1. Second Lecture for Chapter 2

2. Pesticides
A chemical, physical or biological agent that destroys or controls pest organisms
Common: insecticides, herbicides, fungicides
Approximately 500,000 tons applied in the U.S. each year
Public health: disease prevention (malaria, typhus, yellow fever) and increased agricultural production

3. Pesticides
DDT Story
Saved lives through prevention of malaria, DDT kills mosquito’s
Banned later as a result of bioaccumulation in the food chain
DDT was found in marine sediments, wildlife, and human lipids
Caused thinning of eggshells in birds

4. Pesticides
Many hazardous waste sites have been created as a result of pesticide use
Abandoned pesticide manufacturing plants
Mixing and loading areas, surface and GW contamination
Pesticide Nomenclature
Common and Trade names used most often
The farm chemicals handbook
The following is an introduction to different Pesticides

5. Pesticides Insecticides
Natural products were used for centuries (nicotine, rotenone)
Until the “first generation”
Metals – lead arsenate and methylarsenate
Second Generation
Synthetic organic insecticides
Organochlorine compounds, DDT 1939
Organophosphorus ester insecticides,

6. Pesticides Insecticides Second generation continued Third generation
Thousands created from
Now they are banned
More than 400 insect species have developed resistance
Third generation
Natural products and pheremones
Use of these with 2nd generation is called integrated pest management

7. Pesticides Organochlorine Insecticides
Chlorinated aliphatic and aromatic compounds
May contain O and S
Highly lipophilic (fat loving
Disrupt the Na+ and K+ balance of cellular membranes and neurological pathways
Though banned in the U.S. and Europe, still found in the environment
Degrading slowly in U.S., still manufactured here and sold overseas

8. Pesticides Common organochlorine insecticides include:
DDT, methoxychlor, lindane, aldrin, dieldrin, and endosulfan
Organophosphorus esters
Nonselective, broad spectrum insecticides that inhibit acetyl cholinesterase, an important enzyme for neurological function

9. Pesticides Organophosphorus esters
Discovered in 1854, use didn’t start until the 1970’s when the organochlorines were banned
Very low half-life, persist for days or weeks, not years like organochlorines
Acutely toxic however
3 drops of parathion applied to the skin will kill the average adult
Common names
Parathion most widely used, Methyl Parathion, Malathion, and Diazinon

10. Pesticides Insecticides Carbamate Esters
N-methyl carbamates modeled after the natural product physostigmine, a neurotoxic alkaloid
First developed in 1954, by carbamates had been developed
Derivatives of carbamic acid, which is so unstable that it does not exist
HO-C-NH2 O

11. Pesticides Insecticides Carbamate Esters
However, replacing the H attached to the oxygen with an alkyl group and one H attached to the amino group with a methyl
Creates a stable molecule
Carbamates also interfere with acetyl cholinesterase
Common names include: carbaryl, carbofuran, and aldicarb

12. Pesticides Herbicides
Agents that destroy vascular plants and are employed mainly as weed killers
Most widely used class of pesticides
Last in the environment from a few days to over a year
Degradation rates are a function of the herbicide structure and the environmental conditions

13. Pesticides Herbicides Kill through a variety of mechanisms
Interference with DNA replication
Mimicking growth hormones
120 different compounds
20 families
Review of five families

14. Pesticides Herbicide families Acid Amides – alachlor, propanil,
Exact mechanism of kill unknown, appears to interrupt protein synthesis and nucleic acid replication
Aliphatics – Glyphosate (Roundup), Methyl Bromide
Interference with amino acid synthesis
Phenoxy Herbicides – 2,4-D, 2,4,5-T and Silvex
Phenyl ethers with an oxygen link to the benzene ring
27,000 tons of 2,4-D used per year in U.S.
Agent Orange used in Vietnam was 50:50 mixture of 2,4-D and 2,4,5-T
Mimics auxins – growth regulators produced by plants

15. Pesticides Herbicides Substituted Ureas Trazines
Urea – a bound form of N excreted by animals
Common diuron and linuron
Trazines
Predominantly N-alkylated derivatives of 2-chloro-4,6-diamino-s-triazine
Most common are atrazine, cyanazine, and senecor
Work by interfering with photosynthesis
Work well because they lose their phytotoxicity within one growing season and are not very toxic to humans

16. Pesticides Fungicides
Destroys fungi and molds to prevent the deterioration of fruit, grain, and vegetables
70% of fungicides used are from ethylene-bis-dithiocarbamates (EBDC’s), captan, and benzimidazoles
Some contain manganese and zinc (Mancozeb and EBDC)

17. Pesticides Fungicides Pentachlorophenol (penta or PCP)
Used to preserve telephone poles and railroad ties
Also as an insecticide, fungicide, aracacide, herbicide, disenfectant, etc
Hundreds of Hazardous Waste sites are contaminated with PCP
PCP is only moderately toxic, but when degraded dioxins are produced from it and they are highly toxic and biorefractory

18. Pesticides Soil Fumigants Used to control a range of pests
Early fumigants include (HCN) hydrogen cyanide and carbontetrachloride
Resulted in GW contamination

19. Explosives
Explosive
A quasi stable chemical that rapidly changes from a solid or a liquid to a gas following activation or detonation
Pressure from expanding gases release energy of the compound seeking equilibrium
Usually made of aliphatic or aromatic rings with nitro substituent groups

20. Explosives Uses Mining, construction and warfare
Military production and storage has caused most of the problems with the environment
Pink water – TNT contaminated pit or production water
Explosives are environmentally persistent and toxic
Inhibit life through defeating the process of oxidative phosphorylation – ATP production

21. Explosives Characteristics
Low explosive – reacts slowly, burns rapidly instead of detonating
High explosive – rapid detonation, more stable
Three groups of high explosive
Aliphatic nitrate esters – produced by treating polyhydric alcohols with nitric acid (nitroglycerine)
Nitramines – RDX, HMX, Tetryl, Military explosives
Nitroaromatics – TNT, Picric acid, biodegraded under anaerobic conditions

22. Industrial Intermediates
Aliphatic and aromatic compounds used for the synthesis of market chemicals
Most common, benzene and derivatives of benzene, phthalate esters, chlorobenzenes, chlorophenols, and chlorotoluenes
Benzene - styrene, cyclohexane, phenolics, xylenespolymers, phenol  chlorophenols, resins
Phthalate esters – plasticizers in plastics production
Chlorobenzenes and chlorophenols – pesticides, pharmaceuticals, antiseptics and plastics
Chlorinated toluenes – pesticides, drugs, peroxides, and dyes
Anilines are aminobenzenes – inks, dyes, drugs, photographs

23. Polychlorinated Biphenyls (PCBs)
Heat stable oils once used as transformer and hydraulic fluids
Non flammable transformer dielectric cooling oil
Mineral oil was used but PCB was more stable
Also used as a plasticizer and lubricant until banned in 1979
Basic unit aromatic hydrocarbon biphenyl, 10 possible Cl positions on two rings
207 Congeners – compounds formed from the same process

24. Polychlorinated Dibenzodioxins and Dibenzofurans
PCDD’s and PCDF’s
Not produced for a potential use
Waste products of production
Trace impurities formed during the chlorination or combustion of organic compounds
Extremely toxic compounds
A low concentration can be found in burning wood
Aromatic and non-planar
75 possible congeners

25. Metals and Inorganic Nonmetals
Metal defined as an element that:
Conducts electricity
Has a high thermal conductivity
Has a high density
Characterized by malleability and ductility

26. Metals and Inorganic Nonmetals
Most metals wastes is produced during electroplating
Arsenic (As)
Has a complex chemistry
Used to make herbicides to control weeds
Used to make glass, growth stimulants for plants and animals, and fungicides
Used in semiconductor production

27. Metals and Inorganic Nonmetals
Cadmium (Cd)
Found in plastics, household batteries, electronics, pigments and appliances
Metals finishing
Highly toxic, range of health effects from hypertension to cancer
Chromium (Cr)
Used in electroplating, leather tanning, wood preservation, catalysts and commercial electronics

28. Metals and Inorganic Nonmetals
Lead (Pb)
Used in autobatteries, electronics, plastics and glass
Ubiquitous in the environment after use in gas and paint
Nickel (Ni)
Used in stainless steel, iron ferrous alloys, electroplating, catalysts, ceramics, and salt
Mercury (Hg)
Found in three forms, elemental, inorganic, and organic
Used to make electrical products, dental supplies, caustic soda, chlorine, instruments ,and paints

29. Metals and Inorganic Nonmetals
Cyanides (CN-)
An inorganic nonmetal anion
HCN  CN- + H+ Ka = 7.94 x 10-10
Hydrogen cyanide, highly toxic, acute poison
HCN produced by mixing ammonia and methane under controlled conditions
Used in electroplating, stored in ponds, caused dead wildlife and GW contamination

30. Metals and Inorganic Nonmetals
Asbestos
Generic label attached to fibrous metal silicates of sodium, magnesium, calcium, and iron
Asbestos is a commercial label given to six mineral fibers made from magnesium silicates
Uses: roofing products, friction products, asbestos cement pipe, packing, and paper