Laymans Toxicology

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Laymans Toxicology

• An Overview of Toxicology
• for
• Pesticide Applicators
• Developed by Don Mullins and Pat Hipkins
• Department of Entomology / Virginia Tech
  Pesticide Programs
• 1997

Modified by Georgia Agricultural Education
Curriculum Office July, 2002
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TOXIC

• Poisonous.
• Harmful to living things.

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TOXICITY

• The quality of being
• poisonous
• having harmful effects.

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Definitions

• Toxicant
• a toxic substance
• Hazard
• the inherent toxicity of a substance, based on
  appropriate animal models or information from
  human studies

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Definitions (continued)

• Toxication (intoxication)
• a product more toxic than the original compound
• Activation
• a specific reaction (enzymatic) that produces a
  more toxic compound
• Detoxification
• deactivation of a toxic compound

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Routes of Entry

• Oral Ingestion by mouth
• Dermal Skin exposure
• Inhalation Absorbed by lungs
• Ocular Eye exposure

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Dermal Exposure Variables
Area Rate forehead 4.2 forearm
1.0 abdomen 2.1 palm 1.3 scrotum
11.8 ball of foot 1.8
Absorption rate compared to forearm, which is 1.0
mjweaver,1997
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Toxic effects may occur

• during or soon after exposure (acute),
• and
• after repeated exposures over a long time
  (chronic).
• In addition, some people may be especially
  sensitive (allergic) to a substance.

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Acute Toxicity

• (short-term exposure)

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Chronic Toxicity

• (repeated exposures)

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Definitions Chronic Effects

• Carcinogens
• Cause cancer
• Mutagens
• Cause mutations in an organisms genetic material
• Teratogens
• cause birth defects in offspring following
  exposure of a pregnant female

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Toxicity Measure LD50

• The LD50 is the dose of toxin
• that produces 50 mortality
• in a test population.
• LD50 is usually expressed
• in milligrams of toxin
• per kilogram of test animal body weight (mg/kg).

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LD50 Value and Toxic Effect

• The more toxic a material is, the less it takes
  to kill or produce a harmful effect...

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LD50 Value and Toxic Effect

• ...therefore,
• - the lower the LD50 value, the more toxic the
  substance, and
• - the higher the LD50 value, the less toxic the
  substance.

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Toxicity Comparisons
Acute toxicity measurements
Acute oral and/or
LD

Lethal dose
Acute dermal
50
(in mg / kg)
in parts per million
( ppm )
Methoxychlor 6000 Malathion
1500 --- DDT 250 Lindane
125 Dieldrin 100 ------------- Parathion
3 --------------
15 x
33 x
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Toxicity Comparisons (cont.)

• Acute toxicity measurements
• acute inhalation ( lethal concentration )
• LC 50 mg / liter

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Toxicity Measures and Lethal Dose

• Oral LD50 Lethal Dose
• (mg toxin/kg body weight) (for an average
  adult)
• 0 - 5 a drop or a pinch
• 5 - 50 a few drops to 1 teaspoon
• 50 - 500 1 teaspoon to 1 tablespoon
• 500 - 5,000 1 ounce to 1 pint
• 5,000 - 15,000 1 pint to 1 quart
• gt 15,000 gt 1 quart

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Toxicity Information and Clues

• Concentration of Active Ingredient in Product
• Restricted Use (reason?) vs. General Use
• PPE Requirements, Re-Entry Interval (REI), and
  other label Precautions and Instructions
• Label Signal Word
• MSDS for Product

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Toxicity Measures and Signal Word

• Acute Oral LD50 Signal Word
• 0 - 50 DANGER/POISON N (skull and
  crossbones)
• DANGER
• 50 - 500 WARNING
• 500 - 5,000 CAUTION
• gt 5,000 CAUTION

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Label Signal Word and Hazard

• Signal Word Toxicity Hazard
• Danger/Poison N high toxicity
• Danger high toxicity
• (by some entry route and/or
• to some organisms)
• Warning moderate toxicity
• Caution low toxicity

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Sample Oral Toxicity Valuesfor Commonly-Used
Insecticides

• Pesticide (Product) Acute Oral LD50
• (mg/kg - male rat)
• acephate (Orthene) 945
• carbaryl (Sevin) 850
• chlorpyrifos (Dursban, Lorsban) 135 - 163
• diazinon (DZN Diazinon) 300 - 400
• malathion (various) 1,378 - 2,800
• methyl parathion (Penncap-M) 14 - 24
• parathion (Parathion) 3.6 - 13
• terbufos (Counter) 1.6
• The Agrochemical Handbook, Royal Society of
  Chemistry (1991)

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Sample Oral Toxicity Valuesfor
Botanical-Derivative Insecticides

• Active Ingredient Acute Oral LD50
• (mg/kg - rat)
• azadirachtin (neem) 5,000
• nicotine 50 - 60
• pyrethrum 584 - 900
• synthetic pyrethroids 22 - 5,000
• rotenone 39 - 1,500
• ryania 1,200
• The Agrochemical Handbook, Royal Society of
  Chemistry (1991) and
• Agricultural Chemicals Book I Insecticides
  (1994-95)

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Sample Oral Toxicity Valuesfor Commonly-Used
Herbicides, etc.

• Pesticide (Product) Acute Oral LD50
• (mg/kg - male rat)
• acetylsalicylic acid (asprin) 50-500
• caffeine (coffee, tea, some sodas) 50 - 500
• 2,4-D (various) 666 - 805 (salt) 700 (ester)
• dicamba (Banvel, Vanquish) 2,629 - 6,764 (salts)
• glyphosate (Accord, RoundUp) 4,045 (salt)
• imazapyr (Arsenal) gt5,000
• nicotine (tobacco products) 0.5 - 1.0
• sodium chloride (table salt) 430 - 3,750
• triclopyr (Garlon) 713
• The Agrochemical Handbook, Royal Society of
  Chemistry (1991)
• Clinical Toxicology of Commercial Products (1984)

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RISK FACTORS

• 1. Toxicity of the Formulated Product.
• 2. Other Physical and Chemical Characteristics
• (ex. liquid vs. dry formulation).
• 3. Amount of Handling Required.
• 4. Method of Exposure(s) / Route of Entry.
• 5. Frequency and Duration of Exposure(s).

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Special Risk Factors for Children

• lower body weight
• greater surface area
• high metabolism
• habits
• diet

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Surface Area Volume Ratio

• edge (in) surface area (in2) volume (in3) RATIO
• 2 24 8 3 1
• 4 96 64 1.5 1
• 6 216 216 1 1
• 8 384 512 1 1.3
• 10 600 1,000 1 1.7
• 12 864 1,728 1 2

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Surface Area Volume
children
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RISK MANAGEMENT

• RISK TOXICITY X EXPOSURE

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REDUCE TOXICITY

• Reduced Use
• Product Selection

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REDUCE EXPOSURE

• Engineering Controls
• Safe Work Habits
• PPE Use

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Units of Measurement

• parts per million milligrams per kilogram ( mg
  / kg )
• 1 oz of sand in 31 tons of cement
• 1 square foot in 23 acres
• 1 minute in 695 days
• parts per billion micrograms per kilogram (m g
  / kg )
• 1 square foot in 36 square miles
• 1 pinch of salt in 10 tons of potato
  chips
• 1 inch in a 160,000 mile trip
• parts per trillion nanograms per kilogram ( ng
  / kg )
• 1 square inch in 250 square miles
• 1 second in 320 centuries or 11,574,074 days
• 1 postage stamp in an area the size of
  Texas

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Synergist / Synergism
Synergism is increased activity (toxicity)
resulting from the effect of one chemical on
another.
LD50 DDT 250 mg/kg LD50 synergist 1,000
mg/kg LD50 DDT synergist 50 mg/kg