Toxicology Flashcards
Describe the terms
Carcinogenic
A carcinogen is a substance, organism or agent capable of causing cancer. Carcinogens may occur naturally in the environment (such as ultraviolet rays in sunlight and certain viruses) or may be generated by humans (such as automobile exhaust fumes and cigarette smoke).
Any factor or combination of factors that increases the risk of
cancer. Cancer is a disease in which derangement of body cells is involved.
The effects of carcinogens on human tissue, if exposure is sufficient, are
irreversible. Carcinogens that produce cancer in experimental animals are
found in low concentrations in food, food additives, some air and water
pollutants, and certain pesticides. The carcinogenic potential of many car-
cinogenic substances acting singly or in combination with other carcino-
gens and chemicals is unknown.2 Most scientists agree that a chemical
causing cancer in animals is a potential cancer hazard for humans; however,
many chemicals carcinogenic to animals are not carcinogenic to humans.
But chemicals known to cause cancer in humans have been found to do
so in animal species.
Teratogenic
Teratogens are substances that may produce physical or functional defects in the human embryo or fetus after the pregnant woman is exposed to the substance. Alcohol and cocaine are examples of such substances.
SALVADO:
An agent (radiation, virus, drug, chemical) that acts during preg-
nancy to produce a physical or functional defect in the developing off-
spring. Substances that have caused defects are methylmercury and thalidomide. Some environmental pollutants may be both carcinogenic and teratogenic.
mutagenic
cause of a genetic mutation.
Ames test is used to identify the revert mutations which are present in strains, it can also be used to detect the mutagenicity of environmental samples such as drugs, dyes, reagents, cosmetics, waste water, pesticides and other substances which are easily solubilized in a liquid suspension.
Poison
A poison can be described as ‘any substance which when introduced into or absorbed by a living organism, destroys life or injures health’. Toxicology, or the science of poisons, is the study of the adverse effects of chemicals or physical agents on living organisms.
Acute Exposure vs Chronic Exposure
Short-term exposure is called acute exposure. Long-term exposure is called chronic exposure. Either may cause health effects. Acute exposure is a short contact with a chemical.
An example of acute toxicity relates to the over consumption of alcohol and “hangovers”. Chronic toxicity is generally thought of as frequent exposures where effects may be delayed (even for years) and are generally irreversible. Chronic toxicity can also result in acute exposures, with long term chronic effects.
Inhalation
Inhalation toxicology refers to a route of exposure; toxic chemicals inhaled have a potential to produce lung disease and if the chemical is trans-located to other organs disease in those organs as well. Contrast this to pulmonary toxicity which rather than being a route is more of a target organ toxicity.
Ingestion
EPA Source
https://www.epa.gov/expobox/exposure-assessment-tools-routes-ingestion#:~:text=Typically%2C%20exposure%20occurs%20by%20one,chemical%20residues%20as%20a%20result.
Ingestion exposure can occur via consumption of contaminated food, water and other liquids. Food can contain chemical residues as a result.
intentional application (e.g., pesticide use),
deposition of particulate matter onto edible produce (e.g., from atmospheric pollutants), and/or
biotic uptake and accumulation from contaminated soil or water (e.g., irrigation water, uptake of contaminants by fish or livestock).
Injection
CDC Module training:
https://www.atsdr.cdc.gov/training/toxmanual/pdf/module-2.pdf
Injections are another common route for exposure. Injections are mainly used in laboratory studies on experimental animals. Following are the different types of injections:
# Intravenous injections (into a vein).
# Intramuscular injections (into the muscle).
# Intra peritoneal injections (into the abdominal cavity).
# Intradermal injections (into the skin).
# Subcutaneous injections (under the skin).
Dermal
CDC training module
Dermal Absorption
MOST COMMON PATH OF TOXIC SUBSTANCE EXPOSURE
The skin is composed of three layers:
# Epidermis (outer layer). The outermost layer is the stratum corneum
(carnified layer). This is the structure that determines the rate of
absorption of substances through the epidermis. For example, a pesticide
such as Malathion, which easily penetrates the stratum corneum, moves quickly through the other layers of the skin and is rapidly absorbed into the bloodstream. DDT, another type of pesticide, does not easily penetrate the stratum corneum, so the rate of absorption is much slower.
# Dermis (inner layer). The inner layer of the skin is sometimes referred to
as the true skin. In animal hides, this is the layer that turns to leather when
chemically processed. The dermis is the source of oxygen and of nutrients
for the epidermis. The hair follicles, sweat glands, and sebaceous (oil)
glands are found in this layer. These structures play a limited role in the
absorption of substances across the skin.
# Subcutaneous fatty tissue. This layer provides a cushion for the underlying structures and allows the skin to move to some extent.
Factors affecting dermal absorption of toxic substances include
# The condition of the skin. An intact stratum corneum (epidermis) is an
effective barrier to absorption of some toxic chemicals. However, physical
damage to the protective barrier, such as a cut or abrasion, allows toxic
substances to penetrate the epidermis and enter the dermis where they
more readily enter the bloodstream and are carried to other parts of the
body.
# The chemical make up of the substance. Inorganic chemicals and
substances are not easily absorbed through intact, healthy skin (such as
cadmium, lead, mercury, and chromium. Organic chemicals dissolved in
water do not easily penetrate the skin because the skin is impermeable to
water. However, organic solvents, such as paint thinner or gasoline, are
easily absorbed through the epidermis.
# Increasing the concentration of the toxic substance or the exposure time can increase the rate or amount of material absorbed.
LD(50)
LD (50) = Lethal Dose concentration exposure at which 50% of the tested population experiences death. The tested population are rats. LD(50) are usually administered orally and dermally. Inhalation concentrations are referred to as LC(50) or lethal concentration.
(Kimura)
Dose / Response
PDF Mosquito project read :
https://www.cmmcp.org/sites/g/files/vyhlif2966/f/uploads/dose-response_relationships_in_toxicology.pdf
The science of toxicology is based on the principle that there is a relationship between the toxic reactant (the response) and the amount of poison received (the dose). An important assumption in this relationship is that there is almost always as dose provided that creates no response and can be measured. A second assumption is that once maximum response is reached any further increase of the dose will not result in any increase effect.
Time Weighted Average
The TWA for the exposure to a chemical can be used when both the chemical concentration and time for exposure varies over time. It is thus used as the average exposure to a contaminant to which workers may be exposed without adverse effect over a period such as in an 8-hour day or 40-hour week (an average work shift).
