Pesticides in clinical care part i
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Pesticides in Clinical Care Part I. What is a Pesticide?. A substance or mixture used for preventing, destroying, repelling, or mitigating any pest. A pest is any harmful, destructive, or troublesome animal, plant or microorganism.” Environmental Protection Agency (EPA)

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Pesticides in Clinical Care Part I

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Pesticides in Clinical CarePart I

What is a Pesticide?

A substance or mixture used for preventing, destroying, repelling, or mitigating any pest.

A pest is any harmful, destructive, or troublesome animal, plant or microorganism.”

Environmental Protection Agency (EPA)

Federal Insecticide, Fungicide and Rodenticide Act

What is a Pesticide? Examples

HerbicidesGenerally not very toxic to humans: a few exceptions

FungicidesMore frequently sensitizers. Some are carcinogenic, mostly not acutely toxic

InsecticidesGenerally acutely toxic group of pesticides

Fumigants Gasses that kill most everything

Rodenticides Newer rodenticides primarily anticoagulants


Nano-silver (a recent EPA decision). Toxicity yet to be determined

What Do We Know About a Pesticide? Pesticide Registration by EPA

  • EPA responsible for registering pesticides

    • Toxicity tests required in registration process

      • Acute toxicity (LD50)

        • Oral, Dermal, Inhalational

      • Subchronic and Chronic toxicity

        • Delayed neurotoxicity

      • Reproductive toxicity

      • Teratotogenicity

      • Developmental toxicity

      • Mutagenesis-oncogenesis-genotoxicity

      • Metabolism and fate studies

What Don’t We Know

  • Long term effects of low level exposure on human populations

  • Long term neurodevelopmental effects on humans

  • Effects of Mixtures

  • Effects of “inert ingredients”

  • Effects of some newer pesticides on humans

  • Non specific toxicological mechanisms and consequences of some pesticides

Brief History of Major Pesticides

  • Prehistory: Sulfur

    • First seen in Egyptian writings 2400 B.C. and Chinese writings 1500 B.C.

    • Greek writings

      • 700 BC

Before World War IIMetals and Salts

Arsenites. Paris Green,

A gem of a pesticide - copper acetoarsenite. circa 1867 This was introduced and used first as a pigment, known as Emerald Green, later as a pesticide.

Other arsenic preparations and products of the dye industry were also used

Paris Purple

London Purple

The Control of Other Pests

  • Bordeaux mixture

    • (copper sulfate and hydrated lime)

  • First effective fungicide, 1882

    • Pierre M. A. Millardet,

    • French National Hero

Before World War IILead Arsenate Very Important

Lead Arsenate to fight the gypsy moth 1892.

  • Heavily used in much of agriculture

  • Heavily used in apples

  • Soil contamination remains a problem today in many old orchard soils in the Northwest

Other Non-metalic Pesticides

  • Pyrethrum

    • A carefully held secret for many years 1850-

    • Source is Chrysanthemums

  • Nicotine

    • Widely used until WWII

    • Extremely toxic (LD50 = 1mg/kg)

Discover of New Insecticides

  • Discovery of organophosphates

    • Gerhard Shrader: A German Scientist

    • Attempting to replace Nicotine

    • Developed organophosphate esters

    • Tabun, sarin, soman (G gases), parathion

    • First to be poisoned by nerve gas (tabun)

Discover of New Insecticides

  • DDT

    • First synthesized by a German graduate student Othmar Zeidler in 1873

    • Rediscovered by Paul Mueller, a Swiss entomologist, in 1939

    • World War II, Use of DDT to control typhus and malaria.

Paul MüllerNobel Prize 1948

  • “My fly cage was so toxic after a short period that even after very through cleaning of the cage, untreated flies, on touching the walls fell to the floor. I could only carry on my trials after a thoroughly cleaning and after that leaving it for about one month in open air.” Muller Nobel Prize acceptance speech 1948.

DDTSafe, Effective, Inexpensive

Used Everywhere

Rachael Carson: A Silent Spring

  • January 1, 1973 (EPA) canceled all uses of DDT in the US

  • By the time of its cancellation, more than 1 billion kilograms of DDT had been introduced into the United States.

When Did We Become Aware of Pesticide Health Issues?

  • Physicians discussed Lead and Arsenic toxicity in the 1700-1800s

  • Animal & human studies on arsenic up to 1940s

  • The new pesticides showed some early problems

    • 1950s reports of pesticide toxicity from OP’s & OC’s

    • 1960s Increasing literature about DDT Health effects

    • 1960s 15 labs in US study health effects of pesticides

    • 1966 First organized study of human OP Persistent Health effects Tabershaw and Cooper

    • Studies of Neurotoxicity of Organophosphates 1970-2000’s

    • Parkinson’s and pesticides 1990-2009- still working

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