Lethal dose value

Definition

A quantitative measure of toxicity indicating the dose of a substance—such as an insecticide, acaricide, venom, or toxin—required to kill a specified proportion of a test population under controlled conditions. The most common metric is LD₅₀ (lethal dose, 50 percent), the dose that kills half of the exposed organisms; related values include LD₁₀, LD₉₀, and LD₁₀₀ for other mortality thresholds. Expressed typically as mass of toxicant per unit body mass of the organism (e.g., mg/kg) or per individual for uniform test populations. Lethal dose values serve as standardized benchmarks for comparing acute toxicity across compounds, species, and exposure routes, with lower values indicating greater potency.

Etymology

From Latin 'lethalis' (deadly, fatal) + 'dosis' (a giving, portion) + 'valere' (to be strong, to be worth); toxicological usage established in early 20th century quantitative pharmacology.

Example

The LD₅₀ of deltamethrin for adult honey bees (Apis mellifera) is approximately 0.001 µg per bee by topical application, whereas for the parasitoid wasp Cotesia marginiventris it is roughly 0.01 µg per wasp—indicating that the wasp is an order of magnitude less susceptible to this pyrethroid insecticide.

Synonyms

• LD value
• lethal dose

Related Terms

• LC₅₀
• median lethal dose
• toxicity unit
• dose-response curve
• no observed effect level
• Acute toxicity
• insecticide resistance ratio
• synergism ratio

Usage Notes

Distinguished from LC₅₀ (lethal concentration), which measures concentration in air or water rather than administered dose. Values are route-specific (oral, dermal, topical, injection) and species-specific; extrapolation between arthropod groups requires caution. In entomology, LD₅₀ comparisons underpin resistance monitoring, beneficial insect risk assessment, and venom potency studies. Reported values vary with environmental factors (temperature, humidity), test duration, and insect age or nutritional state—methodological details should always accompany cited figures. The term 'lethal dose' alone is often used interchangeably in casual contexts, but 'lethal dose value' emphasizes the quantitative, population-level measurement.