HSCI 204 MODULE 4 EXAM QUESTIONS ANSWERED CORRECTLY LATEST UPDATE 2026
Define toxicology - Answers Toxicology is the study of harmful effects of chemicals or other agents on
living organisms.
Explain why toxicology is important in environmental health - Answers Toxicology helps identify
harmful substances understand their effects on the body and assess potential health risks.
Explain the phrase the dose makes the poison - Answers This means that any substance can be
harmful depending on the amount of exposure and toxicity depends on dose.
Define poison - Answers A poison is any substance that can cause harm or death when introduced
into the body.
Define toxic agent - Answers A toxic agent is any substance such as chemicals or radiation that can
cause harm.
Define toxicity - Answers Toxicity is the degree to which a substance is harmful to an organism.
Define toxin - Answers A toxin is a harmful substance produced naturally by plants animals or
microorganisms.
Define toxicant - Answers A toxicant is a human made chemical that causes harm.
Define xenobiotic - Answers A xenobiotic is a foreign chemical that enters the body.
Define carcinogen - Answers A carcinogen is a substance that can cause cancer.
Define teratogen - Answers A teratogen is a substance that causes birth defects.
Define mutagen - Answers A mutagen is a substance that causes changes in DNA.
Define toxicokinetics - Answers Toxicokinetics describes how a substance moves through the body
including absorption distribution metabolism and excretion.
List the four steps of ADME - Answers Absorption distribution metabolism and excretion.
Explain absorption - Answers Absorption is how a substance enters the body.
Explain distribution - Answers Distribution is how a substance moves through the body to different
tissues.
Explain metabolism - Answers Metabolism is how the body breaks down a substance often in the
liver.
Explain excretion - Answers Excretion is how a substance is eliminated from the body through urine
feces or other routes.
Explain why metabolism can increase toxicity - Answers Some substances become more toxic after
being metabolized such as methanol being converted into toxic metabolites.
Define dose - Answers Dose is the amount of a substance taken into the body.
List types of dose - Answers Exposure dose absorbed dose internal dose and effective dose.
Define dose response relationship - Answers A dose response relationship shows how the magnitude
of exposure relates to the severity or likelihood of a health effect.
Describe a dose response curve - Answers It shows dose on the x axis and response on the y axis
demonstrating how effects change with increasing exposure.
Define threshold - Answers A threshold is the lowest dose at which a measurable effect occurs.
Define subthreshold - Answers Subthreshold refers to doses below the level where effects are
observed.
Define linear phase - Answers The linear phase is where increases in dose lead to proportional
increases in response.
Define maximum response - Answers Maximum response is the plateau where increasing dose no
longer increases effect.
Define LD50 - Answers LD50 is the dose required to kill 50 percent of test animals and is used to
compare toxicity.
Explain what a low LD50 means - Answers A lower LD50 indicates a substance is more toxic because a
smaller dose causes death.
Define NOAEL - Answers NOAEL is the highest dose at which no adverse effects are observed.
Define LOAEL - Answers LOAEL is the lowest dose at which adverse effects are observed.
Explain difference between NOAEL and LOAEL - Answers NOAEL shows safe exposure level while
LOAEL marks the beginning of harmful effects.
List main factors affecting toxicity - Answers Dose route of exposure duration timing individual
sensitivity and chemical interactions.
Explain effect of dose on toxicity - Answers Higher doses generally produce greater harmful effects.
Define toxicology - Answers Toxicology is the study of harmful effects of chemicals or other agents on
living organisms.
Explain why toxicology is important in environmental health - Answers Toxicology helps identify
harmful substances understand their effects on the body and assess potential health risks.
Explain the phrase the dose makes the poison - Answers This means that any substance can be
harmful depending on the amount of exposure and toxicity depends on dose.
Define poison - Answers A poison is any substance that can cause harm or death when introduced
into the body.
Define toxic agent - Answers A toxic agent is any substance such as chemicals or radiation that can
cause harm.
Define toxicity - Answers Toxicity is the degree to which a substance is harmful to an organism.
Define toxin - Answers A toxin is a harmful substance produced naturally by plants animals or
microorganisms.
Define toxicant - Answers A toxicant is a human made chemical that causes harm.
Define xenobiotic - Answers A xenobiotic is a foreign chemical that enters the body.
Define carcinogen - Answers A carcinogen is a substance that can cause cancer.
Define teratogen - Answers A teratogen is a substance that causes birth defects.
Define mutagen - Answers A mutagen is a substance that causes changes in DNA.
Define toxicokinetics - Answers Toxicokinetics describes how a substance moves through the body
including absorption distribution metabolism and excretion.
List the four steps of ADME - Answers Absorption distribution metabolism and excretion.
Explain absorption - Answers Absorption is how a substance enters the body.
Explain distribution - Answers Distribution is how a substance moves through the body to different
tissues.
Explain metabolism - Answers Metabolism is how the body breaks down a substance often in the
liver.
Explain excretion - Answers Excretion is how a substance is eliminated from the body through urine
feces or other routes.
Explain why metabolism can increase toxicity - Answers Some substances become more toxic after
being metabolized such as methanol being converted into toxic metabolites.
Define dose - Answers Dose is the amount of a substance taken into the body.
List types of dose - Answers Exposure dose absorbed dose internal dose and effective dose.
Define dose response relationship - Answers A dose response relationship shows how the magnitude
of exposure relates to the severity or likelihood of a health effect.
Describe a dose response curve - Answers It shows dose on the x axis and response on the y axis
demonstrating how effects change with increasing exposure.
Define threshold - Answers A threshold is the lowest dose at which a measurable effect occurs.
Define subthreshold - Answers Subthreshold refers to doses below the level where effects are
observed.
Define linear phase - Answers The linear phase is where increases in dose lead to proportional
increases in response.
Define maximum response - Answers Maximum response is the plateau where increasing dose no
longer increases effect.
Define LD50 - Answers LD50 is the dose required to kill 50 percent of test animals and is used to
compare toxicity.
Explain what a low LD50 means - Answers A lower LD50 indicates a substance is more toxic because a
smaller dose causes death.
Define NOAEL - Answers NOAEL is the highest dose at which no adverse effects are observed.
Define LOAEL - Answers LOAEL is the lowest dose at which adverse effects are observed.
Explain difference between NOAEL and LOAEL - Answers NOAEL shows safe exposure level while
LOAEL marks the beginning of harmful effects.
List main factors affecting toxicity - Answers Dose route of exposure duration timing individual
sensitivity and chemical interactions.
Explain effect of dose on toxicity - Answers Higher doses generally produce greater harmful effects.
