---
title: "DDT — AP Environmental Science Definition & Exam Guide"
description: "DDT is a synthetic, fat-soluble persistent organic pollutant that biomagnifies up food chains, causing eggshell thinning in top predators like ospreys and falcons."
canonical: "https://fiveable.me/ap-enviro/key-terms/ddt"
type: "key-term"
subject: "AP Environmental Science"
unit: "Unit 8"
---

# DDT — AP Environmental Science Definition & Exam Guide

## Definition

DDT is a synthetic, carbon-based persistent organic pollutant (POP) that resists breaking down, dissolves in fat, and biomagnifies up food chains, famously causing eggshell thinning in top-predator birds.

## What It Is

DDT is a synthetic [pesticide](/ap-enviro/key-terms/pesticide "fv-autolink") and the classic example of a **persistent organic pollutant (POP)**. "Persistent" is the key word: it's a carbon-based molecule that doesn't easily break down in the environment, so it sticks around for years (EK STB-3.H.1). Because DDT is fat-soluble, it doesn't just wash away. It dissolves into the fatty tissues of organisms and stays there, building up over time. That [fat solubility](/ap-enviro/unit-8/persistent-organic-pollutants/study-guide/NGJL9C6G0X404T0kBdaP "fv-autolink") is also why it's toxic (EK STB-3.H.2).

DDT can also travel long distances by wind and [water](/ap-enviro/unit-6/hydrogen-fuel-cell/study-guide/VBHYpOxkIwXQuPkI6px8 "fv-autolink"), so contamination spreads far from where it was sprayed (EK STB-3.H.3). On the AP exam, DDT almost always shows up as the poster child for **biomagnification**, the process where a substance gets more and more concentrated as you move up trophic levels. A little DDT in algae becomes a lot of DDT in the top predator that eats everything below it (EK STB-3.J.3).

## Why It Matters

DDT lives in **[Unit 8](/ap-enviro/unit-8 "fv-autolink"): Aquatic and Terrestrial Pollution**, specifically Topics 8.7 (POPs) and 8.8 (Bioaccumulation and Biomagnification). It's the example used to support three learning objectives: [AP Enviro](/ap-enviro "fv-autolink") 8.7.A (effects of POPs on ecosystems), AP Enviro 8.8.A (defining bioaccumulation and biomagnification), and AP Enviro 8.8.B (the effects of those processes). DDT is useful because it connects so many ideas at once: chemical persistence, fat solubility, food-chain dynamics, and real population-level harm to wildlife. If you understand DDT, you basically understand the whole POP unit.

## Connections

### Biomagnification (Unit 8)

DDT is the textbook proof of [biomagnification](/ap-enviro/unit-8/bioaccumulation-biomagnification/study-guide/Y54MCai6Nx7x01swrTb6 "fv-autolink"). Each trophic level eats many organisms from the level below, so the fat-soluble DDT they each carry piles up. That's why an osprey can end up with DDT about 25 times higher than the fish it eats.

### [Eggshell thinning (Unit 8)](/ap-enviro/key-terms/eggshell-thinning)

This is the signature effect of biomagnified DDT. In top-predator birds like peregrine falcons and bald eagles, DDT interferes with calcium, producing eggs too thin to survive incubation. It's the cause-and-effect link the exam wants you to draw.

### [PCBs (Unit 8)](/ap-enviro/key-terms/pcbs)

[PCBs](/ap-enviro/key-terms/pcbs "fv-autolink") are DDT's partner in crime. Both are synthetic, carbon-based POPs that resist breakdown, dissolve in fat, and biomagnify. If a question lists POP examples, expect DDT and PCBs to appear together.

### Bioaccumulation (Unit 8)

Bioaccumulation is the buildup of DDT inside a single organism over its lifetime. Biomagnification is the buildup across the [food chain](/ap-enviro/key-terms/food-chain "fv-autolink"). DDT does both, which is exactly why the exam pairs the two concepts.

## On the AP Exam

DDT shows up most often in multiple-choice questions on Unit 8. Common stems give you a scenario (a farmer spraying DDT, ospreys with 25x the DDT of their prey, falcons with thin eggshells) and ask you to name the process responsible. The right answer is almost always biomagnification across trophic levels, not just one organism absorbing it. You should also know why DDT was banned in the U.S.: its persistence and biomagnification harmed wildlife, especially top-predator birds through eggshell thinning. No released FRQ has used DDT verbatim, but it's a perfect example to deploy if an FRQ asks you to describe how a pollutant moves through and damages an ecosystem.

## DDT vs Bioaccumulation vs. biomagnification

Bioaccumulation happens inside one organism: DDT builds up in its fatty tissue over time. Biomagnification happens across the food chain: DDT gets more concentrated at each higher trophic level. The osprey-with-25x-the-DDT question is biomagnification, because it compares two different levels of a food chain.

## Key Takeaways

- DDT is a synthetic, carbon-based persistent organic pollutant (POP) that does not easily break down in the environment.
- Because DDT is fat-soluble, it accumulates in organisms' fatty tissues and becomes toxic.
- DDT biomagnifies, meaning its concentration increases at each higher trophic level of a food chain.
- The classic effect of biomagnified DDT is eggshell thinning in top-predator birds like peregrine falcons and bald eagles.
- DDT was banned in the U.S. mainly because its persistence and biomagnification severely harmed wildlife.
- DDT, mercury, and PCBs are the three substances AP Enviro names as bioaccumulating with major environmental impacts.

## FAQs

### What is DDT in AP Environmental Science?

DDT is a synthetic pesticide classified as a persistent organic pollutant (POP). It resists breaking down, dissolves in fat, biomagnifies up food chains, and is the exam's go-to example for explaining biomagnification and eggshell thinning.

### Why was DDT banned in the United States?

DDT was banned primarily because of its environmental persistence and biomagnification, which harmed wildlife. The most famous damage was eggshell thinning in top predators like bald eagles and peregrine falcons, threatening their populations.

### Is DDT an example of bioaccumulation or biomagnification?

Both, but the AP exam usually tests it as biomagnification. Bioaccumulation is DDT building up inside one organism over time; biomagnification is DDT becoming more concentrated at each higher trophic level, which is why an osprey can have far more DDT than the fish it eats.

### Why do top predators like ospreys have higher DDT levels than the fish they eat?

Because of biomagnification. Each predator eats many prey organisms, and the fat-soluble DDT from all of them concentrates in the predator's tissues. That's how ospreys can end up with roughly 25 times the DDT concentration of their prey.

### How is DDT related to PCBs?

Both are synthetic, carbon-based persistent organic pollutants that resist breakdown, dissolve in fat, and biomagnify. AP Enviro lists DDT, mercury, and PCBs together as substances that bioaccumulate and cause significant environmental harm.

## Related Study Guides

- [8.7 Persistent Organic Pollutants (POPs)](/ap-enviro/unit-8/persistent-organic-pollutants/study-guide/NGJL9C6G0X404T0kBdaP)

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