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Lecture 9

EESA10H3 Lecture Notes - Lecture 9: Vapor Pressure

Environmental Science
Course Code
Jovan Stefanovic

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Lecture #9: Toxicology
Wednesday, March 23rd/2011
Study of poisons/science of poisons
the science which studies toxic substances or poisons, that are substances which
cause alteration or perturbation in the function of organisms leading to harmful
effects (Truhaut, 1974)
What does toxicology look at?
1.Chemistry of poisons
2.Distributions of poisons that denies/drives its behaviour
3.How much is it toxic to humans/animals
4.Compare and rank different substances based on toxicity
5.The dose of the substance that makes the substance toxic
Assessing Chemical Hazards
How harmful substance depends on the following chemical properties of the
oPolarity directly affects solubility of substances
Polar substances are soluble in H2O they are found in ECM but not
allowed in cell; mostly inorganic substances
Polar (fet. sol.) are organic enter the cell and accumulate within cell
oOxidation state (e.g. Cr-6 is more toxic than Cr-3)
oMolecular weight
oDissociation what anions and cations are produced
Water soluble toxins

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Fat soluble toxin
Toxicology depends on:
oPersistence of chemical (POP e.g. DDT good as pesticide but not good
for overall health
oBiomagnification building level in the food chain
oChemical interaction (b/w chemicals)
Antagonistic –ones toxicity is higher than the other
Synergistic combined toxicity is higher; e.g. asbestos and
smoking increase the risk of cancer total toxicity = higher than
each individual toxicity
oMultiple Chemicals food additives, pesticides, air pollution
Difficult to assess toxicity and difficult to do risk assessment
= the organism receiving exposure or dose
Frequency of exposure –e.g. everyday, once a month,
Age infant, children = vulnerable; elderly = sensitive
General health (of receptor @ the time)
Genetic makeup –genes and alleles
= the amount of substance the person has:
Ingested (often the greatest source of chemical exposure,
85%) most common route of exposure
Inhaled through air pollution, particles and volatiles, 10%

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Absorbed through the skin (industrial, 5%); dermalimp.
For occupational exposure
Debate about actual amount that receptor site sees vs. amount taken
Acute dose = single dose, usually high; e.g. nuclear blast
Chronic dose = repeated or continuous low dose over time;
e.g. radiation everyday for little period of time if occupation in
nuclear power plant
Long term = low dose over a lifetime; starts from first day of
life; constant; e.g. cosmic rays
Burning destruction of cells caused by exposure to high
concentration of acids or bases
Narcosis depression in sensory activity, reversible, caused by
alcohols, ethers, benzene, drinking
Damage to excretory organs
Damage to respiratory organs
Damage to reproductive function
Acute toxicity = rapid death
Acute dose causes acute toxicity extremely high risk; causes
Chronic toxicity = slow death; e.g. cancer (20-30 years)
Paracelsus Principle: The Dose Makes the Poison
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