Air Pollution in India: Sources, Pollutants, Health Effects and Control

Primary and secondary pollutants

• A primary pollutant enters the air directly. Smoke particles and carbon monoxide are examples.
• A secondary pollutant forms later through reactions in the air.
• Sunlight helps nitrogen oxides and other gases form ground-level ozone.
• Gases can also react to form fine particles.
• Cutting a source can reduce more than one pollutant.

Outdoor and indoor air are linked

• Vehicles, industry, power plants, construction, road dust and burning add to outdoor pollution.
• Their shares differ by place and season.
• Cooking with polluting fuels, tobacco smoke and poor ventilation worsen indoor air.
• Outdoor pollution can enter buildings too.
• Clean cooking helps households. It does not replace citywide controls.
• Source: WHO, household air pollution.

Particles: PM10 and PM2.5

• PM means particulate matter: tiny solid and liquid pieces in air.
• The number is a size class, given as aerodynamic diameter in micrometres.
• PM10 means particles up to about 10 micrometres across. PM2.5 means the finer fraction, up to about 2.5.
• Fine particles reach deep into the lungs.
• Exposure also raises heart and blood-vessel risks.
• PM2.5 is a size group. Its chemical mix changes with source.
• Source: WHO, types of pollutants.

Six gases and one metal

• SO₂ comes from burning sulphur-containing fuel. It irritates airways and helps form acid rain. See sulphur dioxide.
• NOx comes from traffic and combustion. It helps form ozone and particles.
• CO comes from incomplete burning. It lowers the blood’s ability to carry oxygen.
• O₃ is ground-level ozone. It irritates lungs and damages plants. It differs from protective ozone high above Earth.
• Pb (lead) can enter air from some industry. It harms the nervous system, especially in children.
• NH₃ (ammonia) comes from agriculture and waste. It can form fine particles.
• These are starting points, not every pollutant.

Source to body

• Diesel exhaust: people breathe gases and particles near roads.
• Cooking smoke: solid fuels pollute indoor air for long periods.
• Sunny-day ozone: precursor gases react outdoors and irritate airways.
• Exposure can worsen asthma and breathing problems.
• Long exposure raises risks of heart disease, stroke and lung cancer.
• Children, older adults, pregnant people and people with illness need extra care.

Beyond human health

• Ozone damages leaves and slows plant growth.
• Sulphur and nitrogen compounds feed acid rain.
• Particles cut visibility and soil buildings.

Why winter haze lingers

• In the Indo-Gangetic Plain, winter haze mixes traffic, industry, household smoke, dust and farm fires.
• A temperature inversion holds cooler air below warmer air. It traps pollutants near the ground.
• A sunny, warmer day can raise ozone even when winter particles ease.
• Local measurements matter more than one national picture.
• See crop-residue smoke and photochemical smog.
• Source: NASA, haze over the Indo-Gangetic Plain.

AQI is an index, not a pollutant

• India’s AQI turns measured pollution into a health category.
• Higher numbers mean worse reported air.
• It has breakpoints for eight pollutants: PM10, PM2.5, NO₂, SO₂, CO, O₃, NH₃ and lead.
• The reported AQI depends on available monitoring data.
• It is not the same as one PM2.5 concentration.
• See which gases the AQI tracks.
• Source: CPCB, About AQI.

WHO advice versus Indian law

• Both are annual averages. Do not compare one day’s reading with them.
• A legal standard is not a risk-free line.
• See WHO air-quality guidelines.
• Sources: WHO 2021 guidelines; CPCB, NAAQS.

Law, regulators and NCAP

• The Air (Prevention and Control of Pollution) Act 1981 is the legal framework.
• The CPCB and State boards monitor and regulate. See CPCB.
• NCAP began in 2019.
• Its revised goal is up to a 40% PM10 cut by 2025-26, or meeting the 60 µg/m³ national standard. The base year is 2019-20.
• See NCAP.
• Sources: Air Act 1981 (India Code); PIB, NCAP status.

Match source to control

• Homes: cleaner cooking fuels, ventilation, smoke-free rooms.
• Transport: better public transport and emission control.
• Industry and power: stack controls and enforced limits.
• Roads and worksites: control loose dust.
• Farms and waste: crop-residue alternatives, no open waste burning, careful fertiliser use.
• Short-lived climate pollutants are the focus of the Climate and Clean Air Coalition.

Person versus policy

• Check the local AQI before long outdoor exercise.
• Follow health advice when pollution is high.
• One household cannot clean a city.
• Cleaner fuel, transport, industry controls and enforcement need public action.

AATAL air-pollution laboratory for Delhi-NCR, October 2026

[First] On 24 October 2026, Union Minister Jitendra Singh inaugurated the Integrated Atmospheric Chemistry and Aerosol Toxicity Analysis Laboratory (AATAL) at IITM’s Delhi branch. The Minister described it as the world’s first integrated facility of its kind. It was set up under Mission Mausam. It analyses the chemical make-up of gases and fine particles (PM2.5), including metals and other toxic elements. It also estimates the real-time share of sources such as vehicles, industry, crop-residue burning, construction dust and pollution carried in from nearby regions. The lab is linked to IITM’s AIRWISE system, which gives 72-hour air-quality forecasts at 400-metre resolution. It is meant to help CAQM and pollution-control agencies target their actions. (Source: PIB.)

Draft BS-VII emission norms, October 2026

[Policy] In October 2026, the Road Transport Ministry published draft Bharat Stage VII norms. They would start with passenger cars from 1 April 2029. They add limits on brake and tyre particles and on-road testing, not just tailpipe limits. The draft is open for 30 days of public comment. (Source: The Hindu.)