Types of pollution
Pollution is the release of harmful substances or energy into the environment in amounts nature cannot clean. It is grouped by the medium it affects.
Water pollution
Sewage from towns, waste from factories (chemicals, heavy metals), fertilisers and pesticides from farms, and cultural activities like bathing and immersing things in rivers pollute water. Stretches of the Ganga and Yamuna near big cities are badly polluted. Polluted water causes diarrhoea, intestinal worms, hepatitis and kills fish.
Air pollution
Burning of coal, oil and wood, factories, vehicles, and burning crop stubble add sulphur dioxide, nitrogen oxides, carbon monoxide, dust and smoke to the air. It causes breathing and heart diseases, smog and acid rain. The Bhopal gas tragedy (1984) showed how deadly industrial air pollution can be.
Noise pollution
Unwanted loud sound from traffic, factories, construction, loudspeakers and fireworks, measured in decibels (dB). It causes stress, loss of sleep and hearing loss.
Land pollution
Dumping of garbage, plastics and industrial waste, and overuse of farm chemicals spoil the soil and groundwater.
Urban waste disposal
Growing cities produce a lot of solid waste: food scraps, paper, plastic, glass, metal, cloth and e-waste. Much of it is dumped in the open or burnt. This breeds flies and rats, spreads disease, gives off bad smells and harmful gases, and pollutes groundwater. Industrial and hospital waste are especially harmful.
Better ways
- Sort waste at home into wet (biodegradable), dry (recyclable) and hazardous.
- Compost wet waste; recycle paper, plastic, glass and metal.
- Make energy (biogas, electricity) from waste.
- Use scientific landfills, and reduce use of plastic.
Rural–urban migration
Rural–urban migration is the movement of people from villages to towns and cities. It is a big reason why cities are growing fast.
- Push factors (in villages): poverty, few jobs, small or no land, low wages, poor schools and health care, droughts and floods.
- Pull factors (in cities): more jobs, higher wages, better education, health care and entertainment.
Most migrants are young men who send money home. Often the women, children and old people stay in the village. In cities, migrants often work in the informal sector and live in poor housing. Migration puts pressure on city water, transport, housing and sanitation.
Slums: problems of poor urban settlements
A slum is a crowded, unplanned residential area with poor housing and very few basic services. Slums grow on the least useful land: near railway lines, drains, factories and dumps.
Problems
- Small, weak houses made of mud, tin or plastic; many people per room.
- Little clean water, few toilets, open drains, poor garbage collection.
- Diseases like diarrhoea, malaria and tuberculosis spread easily.
- Low and uncertain incomes, poor schooling, risk of eviction.
Large slums exist in many Indian cities; Dharavi in Mumbai is one of the biggest in Asia and also a busy centre of small industries like pottery, leather and recycling. Solutions include in-situ upgrading, affordable housing schemes, basic services and skill training.
Land degradation and case studies
Land degradation is the fall in the land's ability to produce, temporarily or for ever. Causes can be natural (gullies, deserts, flood-hit land) or human-made: waterlogging and salinity from over-irrigation, mining, deforestation, overgrazing and shifting cultivation. Waste lands made by people are harder to fix but can be restored.
Case study: Jhabua district (Madhya Pradesh)
Jhabua, in the west of Madhya Pradesh, is a largely tribal district (mainly Bhil people). Its hills were bare and eroded because of deforestation and overgrazing. Under watershed programmes (run by the Ministry of Rural Development and the state), villagers built check dams, contour trenches and small tanks, planted trees and protected pastures with community rules. Many bare hills turned green, groundwater rose, and people got more fodder, fuel and income. It shows that people's participation can reverse land degradation.
Key formulas and definitions
- Pollution types: air, water, land, noise
- Noise is measured in decibels (dB)
- Waste sorting: wet (compost) + dry (recycle) + hazardous (safe disposal)
- Migration = push factors (village) + pull factors (city)
- Slum: crowded, unplanned area with poor housing and services
- Land degradation: natural or human-made fall in land productivity
Worked examples
1. A town makes 100 tonnes of waste a day; 55% is wet and 30% dry recyclable. How much can be composted and how much recycled?
Compost = 55 tonnes; recycle = 30 tonnes. Only 15 tonnes need landfill.
2. If sorting brings landfill waste from 100 to 15 tonnes a day, by what percent has it fallen?
(100 − 15) ÷ 100 × 100 = 85% less.
3. A young farmer with 1 acre leaves his village for a factory job in Surat. Name one push and one pull factor.
Push: too little land and low income in the village. Pull: steady factory job with higher pay in the city.
4. Why do slums often grow near railway tracks and drains?
That land is left unused and is close to work places, so poor migrants who cannot pay rent build there, though it is unsafe and unhealthy.
5. Why does over-irrigation degrade land?
It raises the water table; water evaporates and leaves salt on the soil (salinity), and land stays waterlogged, so crops fail.
6. What made the Jhabua watershed work successful?
Villagers themselves built check dams and trenches, planted trees and made rules to stop grazing on new plantations, so the hills recovered.
Common mistakes
- Thinking pollution is only smoke. Water, land and noise pollution count too.
- Burning garbage to 'get rid' of it. It only moves the pollution into the air.
- Saying migrants move only because of pull factors. Push factors in villages matter as much.
- Believing degraded land can never be restored. Jhabua shows it can, with watershed work.