Maarg Manthan · Topic 11.6

Arsenic Contamination of Water

Environment & Ecology › Water Resources and Water Pollution · Topic 11.6

Arsenic is a toxic metalloid that occurs naturally in rocks and sediments and can dissolve into groundwater. The WHO guideline and the BIS acceptable limit for arsenic in drinking water is 10 micrograms per litre (0.01 mg per litre), and the BIS permissible limit in the absence of an alternative source is 0.05 mg per litre. In India, high arsenic in groundwater is mostly geogenic and occurs in the alluvial plains fed by the Ganga and Brahmaputra, in states such as West Bengal, Bihar, Uttar Pradesh, Jharkhand, Assam and Manipur, and in pockets of Chhattisgarh and Punjab; Bangladesh has an even larger problem in the same Bengal basin. Arsenic is released when iron oxide minerals in oxygen-poor aquifers dissolve, helped by organic matter and heavy pumping. Long-term exposure causes arsenicosis, with skin lesions, blackfoot disease and cancers of the skin, bladder and lung. Mitigation includes safe alternate sources, treatment plants, rainwater harvesting and testing.

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

At a Glance

WHO limit 10 micrograms per litre
Source Mostly natural
Hotspots Ganga-Brahmaputra plain
Disease Arsenicosis
Worst West Bengal and Bangladesh
Exam link UPSC Prelims, Environment & Ecology: Water Resources and Water Pollution

Where Does It Fit?

This topic follows eutrophication and moves to a specific toxic contaminant of groundwater. Together with mercury, it illustrates the chemical and metal pollution of drinking water. Previous topic: Algal Bloom and Eutrophication. Next topic: Mercury Pollution.

Where and Why Does Arsenic Occur in Water?

Aspect	Details
Natural source	Arsenic in minerals and sediments of the Himalayan rivers’ alluvium, released into groundwater
Release mechanism	Reductive dissolution of iron oxyhydroxides in oxygen-poor aquifers, driven by organic matter
Human trigger	Heavy groundwater pumping can change flow and chemistry; mining, smelting, pesticides and wood preservatives add arsenic
Indian regions	West Bengal (Nadia, Murshidabad, North 24 Parganas), Bihar, Uttar Pradesh, Jharkhand, Assam, Manipur and parts of Chhattisgarh and Punjab
Safe limits	10 micrograms per litre as per WHO and BIS acceptable limit; 50 as permissible limit when no alternative
Exposure routes	Drinking water, cooking and irrigated food, especially rice
Health effects	Skin lesions, keratosis, blackfoot disease, and cancers of skin, lung, bladder and kidney

How Is Arsenic Contamination Managed?

Testing: screening of tubewells and marking safe and unsafe wells
Alternate sources: piped surface water supply, dug wells, deep tubewells and rainwater harvesting
Treatment: community arsenic removal plants using adsorption, coagulation or membrane methods
Household filters: iron-based and activated alumina filters
Policy: Jal Jeevan Mission aims to supply safe tap water to arsenic and fluoride affected habitations
Agriculture: water management to reduce arsenic uptake by rice
Awareness: training and health surveillance in affected villages
Monitoring: Central Ground Water Board and states test groundwater regularly

What Else Should You Remember?

Metalloid: arsenic has properties between metals and non-metals
Inorganic arsenic: the more toxic form found in groundwater
Arsenic III and V: two common forms in water; As(III) is more mobile and toxic
Chronic exposure: effects appear after years of drinking contaminated water
Arsenical keratosis: thickening of palms and soles
Melanosis: dark spots on skin
Blackfoot disease: blood vessel disease leading to gangrene, first described in Taiwan
Bengal delta: the most affected region in the world, with tens of millions at risk across India and Bangladesh
First detection: arsenic in West Bengal groundwater was detected in the 1980s
Tubewell paradox: shallow tubewells replaced polluted surface water to cut disease but brought arsenic exposure
Shallow aquifers: often more affected than deeper ones, so deeper wells may be safer
Seasonal changes: arsenic levels can vary with season and pumping
Rice: irrigation with arsenic water can raise arsenic in rice grain
Arsenic in food: also found in some seafood in organic forms that are less toxic
Industrial sources: smelters, coal ash and pesticide factories
Indian standard: BIS 10500 for drinking water sets limits
Chhattisgarh: Rajnandgaon district has arsenic from a different geological source
Punjab: some districts of the Malwa belt show arsenic along with uranium
Arsenic removal plant: uses an oxidising and adsorption stage to bind arsenic
Sludge disposal: arsenic-rich sludge from treatment plants needs safe disposal
Link to previous: see Algal Bloom and Eutrophication
Link to next: see Mercury Pollution
Link to health: see Biomagnification Ecosystem Fish kills Infant risk Blue baby syndrome…">Harmful Effects of Water Pollution
Caution: the number of affected habitations and people changes with testing, so use official figures
Exam hint: remember natural origin, 10 microgram limit and the Ganga-Brahmaputra states
Safe alternate sources: piped water from treated surface supplies, deep tubewells and rainwater harvesting are the main options
Groundwater contamination: once an aquifer is contaminated with arsenic, the problem can last for decades because the source is the rock itself
BIS limit: the BIS acceptable limit is 0.01 mg per litre and the permissible limit with no alternative source is 0.05 mg per litre
Dug wells: shallow dug wells are often low in arsenic because they draw from oxygen-rich water near the surface
Oxidation: exposing water to air and iron can remove some arsenic, which is the basis of some low-cost filters
Health camps: screening camps find early skin signs so that people can switch to safe water in time
Children: children are more sensitive, so safe water for schools and anganwadis is a priority

Why Does It Matter for the Exam?

Limit: 10 micrograms per litre
Origin: Mostly natural
Belt: Ganga-Brahmaputra plain
Current affairs link: Jal Jeevan Mission
Common errors: assuming arsenic comes only from industry

As an analytical point, arsenic shows how a solution can cause a new problem: shallow tubewells cut germ-borne disease but exposed millions to a natural poison. Safe supply needs testing, deeper or alternate sources and local treatment.

Why Is This Topic Important?

Source Geology
Limit 10 micrograms
Fix Alternate supply

What Came Next?

The next topic covers mercury pollution. Next topic: Mercury Pollution.

Key People and Terms

Arsenic Toxic metalloid
Arsenicosis Chronic arsenic poisoning
Geogenic Of natural origin
Keratosis Skin thickening
Adsorption Binding to a surface
Aquifer Water-bearing layer

Exam Corner

Points to Remember

Limit: 10 micrograms per litre.
Mostly natural origin.
Worst in Bengal basin.
Disease: arsenicosis.
Fix: alternate sources.

Do Not Confuse With

Arsenic and fluoride Skin and cancer effects versus bone and teeth effects
Geogenic and anthropogenic Natural versus human source
Shallow and deep aquifers More arsenic versus often safer

Memory Hook

Ten in a million, nature’s gift, Bengal plains, skin and cancer, test and switch.

Mains Angle

Questions ask for states, limits and effects. These points help.

Cause Geology
Effect Arsenicosis
Fix Alternate supply

A Question You May Face

An original practice question, not a past paper question.

“Discuss the causes, health effects and mitigation of arsenic contamination of groundwater in India.”

How to Answer

Source Natural.
Spread States.
Effects Disease.
Fix Supply.

GS Relevance

Prelims: limits, affected states, health effects. GS Paper 3: groundwater contamination and mitigation.

Frequently Asked Questions

What is the safe limit of arsenic in drinking water?

The WHO guideline value and the acceptable limit under the Bureau of Indian Standards is 10 micrograms of arsenic per litre of water, equal to 0.01 milligrams per litre. The BIS permissible limit in the absence of an alternative source is 0.05 milligrams per litre. Long-term exposure above these limits is harmful.

Where does arsenic in groundwater come from?

In India, arsenic in groundwater is mainly natural, from minerals in the sediments brought down by the Ganga and Brahmaputra. In oxygen-poor aquifers, iron oxides that bind arsenic dissolve, releasing it to the water. Pumping, mining, smelting and pesticide use can add to or speed up contamination.

Which Indian states are affected by arsenic in groundwater?

High arsenic in groundwater is reported mainly in the Ganga-Brahmaputra plains, in West Bengal, Bihar, Uttar Pradesh, Jharkhand, Assam and Manipur, and in pockets of Chhattisgarh and Punjab. West Bengal districts such as Murshidabad, Nadia and North 24 Parganas are among the worst, and Bangladesh shares the same problem.

What is arsenicosis?

Arsenicosis is the chronic poisoning that results from drinking arsenic-contaminated water for years. It shows first as skin changes, such as dark spots and thickened palms and soles, and later as blackfoot disease, damage to the liver and kidneys, and cancers of the skin, bladder, lung and other organs.

How can arsenic contamination be reduced?

Measures include testing all water sources and marking safe ones, shifting to safe alternate supplies such as piped surface water, deep tubewells or rainwater harvesting, setting up community arsenic removal plants and household filters, improving awareness and health surveillance, and managing irrigation to limit arsenic in rice.

PYQ Practice — Statement Analysis

1 Arsenic in Ganga plains groundwater is mostly natural.

True

Geogenic source.

2 The WHO limit for arsenic is 100 micrograms per litre.

False

It is 10 micrograms.

3 Arsenicosis can cause skin lesions.