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Paracelsus
- all substances are poison, the right dose ..
- -contributer to dose response relationship
- -founder of modern toxicology
- -notion of target organ
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toxicology is the study of
- adverse effects of chemicals on living organisms
- -study of how xenobiotics (chemical compounds) affect biological systems
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toxicologist
investigates the adverse effects of chemicals including their celluar, biochemical, and molecular mechanisms of action and asesses the probablity of their occurance.
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Classification levels of environmental hazards to health (5)
- 1. human body
- 2. genes-control organ develp and function
- 3. germ cells-involve reproduction
- 4. somatic cells-all other parts of the body
- 5. cells may grow in an organ in uncontrollable ways.
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Cancer
2 main agents induce cancer
- 1. viral infection (onocogenic viruses Hep C and HPV)
- 2. environmental agents (certain chemicals)
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Toxic Chemicals
# chemical in common use world-wide
___ to ___ chemicals/year
exposures: (3)
esistence: (4)
-related to #2 cause of death-cancer (environmental exposures)
- 80, 0000 chemicala in common use world-wide
- 200___ to 2000 new chemicals/year
- exposures: (3) at home wor,k environment
- esistence: (4) in the food, air, soil, water
- related to #2 cause of death-cancer (environmental exposures)
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Classification of toxic chemicals is based on
(5)
- 1. molecular structure
- 2. physical characteristics
- 3. sources
- 4. end uses
- 5. toxic properties
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2 types of classification
type I--
type II--
- type I- (a-e) based on combo of physical and chemical prop, toxic effects and use (toxic chemicals, fibers and dust)
- type II- (a-g) mechanisms of toxicity(carcinogens, neurotoxins, mutagens, allergens)
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cancer
unregulated growth of cells
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tumor
a clump of cancer cells
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mutation
an alteration in the DNA of the germ cells.
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mutagen
a substance that causes a mutation
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carcinogens
the agents believed to cause cancer
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poison
any agent capable of producing a deleterious response in a biological system
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toxic substance
any substance whose physiological action is harmful to health
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synergism
the combined effect of the two chemical is greater than the sum of the...
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toxin
refers to a toxic substance made by living orgaisms including reptiles, insects, plants and microorganisms
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toxicity
the degree to which something is posionous-related to physical and chemical properties.
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examples of toxins
(5)
- 1.bacteria-botulinum
- 2. fungi-myco
- 3. algae-phyco
- 4. plants- phyto
- 5. animals-zoo toxins
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toxicants
toxic substances that are man-made
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Adverse health impacts of toxic exposure
(3)
1. no exposure...
2. key factors:
3. not all...
- 1. unless exposed to toxic substances no toxic effect on human health
- 2. Key factors: manifestation and magnitude
- 3. not all exposure will lead to a toxic manifestation
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fields within toxicology
- 1. regulatory
- 2. forensic
- 3. clinical
- 4. environmental
- 5. reproductive
- 6. developmental
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environmental toxicology
- examines how environmental exposures to chemical pollutants may present risks to biological organisms, particularly animals, birds, and fish
- -production, fate and effect of the natural and synthetic pollutants in the environment
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sources of harzdous chemicals
- manufactured
- natural
- unintentionally produced
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hazardous chemical in nature
- poisonous materials
- toxic plants
- volcanoes
- animal sting/bite
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manufactured intentionally
- essential for a specific application
- large category
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produced unintentionally
- 1. unwanted material-byproducts
- 2. generated in many industrial processes
- 3. impurity in starting materials
- 4. side reaction of complex chemical pathways
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factors affecting the toxicity of toxic substances
- route of entry
- dose
- duration
- susceptibility
- possible synergistic effects
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routes of exposure (4)
- gastrointensina tract
- respitotory system
- contact with surface skin
- injection into blood stream (blood transplant)
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point of entry effects and systemic distribution
- 1.absorb-skin-irritation-into circulatory system,
- 2. ingestion-mouth and stomach-irriation-circulatory system via biliary-hepatic system distribution
- 3. inhalation-lungs-irritation, particulate, entrapment-alveolar space-through capillaries, circulatory system
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ways of describing a dose
(7)
e
a
a
t
e
i
b
- 1. exposure dose-amt encountered in envir
- 2. absorbed-(avail internal organs)
- 3. administered
- 4. total-adding individ dose
- 5. external-aquired by contact-
- 6. internal-portion that is internalized
- 7. biologically effective
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lethal dose LD50
- the doase mg/kg of body weight causing death in 50% of animals
- -used to compare chemicals
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dose-response relationship
correlative relationship bw the charactertistics of exposure to chemicals and the spectrum of effects caused by the chemical
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duration of exposure terms
- acute-o-24hrs
- subacute-less than one month
- subchronic-1-3 month
- chronic-3 plus
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direct adverse effects of exposure to chemicals
- 1. local effects-damage at the site where a chemicals first comes into contact with the body (cell replacement)
- 2. systemic effects-generalized distribution of the chemical throughout the body by the bloodstream to internal organs (damage to enzyme system)
- 3. target organ effects-some chemical may confine their effects to specific organs (DNA damage)
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latency
time period bw initial exposure and measureable response
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effects of chemical mixtures
(4 types of effects)
- additive
- synergism
- potentiation (2 chemical bring it out)
- antagonism
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biological tests for toxicity:
test subjects (3 types)
- subjects used for testing
- 1. volunteers
- 2. animals exposed purposively (in vitro)
- 3. cells derived from human, animal or plant sources.
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testing for toxicity
(6)
- 1.often difficult to determine
- 2. use eipdemiology
- 3. immunobiological test
- 4. lab test with animal model, cell culcture
- 5. ames test
- 6. ecological risk assessment
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Enzyme Linked Immunosorbant Assay ELISA
-ids the presence of absense of toxins in the environment
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ames test
- -1970
- mutagen test-if it can grow in the environment it may be a mutagent
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ecological risk assessment
it is:
process (3)
- qualitative/quantitative appraissal for actual or potential effect of a contaminant chemical on wildlife
- 1. problem formulation
- 2. analyis
- 3. risk characterization
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risk assessment is...
qualitative or quantitative estimation of the likelihood of adverse effects that may resuls from exposure to specified health hazards or from the absence of beneficial influence.
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Process of Risk Assessment
- 1. hazard id
- 2. dose-response relationship
- 3. exposure assessment-id populations exposed, examines roots, magntitude and frequency)
- 4. risk characterization -estimates number of excess unwarranted health events expected at diff time intervals at each level of exposure
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Risk management
action orientted to control toxic chemicals
(5 strategies)
- 1. exposure standards
- 2. requirements for pre-market testing
- 3. recalls of toxic products
- 4. banning hazardous materials
- 5. develop, eval, and implementation of regulatory options, aimed at risk reduction.
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disposal of toxic chemicals
- 1. incineration
- 2. dumping
- 3. land filling
- 4. land application
- 5. deep-well injection
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