Scientific Foundations: Toxicology Flashcards
0
Q
Target organ
A
The organ that is selectively affected by a harmful agent
1
Q
Toxicology
A
The study of the adverse effects of chemicals on biological systems
2
Q
Five criteria that must all be present to make a chemical toxic
A
- Its properties make it capable of producing harm
- It is present in sufficient amount
- It is present for sufficient time
- It is delivered by an exposure route that allows it to be absorbed
- It reaches the target body organ
3
Q
Toxic agents can be classified by…
A
Their form of action on biologic systems
4
Q
Types of toxic agents
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- Asphyxiants
- Corrosives
- Irritants
- Sensitizers
- Carcinogens
- Mutagens
- Teratogens
5
Q
Asphyxiants
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Deprive the body tissue of oxygen
6
Q
Types of asyphixiants
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- Simple
2. Chemical
7
Q
Simple asphyxiants
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Displace oxygen and cause suffocation
8
Q
Examples of simple asphyxiants
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- Carbon dioxide
- Nitrogen
- Argon
9
Q
Chemical asphyxiants
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Prevent oxygen use by the cell, even when enough oxygen might be present
10
Q
Examples of chemical asphyxiants
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- Carbon monoxide
2. Cyanide
11
Q
Corrosives
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Cause irreversible tissue death
12
Q
Examples of corrosives
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- Ozone
2. Acid
13
Q
Irritants
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Cause temporary, but sometimes severe inflammation of the eyes, skin or respiratory tract
14
Q
Example of irritant
A
Ammonia
15
Q
Sensitizer
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Cause allergic reactions after repeated exposure
16
Q
Examples of sensitizers
A
- Nickel
2. Toluene diisocyanate (TDI)
17
Q
Carcinogens
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Are capable of causing cancer
18
Q
Examples of carcinogens
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- Asbestos
- Coal tar
- Vinyl chloride monomer
19
Q
Mutagens
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Toxins that cause changes to the genetic material of cells that can be passed on to future generations
20
Q
Examples of human mutagens
A
- Ethylene oxide
2. Ionizing radiation
21
Q
Teratogens
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Cause malformations in an unborn child
22
Q
Examples it teratogens
A
- Organic mercury compounds
- Ionizing radiation
- Some pharmaceuticals
23
Q
Formaldehyde is what type of toxic agent?
A
- Irritant to eyes
- Irritant to respiratory tract
- Irritant to skin
- Sensitizer
- Carcinogen
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Dose
Amount of agent that reaches target organ and is usually impossible to determine accurately
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Dose is estimated by...
1. Measuring the amount administered
2. Measuring the amount in the environment which the person was exposed
3. Measuring biomarkers in body tissues
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Vapors of gases are expressed as...
Parts per million (ppm)
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Solids (ie dusts or fumes) are expressed...
According to their weight per volume of air
Usually milligrams per cubic meter (mg/m3)
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Higher concentrations of substances are absorbed in --------- amounts
Greater
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Longer or more frequent periods of exposure lead to -------- absorbed doses
Greater
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Acute exposure
Occurs when exposure in short term and absorption is fairly rapid
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Chronic exposure
Refers to longer duration or repeated periods of contact
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------ toxic exposures tend to be at higher levels, and ------ exposures occur at lower concentrations
Acute
| Chronic
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Examples of workplace guidelines
Threshold limit values
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Examples of workplace standards
Permissible exposure limits
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Guidelines and standards indicate...
Upper limits of exposure concentrations that are not felt to pose a danger to workers who are exposed over normal work hours
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Published limits ----- be viewed as definitely "safe" levels
Cannot
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Why guidelines and standards may be controversial
1. Lack of scientific data
2. Lack if agreement over levels associated with health effects
3. Reality that levels that protect most individuals may not affect susceptible groups
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Three major routes of exposure
1. Inhalation
2. Cutaneous
3. Ingestion
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The most common route of exposure in the occupational environment
Inhalation
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Where does most inhalation absorption take place
Alveoli
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Why does most inhalation absorption take place in the alveoli
Blood flow is high and close to inhaled air
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Common substance absorbed via inhalation route
1. Gas
| 2. Particulate
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Size range of particulate that can be absorbed via inhalation
1-10 microns in diameter
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Absorption is influenced by
1. Rate of respirations
| 2. Depth of respirations
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Individuals performing -------- may absorb substances at a higher rate
Heavy physical labor
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Target organ of most inhaled toxins
Lungs
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Examples of substances that gain entry through the lungs but have their effects elsewhere in the body
1. Solvents
| 2. Carbon monoxide
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Skin provides a ------ to most substances
Barrier
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Skin's effectiveness as a barrier varies according to...
1. Condition
2. Site
3. Properties of the chemical agent
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Modes of cutaneous entry
1. Cross the epidermal layer
2. Enter through hair follicles
3. Trauma of injection or impalement
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Substances that penetrate skin most freely
Gases
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Substances that penetrate skin less freely than gases
Liquids
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Substances that do not penetrate the skin
1. Solids that are insoluble in water
| 2. Fats
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Longer contact promotes --------- of absorption
Higher levels
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Factors that can promote a substances further absorption
Damage to epidermal cells by chemicals or trauma, such as abrasions
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--------or ------- can trap substances and lead to longer exposure periods
1. Clothing
| 2. Gloves
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Least common route of entry in the occupational setting
Ingestion
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Ingestion increases in importance in cases of other types of environmental exposure such as...
1. Food
2. Water
3. Substances encountered through hand-mouth activity
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--------, if ingested can have a direct adverse effect on the gastrointestinal tract
Caustic or irritant chemicals
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Some ingested toxins act ------ following absorption
Systemically
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Smoking or eating at work sites can lead to consumption of toxins by way of contaminated...
1. Hands
2. Food
3. Smoking materials
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Dose-response relationship
Describes the relationship between the level of exposure (dose) and the resulting toxic effects (response) in a susceptible population of humans or experimental animals
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Higher doses are generally associated with....
Responses in a greater proportion of individuals
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Identification of a dose-response relationship lends support to a theory that....
A substance causes a given effect
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-------- provide a basis for evaluating a chemical's relative toxicity
Dose-response curves
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Terms that describe toxicity of a substance
1. Lethal dose, 50% (LD50)
| 2. Lethal concentration, 50% (LC50)
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Lethal dose, 50%
Dose that produces death in 50% of a group of experimental animals
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Lethal concentration, 50%
Concentration that produces death in 50% of a group of experimental animals
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LD50 and LC50 indices are ------ for more toxic agents
Smaller
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LD50 of acetone
5,340 mg/kg
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LD50 of hydrogen cyanide
0.5mg/kg
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Type of study that is useful in providing information about potential toxic effects or target organs of a substance in humans
Animal studies
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When are the effects of toxins with long latency periods apparent?
May not be apparent until years after the exposure
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Work related exposures commonly consist of chemical ------
Mixtures
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Why are work related exposures to chemical mixtures a concern?
Because interactive effects may occur with two or more concurrent exposures
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Types of interactive effects
1. Synergistic effects
2. Antagonism
3. Potentiation
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Synergistic effects
Caused by exposure to more than one toxin that surpass the sum of the separate effects of those toxins
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Antagonism between toxins results in...
An overall effect that is less than the sum of their separate effects
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Potentiation
Means that a chemical has no adverse effect on its own, but its presence increases the effect of another substance or makes that substance capable of exerting an effect
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Potentiation is often seen with....
Carcinogens
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Once toxins are absorbed, their fate in the body....
Varies
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Excretion
Involves the elimination of a material from the body
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Some chemicals are excreted unchanged into...
1. Expired air
2. Urine
3. Feces
4. Bile
5. Perspiration
84
Other avenues of excretion include:
1. Milk
2. Spinal fluid
3. Saliva
4. Hair
85
Most chemicals and their metabolic products are excreted through..
The kidney/urine pathway
86
Transformation
A process that results in a substance being changed in some way
87
Chemicals may be transformed into substances that can be excreted by a process called
Biotransformation
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Products of biotransformation may -------- or ------- than their parent chemical
Either less toxic or more toxic
89
This rate can affect individual susceptibility to a toxin.
The rate at which a person metabolizes a subsance
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Many agents are not metabolized or excreted immediately, but instead are....
Deposited in body tissue and slowly released and excreted over time
91
Half-life
The term that describes the time it takes for one half of the total absorbed amount to be eliminated from the body
92
The length of half-life depends on:
1. The agent
| 2. The tissue in which it is stored
93
Half-life of lead in bone
20 years
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Half-life of lead in blood
25-30 days
