Introduction to Toxicology and Environmental Health

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Questions and Answers

What does NOAEL stand for in toxicity assessment?

  • No Observed Adverse Effects Level (correct)
  • Notable Observed Adverse Effects Level
  • Necessary Observed Adverse Effects Level
  • Normal Observed Adverse Effects Level

What is indicated by a substance classified as a non-threshold toxicant?

  • It only affects certain target organs at high doses.
  • There is a safe level of exposure.
  • The effects are only observed at maximum doses.
  • Any level of exposure can potentially cause harmful effects. (correct)

What does LOAEL stand for in the context of toxicity?

  • Least observed adverse effect level
  • Limited observable adverse effect level
  • Lowest observed adverse effect level (correct)
  • Lowest observable adverse effect level

Which of the following substances is an example of a non-threshold toxicant?

<p>Vinyl chloride (A)</p> Signup and view all the answers

What determines safe exposure levels for toxic substances?

<p>Toxicological Reference Values and LOAEL. (A)</p> Signup and view all the answers

What is environmental toxicology primarily concerned with?

<p>The harmful effects of various agents on living organisms (A)</p> Signup and view all the answers

Which of the following is NOT a phase of toxicokinetics?

<p>Disruption (A)</p> Signup and view all the answers

What defines a xenobiotic?

<p>A substance that is foreign to the body or ecological system (C)</p> Signup and view all the answers

Which of the following processes describes the entry of toxicants into the body?

<p>Absorption (A)</p> Signup and view all the answers

What aspect does toxicodynamics cover?

<p>What the xenobiotic does to the body (D)</p> Signup and view all the answers

Which of the following substances can be classified as a xenobiotic?

<p>Alcohol (B)</p> Signup and view all the answers

Which organ is primarily involved in the metabolism of toxicants?

<p>Liver (B)</p> Signup and view all the answers

What is the main goal of toxicology?

<p>To understand poisons and assess health risks (B)</p> Signup and view all the answers

Which of the following types of toxicity is NOT listed as a typical organ- or tissue-specific toxicity?

<p>Cerebrotoxicity (A)</p> Signup and view all the answers

What is the primary factor that influences the severity of toxic responses?

<p>Duration and frequency of exposures (B)</p> Signup and view all the answers

Chronic toxicity can result from which of the following conditions?

<p>Accumulation of the toxicant within the body (A)</p> Signup and view all the answers

Which mechanism of toxicity is primarily associated with harmful effects on genetic material?

<p>Carcinogenicity (B)</p> Signup and view all the answers

According to Haber’s Law, what happens as the duration of exposure to a toxicant increases?

<p>Less of the toxicant is needed for an adverse effect (C)</p> Signup and view all the answers

In what scenario does subacute exposure typically occur?

<p>Repeated exposure lasting up to one month (B)</p> Signup and view all the answers

Which factor is considered when assessing external doses of toxicants?

<p>Bioavailability adjustments (A)</p> Signup and view all the answers

What process is used to estimate past exposures to toxicants?

<p>Dose reconstructions (C)</p> Signup and view all the answers

Which of the following is a common approach to quantify dose?

<p>By body weight and time (D)</p> Signup and view all the answers

What is a characteristic of acute toxicity?

<p>It typically occurs from a single dose lasting less than 24 hours (C)</p> Signup and view all the answers

Which of the following is considered a blood sample measurement for internal dose assessment?

<p>Blood plasma (C)</p> Signup and view all the answers

Which of the following routes would be considered when evaluating the distribution of a toxicant?

<p>Inhalation (C)</p> Signup and view all the answers

What does the term 'susceptibility' refer to in the context of toxicant exposure?

<p>Differences in individual response based on various factors (D)</p> Signup and view all the answers

What notorious effect did thalidomide have when introduced as a medication?

<p>Limb malformations in infants (B)</p> Signup and view all the answers

Which factor does NOT influence individual susceptibility to toxicant effects?

<p>Duration of exposure (C)</p> Signup and view all the answers

What does the study of toxicology primarily focus on?

<p>The effects of chemicals, including their prevention and treatment (B)</p> Signup and view all the answers

What constitutes a comprehensive assessment of all sources of exposure to a toxicant?

<p>Aggregate internal dose (D)</p> Signup and view all the answers

Which of the following statements about intrinsic toxicity is true?

<p>Intrinsic toxicity varies based on the molecular structure and stability of the toxicant. (D)</p> Signup and view all the answers

Which factor is NOT one of the primary determinants of adverse effects in toxicology?

<p>Environmental temperature (A)</p> Signup and view all the answers

What does the term 'threshold' refer to in toxicology?

<p>The point at which a substance becomes harmful upon exposure (D)</p> Signup and view all the answers

Who is known as the 'father of toxicology'?

<p>Mathieu Orfila (D)</p> Signup and view all the answers

Which of the following was historically used by the Greeks as a state poison?

<p>Hemlock (B)</p> Signup and view all the answers

What does the phrase 'Dose makes the poison' imply?

<p>The toxicity of a substance is dependent on the dosage received. (C)</p> Signup and view all the answers

Approximately how many new chemicals enter the market each year?

<p>500 (B)</p> Signup and view all the answers

Flashcards

Environmental Toxicology

The study of harmful effects of various chemical, biological, and physical agents on living organisms in the environment, including humans.

Xenobiotic

A substance that is foreign to the body or the ecological system.

Exposure

How a xenobiotic comes into contact with the body.

Toxicokinetics

The process of how a xenobiotic is absorbed, distributed, metabolized, and excreted from the body.

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Absorption

The entry of toxicants through external membranes into the body's circulation.

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Distribution

The movement of toxicants through the circulatory system to various organs and tissues.

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Metabolism/Biotransformation

The biochemical processes that convert the original toxicant into different forms.

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Excretion/Elimination

The removal of the toxicant or its metabolites from the body.

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Non-threshold toxicant

A toxic substance where any amount of exposure can potentially cause harmful effects, regardless of how small the dose.

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NOAEL (No Observed Adverse Effect Level)

The highest dose of a substance where no harmful effects are observed. It helps determine safe exposure levels.

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LOAEL (Lowest Observed Adverse Effect Level)

The lowest dose of a substance where adverse effects are observed. It helps understand the onset of toxicity.

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Target organ

The site in the body where a toxicant's effects are most evident.

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Multiple target organs

A single toxicant can have multiple target organs that are each affected at different levels of exposure.

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Toxicology

The study of the harmful effects of chemicals, physical agents, and biological agents on living organisms and ecosystems, including prevention and improvement of such effects.

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Intrinsic Toxicity

The inherent ability of a substance to cause harm, independent of the amount or exposure.

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Dose

The amount of a substance that an organism is exposed to.

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Exposure Conditions

The conditions under which an organism is exposed to a substance, including the route of entry, duration, and frequency of exposure.

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Individual Susceptibility

The susceptibility of an individual organism to a substance, influenced by factors like age, genetics, and health status.

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Threshold

The concentration of a substance at which no adverse effects are observed.

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Target Organ Specificity

The specific organ affected by a toxicant can vary based on factors like age, sex, and ethnicity.

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Organ-Specific Toxicity

While mechanisms of toxic action can be similar across organs and tissues, toxicants may cause specific effects on particular organs or tissues.

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Exposure Duration and Toxicity

A classification of toxic effects based on the length of time exposure occurred.

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Haber's Law

This principle states that the amount of a toxicant needed to cause an adverse effect decreases as the exposure time increases.

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Chronic Toxicity

A toxicant causing long-term effects in the body due to accumulation, exceeding elimination rates, causing irreversible damage, or insufficient recovery time between doses.

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Exposure Assessment

The process of gathering information about how a toxicant is being contacted and absorbed by an organism or population.

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External dose

The amount of a toxicant that enters the body, for example, through drinking contaminated water.

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Internal dose

The amount of a toxicant that is absorbed into the bloodstream and becomes available to the body.

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Exposure route

How a toxicant enters the body, such as through ingestion, inhalation, or skin contact.

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Exposure duration

The way the toxicant affects the body, for example, whether it causes a quick, short-term effect or a slow, long-term effect.

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Susceptible life stage

The period of development when an organism is most vulnerable to the harmful effects of a toxicant.

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Thalidomide

A drug that caused birth defects in thousands of babies after being used during pregnancy.

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Study Notes

Introduction to Toxicology and Environmental Health

  • Environmental toxicology studies harmful effects of chemicals, biological, and physical agents on living organisms in ecosystems, including humans.
  • It connects toxicology, environmental health, and public policy, describing chemical transport, fate, persistence, and bioaccumulation.
  • It analyzes effects on populations and communities.

Causes of Death

  • Chronic obstructive pulmonary disease (lung)
  • Asthma
  • Cardiovascular disease
  • Cancer
  • Congenital diseases

Xenobiotics, Exposure, Toxicokinetics, and Toxicodynamics

  • Xenobiotic: a substance foreign to the body or ecosystem.
  • Exposure: how a xenobiotic comes into contact with the body.
  • Toxicokinetics: describes what happens to a xenobiotic in the body (absorption, distribution, metabolism, and elimination).
  • Toxicodynamics: describes the effect of the xenobiotic on the body.

Absorption

  • Entry of toxicants through external barriers (skin, lungs, gastrointestinal tract) into the circulatory system.

Distribution

  • Movement of toxicants through circulatory fluids to organs and tissues (blood plasma, tissues).

Metabolism/Biotransformation

  • Biochemical processes converting original toxicant to metabolites.

Excretion/Elimination

  • Removal of toxicant or its metabolites from the body (kidneys, liver, lungs, saliva, sweat, breast milk).

Toxicology

  • Study of poisons.
  • Provides information to assess potential health risks from chemical exposures.
  • Examines adverse effects on living organisms and ecosystems.
  • Addresses harmful effects of drugs, environmental contaminants, and naturally occurring substances.
  • Analyzes effects on biological systems, including humans, animals, and ecosystems.
  • Involves identification, analysis, effects, and treatment of poisons.

History of Toxicology

  • Approximately 100,000 chemicals currently in use worldwide.
  • 500 new chemicals enter the marketplace annually.
  • Examples of historical use include hemlock (Greeks), arsenic (Romans), opium (Chinese), and curare.
  • Paracelsus: "Dose makes the poison"
  • Mathieu Orfila: "father of toxicology"

Primary Factors Influencing Toxicity

  • Intrinsic toxicity: harmful effects of a substance on living organisms, regardless of amount or exposure. Affected by chemical properties (molecular structure, solubility, stability, reactivity, volatility), and chemical species.
  • Dose: Amount of substance.
  • Exposure conditions: how the substance enters the body.
  • Individual susceptibility: differences in how individuals respond to toxicants. Factors include sex, age, nutrition, medical history, genetic background, and environmental exposures.

Acute and Chronic Toxicity

  • Acute toxicity: effects observed within 24 hours, typically from a single exposure.
  • Subchronic toxicity: repeated exposure for one to three months.
  • Chronic toxicity: repeated exposure over a period longer than three months, potentially a lifetime.
  • Haber's Law: It takes less of a toxicant to cause an adverse effect as exposure duration increases.

Dose-Response Relationships

  • Dose: amount of substance an organism ingests.
  • Response: the adverse effects.
  • NOAEL: No observed adverse effect level (highest dose showing no adverse effects).
  • LOAEL: Lowest observed adverse effect level.
  • Dose-response relationships explain how the intensity of a toxic effect depends on the dose or exposure amount.

Susceptibility Factors

  • Susceptibility to toxicants differs among individuals based on various factors.
  • Population dose-response relationships show variability in responses among different groups with respect to a given dose.

Toxic Effects

  • Effects are categorized by location (target organ) and mechanisms of action.
  • Toxicants can have multiple target organs.
  • Mechanisms of toxicity include blood effects, skin effects, eye and cellular effects, immunotoxicity, and many more.
  • Time factors: acute, subacute, chronic.
  • Exposures: in utero, chronic.

Measuring Dose

  • External dose: amount of toxicant ingested, breathed,or absorbed through skin.
  • Internal dose: amount of toxicant absorbed into the body.
  • Techniques include measuring toxicant concentrations in various bodily fluids, samples, or tissue.

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