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Layman’s Toxicology

Layman’s 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 . TOXIC:. Poisonous.

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Layman’s Toxicology

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  1. Layman’s 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

  2. TOXIC: Poisonous. Harmful to living things.

  3. TOXICITY: The quality of being poisonous; having harmful effects.

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

  5. 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

  6. Routes of Entry: Oral = Ingestion by mouth Dermal = Skin exposure Inhalation = Absorbed by lungs Ocular = Eye exposure

  7. 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

  8. 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.

  9. Acute Toxicity: (short-term exposure)

  10. Chronic Toxicity: (repeated exposures)

  11. Definitions: Chronic Effects • Carcinogens: • Cause cancer • Mutagens: • Cause mutations in an organism’s genetic material • Teratogens: • cause birth defects in offspring following exposure of a pregnant female

  12. 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).

  13. LD50 Value and Toxic Effect The more toxic a material is, the less it takes to kill or produce a harmful effect...

  14. 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.

  15. 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

  16. Toxicity Comparisons (cont.) Acute toxicity measurements: acute inhalation ( lethal concentration ) LC 50 = mg / liter

  17. 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 > 15,000 > 1 quart

  18. 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

  19. 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 > 5,000 CAUTION

  20. 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

  21. 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)

  22. 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)

  23. 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) >5,000 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)

  24. 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).

  25. Special Risk Factors for Children: • lower body weight • greater surface area* • high metabolism • habits • diet

  26. 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

  27. Surface Area : Volume children

  28. RISK MANAGEMENT: RISK = TOXICITY X EXPOSURE

  29. REDUCE TOXICITY • Reduced Use • Product Selection

  30. REDUCE EXPOSURE • Engineering Controls • Safe Work Habits • PPE Use

  31. 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

  32. 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

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