Environmental Behaviour of Organic Pollutants

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Environmental Behaviour of Organic Pollutants

• Drugs for Bugs
• And other things

http//micro.magnet.fsu.edu/pesticides/pages/ddt.h
tml
WS 2006
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http//www.ecifm.rdg.ac.uk/pesticides.htm
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What are Pesticides?

• Toxic to undesired organisms
• Chemically diverse
• Used in crop and health protection
• Persistence and effectiveness causes
  environemental problems
• Central theme in environmental movement

Introduction
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Types by pest
Introduction
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Organophosphates Carbamates Organochlorines Pyreth
rins Pyrethroids
Insecticides
Dithiocarbamates Mercurials Copper
Herbicides
Carbamates Phenoxyacetic acids Triazine Phenylurea
s
Fungicides
Introduction
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Introduction
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Chlorinated hydrocarbons

• Alkane, Alkene, Aromatic
• Insecticides DDT, Lindan, Toxaphen, Cyclodienes
  (Aldrin, Dieldrin, Heptachlor, Chlordan, Mirex)
• symmetrical compounds, low dipole moment ? highly
  lipophilic and resistant ? bioaccumulate
• Neurotoxins, Activity through MFO (Mixed Function
  Oxidase), Proven resistance development
• Substantial environmental damage, widely
  distributed, wide mode of action, reproductive
  effects (Eggshell thinning, endocrine disruptor
  etc.)

Chlorinated hydrocarbons
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DDT para-Dichlordiphenyltrichlorethane

• substituted ethane (Cl, Chlorobenzene)
• Condensation of chloral with Chlorobenzene, many
  side reactions (14 substances in commercial DDT)
• Degradation e.g. to DDE (dichlordiphenyltrichloret
  hene) via HCl-splitting, e.g. by
  dehydrochlorinase)
• in the environment (Antarctic) and humans
  (Breastmilk) detectable
• Bioaccumulation
• in Industrialised countries banned, in developing
  countries used against malaria

Chlorinated hydrocarbons
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Chlorinated hydrocarbons
Data from Connell, 2005
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Chemical Structures
Chlorinated hydrocarbons
Figure from Connell, 2005
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DDT production
Chlorinated hydrocarbons
Figure from Connell, 2005
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DDT in breastmilk
Chlorinated hydrocarbons
Figure from Baird, 1999
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Lindane, ?-HCH?-Hexachlorcyclohexane

• Synthesis via radical addition of Cl to benzene
  further isomers produced
• in Germany only against bark beetles and headlice
• in developing countries still widely used owing
  to low cost
• Could be in the chocolate you eat!

Chlorinated hydrocarbons
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Cyclodiene Group

• Synthesis via Diels Alder Reaction of
  hexachlorpentadiene with CC-containing
  Substances
• persistent, bioaccumulating and enhanced mammal
  toxicity
• Used mainly from 1950 to 1970 against ground
  insects, locusts, termites, cockroaches
• Main ones Aldrin, Dieldrin, Endrin, Chlordan,
  Mirex, Heptachlor partially banned and on the
  UNEP POP list
• Endosulfan slightly less problematic because of S
  Group polar, less resistant, less bioaccumulating

Chlorinated hydrocarbons
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Chlorodene synthesis
Figure from Connell, 2005
Chlorinated hydrocarbons
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Organophosphates
Figure from Connell, 2005
Organophosphates
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Organophosphates

• PO, P-O (polar), O-R (nonpolar)
• more water soluble, less persistent than
  chlorinated hydrocarbons (hydrolysis,
  photooxidation also possible)
• Toxicity via blocking of ester splitting enzymes,
  especially acetylcholinesterase (ACh) leading to
  blocking of synapses
• Used since 1950s Main compounds Parathion,
  Malathion, Chlorpyrivos, Iodofenphos, Dichlorvos,
  Glyphosat

Organophosphates
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Structures
Figures from Connell, 2005
Organophosphates
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Organophosphates
Data from Connell, 2005
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Carbamate structure
Figure from Connell, 2005
Carbamates
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Carbamates

• Insecticides and herbicides
• Ester/amide groups enhance water solubility
• Ester groups easily hydrolysed, oxidation
  possible, thus low persistence
• toxic effect via Ach blockage
• Some toxic to mammals
• Banned in protected water areas
• Known agents Propoxur (Baygon), Carbaryl,
  Pyrimicarb, Atrazin, Simazin

Carbamates
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Carbamates
Figure from Connell, 2005
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Pyrethrine und Pyrethroide

• Natural pesticides from Chrysanthemum
  cinerariifolium (Dalmatinische Insektenblume),
  now from Kenya
• Six principle active components
• Neurotoxic, alters Na and K conductance
• lipophilic, but degradable (hydrolysis,
  photooxidation)
• Detoxification via MFO, often combined with
  synergistic MFO blockers
• synthetische pyrethroids Allethrin, Fenvalerat,
  Permethrin, Deltamethrin
• Production comparatively expensive

Pyrethroids
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Active pyrethrum constituents
Figure from Connell, 2005
Pyrethroids
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Figure from Connell, 2005
Pyrethroids
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cuticle
http//www.earthlife.net/insects/anatomy.html
Pyrethroids
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Phenoxyacetic acid herbicides

• Based on structure of natural hormones
• Polar, high water solubility
• Problems with dioxin contamination, TCDD,
  produced during productions processes or possibly
  in the environment
• 2,4-D 2,4,5-T, MPCA
• Partially banned

Phenoxyacetic acid herbicides
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Structure
Formation of TCDD
Phenoxyacetic acid herbicides
Figures from Connell, 2005
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