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A Practical Guide to Toxicology and Human Health Risk Assessment von Robinson, Laura (eBook)

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A Practical Guide to Toxicology and Human Health Risk Assessment

Toxicology - the study of the adverse effects of chemicals on living organisms is the cornerstone to all aspects of chemical safety and knowledge of the subject is needed in a wide spectrum of fields from the chemical industry to medicine, emergency services, forensics, and regulatory science. Toxicology involves the study of symptoms, mechanisms, treatments and detection of poisoning ... especially the poisoning of people. The many problems arising from a poor understanding of toxicology and its applications in hazard communication and chemical safety motivated the author's training courses and webinars, leading to this valuable book. Providing a practical and accessible guide, A Practical Guide to Toxicology and Human Health Risk Assessment enables readers to quickly build up knowledge and understanding of toxicology and its use in hazard identification, which is a fundamental part of chemical risk assessment. The book also covers current toxicological testing strategies and the use of physicochemical test data in hazard identification and exposure assessment. Examples are provided throughout the book to highlight important issues along with a summary of the key points that have been covered in each of the respective chapters. The book concludes with a listing of online resources on toxicology and risk assessment. LAURA ROBINSON, MSc, has worked as a toxicologist both in industry and in consultancy for over ten years. She has extensive experience in chemical risk assessments, occupational exposure issues, assessment and interpretation of toxicological data. She is a qualified teacher and has designed and delivered numerous training courses and written two books.

Produktinformationen

    Format: ePUB
    Kopierschutz: AdobeDRM
    Seitenzahl: 400
    Sprache: Englisch
    ISBN: 9781118881903
    Verlag: Wiley
    Größe: 11842 kBytes
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A Practical Guide to Toxicology and Human Health Risk Assessment

2
Basic Toxicological Terminology

Introduction

This chapter explores some of the common toxicological terminology that is useful to understand prior to reading the other chapters of this book.
2.1 The Cell

The cell is the basic building block of all living organisms, and in mammals, the cells typically have a nucleus and cytoplasm, which contains various cellular organelles and a cell membrane ( Figure 2.1 ). They can, however, differ in terms of shape, size, and function. For example, epithelial cells line both internal and external surfaces and are generally cuboidal in shape, whereas nerve cells (neurons) are long structures that transmit messages by means of an electrical impulse ( Figure 2.2 ).

Figure 2.1 Cell structure.

Source: © Vladmir Ischuk/ Shutterstock.com .

Figure 2.2 Different cell types.

Source: © Alila Media Medical/ Shutterstock.com .
2.1.1 Stem Cells, Somatic Cells, and Germ Cells

As will be seen in later chapters, cells can be categorized as stem cells, somatic cells, and germ cells. Stem cells are nondifferentiated cells that can proliferate to produce more stem cells or differentiate into specific cell types. For example, the stem cells present in the bone marrow can differentiate into different blood-cell types. Somatic cells are all the nonreproductive cells of the body; they include the epithelial and nerve cells mentioned earlier. Germ cells or gametes are the sex cells, and in males these are sperm, and in females the ovum or egg. Tissues are groups of similar cells, all with a specialized function and structure. There are four main types of tissue: muscular, epithelial, nervous, and connective tissue . Different types of tissue make up organs, which have a common function and shape. Examples include the liver, kidneys, and the heart. Toxicologists are particularly interested in chemically induced harm to different organs or organ systems. This is known as "target organ toxicity" and is covered in more detail in Chapter 8 .
2.2 Homeostasis

The internal environment of the body is constantly changing not only in response to the external environment but also because of changes in activity. However, the maintenance of a stable internal environment is essential for all the cells of the body to ensure that they can maintain both function and viability. For example, changes in body temperature can have a significant impact on the functioning of enzymes, which are needed for metabolism. Also, concentrations of blood glucose, pH, and specific ions need to be maintained within a narrow range of physiological parameters (Tortora and Grabowski 1996 ). This process of maintaining optimum conditions and making the relevant adjustments by means of feedback loops is called homeostasis . As will be seen in Chapter 8 , both the nervous system and endocrine system are closely involved in homeostasis, albeit in different ways.
2.3 Adaptation and Cell Injury

Homeostasis occurs because of the cells and tissues of the body being able to continually adapt to their ever-changing environment, which enables them to maintain both function and viability.

An adaptive response is a reversible process by which the organism manages an increase in demand or compensates for injury or disease. Once the increased demand or injury has resolved, everything usually returns to normal. For example, in the absence of any hepatocellular injury, chemical induced liver enlargement, which is commonly observed in repeated dose toxicity studies, is generally considered to be an adaptive response. However, if the capacity for an adaptive response is exceeded, this may result in cell injury. At the cellular lev

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