Waste does not disappear when the bin lorry leaves. It moves — into the air, the water, the soil, and very often into someone else’s country. This page covers both halves of the damage: what it does to ecosystems, and who ends up living next to it.
📘 What you need to know
Producing, treating and disposing of waste causes air, water and soil pollution, plus habitat destruction.
Decomposing organic waste in landfill releases methane, a potent greenhouse gas.
Social impacts fall hardest on low-income communities and countries: health risks, poor living conditions and lower quality of life.
Environmental injustice is when the negative impacts of waste are experienced disproportionately by poorer countries.
The Basel Convention (UNEP, 1992) regulates the movement of hazardous waste between countries.
Pollution occurs when harmful substances are added faster than ecosystems can process them into harmless substances.
Biodegradability is how quickly natural processes break something down. Half-life is the time for half of a substance to break down.
Environmental impacts
Air pollution
Burning waste, especially in open landfills, releases harmful gases including methane and carbon dioxide, which contribute to climate change. Even without burning, decomposing organic waste in landfill produces methane as it rots without oxygen. This is why organic material in landfill matters so much: it is the one component that actively generates a greenhouse gas after it is buried.
Water pollution
Improper disposal lets chemicals and hazardous materials leach into rivers, lakes and oceans. That harms aquatic life and contaminates drinking water sources. The liquid that drains out of a waste pile is called leachate, and it is the main route by which a landfill pollutes water.
Soil pollution
Hazardous waste, chemicals and heavy metals seep into the soil from landfills and dumping. Once there, they contaminate soil and harm plant growth — and because plants take them up, they enter food chains through crops.
Habitat destruction
Landfills and waste dumps occupy large areas of land, destroying natural habitats and reducing biodiversity. The Agbogbloshie e-waste dump in Ghana is the standard case study: it has polluted local water sources and destroyed large areas of natural land.
Learn Agbogbloshie properly — it does triple duty. It is an example of habitat destruction, of e-waste toxicity, and of environmental injustice, because much of the electronic waste there came from high-income countries.
Social impacts
Health risks
Exposure to waste, particularly e-waste and biohazardous materials, causes serious health problems including respiratory diseases, skin infections and cancers. Low-income countries that receive waste from high-income nations often lack the facilities to handle and treat it safely, so people end up working with dangerous material in dangerous conditions.
Environmental injustice
High-income countries frequently export their waste to low-income countries that struggle to manage it safely. The result is environmental injustice: the negative impacts of waste are experienced disproportionately by poorer countries that did not create it.
Learn this treatyBasel Convention — introduced by UNEP in 1992
The Basel Convention is an international treaty designed to:
Regulate the movement of hazardous waste between countries
Prevent the export of such waste from high-income to low-income nations
Protect human health and the environment from improper waste disposal
Its weakness is enforcement. Illegal waste exporting and dumping still happens, which is a useful evaluative point: having a treaty is not the same as solving the problem.
Impact on local communities
Living near a landfill or waste processing plant lowers quality of life through bad smells, noise, and contamination of local water and soil. Communities near waste sites also tend to suffer lower property values, reduced economic opportunities and poor health outcomes — and those sites are usually placed in less affluent areas in the first place, which is the same injustice happening within a country rather than between countries.
Pollution and the limits of ecosystems
DefinitionPollution = harmful substances added faster than ecosystems can process or transform them into harmless substances
Read that definition twice, because the important word is faster. Adding a substance to an ecosystem is not automatically pollution. Ecosystems absorb and manage a certain amount of waste naturally, through processes such as photosynthesis and nutrient cycling. Pollution is what happens when the input rate beats the processing rate.
The red shaded wedge is pollution. Notice it does not appear gradually from the start — it appears once the threshold is crossed.
Ecosystems as natural filters
Many ecosystems can absorb pollutants and transform them into less harmful substances:
Forests: trees absorb carbon dioxide during photosynthesis and convert it into oxygen, reducing atmospheric CO2.
Wetlands: salt marshes and mangroves absorb nitrogen, phosphorus and other pollutants from water, trapping them and using them for plant growth.
Grasslands and farmland: plants take up nitrogen and phosphorus from the soil as nutrients, which reduces the impact of agricultural runoff.
Ecosystem services
Carbon sequestration: plants absorb CO2 and store it in their tissues, reducing greenhouse gases.
Water filtration: wetlands and forests filter pollutants out of water before it reaches rivers, lakes or oceans. Salt marshes along coastlines absorb heavy metals and excess nutrients, reducing the flow into the ocean and protecting marine ecosystems.
Limits to absorption
Overload an ecosystem and it stops coping. Two examples worth learning:
Excess CO2: forests absorb carbon dioxide, but deforestation reduces the number of trees, limiting the ability of forests to manage rising CO2 levels. We are increasing the input and shrinking the processing capacity at the same time.
Eutrophication: wetlands absorb nutrients, but when agricultural runoff carries too much nitrogen and phosphorus, the ecosystem is overloaded and water pollution and eutrophication follow.
Biodegradability and half-lives
Biodegradability refers to how quickly natural processes can break a substance down into harmless components.
BIODEGRADABLE
Paper and food waste decompose quickly
Bacteria and other organisms break them down into harmless materials
Short half-life, so environmental impact is lower
NON-BIODEGRADABLE
Plastics, glass and synthetic chemicals do not break down easily
Can remain in the environment for hundreds or thousands of years
Long half-life, so impact persists across generations
DefinitionHalf-life = the time taken for half of a substance to decay or break down
Pollutants with long half-lives, such as pesticides like DDT and radioactive waste, stay dangerous for a very long time and persist in ecosystems for years or decades. DDT has a half-life of around 15 years, so it can remain in soil and water for decades, affecting wildlife, food chains and whole ecosystems. Substances with short half-lives, such as organic waste, decompose quickly and cause less lasting harm.
The curve flattens but never touches the axis. That slow tail is why long half-life pollutants keep turning up in food chains decades after they were banned.
🤔 Why half-life and food chains are a dangerous combination
A pollutant with a long half-life sticks around long enough to be eaten repeatedly. Each organism absorbs a little and cannot break it down, so the concentration climbs as you move up the food chain. A substance that vanishes in a year never gets the chance to do this. So half-life on its own sounds like a chemistry detail, but it is really what decides whether a pollutant stays in the soil or ends up concentrated in a top predator. That link is worth writing out in full in an extended answer.
EXAM-STYLE
Explain what is meant by pollution, with reference to the capacity of ecosystems. [3]
Step 1 — the definition
Pollution occurs when harmful substances are added to the environment faster than ecosystems can process or transform them into harmless substances.
Step 2 — natural capacity
Ecosystems can absorb a certain amount of waste naturally, through processes such as photosynthesis and nutrient cycling.
Step 3 — the threshold
Once the input exceeds that capacity, the excess accumulates and causes harm. For example wetlands absorb nutrients, but too much nitrogen and phosphorus from agricultural runoff overloads them and causes eutrophication.
3 marks: rate-based definition, natural capacity, overload with exampleThe word “faster” is doing the work in the definition. Leave it out and the answer is not quite right.
EXAM-STYLE
Discuss the social impacts of exporting waste from high-income to low-income countries. [4]
Negative impacts
Receiving countries often lack facilities to handle and treat waste safely, so people are exposed to e-waste and biohazardous material. This causes respiratory diseases, skin infections and cancers, and creates dangerous living and working conditions. The Agbogbloshie dump in Ghana polluted local water and destroyed natural land.
The injustice
The harm falls on communities that did not generate the waste, which is environmental injustice.
The other side
Some argue the trade brings income and employment, and exporting can give producers access to specialised treatment facilities.
Regulation and judgement
The Basel Convention (UNEP, 1992) was designed to prevent exports of hazardous waste to low-income nations, but illegal dumping continues, so the harms currently outweigh the benefits.
4 marks: impacts, injustice, counterpoint, treaty and judgement
💡 Exam tip
Define pollution using the word faster — it is a rate, not a quantity.
Split impacts into environmental and social headings. The syllabus does, so the mark scheme does.
Learn Basel Convention, UNEP, 1992 as a single fact, and add that illegal dumping still occurs.
Agbogbloshie, Ghana is your case study for e-waste, habitat loss and injustice all at once.
Use leachate and methane by name. Both are technical terms the mark scheme looks for.
Link half-life to persistence in food chains rather than just quoting the definition.
⚠ Common mix-up
Pollution defined as “any harmful substance in the environment”. Missing the rate makes the definition wrong.
Half-life misunderstood. Each half-life removes half of what remains, not half of the original amount.
Biodegradable treated as harmless. Organic waste in landfill still generates methane.
Confusing leachate with runoff. Leachate is liquid draining out of a waste pile; runoff is water flowing over a surface.
Forgetting ecosystems have natural capacity. Without it, you cannot explain what a threshold is.
Only writing about the environment. Half the marks in this section are for the social side.
Up next: How Waste Is Disposed Of — the six methods, and the honest advantages and disadvantages of each.
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