PUH 5305 Unit II & Unit IV

PUH 5305, Concepts of Environmental Health 1

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

2. Summarize the factors that affect susceptibility to adverse health outcomes following exposure to environmental hazards. 2.1 Examine the adverse impact of toxicity on the environment and humans. 2.2 Describe the history of toxicology and its most important developments.

5. Explain how the general mechanisms of toxicity provoke a toxic response in environmental

exposures. 5.1 Discuss the levels of toxic dosage and risk factors related to this in human and environmental

exposure. 5.2 Explain the difference between toxicants and toxins in the environment.

Course/Unit Learning Outcomes

Learning Activity

2.1 Unit Lesson Chapter 3 Unit IV Assessment

2.2 Unit Lesson Chapter 3 Unit IV Assessment

5.1 Unit Lesson Chapter 3 Unit IV Assessment

5.2 Unit Lesson Chapter 3 Unit IV Assessment

Required Unit Resources Chapter 3: Environmental Toxicology

Unit Lesson Introduction It is widely accepted that there is a complex relationship between the human population and the environment in which they live. Around the 1960s, many citizens in the United States were concerned and made aware of the detrimental effects of pesticides and drugs as well as other chemical substances that could be found in the environment, food, and water (Geo et al., 2015; Hayat, 2014). Communities in the United States pressured the government to provide more information on environmental problems, especially those that could potentially be harmful to the human population. These potentially harmful biological and chemical agents such as toxicants from fertilizers, insecticides, pollutants, and pesticides could affect organisms and the community by reducing species abundance and diversity. These changes in population dynamics could destroy the ecosystem, which, in turn, would reduce stability and productivity (Geo et al., 2015).

UNIT IV STUDY GUIDE

Environmental Toxicology

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Defining the History of Environmental Toxicology: Environmental toxicology inhabits an essential role in public policy, toxicology, and environmental health. This foremost contribution has provided scientific evidence and tools for the public and policymakers to prevent substantial environmental degradation, especially adverse effects on human life.

Rachel Carson, a marine biologist, is said to be the pioneer of advancing environmental toxicology and making it a distinct field within toxicology and environmental health. Her 1962 book, called Silent Spring, covered the harmful impact on unrestrained pesticide use (McCarty, 2013). Carson’s book, despite being met with a lot of criticism, encouraged the reversal of national pesticide policies and finally led to the ban of Dichlorodiphenyltrichloroethane, commonly known as DDT (Conis, 2017). It also stimulated grassroots movements on the environment as well as leading to the formation of the U.S. Environmental Protection Agency (Paull, 2013) and subsequently led to President Jimmy Carter awarding Carson the Presidential Medal of Freedom. DDT was an odorless, colorless, and tasteless chemical introduced by the Paul Hermann Muller, a Swiss chemist, in the late 1930s to fight pests that caused typhus and malaria especially during World War II (U.S. Environmental Protection Agency [EPA], 2017; van den Berg et al., 2017). By 1945, it was sold in the United States to kill insects on farms and in households. But after Carson’s book claimed that it was a threat to agriculture, wildlife, and human beings, including causing cancer, a public manifestation against DDT later led to the ban of the chemical in 1972 (EPA, 2017). Even though DDT has been banned in the United States, it is still widely

used in several developing countries, especially some countries in Africa because the World Health Organization (WHO) argues that the benefits of DDT outweigh the effects to the environment (van den Berg, 2009; van den Berg et al., 2017). It is mainly used to fight malaria. Even though several laws were implemented to limit the damaging effects of toxicants in the environment, it has been warned that long-lasting limitations in the operation of current toxicant aquatic testing procedures could lead to an imminent dark age in environmental toxicology (McCarthy, 2013). One law that has been implanted over the years because of toxicity in the environment and humans is the Toxic Substance Control Act of 1976 (TSCA). TSCA is a federal law that is aimed at regulating industrial chemicals that could potentially be harmful to human beings and the environment (Schwartz et al., 2014). The point of the law is to address the manufacturing, chemical degradation, disposal, importation, use, and storage of chemicals, especially for commercial use. This law is administered by EPA to regulate new and existing chemicals sold or exposed to the public. Types of Toxicology: Toxicology is a multidisciplinary field of discipline, which is divided into several types. The various types of toxicology are outlined below: Analytical toxicology: This branch of toxicology studies the identification and detection of poisonous chemicals that could affect the biological system. Analytical toxicology could assist in managing, preventing, and diagnosing poisoning especially from pesticides and drug abuse (WHO, n.d). Applied toxicology: This applies to the modern and new technologies or methods in early detection of toxicants in a practice area or field setting. Its main purpose is to determine the physiological safety or effect of administered products (Hayat, 2014). Clinical toxicology: This method is used to study epidemiology, diagnosis, mechanisms of toxicity, clinical features, and treatment of poisoning that can happen in humans (Schep et al., 2010).

Rachel Carson (U.S. Fish and Wildlife Service, 1944)

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Veterinary toxicology: This is the study of treating and diagnosing poisoning in animals, including when the toxin is transmitted to human beings through fish, meat, milk, or other food items (Hayat, 2014; Hodgson, 2010). Environmental toxicology: This is our area of attention; it is the study of the various toxicants found in the environment that not only destroy the environment, but also negatively affect animals and human beings (Geo, 2015; Hayat, 2014). Industrial or occupational toxicology: This is the study of harmful effects on individuals by chemicals that are used in the workplace, the wastes created during manufacturing, and the products produced by companies (Hayat, 2014). Some of these toxicants include asbestos, solvents, and other heavy metals especially lead and arsenic. Medical toxicology: This field is dedicated to evaluating and treating patients that have been envenomated or poisoned. It also would include adverse health impacts on environmental and occupational toxins, biological agents, and medications (American College of Medical Toxicology, n.d.). Medical toxicologists are also involved in caring for people that have come into contact with substances, drugs, or other harmful chemicals such as intentional or unintentional overdose, exposure to environmental products and industrial chemical products. Other cases would be drug abuse management, diagnosis of exposure, and medical examinations of disabilities and injuries because of toxic exposure (Hayat, 2014). Toxicologists in general, regardless of the type, usually focus on the following significant information about poisoning: poison detection, poison occurrence, poison properties, poison effects, poison, treatment, and poison regulation (Hayat, 2014). Case Study of Environmental Toxicology –Cancer: There are many instances that have had public health environmentalists and policymakers worried about the toxicology in the environment. Some of these carcinogenic and toxicologic assessments include dietary supplements and herbal products, contaminated drinking water, chemical intermediates, environmental contaminants, and metals. The National Institutes of Health (NIH) have categorized the genetic toxicity of several areas of environmental agents and concluded that genetic toxicity is a major cause of cancer. This knowledge has resulted into some of the most effective early screening procedures for cancer-causing agents and has helped to prevent cancer by reducing many chemicals in the environment, such as urethane, butadiene, and benzene (NIH, n.d.). Some of these examples include barbecued food, tobacco smoking, and polluted air. These toxicants expose individuals to polycyclic aromatic hydrocarbons (PAHs) that, after a while, are absorbed into the liver thus causing genetic damage and cell damage (NIH, n.d.). The chemicals in food, water, and air, as well as the materials in our home (especially lead), usually present the risk for cancer (Westfall, 2016). We are constantly being exposed to toxic elements that can cause cancer through environmental means that are caused by industrial pollution. Damage to DNA that can lead to cancer and hormone disruption are just two ways that the toxic agents affect the body (Westfall, 2016). Although there are many different types of cancer, not many events must occur for a cell to become malignant. There are several ways that cells move toward malignancy, including damage to DNA and disruption or impairment of the liver and immune system. Toxic exposure and radiation can set these events in motion. Some of these toxic elements include tobacco smoke, mercury, ultraviolet light, DDT, and herbicides/pesticides (Westfall, 2016). Difference between Toxicants and Toxins in the Environment While toxicants and toxins are both substances that are harmful to the environment, toxins are the natural harmful products in the environment. Some examples of toxins are snake venom, poisonous mushrooms, bacteria, fungi, and viruses. Toxins, whether formed by microbes, plants, animals, or insects, are mostly products that have progressed as defense mechanisms for killing or repelling pathogens or predators (Hodgson, 2010). Toxicologists believe that toxins should be used only when there is the presence of foreign

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materials coming from biological sources. This means it can only be used if a poisonous substance is formed by living organisms or cells. Toxicants, on the other hand, are artificial or man-made products in the environment (Hodgson, 2010; Preston et al., 2018). These include tobacco smoke, pesticides, or insecticides and industrial products that potentially become environmental wastes. Other toxicants include diesel exhaust, heavy metals, and e-cigarettes. Again, toxicologists believe the term should be used when foreign materials come from man-made sources that are not natural or biologically produced. Conclusion While environmental toxicology is just another part of environmental health, it is important to understand its importance in protecting human beings, animals, and their environments. Using this knowledge, environmental toxicologists can predict where chemicals could end up in environments and in human bodies while also determining the toxic effects depending on the length of exposure and the long-term effect on the environment and future generations. They must constantly address changing concerns about environmental safety.

References American College of Medical Toxicology. (n.d.). About medical toxicology. https://www.acmt.net/overview.html Conis, E. (2017, February 14). Beyond Silent Spring: An alternate history of DDT. Distillations, 2(4), 16–23. Geo, H.-R., Hashim, Z., Su, S.-B., & Bundschuh, J. (2015). Environmental toxicology in addressing public

health challenges in East Asia. BioMed Research International, 2015, Article 920518. https://www.hindawi.com/journals/bmri/2015/920518/

Hayat, K. (2014, February 4). Introduction of toxicology and its types. Medimoon.

https://medimoon.com/2014/02/introduction-of-toxicology-and-its-types/ Hodgson, E. (2010). A textbook of modern toxicology (4th ed.). Wiley. McCarty, L. S. (2013, December). Are we in the dark ages of environmental toxicology? Regulatory

Toxicology and Pharmacology, 67(3), 321–324. https://www.sciencedirect.com/science/article/pii/S0273230013001505?via%3Dihub

National Institutes of Health. (n.d.). Gene toxicity and cancer. U.S. Department of Health and Human

Services. https://report.nih.gov/nihfactsheets/ViewFactSheet.aspx?csid=122 Paull, J. (2013, July-September). The Rachel Carson letters and the making of Silent Spring. Sage Open,

3(3), 1–12. https://journals.sagepub.com/doi/10.1177/2158244013494861#articleCitationDownloadContainer

Preston, J. D., Reynolds, L. J., & Pearson, K. J. (2018). Developmental origins of health span and life span: A

mini-review. Gerontology, 64(3), 237–245. https://doi.org/10.1159/000485506 Schep, L. J., Slaughter, R. J., & Beasley, D. M. G. (2010). The clinical toxicology of metamfetamine. Clinical

Toxicology, 48(7), 675–694. https://www.tandfonline.com/doi/abs/10.3109/15563650.2010.516752?journalCode=ictx20

Schwartz, M. D., Dell'Aglio, D. M., Nickle, R., & Hornsby-Myers, J. (2014, July 15). Federal environmental and

occupational toxicology regulations and reporting requirements: A practical approach to what the medical toxicologist needs to know, part 1. Journal of Medical Toxicology, 10(3), 319–330. https://doi.org/10.1007/s13181-014-0410-7

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U.S. Environmental Protection Agency. (2017). DDT - A brief history and status. https://www.epa.gov/ingredients-used-pesticide-products/ddt-brief-history-and-status

van den Berg, H. (2009, November). Global status of DDT and its alternatives for use in vector control to

prevent disease. Environmental Health Perspectives, 117(11), 1656–1663. https://doi.org/10.1289/ehp.0900785

van den Berg, H., Manuweera, G., & Konradsen, F. (2017, October 5). Global trends in the production and

use of DDT for control of malaria and other vector-borne diseases. Malaria Journal, 16, Article 401. https://doi-org.libraryresources.columbiasouthern.edu/10.1186/s12936-017-2050-2

Westfall, S. (2016, February). Environmental toxins and cancer risk. Life Extension Magazine.

https://www.lifeextension.com/Magazine/2016/2/Environmental-Toxins-and-Cancer-Risk/Page-01 World Health Organization. (n.d.). Analytical toxicology. International Preogramme on Chemical Safety.

https://www.who.int/ipcs/publications/training_poisons/analytical_toxicology/en/

Suggested Unit Resources In order to access the following resource, click the link below. The article below was referenced in the unit lesson. If you are interested in learning more about DDT, take a few minutes to read it. van den Berg, H., Manuweera, G., & Konradsen, F. (2017, October 5). Global trends in the production and

use of DDT for control of malaria and other vector-borne diseases. Malaria Journal, 16, Article 401. https://libraryresources.columbiasouthern.edu/login?url=http://search.ebscohost.com/login.aspx?direc t=true&db=a9h&AN=125509825&site=ehost-live&scope=site

Learning Activities (Nongraded) Nongraded Learning Activities are provided to aid students in their course of study. You do not have to submit them. If you have questions, contact your instructor for further guidance and information. Visit your local environmental health department and review an environmental toxicology report, including drug abuse, ultraviolet (UV) light, and lead. Also, review the cancer statistics to learn which cancer is most related to environmental toxicology. These reports will assist you in understanding the major effects of environmental toxicology.