Transcript Document

Toxicology Basics
An Introduction to the
Concepts of Toxicology
Used in APES
(Building off your knowledge of pesticides to lead into
environmental hazardous chemicals as a whole)
Units Used to Measure Chemicals
in the Environment
 PPM – Parts per million (1 in per 1,000,000 , 10-6 )
 PPB – Parts per billion (1 part in 1,000,000,000 , 10-9 )
 PPT – Parts per trillion (1 in 1,000,000,000,000 , 10-12 )
 Since parts-per notations are quantity-per-quantity measures, they are
known as dimensionless quantities; that is, they are pure numbers with
no associated units of measurement.
Consider A simple cube 1 cubic meter
in
volume
1m
1m
1m
formed of 1,000,000 cubes,
1 cubic centimeter each
100cm
100cm
100cm x
100cm x
100cm =
1,000,000 cc
In 1 m3
block 1cc =
1ppm
100cm
One part per million is
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1 inch in 16 miles
1 minute in two years
1 cent in $10,000
1 ounce of salt in 31 tons of potato chips
1 bad apple in 2,000 barrels of apples
NOW…Divide each 1CC block into
1,000 blocks 0.1cM on a side
1cm
1cm
In 1 m3 block
0.001cm3 =
0.001cc or
1/1000 of a cc =
1ppb
1cm
0.1cm x
0.1cm x
0.1cm =
0.001cm3
One part per billion is


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1 inch in 16,000 miles
1 second in 32 years
1 cent in $10,000,000
1 pinch of salt in 10 tons of potato chips
1 lob in 1,200,000 tennis matches
1 bad apple in 2,000,000 barrels of apples
Next, divide each 0.1cc block into
1,000
blocks 0.01cm on a side
0.1cm
0.1cm
In 1 m3 block
.000,000,001m3 =
0.000,001cc or
1/1,000,000 of a cc
= 1ppt
0.1cm
0.01cm x
0.01cm x
0.01cm =
0.000001cm3
One part per trillion is
 1 postage stamp in the area of the city of Dallas
 1 inch in 16 million miles (more than 600 times
around the earth)
 1 second in 320 centuries
 1 flea on 360 million elephants
 1 grain of sugar in an Olympic sized pool
 1 bad apple in 2 billion barrels
Important Concept
 On the left side of the decimal point ( . )
 1 trillion is bigger than 1 billion
 1 billion is bigger than 1 million
 1 million is bigger than 1 thousand…
 On the right side of the decimal point ( . )
 1 part per trillion is smaller than 1 part per billion
 1 part per billion is smaller than 1 part per million
 1 part per million is smaller than 1 part per thousand
Important Relationship
For water at STP (standard temperature [23oC] and
pressure [15 psi])
1 cc
=
1ml
=
1g
…Which means that
(1000 ml or cc )  1 liter of water = 1 kg  (1000 g)
(1/1000 g)  1 mg / kg  (1000 g) = 1 ppm
(1/1000 cm3 )  1 mm3 / liter  (1000 cm3 ) = 1 ppm
(1/1000 g)  1 mg / liter  (1000 g) = 1 ppm
Measures of Toxicity:
The Median Lethal Dose
LD50
The amount (dose) of a chemical which produces death in
50% of a population of test animals to which it is
administered by any of a variety of methods
Substance (1/1000 g)  mg/kg  (1000 g) body weight
Normally expressed as milligrams of substance per
kilogram of animal body weight (same as ppm)
Your Turn!
 PPM Visualization Worksheet
Primary Routes of Exposure
to Pesticides
There are three primary routes by which organisms are
exposed to pesticides
Oral
Dermal
Inhalation
Primary Routes of Exposure:
Oral Exposure
Any exposure to pesticide which occurs when the
chemical is taken in through the mouth and
passes through the gastrointestinal tract
During oral exposure, although carried within the
body, the pesticide is still outside of the body
proper until it passes through epithelial cellular
membranes.
Primary Routes of Exposure:
Dermal Exposure
Exposure of the skin to a pesticide
Most common route of human exposure
With proper hygiene this type of exposure is
generally not serious unless there is a specific,
rapid toxicological effect (often eye effects)
which is of concern
Primary Routes of Exposure:
Inhalation Exposure
Occurs when a pesticide is breathed into the lungs
through the nose or mouth
Significant route of exposure for aquatic organisms
Not of toxicological concern until it crosses from the
lung into the body (unless the chemical is corrosive)
Remember –
 For pesticides – less is more when dealing with
toxicity
 The less you need to cause a toxic effect – the more
toxic the substance is
 Thus an LD50 of 25 mg/kg is more toxic than is one of
7,000 mg/kg
Signal Words
The relative acute toxicity of a pesticide is reflected on the
label in the form of a “signal word”
The (toxicologically) appropriate signal word MUST appear
on every pesticide label
The three possible signal words are
CAUTION
WARNING
DANGER
Signal Words:
“
” reflects the lowest degree of relative
toxicity
All pesticides with an LD50 of greater than 500
mg/kg must display this word on their label
Actually includes two groups of pesticides – those
classed by the EPA as
“
“
” (>5,000 mg/kg)
and those classed as
” (500 – 5,000 mg/kg)
Signal Words:
WARNING
“Warning” reflects an intermediate degree of
relative toxicity
All pesticides with an LD50 of greater than 50 and
less than 500 mg/kg must display this word on
their label
Pesticides in this category are classed as
“Moderately toxic” (>50 but <500 mg/kg)
Signal Words:
DANGER
“Danger” reflects the highest degree of relative toxicity
All pesticides with an LD50 of less than 50
mg/kg must display this word on their label
Pesticides here are classed as
“Highly toxic” (< 50 mg/kg)
POISON!!!
 Legally defined term – not just anything you don’t like
 Any pesticide with an LD50 of 50 mg/kg or less
 Labels must reflect this classification
 Label must have the signal word “DANGER” plus the
word “POISON”
 Label also must display the skull and crossbones icon
Relative Toxicity:
Are all substances toxic?
YES!
All are toxic to some quantifiable degree
Sugar has an LD50 of
30,000 mg/kg
Ethanol, a party favorite, has an LD50 of only
13,700 mg/kg
Water has a recognized LD50 of slightly greater than
80,000 mg/kg