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20

EnS 115 Module 1

By 202380261

Go to stand
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https://covver.com/magazine/202380261/ens-115-module-1
Published
Jul 27, 2026
Pages
29

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  • OverviewIn this course, the basic concepts, methods, and approaches in environmental toxicology will be introduced. Natural and synthetic chemicals commonly encountered in the air, water, and soil will be discussed regarding their occurrence, fate and transport, and toxicological effects on ecological species and humans. Case studies will be used to illustrate the complexity of environmental toxicology issues. New trends in chemical toxicity testing will be discussed. Contaminants of emerging concerns such as pharmaceutical and personal care products and engineered nanomaterials will also be introduced. This module will introduce you to environmental toxicology. Specifically, the topics include the definition and scope of toxicology, brief history of toxicology, dose-response relationships, sources of toxic compounds, and the movement of toxicants in the environment.
  • Learning ObjectivesAfter going through in this module, you should be able to: ➤ define important terms in environmental toxicology;
  • Initial ActivityI want to know if you have any idea/ knowledge about Environmental Toxicology. First, I know that Secondly, I know that Finally, I know that Please write something about this topic: Environmental Toxicology
  • DiscussionI. DEFINITION AND SCOPE A. DEFINITION OF TERMS
  • DiscussionI. DEFINITION AND SCOPE A. DEFINITION OF TERMS
  • DiscussionI. DEFINITION AND SCOPE A. DEFINITION OF TERMS
  • DiscussionI. DEFINITION AND SCOPE A. DEFINITION OF TERMS
  • Target tissueDiscussion I. DEFINITION AND SCOPE
  • DiscussionI. DEFINITION AND SCOPE B. SCOPE OF TOXICOLOGY
  • DiscussionI. DEFINITION AND SCOPE B. SCOPE OF TOXICOLOGY
  • DiscussionI. DEFINITION AND SCOPE B. SCOPE OF TOXICOLOGY
  • DiscussionII. BRIEF HISTORY OF TOXICOLOGY ➤ 1500 BC: The Ebers Papyrus is among the oldest written documentation of medicines in the ancient world. It is the oldest known ancient Egyptian medical scroll, dating back to a period between 1550 and 1500 BC.
  • DiscussionII. BRIEF HISTORY OF TOXICOLOGY ➤ 1939: DDT: Recognized as insecticide by the Swiss scientist Paul Hermann Müller, who was awarded the 1948 Nobel Prize in Physiology and Medicine. Banned in 1972.
  • DiscussionII. BRIEF HISTORY OF TOXICOLOGY Did you know?
  • DiscussionIII. DOSE-RESPONSE RELATIONSHIPS The first recognition of the relationship between the dose of a compound and the response elicited has been attributed to Paracelsus. His statement includes not only that all substances can be toxic at some dose, but that “the right dose differentiates a poison from a remedy," a concept that is the basis for pharmaceutical therapy.
  • Page 17Dose Discussion
  • DiscussionIII. DOSE-RESPONSE RELATIONSHIPS A typical dose-response curve is shown in Figure 3, which plots the relationship between the toxicant dose and the health effects.
  • Threshold DoseDiscussion III. DOSE-RESPONSE RELATIONSHIPS
  • DiscussionIV. SOURCES OF TOXIC COMPOUNDS Everything in the environment is made out of chemicals. These chemicals can either be naturally occurring or synthetic. Both types can be toxic to living organisms; thus natural chemicals can also cause negative effects. Just because they are "natural," does not mean that they are safe.
  • DiscussionV. MOVEMENT OF TOXICANT IN THE ENVIRONMENT Chemicals released into the environment rarely remain in the form, or at the location, of release.
  • DiscussionV. MOVEMENT OF TOXICANT IN THE ENVIRONMENT Lipophilic Toxicants
  • DiscussionV. MOVEMENT OF TOXICANTS IN THE ENVIRONMENT The transport of chemical toxicants can occur through both aquatic and terrestrial food chains, although in the former, higher members of the chains, such as fish, can accumulate large amounts of toxicants directly from the medium.
  • DiscussionV. MOVEMENT OF TOXICANTS IN THE ENVIRONMENT In order for a chemical substance to have any effect, it must first enter the body. Living organisms can ingest them, inhale them, or absorb them through their skin (Figure 7). They may also travel inside the body via mucous in the nose, eye, or ear canals. These pathways are termed routes of exposure.
  • DiscussionV. MOVEMENT OF TOXICANTS IN THE ENVIRONMENT Toxicokinetics
  • DiscussionV. MOVEMENT OF TOXICANTS IN THE ENVIRONMENT Acute toxic effects
  • DiscussionV. MOVEMENT OF TOXICANTS IN THE ENVIRONMENT Categories of Toxic effects
  • DiscussionV. MOVEMENT OF TOXICANTS IN THE ENVIRONMENT Categories of Toxic effects
  • ReferencesCourse References Dekant W. & Vamvakas S. 2004. Toxicology. In Ullmann's Encyclopedia of Industrial Chemistry, (Ed.). https://doi.org/10.1002/14356007.b07_155.pub2
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Discussion

III. DOSE-RESPONSE RELATIONSHIPS

A typical dose-response curve is shown in Figure 3, which plots the relationship between the toxicant dose and the health effects.

In addition, a chemical can produce harmful effects to one living organism while not harming another (selective toxicology). For example, an antibiotic may kill strep throat bacteria, but it will not kill you.

People can also respond to chemical substances in different ways. Some may be exposed and may not develop a negative effect, while others may be more sensitive to a chemical and can develop negative effects from an exposure.

No two individuals are the same; therefore the response to a dose varies considering age, lifestyle, and genetics (biological variation). Yet, if there is no exposure to a chemical, there will not be an effect.

When an organism is exposed to a toxic substance, it follows toxicity phases.

1st phase: Exposure phase - a toxicant is taken up by the organism's system via the mouth (oral), lungs (inhalation), or skin (dermal).

2nd phase: Processing phase - the toxicant is transported and stored inside the body. The rate at how it is processed varies from person to person.

3rd phase: Expression phase - describes the resulting effects that appear in the organism (e.g. lesion or headache).

  • Response
  • Different substances result in different symptoms.
  • Dose Response Curve
  • Dose [log]

Increasing effect no effect range range of increasing effect with increasing dose

Increasing dose maximum effect range

Figure 3. A dose-response curve showing as the dose increases, so does the response Source: Dose-response curve - Labster/2025 Toxicology Education Foundation.