AP Syllabus focus:
‘Incineration burns waste to reduce volume but releases air pollutants. Illegal disposal (e.g., tire piles) can create disease risks, and ocean dumping contributes to large floating trash accumulations that harm wildlife.’
Incineration and improper disposal are major solid-waste management challenges. This page focuses on how burning waste and dumping it illegally or into oceans reduce waste locally but create significant air, land, and aquatic pollution risks.
Incineration: Volume Reduction With Tradeoffs
Incineration: Controlled combustion of solid waste to reduce its volume and mass, sometimes to recover energy (waste-to-energy).
Incineration is used because it can quickly shrink trash volumes and reduce the need for landfill space, especially in densely populated regions.
What incineration accomplishes
Reduces volume of municipal solid waste substantially, leaving a smaller amount of ash to manage.
Can generate usable heat/electricity, but energy recovery does not eliminate pollution concerns.
Air pollutants released
Even modern incinerators can emit harmful pollutants if not well controlled or if waste streams contain problematic materials.
Particulate matter (PM): fine particles that can irritate lungs and worsen respiratory disease.
Nitrogen oxides (NOₓ) and sulfur dioxide (SO₂): contribute to smog and acid deposition.
Heavy metals (e.g., mercury, lead, cadmium): can be released from certain products and industrial wastes mixed into trash.
Dioxins and furans: toxic byproducts that can form when burning chlorine-containing materials (notably some plastics) under certain conditions.
Residual waste issues
Incineration transfers some pollution from “solid waste” to air emissions and toxic ash.
Fly ash (captured from exhaust) is typically more hazardous than bottom ash because it can concentrate toxins and must be managed to prevent environmental release.
Improper Disposal: Illegal Dumping on Land
Illegal dumping: Disposal of waste in unauthorized locations (vacant lots, ravines, waterways) to avoid fees, regulation, or transport costs.
Illegal dumping is difficult to monitor because it is dispersed, often occurs at night, and may involve many small events rather than one controlled site.
Environmental and community risks
Chemical contamination: dumped materials can leach toxins into soils and nearby waters after rain.
Physical hazards: sharp debris, unstable piles, and blocked drainage channels can increase flooding or injury risk.
Fire risk: piles can ignite (accidentally or intentionally), producing dense smoke and toxic compounds.
Tire piles as a high-risk example
The syllabus highlights tire piles because they are uniquely hazardous when stored or dumped improperly.
Disease risks: tires trap rainwater, creating breeding habitat for mosquitoes that can spread disease.
This CDC image shows mosquito larvae being collected from water held inside a discarded tire. It demonstrates how tire piles act as container habitats that retain stagnant water, allowing mosquitoes to develop from larval stages and increasing disease-vector risk. Source
Difficult-to-extinguish fires: tire fires can burn for long periods and produce highly toxic smoke and oily residues.
Long-term contamination: runoff from tire piles or fire residues can pollute surrounding soils and waterways.
Ocean Dumping and Floating Trash Accumulations
How ocean dumping creates large trash patches
When waste enters the ocean—directly by dumping or indirectly via rivers and storm drains—winds and currents can concentrate buoyant debris into large floating trash accumulations.
This labeled NOAA map illustrates how major surface currents in the North Pacific form a subtropical gyre that concentrates buoyant debris into accumulation zones. It visually reinforces that “garbage patches” are diffuse regions of elevated debris density shaped by circulation patterns, not solid islands of trash. Source
Many plastics persist for decades and fragment into smaller pieces rather than fully biodegrading.
This Woods Hole Oceanographic Institution (WHOI) map uses a color scale to show measured surface plastic concentrations (plastic pieces per km²) across the western North Atlantic. The highest-density region aligns with the subtropical gyre, highlighting how large-scale circulation patterns create persistent hotspots for floating plastic and microplastic accumulation. Source
Wildlife impacts (central AP focus)
Ocean dumping and marine debris harm wildlife through:
Entanglement: animals caught in nets/lines can drown, starve, or suffer amputations.
Ingestion: seabirds, turtles, and fish may mistake plastics for food, causing blockage, reduced feeding, or death.
Toxic exposure: plastics and associated chemicals can introduce toxins into marine food chains when ingested.
Why this is hard to solve
Debris is widely dispersed and constantly moving.
Cleanup is challenging because much of the material is small, mixed with plankton, or sinks below the surface over time.
FAQ
Continuous emissions monitoring systems (CEMS) can track pollutants such as NOₓ, SO₂, CO, and particulate levels.
Operators use these data to adjust combustion conditions and verify compliance.
Tyres contain synthetic rubber and additives that can generate complex toxic smoke.
They can also produce oily runoff that spreads contamination beyond the burn site.
Methods include surveillance (cameras), community reporting, waste “tagging” (mail/labels), and mapping repeat sites.
Enforcement often targets haulers as well as property owners enabling access.
Agreements such as MARPOL (ship-source pollution) and the London Convention/Protocol restrict ocean disposal of wastes.
Enforcement varies by country and by the ability to inspect vessels and ports.
Surface skimmers and nets can capture plankton, fish larvae, and other neuston that share the same surface zone as debris.
This creates a tradeoff between debris removal and ecosystem disturbance.
Practice Questions
State one benefit and one environmental drawback of incineration. (2 marks)
Benefit: reduces waste volume / reduces landfill demand (1)
Drawback: releases air pollutants (e.g., PM, NOₓ, dioxins, heavy metals) (1)
Explain how improper disposal can create both human health and ecological impacts, using (i) tyre piles and (ii) ocean dumping. (6 marks)
Tyre piles hold water and increase mosquito breeding, raising disease risk (1)
Tyre piles increase fire risk; fires produce toxic smoke/residues (1)
Illegal dumping can contaminate soil/water via toxic runoff/leaching (1)
Ocean dumping leads to large floating trash accumulations via currents/wind concentration (1)
Marine wildlife harmed by entanglement (1)
Marine wildlife harmed by ingestion and/or toxin transfer through food chains (1)
