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”
How harmful a substance is depends on the chemical characteristics of the substances:
o 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
o Persistence of the chemical: do they break down or remain in the same chemical
configuration (e.g. DDT).
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
o Multiple chemicals – food additives, pesticides, air pollution—complicates 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)
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%) 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
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
o Damage to excretory organs
o Damage to respiratory organs
o Damage to reproductive function
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
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
Methods of determining toxicity
o We conduct laboratory experiments on animals (e.g. mice and rats and snitches) to find
the Lethal dose (L50): 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 o Computer simulations
o Tissue cultures of cells and bacteria
o It is difficult to compare studies on animals and bacterium to human cases
o Curve displays how the response will change in relation to dose increments
o Used for acute toxins
o The green line represents non-threshold chemicals: carcinogenic – one molecule causes
o Threshold chemical are non-carcinogenic
Risk and Risk Assessment
o Risk – possibility of suffering harm from a hazard. It contains the possibility and
probability suffering harm from hazards.
o Risk assessment: scientific processes in estimating how much harm a particular hazard
can cause (e.g. if someone is smoking, they have a