Maarg Manthan · Topic 11.7

Mercury Pollution

Environment & Ecology › Water Resources and Water Pollution · Topic 11.7

Mercury is a heavy metal that is liquid at room temperature and highly toxic, especially in its organic form, methylmercury. It enters the environment from burning coal, small-scale gold mining, chlor-alkali plants, cement and metal smelting, waste incineration, and products such as thermometers, fluorescent lamps and dental amalgam. Mercury in water and sediments is converted by bacteria into methylmercury, which accumulates in aquatic organisms and biomagnifies in food chains, so large predatory fish such as tuna and swordfish carry the highest levels. Eating contaminated fish causes damage to the nervous system, kidneys and developing brain of children; the disaster at Minamata Bay in Japan, first identified in 1956, showed this. The global Minamata Convention on Mercury was adopted in 2013 and came into force on 16 August 2017, and India ratified it in 2018. The BIS limit for mercury in drinking water is 0.001 mg per litre.

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

At a Glance

Form most toxic Methylmercury
Disaster Minamata, Japan
Convention adopted 2013
In force 16 August 2017
India ratified 2018
Exam link UPSC Prelims, Environment & Ecology: Water Resources and Water Pollution

Where Does It Fit?

This topic follows arsenic and covers another toxic metal contaminant that enters water and food chains. It also links with the global conventions covered in a later macro. Previous topic: Arsenic Contamination of Water. Next topic: Oxygen Stratification in Water Bodies.

How Does Mercury Pollute and Harm?

Aspect	Details
Major sources	Coal-fired power plants, small-scale gold mining, chlor-alkali plants, cement, metal smelting and waste burning
Products	Thermometers, switches, batteries, fluorescent lamps and dental amalgam
Conversion	Bacteria in sediments convert inorganic mercury into methylmercury, which is readily absorbed by organisms
Biomagnification	Concentrations rise at each step of the food chain, highest in large predatory fish
Health effects	Damage to nerves, brain, kidneys; tremors, vision and hearing loss; birth defects
Minamata disease	Mercury poisoning from fish in Minamata Bay, Japan, from factory discharge, first recognised in 1956
Safe limit	BIS limit of 0.001 mg per litre in drinking water

What Controls Exist for Mercury?

Minamata Convention on Mercury: adopted in Kumamoto, Japan in October 2013; in force from 16 August 2017
Convention measures: bans new mercury mines, phases out many mercury products, cuts use in processes, and controls emissions and releases
Gold mining: reduce mercury in artisanal gold mining
India: ratified the convention in 2018 and has rules to restrict mercury use and waste
Chlor-alkali shift: industry is moving from mercury cell to membrane technology
Waste handling: mercury-containing lamps and devices need safe collection
Coal power: emission norms for mercury were set for thermal power plants in 2015
Fish advice: limit eating large predatory fish in contaminated areas

What Else Should You Remember?

Liquid metal: mercury is the only common metal that is liquid at ordinary temperature
Quicksilver: an old name for mercury
Elemental mercury: evaporates and is inhaled as vapour
Inorganic mercury: salts of mercury, toxic to kidneys
Organic mercury: methylmercury, the form which accumulates in fish
Atmospheric transport: mercury travels far in air and is deposited on distant land and seas
Global source: small-scale gold mining and coal burning are leading sources worldwide
Minamata: Chisso Corporation released methylmercury waste into the bay; thousands were affected over decades
Niigata: a second outbreak of Minamata disease occurred in Niigata, Japan
Iraq grain poisoning: in 1971 wheat treated with a mercury fungicide caused mass poisoning
Kodaikanal: a mercury thermometer factory in Kodaikanal, Tamil Nadu, was closed in 2001 after contamination and clean-up and compensation issues followed
Fish consumption: pregnant women are advised to avoid high-mercury fish
Dental amalgam: the convention calls for phase down of dental amalgam
CFL: compact fluorescent lamps contain small amounts of mercury and need safe disposal
Hazardous waste rules: India regulates mercury waste under hazardous waste rules
Chlor-alkali industry: uses mercury cells in older plants for making chlorine and caustic soda
Coal in India: coal contains traces of mercury, and large coal use makes India a significant emitter
Sediment cleanup: contaminated sediments are difficult and costly to clean
Detection: blood, hair and urine tests show exposure
Pregnancy risk: mercury crosses the placenta and harms the fetal brain
Link to previous: see Arsenic Contamination of Water
Link to next: see Oxygen Stratification in Water Bodies
Caution: check the latest on ratification status, rules and site-specific cases
Exam hint: learn the Minamata story, 2013 adoption, 2017 entry into force and India’s 2018 ratification
Coal combustion: burning coal releases mercury to air, and India is among the largest coal users
Artisanal gold mining: miners use mercury to separate gold from ore and release vapour and waste into rivers
Mercury cell plants: old chlor-alkali plants can lose mercury to air, water and waste
Fish advice for health: local fish advisories help communities near polluted waters
Tuna and swordfish: large long-lived predatory fish carry the highest levels in the diet
Wastewater and landfill: broken lamps and devices in landfills release mercury to air and groundwater

Why Does It Matter for the Exam?

Toxic form: Methylmercury
Disease: Minamata
Treaty: Minamata Convention
Current affairs link: Mercury rules for coal plants
Common errors: confusing Minamata disease with Itai-itai disease

As an analytical point, mercury is a global pollutant because it travels in air and concentrates in fish, so local clean-up is not enough. The Minamata Convention treats it as a shared problem, with controls on mining, coal and products.

Why Is This Topic Important?

Form Methylmercury
Path Fish
Rule Minamata Convention

What Came Next?

The next topic covers oxygen stratification in water bodies. Next topic: Oxygen Stratification in Water Bodies.

Key People and Terms

Methylmercury Organic toxic form
Minamata disease Mercury poisoning
Chlor-alkali Chlorine production industry
Amalgam Mercury alloy
Artisanal mining Small-scale mining
Biomagnification Increase up the chain

Exam Corner

Points to Remember

Toxic form: methylmercury.
Disaster: Minamata, 1956.
Convention adopted 2013.
In force 2017.
India ratified 2018.

Do Not Confuse With

Minamata disease and Itai-itai disease Mercury versus cadmium
Mercury and methylmercury Metal versus toxic organic form
Minamata Convention and Basel Convention Mercury versus hazardous waste movement

Memory Hook

Mercury turns methyl, climbs the fish chain, Minamata taught the world, 2013 signed.

Mains Angle

Questions ask for sources and the convention. These points help.

Sources Coal, mining
Effects Nerve damage
Control Convention

A Question You May Face

An original practice question, not a past paper question.

“Discuss the sources and health effects of mercury pollution. What is the Minamata Convention?”

How to Answer

Sources Coal, mines.
Path Fish chain.
Effects Nerves.
Rule Convention.

GS Relevance

Prelims: sources, Minamata, convention. GS Paper 3: heavy metal pollution and international agreements.

Frequently Asked Questions

What are the main sources of mercury pollution?

The main sources are burning of coal, small-scale gold mining that uses mercury, chlor-alkali plants, cement production, metal smelting and waste incineration. Products such as thermometers, switches, fluorescent lamps, batteries and dental amalgam also release mercury when broken or discarded. Mercury released into the air is carried far and settles in water.

What is methylmercury and why is it dangerous?

Methylmercury is an organic form of mercury made from inorganic mercury by bacteria in sediments and water. It is easily absorbed by organisms, accumulates in tissues and magnifies along the food chain, reaching high levels in large predatory fish. It attacks the nervous system and can harm the developing brain.

What was the Minamata disaster?

Minamata disease was identified in 1956 in Minamata, Japan, where a chemical factory released waste containing methylmercury into the bay. Fish and shellfish eaten by local people became contaminated, causing severe nerve damage, birth defects and deaths. It became a global symbol of industrial pollution and led to the Minamata Convention.

What is the Minamata Convention on Mercury?

The Minamata Convention on Mercury is a global treaty adopted in 2013 and in force since 16 August 2017 to protect health and the environment from mercury. It bans new mercury mines, phases out many mercury products and processes, and regulates emissions, releases, storage and waste. India ratified it in 2018.

How can mercury exposure be reduced?

Exposure can be reduced by cutting emissions from coal plants and industry, replacing mercury cell technology and mercury products, safely collecting and disposing of mercury waste such as lamps, ending mercury use in gold mining and advising people, especially pregnant women, to limit eating large predatory fish from contaminated waters.

PYQ Practice — Statement Analysis

1 Minamata disease is caused by mercury.

True

Methylmercury poisoning.

2 The Minamata Convention was adopted in 1992.

False

In 2013.

3 Mercury biomagnifies in food chains.