History of pesticides - Pesticide Health Effects Medical Education

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)
Federal Insecticide, Fungicide and Rodenticide Act
What is a Pesticide? Examples
Generally not very toxic to humans: a few
More frequently sensitizers. Some are carcinogenic,
mostly not acutely toxic
Generally acutely toxic group of pesticides
Gasses that kill most everything
Newer rodenticides primarily anticoagulants
Nano-silver (a recent EPA decision). Toxicity yet to be
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
Developmental toxicity
Metabolism and fate studies
What Don’t We Know
• Long term effects of low level exposure on
human populations
• Long term neurodevelopmental effects on
• 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 II
Metals 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
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,
– Pierre M. A. Millardet,
– French National Hero
Before World War II
Lead 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
• 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
– 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
Paul Müller
Nobel 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.
Safe, 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 19702000’s
– Parkinson’s and pesticides 1990-2009- still working