Scientific Foundations: Toxicology Flashcards
Target organ
The organ that is selectively affected by a harmful agent
Five criteria that must all be present to make a chemical toxic
- 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
Toxic agents can be classified by…
Their form of action on biologic systems
Types of toxic agents
- Asphyxiants
- Corrosives
- Irritants
- Sensitizers
- Carcinogens
- Mutagens
- Teratogens
Asphyxiants
Deprive the body tissue of oxygen
Types of asyphixiants
- Simple
2. Chemical
Simple asphyxiants
Displace oxygen and cause suffocation
Examples of simple asphyxiants
- Carbon dioxide
- Nitrogen
- Argon
Chemical asphyxiants
Prevent oxygen use by the cell, even when enough oxygen might be present
Examples of chemical asphyxiants
- Carbon monoxide
2. Cyanide
Corrosives
Cause irreversible tissue death
Examples of corrosives
- Ozone
2. Acid
Irritants
Cause temporary, but sometimes severe inflammation of the eyes, skin or respiratory tract
Example of irritant
Ammonia
Sensitizer
Cause allergic reactions after repeated exposure
Examples of sensitizers
- Nickel
2. Toluene diisocyanate (TDI)
Carcinogens
Are capable of causing cancer
Examples of carcinogens
- Asbestos
- Coal tar
- Vinyl chloride monomer
Mutagens
Toxins that cause changes to the genetic material of cells that can be passed on to future generations
Examples of human mutagens
- Ethylene oxide
2. Ionizing radiation
Teratogens
Cause malformations in an unborn child
Examples it teratogens
- Organic mercury compounds
- Ionizing radiation
- Some pharmaceuticals
Formaldehyde is what type of toxic agent?
- Irritant to eyes
- Irritant to respiratory tract
- Irritant to skin
- Sensitizer
- Carcinogen
Dose
Amount of agent that reaches target organ and is usually impossible to determine accurately
Dose is estimated by…
- Measuring the amount administered
- Measuring the amount in the environment which the person was exposed
- Measuring biomarkers in body tissues
Vapors of gases are expressed as…
Parts per million (ppm)
Solids (ie dusts or fumes) are expressed…
According to their weight per volume of air
Usually milligrams per cubic meter (mg/m3)
Higher concentrations of substances are absorbed in ——— amounts
Greater
Longer or more frequent periods of exposure lead to ——– absorbed doses
Greater
Acute exposure
Occurs when exposure in short term and absorption is fairly rapid
Chronic exposure
Refers to longer duration or repeated periods of contact
—— toxic exposures tend to be at higher levels, and —— exposures occur at lower concentrations
Acute
Chronic
Examples of workplace guidelines
Threshold limit values
Examples of workplace standards
Permissible exposure limits
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
Published limits —– be viewed as definitely “safe” levels
Cannot
Why guidelines and standards may be controversial
- Lack of scientific data
- Lack if agreement over levels associated with health effects
- Reality that levels that protect most individuals may not affect susceptible groups
Three major routes of exposure
- Inhalation
- Cutaneous
- Ingestion
The most common route of exposure in the occupational environment
Inhalation
Where does most inhalation absorption take place
Alveoli
Why does most inhalation absorption take place in the alveoli
Blood flow is high and close to inhaled air
Common substance absorbed via inhalation route
- Gas
2. Particulate
Size range of particulate that can be absorbed via inhalation
1-10 microns in diameter
Absorption is influenced by
- Rate of respirations
2. Depth of respirations
Individuals performing ——– may absorb substances at a higher rate
Heavy physical labor
Target organ of most inhaled toxins
Lungs
Examples of substances that gain entry through the lungs but have their effects elsewhere in the body
- Solvents
2. Carbon monoxide
Skin provides a —— to most substances
Barrier
Skin’s effectiveness as a barrier varies according to…
- Condition
- Site
- Properties of the chemical agent
Modes of cutaneous entry
- Cross the epidermal layer
- Enter through hair follicles
- Trauma of injection or impalement
Substances that penetrate skin most freely
Gases
Substances that penetrate skin less freely than gases
Liquids
Substances that do not penetrate the skin
- Solids that are insoluble in water
2. Fats
Longer contact promotes ——— of absorption
Higher levels
Factors that can promote a substances further absorption
Damage to epidermal cells by chemicals or trauma, such as abrasions
——–or ——- can trap substances and lead to longer exposure periods
- Clothing
2. Gloves
Least common route of entry in the occupational setting
Ingestion
Ingestion increases in importance in cases of other types of environmental exposure such as…
- Food
- Water
- Substances encountered through hand-mouth activity
——–, if ingested can have a direct adverse effect on the gastrointestinal tract
Caustic or irritant chemicals
Some ingested toxins act —— following absorption
Systemically
Smoking or eating at work sites can lead to consumption of toxins by way of contaminated…
- Hands
- Food
- Smoking materials
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
Higher doses are generally associated with….
Responses in a greater proportion of individuals
Identification of a dose-response relationship lends support to a theory that….
A substance causes a given effect
——– provide a basis for evaluating a chemical’s relative toxicity
Dose-response curves
Terms that describe toxicity of a substance
- Lethal dose, 50% (LD50)
2. Lethal concentration, 50% (LC50)
Lethal dose, 50%
Dose that produces death in 50% of a group of experimental animals
Lethal concentration, 50%
Concentration that produces death in 50% of a group of experimental animals
LD50 and LC50 indices are —— for more toxic agents
Smaller
LD50 of acetone
5,340 mg/kg
LD50 of hydrogen cyanide
0.5mg/kg
Type of study that is useful in providing information about potential toxic effects or target organs of a substance in humans
Animal studies
When are the effects of toxins with long latency periods apparent?
May not be apparent until years after the exposure
Work related exposures commonly consist of chemical ——
Mixtures
Why are work related exposures to chemical mixtures a concern?
Because interactive effects may occur with two or more concurrent exposures
Types of interactive effects
- Synergistic effects
- Antagonism
- Potentiation
Synergistic effects
Caused by exposure to more than one toxin that surpass the sum of the separate effects of those toxins
Antagonism between toxins results in…
An overall effect that is less than the sum of their separate effects
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
Potentiation is often seen with….
Carcinogens
Once toxins are absorbed, their fate in the body….
Varies
Excretion
Involves the elimination of a material from the body
Some chemicals are excreted unchanged into…
- Expired air
- Urine
- Feces
- Bile
- Perspiration
Other avenues of excretion include:
- Milk
- Spinal fluid
- Saliva
- Hair
Most chemicals and their metabolic products are excreted through..
The kidney/urine pathway
Transformation
A process that results in a substance being changed in some way
Chemicals may be transformed into substances that can be excreted by a process called
Biotransformation
Products of biotransformation may ——– or ——- than their parent chemical
Either less toxic or more toxic
This rate can affect individual susceptibility to a toxin.
The rate at which a person metabolizes a subsance
Many agents are not metabolized or excreted immediately, but instead are….
Deposited in body tissue and slowly released and excreted over time
Half-life
The term that describes the time it takes for one half of the total absorbed amount to be eliminated from the body
The length of half-life depends on:
- The agent
2. The tissue in which it is stored
Half-life of lead in bone
20 years
Half-life of lead in blood
25-30 days
Toxicology
The study of the adverse effects of chemicals on biological systems
