CIVTECH 3CS3 Lecture Notes - Lecture 9: Health Canada, Chronic Toxicity, Risk Assessment

55 views5 pages
Published on 19 Apr 2013
School
McMaster University
Department
Civil Engineering Infrastructure Technology
Course
CIVTECH 3CS3
Lecture 9
Toxicology:
Definition:
o Study of poisons
o “the science which studies toxic substances or poisons, that are substance which cause
alteration or perturbation in the function of an organisms leading to harmful effects”
(Truhaut, 1974).
How harmful a substance is depends on the chemical characteristics of the substances:
o Some characteristics to consider are:
Electronegativity
Polarity
Oxidation State
Molecular Weight
Dissociation
Solubility water soluble toxins (hard to enter human cells) and fat soluble
toxins (can easily enter the human cell and bioaccumulate).
Assessing Chemical Hazards
o Persistence of the chemical: do they break down or remain in the same chemical
configuration (e.g. DDT).
o Bioaccumulation
o Biomagnification
o Chemical interaction
Antagonistic effects: two different chemicals taken up by the same given
individuals and behave antagonistic towards each other; however, they are very
toxic if taken up separately. One chemical reduces the toxicity of the other if
mixed or existing together. For example, Vitamins A and E may decrease
chemical toxins that may induce cancer
Synergistic effects: one chemical enhances the toxicity of the other chemical
present. For example, exposure to asbestos can lead to lung cancer by 20-fold.
However, smoking in the presence of asbestos increases the risk of lung cancer
by 400-fold.
o Multiple chemicals food additives, pesticides, air pollutioncomplicates the risk of
getting harmed and diseased even more
o When studying toxicology, it is important to determine three things:
Who the receptor is
Any organism that receives exposures to toxins.
To study the receptor, we must understand the frequency of the
exposure that person has undergone
Age is important (i.e. a child, elder are more vulnerable)
General health
Genetic makeup
What dose they received
Amount of chemical a person takes up
Ingested (greatest source of exposure-95%)
Inhalation (air pollutants, particles, and volatiles -10%)
Absorbed through the skin (industrial -5%)
Unlock document

This preview shows pages 1-2 of the document.
Unlock all 5 pages and 3 million more documents.

Already have an account? Log in
There is a debate between how much chemical is taken up into the
body and how much the receptor really receives.
o Individual takes up a higher concentration of the chemical than
the receptor (proteins) receive. Why? They can be metabolized
before reaching the targets.
o There are three types of doses
Acute dose refers to single dose, usually high
Chronic dose repeated or continuous low dose over
time
Long term low dose over a life time (many professional
doses are long term, approx. 45 years).
What is the receptor’s response (e.g. illness)
Nonspecific: attack any tissue (general), the whole system is affected
o Burning: destruction of cells caused by exposure to high
concentration of strong acids or bases
o Narcosis: depression in sensory activity, reversible, caused by
alcohols, ethers, benzene
Specific
o Damage to excretory organs
o Damage to respiratory organs
o Damage to reproductive function
o Mutagenesis
o Carcinogenesis
Acute toxicity leads to rapid death
Chronic toxicity delayed response; you are poisoned today and you die
on your birthday next year
Is every chemical poisonous?
o Yes it can be at certain levels of exposure
o Even water. If you drink 3L or more at once, it may lead to dangerous health effects (e.g.
the lady who died drinking water non-stop to win a Wii and her bladder busted).
o Any substance is poisonous, but the question is how often or how much of a given
substance is considered poisonous
Measuring Manifestations
o It is hard to define a start and endpoint of measuring toxicity
o Endpoint toxicological manifestation is impossible to measure so we have to wait for…
o …Measurement Endpoint – physiological manifestation
Can be readily measured
More easily measured than endpoint
Use of “biomarkers” e.g. changes in hormone levels, protein markers, enzyme
induction
Methods of determining toxicity
o We conduct laboratory experiments on animals (e.g. mice and rats and snitches) to find
the Lethal dose (LD50): amount of chemical received at a single dose that will cause the
mortality of 50% of experimental animals after a period of 14 days.
o Case reports: family physician makes a report of the last 5 years of the cases of
poisoning and its characteristics
o Epidemiological studies
Unlock document

This preview shows pages 1-2 of the document.
Unlock all 5 pages and 3 million more documents.

Already have an account? Log in

Document Summary

Definition: study of poisons, the science which studies toxic substances or poisons, that are substance which cause alteration or perturbation in the function of an organisms leading to harmful effects (truhaut, 1974). How harmful a substance is depends on the chemical characteristics of the substances: some characteristics to consider are: Solubility water soluble toxins (hard to enter human cells) and fat soluble toxins (can easily enter the human cell and bioaccumulate). Assessing chemical hazards: persistence of the chemical: do they break down or remain in the same chemical configuration (e. g. ddt), bioaccumulation, biomagnification, chemical interaction. Antagonistic effects: two different chemicals taken up by the same given individuals and behave antagonistic towards each other; however, they are very toxic if taken up separately. One chemical reduces the toxicity of the other if mixed or existing together. For example, vitamins a and e may decrease chemical toxins that may induce cancer.

Get OneClass Grade+

Unlimited access to all notes and study guides.

YearlyMost Popular
75% OFF
$9.98/m
Monthly
$39.98/m
Single doc
$39.98

or

You will be charged $119.76 upfront and auto renewed at the end of each cycle. You may cancel anytime under Payment Settings. For more information, see our Terms and Privacy.
Payments are encrypted using 256-bit SSL. Powered by Stripe.