Toxicology. What is toxicology ? The study of the effects of poisons. Poisonous substances are produced by plants, animals, or bacteria. Phytotoxins Zootoxins Bacteriotoxins Toxicant - the specific poisonous chemical.
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What is toxicology? The study of the effects of poisons.
Poisonous substances are produced by plants, animals, or bacteria.
Toxicant - the specific poisonous chemical.
Xenobiotic - man-made substance and/or produced by but not normally found in the body.
Did You Know ?
Swiss physician Paracelsus (1493-1541) credited with being
“the father of modern toxicology.”
“All substances are poisons: there is none which is not a poison. The right dose differentiates a poison from a remedy.”
“Everything is poisonous, yet
nothing is poisonous”
Most substances in too great amounts
can be dangerous, but in small
amounts are harmless.
Ex: table salt, vitamins
Dose response curves illustrate the
relationship between concentration
Trace concentrations may be very
useful, then a certain concentration
is reached where the substance
Individuals differ in their response
to an environmental toxin, so a way
to measure the overall toxicity is
LD-50 represents the concentration
that is lethal to 50% of the
population exposed to the toxin.
The lower the LD-50, the more
toxic the substance.
Sodium Chloride- 4000 mg/kg
2,4-D (weed killer) 368 mg/kg
DDT 135 mg/kg
Caffeine 127 mg/kg
Nicotine 24 mg/kg
Strychnine sulfate (rat poison) 3 mg/kg
Botulinum toxin 0.00001 mg/kg
In toxicology testing, the most
common route of exposure is tested,
and is the basis for setting rules for
exposure to the toxins
Ex: inhalation, skin and eye exposure,
Acute vs. Chronic Toxicity Tests
Can broadly classify toxicity tests based on length of exposure
Acute vs chronic toxicity testing (con’t)
Acute Testing - theory
Acute Toxicity Test Organisms
Normal distribution of resistance/sensitivity
5% allowable impact
Chronic toxicity testing
The ED-50 represents the amount
that is effective in 50% of the
Ex: concentration of aspirin needed
to be effective in 50% of the
The TD-50 is defined as the dose
that is toxic to 50% of the population.
Toxic responses can be things such
as reduced enzyme activity, lowered
reproduction, or onset of specific
symptoms (known to be associated
with the toxin. )
All toxicity tests try to determine level of toxicant which will or will not cause an effect
MATC = √NOEC + LOEC
Sources of Pollution
Point Source vs. Non-Point Sources:
-Point source polluters are single
sources of pollution, such as pipes,
smokestacks, or spills
Non-Point sources (also Area Sources)
are spread over the land, and do not
have a single outflow of pollution.
Ex: runoff from polluted land areas,
Categories of Pollutants
EX: Salmonella, a food poisoning bacteria spread
via water or food.
Giardiasis, a protozoan infection spread via water,
or person-to-person contact.
2) Toxic Heavy Metals:
-metals with high atomic weight
-Pose health hazards to humans and ecosystems
chromium, vanadium, thallium
-most of these metals are by-products
of a modern industrialized society
Body Burden of Heavy Metals
-Body Burden is defined as the amount
of heavy metals contained within an
-heavy metals are accumulated over
an organisms lifetime, and biomagnify
in the food chain.
Human averages: 13 mg mercury, 150mg lead
Biomagnification is the accumulation of
a substance up the food chain by transfer
of residues of the substance in smaller
organisms that are food for larger
organisms in the chain.
Biomagnification can result in higher
concentrations of the substance than
would be expected if water were the only
One small fish needs 10 insects to live, if each insect has 25 microscopic drops
of methylmercury in its body, then one fish would have __________
microscopic drops of methylmercury.
One big fish eats 5 small fish to live. Each small fish has __________
microscopic drops of methylmercury in its body, therefore, one big fish would
collect a total of __________ microscopic drops of methylmercury in its body.
What about you and me? Lets say we eat 1 big fish a day for 3 days. If each
big fish has __________ drops of methylmercury in its body then we would
collect a total of __________ drops of methylmercury in our body over the 3
3) Organic Compounds:
-produced naturally, or synthetically
-compounds containing carbon as an
-many synthetic organic compounds
are used in industrial processes, food
additives, pesticides, and drugs.
-Some synthetic organics are called
“persistent organic pollutants” or
POP’s have several characteristics that
make them particularly bad for the
2) They are synthetic
3) They are long-lived in the environment
4) They are very toxic to a variety of organisms
5) They are soluble in fat, so they accumulate
within the fatty tissue of organisms
6) They occur in forms which allow them to be
transported in a large variety of ways (wind,
Some Organic Pollutants
-Aldrin (1949) :Insecticide
-Dieldrin (1948) :Insecticide
-DDT (1942): Insecticide
-PCB’s (1929) : Electrical Insulators
-Dioxins (1920’s) :by-product of
-small particles of dust, released
into the atmosphere by many
Ex: construction, exhaust
-Particulates are also released
Into the atmosphere by natural
processes as well.
Ex: volcanoes, wind erosion
Particulates can cause many
respiratory problems, from asthma
Particulate pollution has been
declining in the U.S., mostly due
to pollution limits on coal fired