What are the main types of pollution studied in the IB MYP Science curriculum?

In the IB MYP Science curriculum, the main types of pollution include air pollution, water pollution, soil pollution, and noise pollution. Each type affects the environment and human health in different ways. Air pollution involves harmful substances in the atmosphere, water pollution affects rivers, lakes, and oceans, soil pollution degrades land quality, and noise pollution disrupts the natural soundscape.

How does air pollution impact human health and the environment?

Air pollution can have severe impacts on human health, including respiratory diseases, cardiovascular problems, and even cancer. It also affects the environment by contributing to climate change, acid rain, and harming wildlife. Pollutants like carbon monoxide, sulfur dioxide, and nitrogen oxides are particularly harmful and are a focus in the IB MYP Science studies on human influences on the environment.

What are some common sources of water pollution?

Common sources of water pollution include industrial discharge, agricultural runoff, sewage and wastewater, and oil spills. These pollutants can lead to the degradation of aquatic ecosystems, harm marine life, and contaminate drinking water sources. Understanding these sources is crucial in the IB MYP curriculum to develop strategies for reducing human impact on the environment.

How does soil pollution occur and what are its effects?

Soil pollution occurs when harmful chemicals, such as pesticides, heavy metals, and industrial waste, contaminate the soil. This can lead to reduced soil fertility, loss of biodiversity, and contamination of food crops. In the IB MYP Science program, students explore how human activities contribute to soil pollution and the importance of sustainable practices to mitigate these effects.

What measures can be taken to reduce noise pollution in urban areas?

To reduce noise pollution in urban areas, measures such as implementing stricter regulations on vehicle emissions, promoting the use of public transportation, and creating green spaces can be effective. Additionally, using soundproof materials in buildings and encouraging quieter machinery can help. These strategies are part of the IB MYP Science focus on reducing human impact on the environment and improving quality of life.

Why is "Saying CO₂ is toxic." a common mistake in Pollution?

Why it happens: Confusion with CO. How to avoid it: CO (carbon monOxide) is toxic — blocks O₂ in blood. CO₂ (carbon diOxide) is not directly toxic in normal concentrations, but is a greenhouse gas driving climate change.

Why is "Saying the algae themselves use up the O₂ in eutrophication." a common mistake in Pollution?

Why it happens: Algae are alive. How to avoid it: ALGAE PHOTOSYNTHESISE and RELEASE O₂ while alive. The problem is when they DIE — then DECOMPOSERS break them down and consume O₂.

Human influences on environmentIB MYP Sciences (Years 1-5)

Pollution

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Pollution — IB MYP Sciences: air, water and land

Pollution is when human activity puts substances into the environment at concentrations that cause harm. This MYP Sciences note covers the main types and what can be done about each.

What you’ll learn

Mapped to the IB MYP Sciences subject guide (2026 onwards).

MYP Sciences A — Identify major air, water and land pollutants.
MYP Sciences A — Define bioaccumulation, eutrophication.
MYP Sciences C — Explain a specific pollution pathway.
MYP Sciences D — Discuss mitigation and trade-offs.

Air pollution

Mostly from burning fuel.

Most air pollution comes from burning fossil fuels (and biomass). Key pollutants:

Pollutant	Source	Effect
CO (carbon monoxide)	Incomplete combustion (engines, faulty boilers)	Binds to haemoglobin → suffocation
NOₓ (NO and NO₂)	Hot combustion engines	Acid rain, smog
SO₂	Burning sulfur-containing coal/oil	Acid rain (pH 4-5)
Particulates (PM2.5, PM10)	Diesel engines, wood smoke	Lung damage, asthma
CO₂	All combustion	Greenhouse gas — climate change
Methane (CH₄)	Livestock, landfills, gas leaks	Greenhouse gas (~80× more potent than CO₂)

Acid rain forms when SO₂ and NOₓ dissolve in atmospheric water: SO₂ + H₂O → H₂SO₃ (then H₂SO₄). Acid rain (pH 4-5) damages forests, dissolves limestone buildings, acidifies lakes (killing fish).

Mitigation:

Catalytic converters convert CO and NOₓ in vehicle exhausts to CO₂ and N₂.
Flue-gas desulphurisation removes SO₂ from power-station exhaust.
Switch to electric vehicles, public transport, walking, cycling.
Switch to renewable electricity.

Major air pollutants: CO, NOₓ, SO₂, PM2.5, CO₂, CH₄.
Acid rain: SO₂/NOₓ + H₂O → H₂SO₄/HNO₃.
Mitigation: catalytic converters, EVs, renewables.

Water pollution

Sewage, fertilisers, plastics, chemicals.

Main water pollutants:

Sewage — untreated human waste introduces pathogens (cholera, typhoid) and excess nutrients.
Fertiliser runoff — nitrates and phosphates from fields wash into rivers → trigger algal blooms → EUTROPHICATION.

Eutrophication chain:

Excess fertiliser washes into water.
Algae bloom — population explodes due to nutrient abundance.
Algae block light → underwater plants die.
Decomposers break down dead matter, consuming all dissolved O₂.
Fish and other aerobic life suffocate → 'DEAD ZONES'.

Oil spills — coat birds and mammals (loss of insulation), poison marine life.
Microplastics — plastic fragments < 5 mm, ingested by marine animals, end up in our seafood.
Heavy metals (mercury, lead, cadmium from industry/mining) — bioaccumulate.
Thermal pollution — warm water from power station outflows reduces dissolved O₂ → harms fish.

Eutrophication: too much fertiliser triggers an algal bloom, which depletes dissolved oxygen and kills fish — creating 'dead zones'.

Mitigation:

Wastewater treatment plants.
Buffer strips of vegetation along rivers to absorb runoff.
Reduce fertiliser use; precision agriculture.
Plastic bans + recycling.

Fertiliser → algal bloom → O₂ depletion → fish die (eutrophication).
Oil spills, microplastics, heavy metals — long-lasting impacts.
Mitigation: treatment, buffer strips, precision farming.

Bioaccumulation

Pollutants concentrate up the food chain.

Some pollutants (mercury, DDT, certain plastics) are not easily broken down. They build up in the body of an organism that eats them. Worse, a predator eating many such organisms accumulates the pollutant from ALL of them.

Example: mercury in tuna.

Plankton absorb tiny amounts of mercury from polluted water.
Small fish eat thousands of plankton → mercury level higher.
Larger fish eat the smaller fish → higher still.
Tuna eat thousands of smaller fish → very high mercury.
Humans eating tuna receive mercury concentrated through 4 trophic levels.

This is why pregnant women are advised to limit tuna intake — mercury affects brain development.

DDT (banned pesticide):

DDT was sprayed widely from the 1940s to control mosquitoes.
It accumulated in fish.
Birds eating fish accumulated DDT.
Predatory birds (eagles, falcons) at the top of the chain accumulated huge amounts → thinned eggshells → eggs broke → populations crashed (Rachel Carson, 'Silent Spring', 1962).
DDT was banned in most countries; bird populations recovered.

This is an MYP criterion-D classic case: a chemical that 'works' against one pest can cascade through ecosystems with devastating unintended consequences.

Bioaccumulation: pollutants concentrate up the food chain.
Mercury in tuna. DDT in birds of prey.
Top predators get the highest doses.

How it’s examined

Criterion A: name pollutants and effects. Criterion C: explain a pollution pathway (e.g. eutrophication). Criterion D: discuss mitigation trade-offs.

Sources: IB MYP Sciences guide (IBO, official subject guide). Last reviewed 2026-05-25.

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Step-by-step worked examples — Pollution

Step-by-step solutions to past-paper-style questions on pollution, written exactly the way a tutor would explain them at the board.

1Eutrophication chain
Building confidence• water
Question
Excess fertiliser runs off a farm field into a river. Explain how this can lead to fish dying.
Step-by-step solution
1. Step 1
  Fertiliser carries NITRATE and PHOSPHATE — nutrients that algae need.
2. Step 2
  Algae bloom — population explodes due to abundant nutrients.
3. Step 3
  Algae block sunlight → underwater plants can't photosynthesise and die.
4. Step 4
  Decomposer bacteria break down dead algae and plants, consuming dissolved O₂.
5. Step 5
  Aerobic life (fish etc.) suffocate from lack of O₂. Result: dead zone.
Answer
Fertiliser → algal bloom → light blocked + plants die → decomposers use O₂ → fish suffocate.
2Mercury in tuna
Building confidence• bioaccumulation
Question
Why is mercury in tuna a greater health risk than mercury in sardines, even though they swim in the same waters?
Step-by-step solution
1. Step 1
  Mercury BIOACCUMULATES — it isn't easily broken down or excreted.
2. Step 2
  Sardines are LOW in the food chain (eat plankton) → low concentration.
3. Step 3
  Tuna eat THOUSANDS of smaller fish, each carrying mercury → mercury accumulates to high levels in the tuna's tissue.
4. Step 4
  Top predators get the highest dose. Humans eating tuna get a concentrated portion.
Answer
Mercury bioaccumulates up the food chain — sardines (low trophic level) have less than tuna (top predator).
3Reducing urban air pollution
Stretch• air
Question
A city wants to reduce CO, NOₓ and particulate emissions from traffic. Suggest two measures and explain how each works.
Step-by-step solution
1. Step 1
  (i) Mandate catalytic converters on all petrol vehicles — convert CO → CO₂ and NOₓ → N₂ before the exhaust leaves the tailpipe.
2. Step 2
  (ii) Low-emission zone / EV incentives — charge older polluting vehicles to enter the city centre, give subsidies for EVs and public transport. Fewer combustion engines means less pollution at source.
Answer
Catalytic converters convert CO and NOₓ in exhausts. Low-emission zones + EV incentives reduce combustion at source.

Key Definitions and Keywords — Pollution

Definitions to memorise and the exact keywords mark schemes credit for pollution answers — sharpened from recent examiner reports for the 2026 IB MYP Sciences sitting.

Pollution
Examiner keyword
The introduction by human activity of substances at levels that harm the environment.
Eutrophication
Examiner keyword
Nutrient enrichment of water (often from fertiliser) → algal bloom → O₂ depletion → fish die.
Bioaccumulation
Examiner keyword
The build-up of a persistent pollutant in an organism's body, with concentration rising at each step up the food chain.
Particulates (PM2.5, PM10)
Examiner keyword
Tiny solid particles in air that cause lung and heart disease.
Acid rain
Rain with pH 4-5 caused by SO₂ and NOₓ dissolving in water vapour.

Common Mistakes and Misconceptions — Pollution

The traps other students keep falling into on pollution questions — taken from recent IB MYP Sciences examiner reports and mark schemes — and how to avoid them.

✕Saying CO₂ is toxic.
Why it happens
Confusion with CO.
How to avoid it
CO (carbon monOxide) is toxic — blocks O₂ in blood. CO₂ (carbon diOxide) is not directly toxic in normal concentrations, but is a greenhouse gas driving climate change.
✕Saying the algae themselves use up the O₂ in eutrophication.
Why it happens
Algae are alive.
How to avoid it
ALGAE PHOTOSYNTHESISE and RELEASE O₂ while alive. The problem is when they DIE — then DECOMPOSERS break them down and consume O₂.

Practice questions

Exam-style questions with step-by-step worked solutions. Try one before checking the method.

Past paper style quiz

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Pollution — frequently asked questions

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Pollution

Short Study Notes in the form of Slides

Short Study Notes — Pollution

Detailed Notes

What you’ll learn

How it’s examined

1Eutrophication chain

2Mercury in tuna

3Reducing urban air pollution

Pollution

Eutrophication

Bioaccumulation

Particulates (PM2.5, PM10)

Acid rain

✕Saying CO₂ is toxic.

✕Saying the algae themselves use up the O₂ in eutrophication.

Practice questions

Past paper style quiz

Assess your understanding

Pollution — frequently asked questions