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Industrial Toxicology. HS 432. Toxicology. Toxicology is the study of the adverse effects of chemicals on living systems, the mechanisms underlying those effects and the conditions under which they are likely to occur.
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Industrial Toxicology HS 432
Toxicology • Toxicology is the study of the adverse effects of chemicals on living systems, the mechanisms underlying those effects and the conditions under which they are likely to occur. “All substances are poisons; there is none which is not a poison. The right dose differentiates a poison and a remedy” Pracelsus (1493-1541).
Routes of Entry • Inhalation – most common route of infection • Skin absorption & mucous membranes • Ingestion • Injection –2nd most common route of infection in a hospital setting
How can we classify toxicants? Acute Toxicity: occurs due to short-term exposure to high levels of toxic substance. Generally has a sudden onset for a short period of time (usually reversible). Chronic Toxicity: occurs due tolong-term exposure to low levels of toxic substance. Resulting health effect is generally of long or permanent duration (usually irreversible).
How can we classify toxicants? Local Toxicity: occurs at the site of application or exposure. E.g. Acid on the skin Systemic Toxicity: requires absorption of the toxicant by the body and distribution via the bloodstream to target organ(s). E.g. Lead ingestion and neurological effects.
Note Whether the toxic effects are systemic or local, they can be acute or chronic, and reversible or irreversible. E.g. Carbon tetrachloride
Toxicology • Terms: • Toxic effect: reversible or irreversible effect on the body • Exposure • Quantity or dose • Toxicity (ability to produce harmful effects at certain concentrations) • Hazard (probability that this concentration will be reached at the site)
The Toxic Triangle Environment HAZARD Toxic Substance Host
Factors that Affect Disease Development • Characteristics of the toxic substance • Characteristics of the host • Characteristics of the environment
Factors that Affect the Outcome of an Exposure to a Toxicant • Threshold concept • Lethal dose • Lethal concentration • Timing of exposure • Chronic vs. Acute
Factors That Affect the Outcome of an Exposure to a Toxicant • Chemical properties of toxicant • Concentration of toxicant • Length of exposure • Interactions between chemicals • Additive 1+1 = 2 • Synergism 1+1=5 • Potentiation 0+2=10 • Antagonism 4+6=8; 4+0=1 • Characteristics of exposed individual E.g. age, activity level, health status
Factors That Affect the Outcome of an Exposure to a Toxicant • Absorption: entry into the body • Bioavailability: the rate at which a substance enters the blood. It affects the internal dose. • Biotransformation: metabolic processes that change the structure and characteristics of a chemical • Storage • Elimination
What Are Some Toxicological Effects? • Infectious or Communicable Disease: respiratory, waterborne, food-borne diseases. • Reproductive Toxicity: occurs when toxic substances affect the male or female reproductive system. • Developmental Toxicity (teratogenesis): occurs when when mistakes occur within genes (chromosomes) or when stages of fetal development are disturbed. • Neurotoxicity: damage to the neurological system. • Immunotoxicity: suppression of the immune system or production of exaggerated immune reactions. • Cancer: a result of multiple genetic and non-genetic effects that may lead to uncontrolled proliferation of cells.
