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Lecture

Lecture note 9

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Department
Environmental Science
Course Code
EESA10H3
Professor
Jovan Stefanovic

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Lecture 9
During the lecturre we will come on formulas and everything needed on questions 1.
Todays topic is TOXICOLOGY and RISK ASSESMENT
Very basic
What is Toxicology? Science that studies poisons. How they are produced? How they are
removed from the environment? Where can they be find? How they affect the organism? That’s
the study of poison .
Tocicisty of some chemicals basically depends on
1) Chemical characteristics of the poison that are:
Polarity
Electronegativity
Oxidation state: When we talked about arsenic 3 and 5 are different
Molecular weight
Dissociation
Solubility
Water soluble toxins: Inorganic chemical dissolve in water, difficult for them
human cell. They surround the cell but they don’t enter
Fat soluble toxins: Organic chemical are dissolved in fats. Fat soluble cell easily
enter the cell, that’s why they bioaccumalate.
Persistence of chemical: Some chemicals can break down easily, some stay persistence
for years without much change.
Bioaccumulation
Biomagnification
Chemical interaction
Antagonistic effect: One chemical reduces the toxicity of another chemical eg.
Vitamin A and E might reduce cacogenic effect for some chemicals.
Synergistic: 2 different chemicals taken up at the same time by a person
increase the risk of a disease eg. Smoking and
Multiple chemicals food additives, pesticides, air pollution
Very rare human is exposed to one chemical, usually exposed to multiple
chemicals.
Receptor:
Anybody can be the receptor, any organisms that receive exposure or dose, this course
focoused on human.
Frequency of the exposure is important to know
Age: Child or elder person
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General Health: can be more prone for some respeonses, even some people of same age
or same general health can have different effect.
Dose: Amount of chemical that person takes up or been exposed too.
Three major routes for exposure:
Ingestion through food, water etc, greatest exposure 95% going through ingestion
Inhalation about 10%
Transfer through the skin: Industrial chemicals could be absobs through the
skin 5%
Three different types of doses:
Acute Dose: one single dose, usually high dose received in short time
Chronic Dose: continuous dose but low dose
Long term dose: low dose but receive for long time.
Response
Syptoms that can be measured
Response can be divided into 2 groups:
Non specific: No certain tissue is attacked, the whole system is attacked. Eg. Burning,
everything is destroyed and also when Narcosis(drunk) effects nervous system, vision,
liver or some other organs. No specific tissue that is effected
Specific: We know the tissue.
Two different type of responses:
Acute: Rapid response or death
Chronic : Delay response
Every chemical is harmful at some level, Water is poison if u drink 3 litters or more at once, can
cause every serious health effects. About 100 cups of coffee for some people can cause death. Or
100 pills of aspirin. Question is How much can cause harmful effect.
Its really hard from where to start measuring toxicology, if we measure right after we are
exposed then there will be no good result
Measurement endpoint is easier to measure, we measure biomarkers such as hormones and
protein marker thats tells about enzyme induction.
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