Question 1

Which of the following best describes the term LD$$_{50} in $$toxicology?

Accepted Answer

The dose at which 50% of a test population dies, measured in mg of substance per kg of body mass.

Question 2

Mercury (Hg) is most toxic in which of the following forms?

Accepted Answer

Mercury vapor or ionic mercury (salt)

Question 3

A chemical is classified as a teratogen if it:

Accepted Answer

Causes birth defects

Question 4

Which of the following statements about heavy metal poisons is correct?

Accepted Answer

They are metals of high atomic mass that exhibit toxic effects, such as copper, lead, and arsenic.

Question 5

Which parameter of toxicity is directly measured by LD$$_{50}$$?

Accepted Answer

Dose (amount of substance)

Question 6

A neurotoxin is a substance that:

Accepted Answer

Interferes with neurotransmission and nerve function

Question 7

Why do regulatory bodies establish upper limits for nutrient intake?

Accepted Answer

To prevent adverse effects associated with excessive intake

Question 8

Which of the following is an example of a corrosive poison?

Accepted Answer

Laundry bleach (oxidizing agent)

Question 9

If a substance has an LD$$_{50} of 0.000002 mg/kg $$when taken orally, what does this indicate about its toxicity?

Accepted Answer

It is extremely toxic; only a very small amount can be lethal.

Question 10

Which of the following best explains why the route of exposure affects toxicity?

Accepted Answer

The body absorbs and processes chemicals differently depending on whether they are inhaled, swallowed, or injected.

Question 11

A mutagen is most likely to:

Accepted Answer

Induce mutations in DNA

Question 12

Which of the following is a correct statement about the toxicity of vitamins and minerals?

Accepted Answer

Excessive intake can lead to adverse effects, so safe upper limits are established.

Question 13

Which chemical property makes mercury vapor more toxic than liquid mercury?

Accepted Answer

Mercury vapor is more easily absorbed by the lungs.

Question 14

Which of the following is NOT a correct match between toxicology term and its definition?

Accepted Answer

Neurotoxin – Causes birth defects

Question 15

A chemical warfare agent with an LD$$_{50} of 0.01 mg/kg is $$used in skin contact. What does this imply about its safety?

Accepted Answer

It is highly toxic; even small skin contact can be lethal.

Question 16

Which of the following best describes the action of mercury ions (Hg$$^{2+}) on $$enzymes?

Accepted Answer

Hg$$^{2+}$$ binds to the active site, inactivating the enzyme.

Question 17

Which of the following is a real-world example of a mutagen?

Accepted Answer

Tobacco smoke

Question 18

Why is it important for manufacturers to provide safety data sheets for chemicals?

Accepted Answer

To ensure workers understand the hazards and can handle chemicals safely.

Question 19

Which of the following substances has the lowest LD$$_{50}$$ value and is therefore the most toxic?

Accepted Answer

Castor beans (LD$$_{50} = 0.000005 mg/kg)$$

Question 20

A patient is exposed to a chemical that is both a mutagen and a carcinogen. What is the most likely health risk?

Accepted Answer

The patient is at increased risk of developing cancer due to DNA mutations.

Chemical Toxicology: Principles, Parameters, and Key Terms

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