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UGC NET PAPER 1 · UNIT 09 · MODULE 2: POLLUTION, HEALTH AND RESOURCES · TOPIC 4

Impacts of Pollutants on Human Health

The exposure chain from source to effect, then air pollutants, water, food and soil contaminants, and biological and physical agents, each with its health effect.

  • 4 sub-topics
  • Analysis Angle
  • 4 min read
  • Topic 4 of 10

What this topic covers

4 sub-topics, in the order to study them. Tap one to jump to it.

  1. 4.1Concept: the exposure chain from source to effectA pollutant harms health through a chain: source, release, transport in air, water, soil or food, exposure by inhalation, ingestion or skin contact, absorption, and then an…
  2. 4.2Air pollutants and their effectsPollutant Main source Health effect Particulate matter (PM2.5, PM10) Vehicles, coal, biomass, dust, stubble burning Chronic bronchitis, COPD, asthma, heart disease, lung…
  3. 4.3Water, food and soil contaminantsContaminant Source Condition or effect Mercury (methylmercury) Industrial discharge, fish Minamata disease, nervous system damage; foetal brain damage if the mother eats…
  4. 4.4Biological and physical agentsWaterborne diseases: cholera (Vibrio cholerae), typhoid, hepatitis A, giardiasis (a protozoan), amoebiasis; guinea worm (through Cyclops in water); schistosomiasis…
  5. ★Analysis AngleHow examiners twist this topic, and how to reason through scenario questions.

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4.1Concept: the exposure chain from source to effect#

In brief

A pollutant harms health through a chain: source, release, transport in air, water, soil or food, exposure by inhalation, ingestion or skin contact, absorption, and then an…

A pollutant harms health through a chain: source, release, transport in air, water, soil or food, exposure by inhalation, ingestion or skin contact, absorption, and then an effect on a target organ. The size of the effect depends on the dose, the duration of exposure and the vulnerability of the person, which is why toxicology talks about dose-response relationships. Acute exposure is short and intense (the Bhopal gas leak), while chronic exposure is long-term and often low-level (arsenic in drinking water, particulate matter, lead). Children, pregnant women, the elderly and people with existing lung or heart disease are more vulnerable, and children are especially at risk because they breathe more air per unit body weight and their organs are still developing.

Some pollutants are carcinogens (cause cancer), mutagens (cause changes in DNA), teratogens (cause birth defects), endocrine disruptors (interfere with hormones), or neurotoxins (damage the nervous system). The International Agency for Research on Cancer classifies substances in Group 1 when they are carcinogenic to humans, and outdoor air pollution and particulate matter were classified in Group 1 in 2013. Persistent substances (DDT, PCBs, mercury) bioaccumulate in body fat or tissue and biomagnify along the food chain, so top consumers, including humans, carry the highest burdens. Air pollution is generally regarded as the largest single environmental health risk worldwide.

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4.2Air pollutants and their effects#

In brief

Pollutant Main source Health effect Particulate matter (PM2.5, PM10) Vehicles, coal, biomass, dust, stubble burning Chronic bronchitis, COPD, asthma, heart disease, lung…

Pollutant Main source Health effect
Particulate matter (PM2.5, PM10) Vehicles, coal, biomass, dust, stubble burning Chronic bronchitis, COPD, asthma, heart disease, lung cancer; PM2.5 reaches deepest into lungs
Carbon monoxide Incomplete combustion, vehicles Binds haemoglobin to form carboxyhaemoglobin, reducing oxygen transport; colourless and odourless
Sulphur dioxide Coal burning, smelters Bronchoconstriction, aggravates asthma; lichens are bioindicators
Nitrogen dioxide Vehicles, power plants Respiratory infection, reduced lung function, effects on children's lung growth
Ground-level ozone Secondary pollutant from NOx and VOCs Reduced lung function, airway inflammation, asthma attacks
Lead Leaded petrol (tetraethyl lead), batteries, paints Nervous system damage, anaemia, lower IQ in children (plumbism)
Benzene Petrol vapour, industry Leukaemia (carcinogen)
Radon Soil gas in poorly ventilated buildings Lung cancer (radioactive gas)
Biomass smoke (indoor) Traditional stoves Acute respiratory infection in children, COPD in adults
Tobacco smoke (second-hand) Smoking Respiratory illness, heart disease, cancer in non-smokers
UV-B (from ozone depletion) Ozone layer thinning Skin cancer, melanoma (from melanocytes), cataract

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4.3Water, food and soil contaminants#

In brief

Contaminant Source Condition or effect Mercury (methylmercury) Industrial discharge, fish Minamata disease, nervous system damage; foetal brain damage if the mother eats…

Contaminant Source Condition or effect
Mercury (methylmercury) Industrial discharge, fish Minamata disease, nervous system damage; foetal brain damage if the mother eats contaminated fish
Cadmium Mining, batteries, phosphate fertilizers Itai-itai disease (bone and kidney damage); accumulates in kidneys
Arsenic Groundwater (geogenic), pesticides Arsenicosis: skin lesions, keratosis, cancers; blackfoot disease; West Bengal and Bangladesh
Fluoride (above 1.5 mg/L, WHO) Groundwater Dental fluorosis (mottled teeth), skeletal fluorosis
Nitrate Fertilizer runoff Blue baby syndrome (methaemoglobinaemia)
Chromium (hexavalent) Tanneries, electroplating Lung cancer, skin ulcers
Pesticides (organophosphates) Agriculture Inhibit acetylcholinesterase; neurological effects
DDT Pest control Stored in fatty tissue, biomagnifies; thinning of bird eggshells
Dioxins Incineration, chemical industry Chloracne, cancer, reproductive effects
PCBs Electrical equipment Endocrine disruption; Yusho disease in Japan (1968) from contaminated rice oil
Bisphenol A Some plastics Endocrine disruptor
Aflatoxin Mould (Aspergillus flavus) on stored grain Liver cancer
Vinyl chloride Plastics (PVC) industry Angiosarcoma of the liver

WHO guideline values worth knowing: arsenic 10 micrograms per litre, fluoride 1.5 mg/L, and the 2021 annual PM2.5 guideline of 5 micrograms per cubic metre.

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4.4Biological and physical agents#

In brief

Waterborne diseases: cholera (Vibrio cholerae), typhoid, hepatitis A, giardiasis (a protozoan), amoebiasis; guinea worm (through Cyclops in water); schistosomiasis…

  • Waterborne diseases: cholera (Vibrio cholerae), typhoid, hepatitis A, giardiasis (a protozoan), amoebiasis; guinea worm (through Cyclops in water); schistosomiasis (freshwater snails)

  • Vector-borne diseases linked with water and climate: malaria (Anopheles), dengue (Aedes aegypti, breeds in clean stagnant water)

  • Legionnaires' disease: Legionella bacteria in cooling towers and water systems; aspergillosis: fungal disease of damp indoor spaces

  • Heat stroke and heat exhaustion from heat waves; vulnerable groups include outdoor workers, children and the elderly

  • Noise: hearing loss, tinnitus, sleep disturbance, hypertension and stress; prolonged exposure above about 85 dB is harmful

  • Radiation units: becquerel (radioactivity), gray (absorbed dose), sievert (equivalent dose); radioiodine (I-131) from nuclear accidents raises the risk of thyroid cancer, as seen after Chernobyl

  • Occupational lung diseases: coal worker's pneumoconiosis (coal dust), silicosis (silica dust), asbestosis and mesothelioma (asbestos), byssinosis (cotton dust), bagassosis (sugarcane bagasse), farmer's lung (mouldy hay)

  • Disasters with health consequences: Bhopal (methyl isocyanate, 1984), Chernobyl (1986), Fukushima (2011), Seveso (dioxin, 1976), Love Canal, Minamata, endosulfan in Kasaragod

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★Analysis Angle: Impacts of Pollutants on Human Health

Analyse / traps

  • Link the pollutant to the organ and then to the disease name: mercury to nervous system and Minamata, cadmium to kidney and bone and Itai-itai, fluoride to teeth and bone, nitrate to infant blood and blue baby syndrome, silica to lungs and silicosis. Matching questions use exactly these pairs.

  • Persistence, not just toxicity, makes DDT, PCBs and mercury dangerous: they last long, enter fat, and magnify up the food chain, so effects appear far from the source and years later.

  • Poverty and exposure are connected. Rural households using biomass stoves, informal e-waste or battery recyclers and communities near mines and tanneries carry the highest burden, so health impacts are also equity issues, which links back to SDG 3, 6, 7 and 10.

  • Climate change adds health impacts indirectly: heat stress, spread of vector-borne diseases, food and water insecurity and displacement. An assertion that climate change affects health because it increases heat stress and widens the range of vector-borne diseases is correct.

  • Do not mix up units: becquerel measures how many atoms decay, gray measures energy absorbed, sievert measures biological effect; decibel measures sound; Dobson unit measures ozone column; NTU measures turbidity.

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↑ Module 2: Pollution, Health and Resources · All 10 topics in People, Development and Environment · Unit overview and sample MCQs

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