LD50 (Lethal Dose): The LD50 is the dose at which 50% of exposed organisms die. It is used to measure acute toxicity.
NOAEL (No Observed Adverse Effect Level): The NOAEL is the highest tested dose of a substance that does not produce any adverse effects in test subjects.
LOAEL (Lowest Observed Adverse Effect Level): The LOAEL is the lowest tested dose of a substance that produces adverse effects in test subjects.