Aquatic & Terrestrial Pollution
What does LD50 represent in toxicology?
The dose that causes any observable effect in 50% of the population.
The dose that kills 100% of the test population.
The dose that is lethal to 50% of a test population.
The concentration in the environment that causes any observable effect in 50% of the population.
Which of the following statements correctly differentiates between LD50 and LC50?
LD50 measures concentration in air, while LC50 measures direct dosage.
LD50 is used for aquatic organisms, while LC50 is used for terrestrial organisms.
LD50 measures the dose of a substance, while LC50 measures the concentration of a substance in air or water.
LD50 measures chronic toxicity, while LC50 measures acute toxicity.
In which of the following scenarios would LD50 and LC50 measurements be insufficient for a complete risk assessment?
Assessing the acute toxicity of a new pesticide.
Comparing the relative toxicity of different industrial chemicals.
Determining safe exposure limits for workers handling hazardous materials.
Evaluating the long-term health effects of chronic exposure to low levels of a pollutant.
Based on the LD50 values provided in the table, which substance is the MOST toxic to rats?
Ethanol (Alcohol) with an oral LD50 of ~7,000 mg/kg
Table Salt with an oral LD50 of ~3,000 mg/kg
Caffeine with an oral LD50 of ~190 mg/kg
Nicotine with an oral LD50 of ~50 mg/kg
Substance A has an LD50 of 10 mg/kg, and Substance B has an LD50 of 1000 mg/kg. Which substance is more toxic, and why?
Substance B is more toxic because it has a higher LD50 value.
Substance A is more toxic because it has a higher LD50 value.
Substance A is more toxic because it has a lower LD50 value.
Both substances have equal toxicity since LD50 values are relative and not absolute.
A pesticide has an oral LD50 of 50 mg/kg and a dermal LD50 of 500 mg/kg. Which route of exposure poses a greater risk, and why?
Dermal exposure poses a greater risk because it is more readily absorbed into the body.
Oral exposure poses a greater risk because it has a higher LD50 value.
Dermal exposure poses a greater risk because it has a higher LD50 value.
Oral exposure poses a greater risk because it has a lower LD50 value.
Which of the following best describes the term NOAEL?
Dose that causes a therapeutic effect in 50% of the population.
Highest dose with no adverse effects.
Dose that kills 100% of the test population.
Dose at which an effect is likely to occur.

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In a dose-response study, researchers find that a dose of 10 mg/kg of a substance causes no observable adverse effects in the test animals. However, at 15 mg/kg, some animals begin to show signs of liver damage. Based on this data, what is the NOAEL for this substance?
15 mg/kg
25 mg/kg
10 mg/kg
5 mg/kg
Which of the following is a potential source of error or variability in LD50/LC50 testing?
Using a standardized testing protocol.
Dividing animals into groups.
Differences in species sensitivity to the test substance.
Observing animals for signs of toxicity or death.
Which of the following is an ethical consideration regarding animal testing for LD50/LC50 values?
Animals are observed over a specific period for signs of toxicity or death.
It is a standardized way to measure and compare chemical toxicity.
The potential for animal suffering and death during the testing process.
Animals are exposed to different doses or concentrations of the test substance.