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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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Dose

Discussion

III. DOSE-RESPONSE RELATIONSHIPS

➤ used to characterize the total amount of material to which an organism is exposed;

➤ defines the amount of chemical given in relation to body weight.

➤ usually implies the exposure dose, the total amount of chemical administered to an organism or incorporated into a test system.

➤ may not be directly proportional to the toxic effects since toxicity depends on the amount of chemical absorbed.

correctly describes only the actual amount of chemical absorbed when the chemical is administered orally or by injection.

➤ Under these circumstances, the administered dose is identical to the absorbed dose; other routes of application such as dermal application or inhalation do not define the amount of agent absorbed.

Different chemicals have a wide spectrum of doses needed to induce toxic effects or death.

➤ To characterize the acute toxicity of different chemicals, LD 50 values are frequently used as a basis for comparisons.

➤ Certain chemicals are very toxic and produce death after administration of microgram doses, while others are tolerated without serious toxicity in gram doses.

Table 2. LD 50 values (rats) for some chemicals

  • Ethanol
  • Sodium bicarbonate
  • Phenobarbital sodium
  • Paraquat
  • Aldrin
  • Sodium cyanide
  • Strychnine
  • 1,2-Dibromoethane
  • Sodium fluoroacetate
  • 2,3,7,8-Tetrachlorodibenzodioxin