What type of exposure does LD50 relate to?

LD50, or lethal dose 50, is a widely used measure in toxicology that indicates the dose of a substance required to kill half the members of a tested population after a specified test duration. It is primarily relevant for assessing the acute toxicity of chemicals, which encompasses various routes of exposure.

The correct focus is on ingestion or injection, as LD50 values are often determined based on how much of a certain substance is administered to an organism and through which route—specifically oral (ingestion) or parenteral (injection) routes. This is crucial in evaluating the immediate lethal effects of a substance when it enters the body either through eating/swallowing or through needles or other means that bypass the gastrointestinal tract.

In contrast, while skin contact and inhalation are important routes of exposure in toxicological assessments, they are typically not the avenues through which LD50 values are primarily calculated or reported. Long-term exposure is also distinct from the acute exposure measured by LD50, as it pertains to the effects of a substance over an extended period rather than a single high dose. Thus, the emphasis on ingestion or injection directly aligns with the foundational purpose of LD50 in toxicology.