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Unformatted text preview: LIVING WITH THE EARTH CHAPTER 5 TOXICITY AND TOXINS OBJECTIVES A student reading this chapter will be able to: o 1. Discuss and define the concepts of toxic triangle, poison, hazardous material, and hazardous waste. o 2. List and explain the various methods of absorption including diffusion, facilitated diffusion, active transport, and special processes. o 3. Explain the processes of endocytosis including phagocytosis, pinocytosis, and receptor- mediated endocytosis. o 4. Describe and discuss the major mechanisms by which toxic materials produce their adverse effects including: (1) inactivation of enzymes, (2) direct effect on cells and tissues, and (3) production of intermediate compounds or secondary action. o 5. Describe and provide an overview of the immune system, the cellular and humoral immune system, and allergic mechanisms. o 6. Discuss and describe the adverse health effects associated with endocrine disruptors, PCBs, dioxin, lead, mercury, asbestos, and organic solvents. INTRODUCTION In the United States, there are currently more than 70,000 synthetic chemicals currently in commercial use, and for most of them, their toxicity is not widely known or understood. Since 1,000 - 2,000 new chemicals are introduced each year into our society, there is significant opportunity for untested materials to enter our environment and expose humans, wildlife, and plants to toxic effects. A potentially toxic substance produces its adverse effect by interacting with humans (or organisms) and the environment in a relationship referred to as the toxic triangle ( Fig. 5-1 ). A poison or toxic substance does not constitute a hazard unless contact is made with the organism in a form and quantity that can cause harm. o Hazardous Substance A hazardous substance is defined in the Comprehensive Environmental Response Compensation and Liability Act (CERCLA) as any chemical regulated under the following acts: Clean Air Act (CAA) Toxic Substances Control Act (TSCA) Clean Water Act (CWA) Toxic substance Toxic substances are those that: (1) can produce reversible or irreversible bodily injury; (2) have the capacity to cause tumors, neoplastic effects, or cancer; (3) can cause reproductive errors including mutations and teratogenic effects; (4) produce irritation or sensitization of mucous membranes; (5) cause a reduction in motivation, mental alertness, or capability; (6) alter behavior; or cause death of the organism. EXPOSURE AND ENTRY ROUTES Exposure o In order for a toxic substance to produce its harmful effects on the human body, a person must first be exposed to the chemical. Absorption o The passage of substances across the membranes through some body surfaces into body fluids and tissues by a variety of processes that may include diffusion, facilitated diffusion, active transport, or special processes....
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- Summer '08
- toxic substances, endocrine disruptors, GUIDE MAIN PAGE