RT Book, Section A1 Aleksunes, Lauren M. A1 Eaton, David L. A2 Klaassen, Curtis D. SR Print(0) ID 1158495530 T1 Principles of Toxicology T2 Casarett & Doull’s Toxicology: The Basic Science of Poisons, 9th edition YR 2019 FD 2019 PB McGraw-Hill Education PP New York, NY SN 9781259863745 LK accesspharmacy.mhmedical.com/content.aspx?aid=1158495530 RD 2024/03/29 AB Toxicology is the study of the adverse effects of chemical, biological, or physical agents on living organisms and the environment. These toxic substances include naturally occurring harmful chemicals, or toxins, as well as foreign substances called xenobiotics. Toxins are poisons that originate from plants and microbial organisms and also include venoms released by animals in order to injure predators. Aflatoxin is an example of a toxin; it is produced and released from the fungus Aspergillus that grows on foods such as corn and nuts. Exposure to aflatoxin is associated with an increased risk of liver cancer. By comparison, xenobiotics include a variety of synthetic chemicals with different intended purposes. Pharmaceuticals are xenobiotics developed to treat disease, whereas pesticides are used to deter pests. In addition, a large number of chemicals are used in manufacturing and industrial processes. For example, the chemical “dioxin” (2,3,7,8-tetrachlorodibenzo-p-dioxin [TCDD]) is generated during the production and/or combustion of certain chlorinated organic chemicals. A unique skin toxicity, called chloracne, has been observed in individuals exposed to dioxin. Some toxic substances can be produced by both natural and anthropogenic activities. For example, polyaromatic hydrocarbons are produced by the combustion of organic matter through ordinary processes (e.g., forest fires) and human activities (e.g., combustion of coal for energy production and cigarette smoking). Arsenic, a toxic metalloid, largely appears in groundwater as a natural contaminant, but also enters groundwater from other sources as well. Generally, such toxic chemicals are referred to as toxicants, rather than toxins, because, although they may be naturally produced, they are not produced by biological systems.