8.12 Lethal Dose 50% (LD₅₀)

• What does Lethal Dose 50% (LD₅₀) represent in environmental toxicology?

  Dose causing death in 50%
• The Lethal Dose 50% (LD₅₀) is expected to cause death in 50% of the individuals in a test population
• The Lethal Dose 50% (LD₅₀) is a standard way to compare the toxicity of different substances.
• What is the primary use of LD₅₀ in toxicology?

  Risk assessment
• If the LD₅₀ of a substance is 100 mg/kg, it means 100 milligrams of the substance per kilogram of body weight will kill 50% of the test animals
• The Lethal Dose 50% (LD₅₀) standardizes the comparison of toxic effects between substances.
• How does LD₅₀ aid in risk assessment?

  Evaluates potential hazards
• The Lethal Dose 50% (LD₅₀) helps establish safe levels of exposure for human and animal health
• What is the LD₅₀ of ethanol in mg/kg?

  7,060
• Ethanol has a higher LD₅₀ than botulinum toxin.
• What is the LD₅₀ of caffeine in mg/kg?

  192
• What is the LD₅₀ of nicotine in mg/kg?

  50
• What is the LD₅₀ of botulinum toxin in mg/kg?

  0.000001
• The Lethal Dose 50% (LD₅₀) is the dose of a substance that is expected to cause death in 50% of the individuals in a test population
• Match the substance with its LD₅₀ value in mg/kg:

  Ethanol ↔️ 7,060

  Caffeine ↔️ 192

  Nicotine ↔️ 50

  Botulinum Toxin ↔️ 0.000001
• LD₅₀ values can differ greatly between species due to varying sensitivities to toxins.
• Younger and older individuals are often more sensitive to toxins, resulting in a lower LD₅₀
• How does the route of exposure affect LD₅₀ values?

  Influences absorption
• Pre-existing health conditions can increase sensitivity to toxins, lowering the LD₅₀ value.
• Environmental conditions such as temperature and humidity can affect toxicity
• What is the LD₅₀ of ethanol in mg/kg, and where is it commonly found?

  7,060; Alcoholic beverages
• LD₅₀ values are used to inform environmental regulations, such as EPA standards, to protect ecosystems.
• The Lethal Dose 50% (LD₅₀) is defined as the dose of a substance required to cause death in 50% of the individuals in a test population
• If the LD₅₀ of caffeine is 192 mg/kg in rats, what does this mean?

  192 mg/kg kills 50%
• Order the factors affecting LD₅₀ values from most biological to most environmental:

  1️⃣ Species

  2️⃣ Age

  3️⃣ Sex

  4️⃣ Route of Exposure

  5️⃣ Health Condition

  6️⃣ Environmental Factors
• What is one purpose of LD₅₀ in toxicology?

  Toxicity comparison
• LD₅₀ is the dose that kills50% of test subjects
• The LD₅₀ of ethanol is 7,060
• Which substance has the lowest LD₅₀ value listed in the examples?

  Botulinum toxin
• Match the substance with its LD₅₀ value (mg/kg):

  Ethanol ↔️ 7,060

  Caffeine ↔️ 192

  Nicotine ↔️ 50

  Botulinum Toxin ↔️ 0.000001
• Order the factors affecting LD₅₀ values based on their general impact on toxicity:

  1️⃣ Species

  2️⃣ Age

  3️⃣ Sex

  4️⃣ Route of Exposure

  5️⃣ Health Condition

  6️⃣ Environmental Factors
• Why does the species of a test subject affect LD₅₀ values?

  Varying sensitivities to toxins
• Younger and older individuals are often more sensitive to toxins
• Pre-existing health conditions can decrease LD₅₀ values.
• What does the sensitivity factor represent in the LD₅₀ formula?

  Variations in tolerance
• How is LD₅₀ data used in environmental science for regulatory compliance?

  Provides toxicity data
• LC₅₀ measures the concentration of a substance in air or water
• Match the toxicity measure with its description:

  $LD₅₀$ ↔️ Dose causing death in 50% of subjects

  $LC₅₀$ ↔️ Concentration causing death in 50% of subjects

  $NOAEL$ ↔️ Highest dose without harmful effects

  $LOAEL$ ↔️ Lowest dose with harmful effects
• What units are used for LD₅₀?

  mg/kg
• LC₅₀ measures the concentration of a substance in air or water.