An LD50 value alone is sufficient to determine safe exposure levels for humans.

• A. True
• B. False
• C. Only for inhalation
• D. Only for dermal exposure

Answer: (B)

Lethal dose for 50% of animals (LD50) measures acute lethality for a specific species and exposure route, but it cannot by itself set safe human exposure levels. Setting safe levels requires considering how exposure occurs (inhalation, skin contact, ingestion), how long and how often exposure happens, and whether effects are acute or chronic. LD50 reflects a median lethal dose at a single time point in animals and does not capture human variability, differences between species, or nonlethal and long-term effects such as carcinogenicity or reproductive toxicity. For human risk management, scientists derive reference doses or acceptable daily intakes from NOAEL or LOAEL data and apply uncertainty factors to account for inter-individual differences and extrapolation from animals to humans, often separately for different routes of exposure. So, an LD50 value alone is not sufficient to determine safe exposure levels for humans.