flowchart LR
P[Plankton<br/>0.04 ppm] --> F[Small fish<br/>0.5 ppm]
F --> L[Large fish<br/>2 ppm]
L --> E[Eagle<br/>25 ppm]
classDef default fill:#003366,color:#ffffff,stroke:#ffcc00,stroke-width:3px,rx:10px,ry:10px;
40 Impacts of Pollutants on Human Health
Pollutants reach human bodies through inhalation, ingestion, and skin contact. The route of exposure matters: airborne fine particles enter the lungs; waterborne contaminants travel through the gut; skin-contact pollutants accumulate in fat.
40.1 Air Pollutants — Health Effects
TipMajor Air Pollutants and Their Health Effects
| Pollutant | Source | Health effect |
|---|---|---|
| PM2.5 | Combustion, vehicles, industry | Penetrates alveoli; cardiovascular and respiratory disease, lung cancer; premature death |
| PM10 | Dust, construction | Respiratory irritation, asthma |
| SO₂ | Coal-burning | Bronchitis, asthma exacerbation |
| NO₂ | Vehicle exhaust, power plants | Respiratory inflammation, asthma |
| CO | Incomplete combustion | Binds to haemoglobin (carboxyhaemoglobin); reduces oxygen delivery; fatal at high levels |
| Ground-level O₃ | Photochemical smog | Cough, chest pain, reduced lung function |
| Lead (Pb) | Older paint, fuels, batteries | Neurotoxic; reduces IQ in children |
| Mercury (Hg) | Industrial; coal | Neurological damage; Minamata disease |
| Asbestos | Insulation, mining | Asbestosis, mesothelioma |
| Radon | Natural radioactive gas | Lung cancer (second-leading cause after smoking) |
| VOCs | Solvents, paints | Headaches, eye irritation, cancer (long-term) |
| Indoor smoke | Cooking with biomass | Acute lower-respiratory infections in children |
TipWHO Guidelines and Health Risk
The WHO 2021 Air Quality Guidelines tightened acceptable annual averages: - PM2.5 ≤ 5 μg/m³ - PM10 ≤ 15 μg/m³ - NO₂ ≤ 10 μg/m³
Exceeding these is associated with measurable health risk.
40.2 Water-Borne Diseases
TipMajor Water-Borne Diseases
| Disease | Cause | Symptoms |
|---|---|---|
| Cholera | Vibrio cholerae bacteria | Severe diarrhoea, dehydration |
| Typhoid | Salmonella typhi | Sustained fever, abdominal pain |
| Hepatitis A and E | Hepatitis virus | Liver inflammation, jaundice |
| Diarrhoeal diseases | Various pathogens | Dehydration, especially in children |
| Polio | Poliovirus | Paralysis (now eradicated in India since 2014) |
| Schistosomiasis | Parasitic flatworm | Chronic infection of urinary/intestinal tract |
40.3 Heavy-Metal Poisoning
TipHeavy-Metal Pollutants and Their Effects
| Metal | Source | Health effect |
|---|---|---|
| Lead (Pb) | Old paint, batteries, fuels | Neurotoxic; affects brain development in children; anaemia |
| Mercury (Hg) | Coal, industrial, fish | Minamata disease — neurological damage |
| Cadmium (Cd) | Batteries, electroplating, smelting | Itai-Itai disease — kidney damage, bone weakening |
| Arsenic (As) | Groundwater (West Bengal, Bangladesh) | Skin lesions, cancer, black-foot disease |
| Chromium (Cr-VI) | Tanneries, plating | Cancer, skin ulcers |
| Aluminium | Cooking utensils, smelters | Linked to dementia (debated) |
| Nickel (Ni) | Industry, batteries | Skin allergy, cancer |
| Iron | Excess in water | Hemochromatosis |
40.4 Famous Pollution-Linked Diseases
TipPollution Diseases — Names to Remember
| Disease | Cause | Place of origin |
|---|---|---|
| Minamata | Mercury poisoning (organic methyl mercury) | Minamata Bay, Japan (1950s) |
| Itai-Itai (“It hurts! It hurts!”) | Cadmium poisoning | Toyama, Japan (1912) |
| Black-foot disease | Arsenic from groundwater | Taiwan, West Bengal |
| Pneumoconiosis / Silicosis | Silica dust | Mining and quarrying |
| Bhopal Gas Tragedy disease | Methyl isocyanate (MIC) | Bhopal, India (1984) |
| Asbestosis | Asbestos fibres | Asbestos workers |
| Mesothelioma | Asbestos | Asbestos workers |
| Byssinosis | Cotton dust | Textile workers |
| Aerotoxic syndrome (debated) | Aircraft cabin air | Air crew, frequent flyers |
| Silicosis | Silica dust | Mining, stone-cutting |
40.5 Bioaccumulation and Biomagnification
TipTwo Working Concepts
- Bioaccumulation — build-up of a substance within an individual organism over time (DDT in a fish’s tissue).
- Biomagnification — concentration of substance increases up the food chain.
Tertiary consumers like top predators (eagles, sharks, humans) end up with the highest concentrations of persistent pollutants — DDT, PCBs, mercury, dioxins.
40.6 Pesticide Effects on Health
Persistent organic pollutants (POPs) like DDT, lindane, endosulfan persist in the environment, biomagnify up food chains, and accumulate in fatty tissue.
The Stockholm Convention on POPs (2001) lists “dirty dozen” persistent organic pollutants for elimination, including DDT (with malaria-control exemption), aldrin, dieldrin, PCBs.
40.7 Indoor Air Pollution
In India, indoor air pollution from biomass cooking (wood, dung, coal) is a major cause of respiratory disease, especially among women and children. The Pradhan Mantri Ujjwala Yojana (2016) provides LPG connections to poor households to address this.
40.8 Ozone Depletion and UV Effects
Stratospheric ozone shields humans from harmful UV-B radiation. Depletion increases:
- Skin cancer (especially melanoma)
- Cataracts
- Suppression of immune system
- Damage to crops and marine ecosystems
40.9 Practice Questions
Q 01
Minamata
Medium
Minamata disease is caused by:
View solution
Correct Option: B
Minamata disease is mercury (specifically methyl-mercury) poisoning, named after Minamata Bay, Japan, where industrial discharge contaminated fish in the 1950s.
Q 02
Itai-Itai
Medium
Itai-Itai disease, characterised by bone weakening and kidney damage, is caused by:
View solution
Correct Option: A
Itai-Itai ("It hurts! It hurts!") is caused by cadmium poisoning — first reported in Toyama, Japan in 1912.
Q 03
CO Mechanism
Medium
Carbon monoxide (CO) poisoning is harmful because CO:
View solution
Correct Option: B
CO binds 200× more strongly than O₂ to haemoglobin, forming carboxyhaemoglobin and reducing oxygen delivery.
Q 04
Black-foot Disease
Hard
Black-foot disease, observed in groundwater-affected regions of West Bengal and Bangladesh, is caused by:
View solution
Correct Option: C
Arsenic contamination in groundwater causes black-foot disease and skin/internal cancers.
Q 05
Biomagnification
Medium
The increase in concentration of a persistent pollutant as it moves up the food chain is called:
View solution
Correct Option: B
Biomagnification is the rising concentration of persistent pollutants at higher trophic levels (DDT in eagles, mercury in tuna).
Q 06
PM2.5
Medium
PM2.5 is particularly dangerous to human health because:
View solution
Correct Option: B
PM2.5 is fine enough (≤ 2.5 μm) to penetrate alveoli and enter the bloodstream, contributing to cardiovascular and respiratory disease.
Q 07
Asbestos
Medium
Mesothelioma — a rare form of cancer affecting the lining of the lungs — is most strongly associated with exposure to:
View solution
Correct Option: B
Mesothelioma is strongly linked to asbestos exposure (often decades after exposure).
Q 08
Bhopal
Medium
The 1984 Bhopal Gas Tragedy was caused by the leak of:
View solution
Correct Option: B
The Bhopal Gas Tragedy (2-3 December 1984) was caused by the leak of methyl isocyanate (MIC) from the Union Carbide pesticide plant.
ImportantQuick recall
- Pollution diseases: Minamata (Hg), Itai-Itai (Cd), Black-foot (As), Mesothelioma/Asbestosis (asbestos), Silicosis (silica), Byssinosis (cotton dust), Bhopal (MIC, 1984).
- Bioaccumulation in individual; biomagnification up food chain.
- CO binds haemoglobin → reduces O₂ delivery (carboxyhaemoglobin).
- PM2.5 ≤ 2.5 μm — penetrates alveoli, enters bloodstream.
- WHO 2021 PM2.5 guideline: ≤ 5 μg/m³ annual.
- POPs: Stockholm Convention 2001 lists DDT, lindane, PCBs, etc.
- PMUY (Ujjwala) 2016 — LPG to reduce indoor air pollution.
- Stratospheric ozone depletion → skin cancer, cataracts, immune suppression.