Advanced Toxicology

MOS 5425, Advanced Toxicology 1

Course Learning Outcomes for Unit VIII Upon completion of this unit, students should be able to:

2. Summarize the principles of toxicology. 2.1 Discuss the toxicological effects of a carcinogen.

5. Examine toxic substances that pose a risk to human population and the environment.

5.1 Discuss methods of exposure to carcinogens.

8. Evaluate risk assessment procedures related to chemical carcinogenicity. 8.1 Explain the models for assessing cancer risks.

Course/Unit Learning Outcomes

Learning Activity

2 Unit Lesson Chapter 21

2.1 Unit Lesson Chapter 15 Scholarly Activity

5 Unit Lesson Chapter 21

5.1 Unit Lesson Chapter 15 Scholarly Activity

8.1 Chapters 15 and 23 Scholarly Activity

Reading Assignment Chapter 15: Chemical Carcinogenesis, pp. 259-280 Chapter 21: Epidemiological Issues in Occupational and Environmental Health, pp. 391-394 Chapter 23: Human Health Risk Assessment, pp. 425-440

Unit Lesson Unit VIII is the second of a two-part discussion on toxic substances and risk assessment. The last unit of this course covers chemical carcinogens, environmental pollutants, occupational toxicology, and toxicological evaluation. Chemical Carcinogens According to the textbook, cancer is the second leading cause of death in the United States. There are one million newly diagnosed cases of cancer each year and 1.5 million deaths annually (Roberts, James, & Williams, 2015). Many factors can contribute to the development of cancer. Genetics, lifestyle choices, and exposure to environmental factors can all play roles in initiating cancer. Inherited genes at the present time cannot be controlled, but the latter two factors, lifestyle choices and environmental factors, can be controlled to a certain extent to reduce the risk of developing cancer. Lifestyle choices include diet, exercise, exposure

UNIT VIII STUDY GUIDE

Chemical Carcinogenesis, Epidemiology, and Human Health Risk Assessment

MOS 5425, Advanced Toxicology 2

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to the sun, and use of tobacco. Infectious agents, radiation, and xenobiotic chemicals can also induce cancer (Roberts et al., 2015). What is cancer? Cancer, or malignant neoplasm, is the uncontrolled replication of cells that invade other tissues and organs, often damaging and interfering with the function of the organs that are invaded. Types of cancer are often named for the site of origin. If the neoplasm originated in the lungs and metastasized or migrated to the liver, it is still considered lung cancer, although the cancer would now be in the lungs and liver. The xenobiotics that cause cancer are referred to as carcinogens. The development of cancer is referred to as carcinogenesis. Carcinogenesis occurs in several stages, which include initiation, promotion, and progression of the tumor. Initiation is the conversion of a normal cell to a mutated cancer cell. Promotion is the replication of the initial mutated cell. Progression is the conversion of preneoplasia to malignant (or benign) neoplasm (Roberts et al., 2015). There are many agents that are not classified as carcinogens but are listed as potential carcinogens. Carcinogens can be chemicals, viruses, hormones, radiation, or solid-state materials (Roberts et al., 2015). According to the textbook, carcinogens either initiate the neoplastic growth in a tissue or increase the incidence of background spontaneous neoplastic formation in the target tissue (Roberts et al., 2015). Carcinogens can be divided into two basic categories: genotoxic and epigenetic (non-genotoxic) carcinogens. In simple terms, genotoxic carcinogens directly alter the DNA, causing mutations. Epigenetic carcinogens do not alter the DNA but interfere with the expression of the DNA. The authors discuss many chemical classes of known carcinogens. These chemical classes include polyaromatic hydrocarbons (PAHs) such as PAHs found in charcoal broiled foods (that indeed refers to meat cooked on the grill at a barbeque), cigarette smoke, and diesel exhaust. In addition, many metals such as arsenic, chromium, nickel, and lead are carcinogens (Roberts et al., 2015). Environmental Pollutants Have you considered how environmental pollutants may affect the normal, everyday individual? In large cities such as Atlanta, cyclists who often ride in high traffic areas ironically have to be concerned about their health. This is due to the cyclists’ continual inhalation of air pollution from passing vehicles. The burning of fossil fuels is a major contributor to air pollution in many developed countries (Roberts et al., 2015). For many people, outdoor air pollutants come to mind when environmental air pollutants are mentioned. What about indoor pollutants? Have you ever worked in an older office building and felt ill on Monday morning when you returned to work from the weekend away from the building? Perhaps every time you enter the building you develop a non-stress related headache or other ailment. Indoor air pollutants may be referred to as sick building syndrome. Sick building syndrome can be caused by many unidentified agents or environmental factors within a building and in fact is a real condition. It is not simply the Monday work blues. Environmental toxicants can move through one medium to another. It is not uncommon for air pollutants to cross media to contaminate soil and water. Water contaminants include pesticides, metals, fertilizers, and even medications that are disposed of incorrectly by flushing down the toilet or throwing in the trash can. Occupational Toxicology There once was an older gentleman who worked for a factory for many, many years. He retired from his position after more than 30 years of work at the same company. Within five years of retirement, the gentlemen was diagnosed with lung cancer. He fought the cancer with the support of his family. This man had a small pharmacy of drugs in his home. He took drugs to fight the cancer and drugs to combat the side effects of the cancer drugs. After almost two years of chemotherapy and radiation, he lost his battle with cancer. Within a few years of his death, it was revealed to his family that more than 50% of former employees of the company had developed lung cancer. This is a major topic of concern for safety professionals. Toxicants can enter the body by various means. Although we aim to eliminate the possible exposure to various pollutants in normal everyday life, some occupations do not allow employees to totally avoid toxicants in their work environment. It is vital for the health of employees for these individuals to be protected from all means of harmful exposure of the toxicants. Your textbook discusses the effects of various toxicants if the safe exposure limits are exceeded. Some effects of exposure may be very minor, such as headaches, or can potentially increase in range of severity from nausea to organ damage and cancer.

MOS 5425, Advanced Toxicology 3

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Epidemiological Studies In simple terms, epidemiology is the study of the causes as well as the effects of disease within a defined population of people. Controlled laboratory experiments and studies can tell us a great deal in terms of the risk factors of an agent. On the other hand, human studies that are less controlled address the everyday factors and elements that humans encounter in association with toxicants; human studies can expose various risk factors. Epidemiological studies can reveal exactly what occurs within the human body due to exposure to an agent rather than extrapolating data from animal models to suggest what could happen in humans. Human studies are limited by what is ethical. Some studies are very slow in gathering data because many epidemiological studies make observances and collect data rather than intentionally induce a disease state or risk as in animal studies. Environmental epidemiology examines populations that are exposed to airborne, ingested, or dermally absorbed agents. An study in Flint, Michigan, on the population exposed to contaminated tap water that is used in cooking, drinking, and bathing, is a good example of an environmental epidemiological study. Occupational epidemiology simply refers to studies that examine a population that experiences exposure to an agent in a work-related environment. An example of this would be the emergency response workers who were engaged in the rescue of people in New York during the events of 9-11. Many of the emergency response workers and volunteers experienced chronic health issues that epidemiologists were able to trace back to the exposure to airborne agents during that time. Health Risk Assessment Risk assessment utilizes scientifically collected data of the hazardous properties of a chemical and duration of exposure to determine the level of harm the agent poses to the population (Roberts et al., 2015). There are basic steps to risk assessment that every student should know. These four steps include hazard identification, dose-response assessment, exposure assessment, and risk characterization (Roberts et al., 2015). Hazard identification is simply assessing the increased health risk caused by exposure to an agent. Dose-response assessment is relating the concentration and duration of exposure to adverse effects. Factors that can alter a response such as health issues, sex, age, and lifestyle may also be examined in conjunction with the dose- response assessment of an agent (Roberts et al., 2015). Exposure assessment identifies what population, routes of exposure, concentration, and duration of exposure are encountered. Risk characterization is compiling the information from the previous steps to determine the likelihood of the hazards developing in the population (Roberts et al., 2015). The textbook goes into detail about each step of risk assessment. Take some time to read and understand the process; however, do not get caught up in the details of the mathematical formulas for calculating risks and concentration of exposure. Pay special attention to the information in the textbook, but utilize it as a springboard to investigate the subject matter of occupational and environmental toxicology further and learn as much as you can. It is important to be up to date on the latest information, not only while obtaining your degree, but throughout your career. New equipment for personal protection against toxicants are always being developed as well as technology to measure levels to toxic exposure. Congratulations on completing the last lesson. Let’s make this unit your best!

Reference Roberts, S. M., James, R. C., & Williams, P. L. (Eds.). (2015). Principles of toxicology: Environmental and

industrial applications (3rd ed.). Hoboken, NJ: Wiley.

MOS 5425, Advanced Toxicology 4

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Suggested Reading In order to access the following resource, click the link below. The following article outlines some occupational toxicology issues that face the oil and gas industry. While some concerns get attention, many dangers in the industry remain that do not receive the attention they deserve, and the article highlights some recommendations for worker protection. Johnson, D. (2015). Industrial hygiene practices are often overlooked on oil and gas fields. ISHN, 49(11).

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