of it.

For how the NGT treats photos, lab reports and RTI replies, see our guide on evidence in an NGT case.

Can I measure PM2.5 myself and use it as evidence?

You can, within limits. Low-cost sensors are good at showing patterns: when the air gets worse, how readings at two points compare, whether a spike lines up with a unit starting work. They are not calibrated reference instruments, they are affected by humidity, and a factory's lawyer will say so. Treat them as a guide for where and when official monitoring should be done.

If you want numbers that can stand on their own, the monitoring has to be done by a laboratory recognised under the Environment (Protection) Act, following the prescribed method, with a record of where and when the sample was taken. That costs money and takes planning, which is why most residents use their own data to push the board or the tribunal into ordering proper monitoring rather than paying for it themselves.

When Advocate B.K. Singh prepares an air pollution matter for the NGT, he keeps residents' sensor logs in the annexures as supporting material but builds the main case on the board's own data, the unit's consent conditions and the videos. It keeps the argument on ground that the other side cannot easily attack.

PM levels, GRAP and CAQM in Delhi NCR

In Delhi NCR, PM levels have a direct operational effect. The Commission for Air Quality Management runs the Graded Response Action Plan, under which restrictions on construction, diesel generators, certain industries and vehicles step up as the AQI moves through its bands. Our guide on GRAP stages explained sets out what applies at each stage.

For residents this means a complaint about dust from a construction site or a unit running coal or diesel on a Severe day can be framed as a breach of GRAP directions, which CAQM and the boards enforce with inspection drives. For businesses it means checking the AQI forecast is part of compliance; see our page on GRAP and CAQM compliance for NCR units.

What the standards mean for your health

The Indian standards are a legal and policy line, not a guarantee of safety. The World Health Organization's 2021 air quality guidelines are considerably stricter than India's standards for both PM10 and PM2.5. Fine particles can reach deep into the lungs, and children, older people and those with heart or lung disease are most affected. Your doctor is the right person to advise on precautions for your family.

In legal terms, health effects add weight. A complaint or NGT application that records breathing problems in a colony next to a unit, supported by prescriptions or a local doctor's note, shows real harm rather than inconvenience. Do not exaggerate it or claim a medical link you cannot support; the tribunal is used to measured evidence and reacts badly to inflated claims.

Before you rely on a PM10 or PM2.5 number

When the PM numbers will not get you very far

If your concern is that the whole city's air is bad, a single resident's complaint to the board will not change much. City-wide pollution is handled through action plans, CAQM in NCR, and NGT proceedings that deal with whole regions; those are usually brought by organisations or taken up by the tribunal itself. Your effort is better spent on an identifiable local source you can do something about: a hot mix plant, a crusher, a dump that keeps catching fire, an industrial area burning prohibited fuel.

The numbers also will not help if the source is a lawful unit operating within its consent. In that case the complaint has to be about siting, inadequate conditions or cumulative impact, which is a harder argument and usually a matter for the board and the NGT together. For local sources such as plants and dust-heavy construction, our guides on hot mix plant pollution and construction dust and noise from large projects give the practical route.

Related guides

For dust from heavy industry, see our guide on cement plant dust and stack emissions. Construction sites in NCR have their own dust rules, covered on our page on construction dust compliance, and if you are ready to take a matter to the tribunal, read about filing a case in the NGT.