Chronic toxicity is the ability of a chemical to cause harm to an organism only after accumulation to a specific level after many exposures over time.

• A. The ability of a chemical to cause harm only after accumulation from many exposures over time
• B. Harm caused by a single exposure
• C. Immediate death after exposure
• D. Toxic effects observed only in aquatic organisms

Answer: (A)

Chronic toxicity refers to harm that only appears after a chemical has built up in an organism through repeated exposures over time. This is why the statement describing harm that occurs after accumulating to a threshold from many exposures best fits the concept—the effect depends on gradual buildup rather than a single event. In practice, small, repeated exposures can lead to accumulation in tissues or organs, and once a certain level is reached, adverse effects emerge, such as growth inhibition, organ damage, or metabolic disruption. By contrast, harm from a single exposure is acute toxicity and would show up quickly rather than after long-term accumulation. The idea of effects only in aquatic organisms points to ecotoxicology, which is a broader field and not the defining feature of chronic toxicity.