Maarg Manthan · Topic 11.4

Harmful Effects of Water Pollution

Environment & Ecology › Water Resources and Water Pollution · Topic 11.4

Water pollution harms human health, aquatic life, agriculture and the economy. Polluted drinking water spreads waterborne diseases such as cholera, typhoid, dysentery, hepatitis A and E and diarrhoea, which are a major cause of illness and death among children in developing countries. Chemical contaminants cause long-term illnesses: arsenic leads to skin lesions and cancers, excess fluoride to dental and skeletal fluorosis, nitrate to methaemoglobinaemia or blue baby syndrome in infants, lead to nervous system damage and mercury to neurological disease. Toxic substances such as DDT and mercury accumulate in organisms and magnify up the food chain through bioaccumulation and biomagnification. In water bodies, organic and nutrient pollution cuts dissolved oxygen, causes eutrophication and fish kills, and destroys biodiversity, while sediments, oil and heat damage habitats. Pollution also raises water treatment costs, reduces crop yields when polluted water is used for irrigation, damages fisheries and tourism, and affects livelihoods.

5 min read · UPSC Prelims · Environment & Ecology · Water Resources and Water Pollution

At a Glance

Germ-borne Cholera, typhoid, hepatitis
Chemical Arsenic, fluoride, nitrate
Food chain Biomagnification
Ecosystem Fish kills
Infant risk Blue baby syndrome
Exam link UPSC Prelims, Environment & Ecology: Water Resources and Water Pollution

Where Does It Fit?

This topic follows the measurement of water pollution and sets out what contamination does. It leads to the detailed topics on eutrophication, arsenic, mercury and oxygen stratification. Previous topic: Measurement of Water Pollution. Next topic: Algal Bloom and Eutrophication.

What Are the Health Effects of Water Pollution?

Contaminant	Effect on health
Pathogens (bacteria, viruses, protozoa)	Cholera, typhoid, dysentery, hepatitis A and E, polio, diarrhoea and giardiasis
Arsenic	Skin lesions, blackfoot disease, and cancers of skin, lung and bladder
Fluoride	Dental and skeletal fluorosis when above about 1.5 mg per litre
Nitrate	Blue baby syndrome in infants when above 45 mg per litre
Lead	Brain and nerve damage, especially in children
Mercury	Nervous system damage as in Minamata disease
Pesticides and toxic organics	Cancer, hormone disruption and effects on reproduction

What Are the Ecological and Economic Effects?

Oxygen depletion: organic pollution lowers dissolved oxygen, killing fish and other aquatic life
Eutrophication: nutrients cause algal blooms and dead zones
Bioaccumulation and biomagnification: toxins build up in organisms and increase at higher trophic levels
Habitat damage: sediments smother reefs and spawning grounds; oil coats birds and shores
Biodiversity loss: sensitive species such as dolphins and mayflies decline
Agriculture: polluted irrigation water harms soil and crops and enters the food chain
Economic cost: higher treatment costs, health costs, and lost fisheries and tourism
Social effects: women and children spend time collecting safe water, and poor communities suffer most

What Else Should You Remember?

Waterborne disease: spread by drinking or contact with contaminated water
Water-washed disease: such as trachoma and scabies, linked to lack of enough water for hygiene
Water-based disease: such as schistosomiasis, carried by hosts living in water
Water-related vector disease: such as malaria and dengue, spread by mosquitoes that breed in water
Cholera: caused by Vibrio cholerae, spread through faecal contamination of water
Typhoid: caused by Salmonella Typhi
Hepatitis A: a viral liver infection spread by contaminated water or food
Fluorosis in India: widespread in Rajasthan, Andhra Pradesh, Telangana and other states
Arsenicosis: chronic arsenic poisoning in Bengal basin and other areas
Methaemoglobinaemia: nitrate converts haemoglobin so that it cannot carry oxygen
Minamata disease: mercury poisoning from industrial waste in Minamata Bay, Japan, first recognised in 1956
Itai-itai disease: cadmium poisoning in Japan that caused painful bone disease
DDT: persistent pesticide that biomagnifies and thins bird egg shells
Bioaccumulation: build-up of a substance in a single organism over time
Biomagnification: increasing concentration of a substance at higher levels of a food chain
Fish kills: mass deaths of fish from low oxygen or toxic discharge
Coral and seagrass: damage from sediment, sewage and chemicals
Groundwater contamination: hard and slow to clean, often permanent for decades
Child health: diarrhoea is a leading cause of death in young children in poor areas
Sanitation link: unsafe water and poor sanitation together cause most waterborne disease
Jal Jeevan Mission: aims to give tap water to rural households, with water quality testing
Link to previous: see Measurement of Water Pollution
Link to next: see Algal Bloom and Eutrophication
Link to mercury: see Mercury Pollution
Caution: permissible limits differ by standard, so cite the standard when quoting
Exam hint: connect each contaminant with its disease and each disease with a place or incident
Ganga basin burden: dense population, sewage and industry along the Ganga basin raise exposure to waterborne disease, so cleaning programmes are tied to health goals
Lead in pipes: old pipes and solder can leach lead into household water
Cost of treatment: polluted sources need more chemicals and energy to treat, raising water bills
Livelihood loss: fishers lose income when catches fall because of pollution and fish kills
Recreational loss: beaches, lakes and rivers become unsafe for bathing and tourism
Ecosystem services: polluted wetlands and rivers lose their ability to filter water and support fish

Why Does It Matter for the Exam?

Infant risk: Nitrate
Bones and teeth: Fluoride
Food chain: Biomagnification
Current affairs link: Jal Jeevan Mission testing
Common errors: confusing bioaccumulation and biomagnification

As an analytical point, polluted water works as a hidden tax on health, farms and fisheries, and falls most on poor households. Clean supply, sanitation and treatment are among the cheapest health measures.

Why Is This Topic Important?

Health Diseases
Nature Oxygen loss
Chain Biomagnification

What Came Next?

The next topic covers algal bloom and eutrophication. Next topic: Algal Bloom and Eutrophication.

Key People and Terms

Fluorosis Fluoride disease
Blue baby syndrome Nitrate infant illness
Biomagnification Increase up the chain
Bioaccumulation Build-up in organism
Arsenicosis Arsenic poisoning
Minamata disease Mercury poisoning

Exam Corner

Points to Remember

Nitrate causes blue baby syndrome.
Fluoride causes fluorosis.
Mercury: Minamata.
Cadmium: Itai-itai.
DDT biomagnifies.

Do Not Confuse With

Bioaccumulation and biomagnification Within an organism versus along a food chain
Waterborne and water-based disease Drunk germs versus water-hosted vectors
Fluorosis and arsenicosis Fluoride versus arsenic poisoning

Memory Hook

Germs make you sick, metals stay, nitrate chokes babies, toxins climb the chain.

Mains Angle

Questions ask for contaminant and disease matches. These points help.

Health Disease
Ecology Oxygen, chain
Cost Economic

A Question You May Face

An original practice question, not a past paper question.

“Discuss the harmful effects of water pollution on human health and ecosystems with examples.”

How to Answer

Health Disease.
Chemicals Arsenic, fluoride.
Ecology Chain.
Cost Economy.

GS Relevance

Prelims: diseases, contaminants, biomagnification. GS Paper 3: pollution impacts on health and environment.

Frequently Asked Questions

What diseases are caused by polluted water?

Polluted water spreads waterborne diseases such as cholera, typhoid, dysentery, hepatitis A and E, polio and diarrhoea, which are caused by bacteria, viruses and parasites from faecal contamination. It also causes illnesses from chemicals, such as fluorosis, arsenicosis, lead poisoning and blue baby syndrome.

What is blue baby syndrome?

Blue baby syndrome, or methaemoglobinaemia, occurs when infants drink water with high nitrate levels, usually from fertiliser runoff or sewage contamination of groundwater. Nitrate is converted in the baby's gut to nitrite, which stops the blood from carrying oxygen properly and turns the skin bluish. The limit for nitrate in drinking water is 45 mg per litre.

What is biomagnification?

Biomagnification is the increase in concentration of a persistent toxic substance, such as DDT or mercury, as it moves up the food chain. Small organisms absorb the substance, and predators eating many of them accumulate higher levels, so top predators like fish-eating birds and humans can carry the highest concentrations.

What is Minamata disease?

Minamata disease is mercury poisoning that was first identified in 1956 in Minamata, Japan, where a chemical factory discharged methylmercury into the bay. The mercury built up in fish and shellfish eaten by local people, causing severe damage to the nervous system, and it led to the global Minamata Convention on Mercury.

How does water pollution affect aquatic life?

Organic and nutrient pollution lowers dissolved oxygen and can cause algal blooms and fish kills, while toxic chemicals poison organisms and accumulate in food chains. Sediments smother habitats such as reefs and spawning grounds, oil coats animals, and heat reduces oxygen, so sensitive species decline and ecosystems lose diversity.

PYQ Practice — Statement Analysis

1 Nitrate in drinking water can cause blue baby syndrome.

True

In infants.

2 Fluorosis is caused by excess arsenic.

False

It is caused by fluoride.

3 Biomagnification increases along the food chain.