Which term describes a substance that tends to remain in the environment for a long time and breaks down very slowly or not at all?

• A. Toxic
• B. Persistent
• C. Biodegradable
• D. Reactive

Answer: (B)

Persistence in the environment means a substance resists breakdown and stays around for a long time. The term that fits describes compounds that linger and break down very slowly or not at all, so their environmental half-lives are long. This happens when chemical structures are stable or microbes can’t easily degrade them, allowing them to persist in soil, water, and even organisms for years. Examples include PFAS and older pesticides like DDT, which can remain in ecosystems long after their use.

Toxic describes harmful effects, not how long a substance lasts in the environment. Biodegradable means something can be broken down by living organisms, which is the opposite of persisting. Reactive means a substance tends to undergo chemical reactions, which again is a different property from lasting in the environment.