Advanced Toxicology

MOS 5425, Advanced Toxicology 1

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

2. Summarize the principles of toxicology. 2.1 Discuss the cornerstone xenobiotic pharmacokinetic properties (absorption, distribution,

metabolism, and excretion) and common effects of metals.

5. Examine toxic substances that pose a risk to human population and the environment. 5.1 Explain the bioaccumulation of metals as it affects ecology and humans.

Course/Unit Learning Outcomes

Learning Activity

2 Unit Lesson Chapter 19

2.1 Unit Lesson Chapter 16 PowerPoint Presentation

5 Unit Lesson Chapter 19

5.1 Unit Lesson Chapter 16 PowerPoint Presentation

Reading Assignment Chapter 16: Properties and Effects of Metals, pp. 283-304 Chapter 19: Nanotoxicology, pp. 359-370

Unit Lesson Unit VII is the first of a two-part discussion on toxic substances and risk assessment. The assigned textbook reading covers topics such as toxicity of metals and nanotoxicity. You will find noteworthy discussion on additional topics such as food additives, contaminants, and over-the-counter preparations. Although the latter is not assigned reading, you may find more on some of these topics in the textbook as well as in the CSU Online Library. Toxicity of Metals As you know, many factors can determine the toxicity of a toxicant. These factors include the type of exposure and duration of exposure as well as various characteristic properties of the toxicant as it undergoes biotransformation. Metals are naturally occurring elements that do not degrade in the environment. The inability of metals to be broken down means that they persist in the environment as elements, and they are also able to react with other molecules to form numerous compounds. Metal speciation is the main factor in determining the toxicity potential of a metal. Human activity can alter the degree of exposure to metals by impacting the movement and transformation of metals (Roberts, James, & Williams, 2015). The general properties of exposure, how the metal enters the body, and how it is processed through the body can greatly affect toxicity.

UNIT VII STUDY GUIDE

Nanotoxicity and Toxicology of Metals and Food Additives

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The textbook discusses various common toxic mechanisms of metals that include direct effects, indirect effects, substitution, and metal imbalance (Roberts et al., 2015). Direct effects cause damage to the cells by interrupting their structure or function. Indirect effects interrupt biological functions by binding to molecules and inhibiting certain events from taking place. Substitution is when the metal is similar to other biological molecules and binds or accumulates in place of an essential element, interrupting the activity of the essential element. Metal imbalance is due to an overexposure of some metals, causing disruption to homeostasis and normal movement of essential metals (Roberts et al., 2015). When discussing toxicity of metals, a common metal that comes to mind is lead. Lead toxicity through paint has been in the news in the recent years. For parents of small children, recalls for toys with lead paint are a major concern. In 2007, a major toy company had a recall on toys from China because of the lead content in the toys. Lead toxicity can have major neurotoxic effects. Take some time to read about the factors—such as level and duration of exposure, chemical form, and metal-protein complexes—that would affect the level of toxicity of a metal, as discussed in the textbook. While some metals are necessary nutrients that we need, metals can be very toxic, depending on the type of metal, the type of exposure, and the level of exposure to the metal. Mercury poisoning is a major concern as it can severely affect the nervous system. Pregnant women are warned of limiting the consumption of certain types of fish because of high mercury content (Roberts et al., 2015). As previously discussed, lead is also a major concern. Children are at a higher risk of exposure to lead because of the increased likelihood of ingestion of lead by putting various nonfood items in their mouths. Cadmium, arsenic, beryllium, chromium, and copper are some additional metals with major toxicological issues that are worth reading about. Please take time to focus on the sources of exposure and the toxic effects each one of these metals has on humans. Solvents Solvents are substances that are able to dissolve other substances. The properties of solvents have been commonly utilized in cleaning products such as degreasers and stain removers. Industry has made exposure to solvents common due to industrial as well as in household products (Roberts et al., 2015). There are vast numbers of carbon-based or organic solvents. The class and variations in properties such as molecular weight of solvents even within a single class can result in an extreme difference in toxic effects. Solvents can have acute as well as chronic effects on a variety of target organs including the central nervous system (CNS) and hepatic and renal systems (Roberts et al., 2015). Some of the effects of solvents include respiratory depression, dermal irritation, and cancer (Roberts et al., 2015). Take some time to review some of the common examples and effects of solvents in the textbook. Food Additives and Contaminants Have you ever gone to the doctor with the symptoms of severe stomach cramps and vomiting, only to realize that you had some type of food poisoning? Food poisoning is a result of food contamination. The symptoms can be visible in as soon as a few hours or delayed for several days. Food may become contaminated as a result of improper handling of the raw food and/or improper cooking of the foods. Consumed foods may also be harmful due to food additives. Many years ago, the red dye in a certain chocolate candy products was discontinued because the dye was found to be harmful. Food additives are substances that are not normally found in the food items, such as dyes to make it more visibly appealing to the consumer or preservatives to make it last longer. In addition to the direct food additives, consideration must be given to indirect additives that can cause toxicity. This may occur when antibiotics are given to livestock to keep them healthy while being raised, but they can be carried in the meat and passed on during consumption. The consumption of antibiotics in this manner can contribute to antibiotic resistance in the population. In past years, the use of steroids in farm animals has been highly debated. You may notice on regular (not organic) milk bottles the pledge that the farmers who produce the milk promise that the milk is steroid free as well as a statement in regards to steroid use in the animals not showing any significant ill effect on humans who consume the products. Nanotoxicity Nanotoxicity, in very simplified terms, is the toxic effect of extremely small particles in the 10-9m range. Shortly before returning home from his second tour in Iraq, an Army member was given paperwork that explained he

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was exposed to particulate matter for the duration of his tour. He was concerned about what this exposure meant and contacted a toxicologist in regards to the possible effects of the exposure. The toxicologist’s concern was predominately focused on the development of lung disease in the future. As you read the textbook in regards to nanotoxicity, you will find that there are different classifications of nanomaterials. The effects of nanotoxicity are not limited to pulmonary disease but extend to various effects of skin toxicity, cancer, mutations, immunotoxicity, neurotoxicity, as well as endocrine and reproductive toxicity (Roberts et al., 2015). Over-the-Counter Preparations The last topic of discussion for this unit is that of over-the-counter preparations. Over-the-counter drugs can be found in almost every household. A consumer can go into a local store and literally walk through aisles and aisles of over-the-counter drugs that are available for purchase. The textbook discusses the fact that many over-the-counter drugs do not undergo a stringent testing process. Some over-the-counter drugs are simply lower concentrations of prescription medicines, and some drugs that are found in the over-the-counter drug aisle are actually herbal supplements that are not regulated by the Food and Drug Administration. Many consumers lack proper knowledge on the proper use of over-the-counter drugs, which puts the users at risk for toxic effects if used improperly. There are also possible additive or adverse effects when taken in conjunction with other over-the-counter drugs, prescription drugs, or herbal supplements.

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

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