Air Pollution and Its Control: Causes, Effects and Solutions
Air pollution is the presence of harmful gases and particles in air at levels that damage health, crops and climate. Major sources are vehicles, industries, burning of fossil fuels and biomass, and dust.
Polluted air causes breathing diseases, heart problems and reduced crop yields. Controlling it improves public health, visibility and life expectancy, especially in cities.
Key Concepts
Particulate matter includes PM10 (diameter 10 micrometres or less) and PM2.5 (2.5 micrometres or less) measured in micrograms per cubic metre (ug m-3). Primary pollutants are emitted directly like carbon monoxide (CO) and sulphur dioxide (SO2). Secondary pollutants form in air, like ozone (O3) and acid rain. Air Quality Index (AQI) converts pollutant levels into a 0 to 500 scale for public information. Electrostatic precipitator is a control device that removes dust from industrial smoke using electric charge.
How It Works
- Fuels burn incompletely and release CO, unburnt hydrocarbons, nitrogen oxides and particles.
- Sunlight reacts with nitrogen oxides and hydrocarbons to produce ground-level ozone and smog.
- Wind disperses pollutants, but temperature inversion can trap them near ground in winter.
- Control works at source by cleaner fuels and filters, and by dispersion through tall chimneys, though prevention is better than dilution.
Worked Example
A factory emits flue gas with 5,000 mg m-3 of dust. An electrostatic precipitator removes 99 percent.
Step 1: Dust removed = 5,000 x 0.99 = 4,950 mg m-3.
Step 2: Dust remaining = 5,000 - 4,950 = 50 mg m-3.
If the emission standard is 50 mg m-3, the outlet just meets it. Efficiency calculation shows why high removal percentages are needed when inlet dust is very high.
Common Misconceptions
- Clear-looking air is always clean. PM2.5 and gases like CO are invisible but harmful.
- Ozone is always good. Ozone in the stratosphere protects us, but ground-level ozone damages lungs and crops.
- Planting trees alone solves air pollution. Trees help, but emission reduction at source is essential.
Real-World Applications
Cities promote public transport, electric vehicles and Bharat Stage emission norms for vehicles. Industries install scrubbers and electrostatic precipitators. Farmers are encouraged to avoid stubble burning and use happy seeders. Household use of LPG and improved stoves reduces indoor smoke exposure. Continuous monitoring stations, public display of AQI, health advisories on high pollution days, inspection of vehicle emissions, and dust control at construction sites through water sprinkling and covering materials are practical steps that Indian cities now use regularly.
Overall, air pollution arises from combustion and reactions in air, tiny PM2.5 is especially dangerous, and control combines clean technology, fuels, regulation and public awareness.