Organochlorine Pesticides

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Organochlorine Pesticides

• CHEM 471/ ENVS 531
• Ch. 13
• Liz Love

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Organochlorine Pesticides

• Background Information
• 7 Common Characteristics
• 5 Major Groups of OCs

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Background

• DDTs success stimulated the production of
  several OC pesticides
• Successful eradicators
• Severe toxic effects
• Currently in the U.S. and Europe OCs are not a
  major pesticide, but they are in developing
  countries and tropical regions
• Cost-benefit

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7 Common Characteristics

• Atomic structure
• Lipid solubility
• Persistence
• Bioaccumulation
• Toxicity
• Physiological Response
• Interactions

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1. Atomic Structure

• Characterized by the presence of carbon,
  chlorine, and hydrogen (sometimes oxygen)
• Cyclic carbon chains (benzene ring)

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Atomic Structure
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2. Lipid Solubility

• High lipid solubility (non-polar)
• High log Kow
• Stored in lipids/fat
• Fasting can cause reentry into circulation
• The concentration in biota has decreased since
  the banning of several OCs

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3. Persistence

• Persistence is based on the half lives in the
  organism and in the environment
• Stable compounds
• Physical and biological influences
• Environmental
• Organism

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Persistence Cont.

• Dependent on the compound
• Aldrin is rapidly metabolized
• Endrin and dicofol have short half lives in an
  organism and in the environment
• DDT, its metabolites and dieldrin are extremely
  persistent

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4. Bioaccumulation

• Accumulation of pesticides through absorption
  through skin, gills, or food
• Bioconcentration and biomagnification
• Aquatic organisms vs. terrestrial organisms

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5. Toxicity

• Biochemical lesions
• Neuroactive agents
• Ingestion, inhalation and dermal absorption
• Mortality
• Lethal brain and liver residues indicate
  biochemical lesions
• Influences on toxicity

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Toxicity Cont.

• DDT
• Acts on CNS by interfering with ion movement
  through neuronal membranes
• 4 mechanisms
• Na2 and K
• ATP
• Ca 2 inhibition
• Ca2Mg2
• Maintain depolarization, which leads to
  hypersensitive neurons
• Persistent tremoring, seizures or convulsions

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Toxicity Cont.

• Cyclodienes
• Alter the neurotransmitter gamma-aminobutyric
  acid (GABA)
• Inhibit Na2, K, and Ca2Mg2 channels
• HCH
• Block chloride ion
• Alter Ca2 levels

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6. Physiological Response

• Induced enzyme activity
• Species variations
• Persistence and excretion
• Endocrine disruptors

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7. Interactions

• Synergism, potentiation, antagonism, or additive
  toxic effects
• Antagonistic Japanese quail were treated with
  chlordane and later with parathion
• Synergism Aldrin increases the storage of DDT
• Additive effects are most common for industrial
  chemicals and pesticides

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5 major groups of OCs

• Dichlorodiphenylethane
• DDT, dicofol, and methoxychlor
• Cyclohexane
• Hexachlorocyclohexane (HCH)
• Chlorinated cyclodiene
• Aldrin, dieldrin, and endrin
• Toxaphene
• Mirex and chlordecone

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DDT, DDD, and DDE(Dichlorodiphenylethane)

• Paul Muller (1939)
• Subsequent discovery of large-scale mortality of
  birds, insects, and invertebrates
• Determination lethal brain residues
• DDE

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DDT, DDD, and DDE Cont.

• Adverse affects on wildlife
• Avian populations
• Brown pelicans
• Peregrine falcons
• Osprey and bald eagles
• Fish and bats

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DDT, DDD, and DDE Cont.

• DDD sprayed 3 times on Clear Lake, which lead to
  bioaccumulation data
• Resistance to DDT
• DDT was banned in 1972
• DDT has estrogenic activity

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Aldrin/Dieldrin (cyclodiene)

• Very toxic
• Aldrin is quickly transformed into Dieldrin
• Adverse affects on wildlife
• Aldrin/Dieldrin spraying in 1960 and 1961 for
  Japanese beetles
• Whistling ducks, snow geese, and others
• Gray bats in Missouri
• The combined effects of DDE and Dieldrin
• Aldrin/Dieldrin were banned in 1974

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Endrin (cyclodiene)

• Short half life, but very acutely toxic
• Adverse affects on wildlife
• Brown pelican
• Voles, birds, and quail
• Metabolic pathways
• 12-Ketoendrin is more toxic than endrin
• Endrin was banned in 1979

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Hexachlorocyclohexane (HCH)(Cyclohexane)

• Lindane (gamma isomer)
• Persistent or easily eliminated?
• Veterinary and human medicine
• Some isomers were voluntarily canceled by the
  primary manufacturer in 1978 lindane is still in
  use

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Dicofol (dichlorodiphenylethane)

• Produced from DDT
• Persistence or Elimination?
• Adverse affects on wildlife
• Ecotoxicological studies
• Dicofol products that contain gt1 of DDT ceased
  in 1989, products with lt1 are still in use

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Methoxychlor (dichlorodiphenylethane)

• Replaced DDT in treating Dutch elm disease
• Rapidly broken down
• Estrogenic activity
• Still in use

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According to the Author

• It is likely that no other group of contaminants
  of anthropogenic origin has exacted such a heavy
  toll on the environment as have the
  organochlorine pesticides

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Works Cited

• Hoffman et al. 1995. Handbook of Ecotoxicology
  (HE). Lewis Press. Boca Rotan 275-299.
• Klassen, C.D. 1996/2001. Casarett and Doulls
  Toxicology The basic science of poisons (CD).
  5th/6th Edition. McGraw-Hill, New York.
• Matsumura, F. 1975. Toxicology of Insecticides.
  Plenum Press, New York.
• Suwalsky, M. c. R., Fernando Villena, Felipe
  Aguilar and Carlos P Sotaomayor (1998). "The
  organochlorine pesticide lindane interacts with
  the human erythrocyte membrane." Pesticide
  Biochemistry and Physiology 62(2) 87-95.

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Questions

• How is it possible for OCs that were banned 30
  years ago to still be present in the environment
  and in biological systems (i.e. humans)?
• Considering the VOD equation
• VOD dose L
• plasma
• Would OCs have a high or low VOD?