Environmental Pollution

9 min read

Pollution is the introduction into the environment of substances or energy at rates exceeding the capacity of natural systems to absorb, disperse or recycle them, resulting in harm to living organisms or property.

Pollutant

Any solid, liquid, gas, energy form (heat, sound, light) or biological agent that, when present in sufficient quantity, degrades environmental quality. Pollutants are classified as primary (released directly) or secondary (formed in the environment by reaction, e.g. ozone, PAN).

Air pollution

Major air pollutants

Pollutant	Source	Health effect
Particulate Matter (PM2.5, PM10)	Combustion, dust	Respiratory, cardiovascular disease
Sulphur dioxide (SO₂)	Coal, oil burning	Bronchoconstriction, acid rain
Nitrogen oxides (NOₓ)	Vehicles, power plants	Smog precursor, asthma
Carbon monoxide (CO)	Incomplete combustion	Blocks haemoglobin
Ground-level ozone (O₃)	NOₓ + VOCs + sunlight	Lung irritation
Lead (Pb)	Old paints, leaded fuel	Neurotoxin
Volatile organic compounds	Solvents, paints	Carcinogens

Smog

Industrial (London) smog — SO₂ + soot + fog. The Great Smog of London (1952) killed ~12,000 and led to the UK Clean Air Act 1956.
Photochemical (LA) smog — NOₓ + hydrocarbons + sunlight → ozone and PAN.
Lahore smog — recurring winter crisis. Lahore frequently records PM2.5 > 300 µg/m³, against a WHO 24-hr guideline of 15 µg/m³.

Stratospheric ozone depletion

CFCs released since the 1930s catalyse the destruction of stratospheric O₃, producing the Antarctic "ozone hole". Addressed by the Montreal Protocol (1987), the most successful environmental treaty in history — Pakistan ratified in 1992.

Water pollution

Categories of water pollutants:

Pathogens — bacteria, viruses (cholera, typhoid, hepatitis A/E).
Organic wastes — sewage, animal waste; depletes dissolved oxygen via BOD.
Plant nutrients — nitrates, phosphates → eutrophication → algal bloom → hypoxia → "dead zones".
Toxic heavy metals — Hg, Pb, Cd, As. Arsenic contamination affects ~50 million people in the Indus basin.
Industrial chemicals — dyes, solvents, PCBs.
Plastics and microplastics.
Thermal pollution — heated effluent from power plants reduces DO.

Key Points

BOD (Biochemical Oxygen Demand) measures organic pollution by microbial O₂ consumption over 5 days at 20 °C.
COD measures total oxidisable matter (chemical).
Eutrophication = nutrient enrichment leading to algal bloom and oxygen depletion.
Bioaccumulation = build-up of toxins in an organism; biomagnification = increasing concentration up the food chain (DDT, Hg).
Pakistan's Punjab Environmental Quality Standards (PEQS) apply to industrial effluent and air emissions.

Soil and land pollution

Agrochemicals: DDT (banned in Pakistan since 1996 for agriculture; still some vector-control use), other persistent organochlorines.
Salinity and waterlogging — Pakistan's irrigated Indus basin loses ~40,000 ha/yr to salinity.
Solid waste — Pakistan generates ~49 million tonnes of municipal solid waste annually; only ~60% is collected.
E-waste — informal disposal hubs in Karachi and Lahore.

Noise pollution

Measured in decibels (dB) on a logarithmic scale.
WHO recommends < 55 dB outdoor day, < 45 dB outdoor night.
Pakistan's NEQS sets industrial limit at 75 dB day / 65 dB night.
Sources: traffic, generators, industry, weddings, pressure horns.

Radioactive and thermal pollution

Chernobyl (1986) and Fukushima (2011) are the canonical case studies.
Pakistan operates the KANUPP, Chashma (C-1 to C-4) and K-2/K-3 reactors; PNRA regulates radiological safety.

Pollution control: principles

Polluter Pays Principle (OECD 1972, codified in Rio Principle 16, 1992).
Precautionary Principle (Rio Principle 15).
Environmental Impact Assessment (EIA) — mandated in Pakistan under the Pakistan Environmental Protection Act 1997 (Section 12).
Command-and-control regulation (emission limits) vs economic instruments (taxes, tradable permits).
Cleaner production — process redesign to prevent rather than treat pollution.

Key Pakistani institutions

Ministry of Climate Change (federal).
Pakistan Environmental Protection Agency (Pak-EPA) and provincial EPAs.
National Environmental Quality Standards (NEQS) — first issued 1993, revised since.

For pollution questions, always specify the pollutant, source, mechanism of harm, and a regulatory instrument. Citing PEPA 1997 Section 12 (EIA) or NEQS limits gives precision that examiners reward.

Health burden in Pakistan

Air pollution shortens average life expectancy in Punjab by an estimated ~3–5 years (AQLI 2023).
Diarrhoeal disease — driven mainly by water contamination — remains a leading cause of child mortality.
Lead poisoning, cement-dust silicosis in industrial belts.

The path forward combines stricter emission standards, fuel quality reform (Euro-V was mandated for diesel in 2020), clean stove transitions for the ~50% of rural households still using biomass, and circular-economy waste systems.