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Env. Chemistry, Baird Cann

Env. Chemistry, Baird

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Env. Chemistry, Baird Cann

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    1. Env. Chemistry, Baird & Cann

    2. Env. Chemistry, Baird & Cann Pesticides Kill an unwanted organism usually by interrupting a critical metabolic process About 1 billion kg used/year in N. America, about 50% used in agriculture (85% used in agriculture worldwide) Greatest use of insecticides in growing of cotton; herbicides corn & soybeans 80-90% of US households contain at least on synthetic pesticide. Typical household pesticides: weed killer, bug spray, flea powders, and algicides About the foods eaten in the US contain measurable levels of at least one pesticide Plants have natural pesticides which we are exposed to in much higher concentrations than synthetic ones Types: Table 7-1

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    4. Env. Chemistry, Baird & Cann Traditional Insecticides Control of diseases; malaria, yellow fever, bubonic plague, sleeping sickness etc. Control of mosquitoes and flies in households Prevent insects from attacking crops

    5. Env. Chemistry, Baird & Cann First Pesticides were Mostly Inorganic 1000 B.C. Greece: Fumigants: burning S to produce SO2 Elemental S in spays & dusts; insecticide & fungicides; still used to control mildew on plants NaF control ants; NaF/boric acid cockroaches Oils (petroleum, fish, whale) kill insect eggs

    6. Env. Chemistry, Baird & Cann First Pesticides were Mostly Inorganic CuAsO3 insecticide acts as a stomach poison Many of these pesticides also are quite toxic to humans and other mammals especially at dosages required for effective pesticides Inorganic pesticides are not biodegradable Mass poisonings from Hg based fungicides chapter 11

    7. Env. Chemistry, Baird & Cann Organochlorine Insecticides Organic insecticides developed after WWII were less acutely toxic to humans and mammals in general, especially in the small doses necessary for use as a pesticide Organochlorine insecticides were some of the first organic insecticides Properties Stability in the environment Very low solubility in water but bind to organic sediments High solubility in non-polar environments, tend to concentrate in fatty tissues of organisms Relatively high toxicity to insects and low to humans

    8. Env. Chemistry, Baird & Cann Hexachlorobenzene (HCB) Fungicide for cereal crops; used for several decades after WWII Very non-polar; 99% of Americans detectable levels in their body fat Spread widely in the environment Liver cancer in rats perhaps also in humans Drinking water standard set by U.S. EPA of 0.001 mg/L (0.001 ppm); solubility in water 0.0062 ppm Very persistent; UN POP, One of the Dirty Dozen (Table 7-2)

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    10. Env. Chemistry, Baird & Cann 1,4-Dichlorobenzene Insecticidal fumigant mothballs, & solid & liquid room deodorizers, soil fumigant High vapor pressure Animal carcinogen Some accumulation in the environment May be the VOC with the greatest carcinogenic risk

    11. Env. Chemistry, Baird & Cann DDT Mosquitoes malaria (reduction programs including DDT estimated by WHO to have saved 5 million lives), yellow fever Lice typhus Fleas plague Winston Churchill miraculous Peter Muller discovered DDT 1939 (Geigy), Nobel Prize Physiology Medicine 1948 Agricultural crops -fruit trees, vegetables, cotton; 80% used in agriculture + forestry

    12. Env. Chemistry, Baird & Cann DDT Persistent gives protection from weeks to years, stable to air/other chemicals, microorganisms and sunlight; low vapor pressure; low solubility in water Accumulates in body fat; 3 ppm (mostly DDE) in N. American adults Insects became resistant farmers applied more Animals able to metabolize to DDE loss of HCl; also to DDE under basis conditions; DDT resistant insects metabolize to DDE DDE is persistent; interferes with enzyme that regulates calcium distribution, eggs of some birds had insufficient shell thickness; significant decline in eagle (and other birds of prey) population Rachel Carson 1962 proclaimed DDT the elixir of death in her book Silent Spring

    13. Env. Chemistry, Baird & Cann DDT DDT banned in USA in 1973 (except for essential uses); most developed countries banned around the same time; UN list of POPs Still used today in some developing countries in particular to control mosquitoes carrying malaria; UN treaty: countries can continue using DDT against malaria until effective and affordable alternatives are available; still in use: 11 countries in Africa, 7 Asia, 5 Latin America (Table 7-2) DDT & DDE levels in animals and humans has dropped since partial ban Figure 7-1, 7-2; predatory birds have made a comeback in many areas; fewer preterm babies now than in the 60s

    14. Env. Chemistry, Baird & Cann Accumulation of Organochlorines in Biological Systems Bioaccumulation higher concentration in biological systems than surroundings e.g. accumulation in fish vs. water Bioconcentration fish swimming through water absorbs non-polar materials through gills and this concentrates in the fatty tissues

    15. Env. Chemistry, Baird & Cann Bioconcentration Factor (BCF) Concentration of a chemical vs. surroundings Partition coefficient approximation of BCF Kow = [S]octanol/[S]water For DDE is about 100,000 while bioconcentration between 3,000 and 60,000 Table 7-3 logKow in the range of 4-7 tend to bioconcentrate to the greatest extent; higher than 7 strong absorption to sediments Fish bioconcentrate from water, food, sediments

    16. Env. Chemistry, Baird & Cann Biomagnification Biomagnification concentration of chemicals increases as one proceeds up the food chain Figure 7-3, 7-4 (food web), 7-5 L.I. Sound [DDT] = 3x10-6 ppm water; plankton 0.04 ppm; needlefish 2 ppm; osprey & cormorants 25 ppm; -biomagnification 107

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    18. Env. Chemistry, Baird & Cann Analogs of DDT Mode of action of DDT see Figure 1 http://academic.scranton.edu/faculty/CANNM1/toxicologymodule.html DDT wedges in nerve channel channel continues to fires nerve impulses by passage of sodium insects muscles continue to twitch, exhausted via convulsion leads to death DDD and methoxychlor (biodegradable to water soluble compounds) similar shape to DDT

    19. Env. Chemistry, Baird & Cann Other Organochlorine Pesticides Toxaphene Replaced DDT for soybeans, cotton Mixture of chlorinated molecules with average of 6 chlorines; derived from camphene Most heavily used pesticide in US before ban in 1982 Extremely toxic to fish used to kill population of unwanted fish, so persistent lakes could not be restocked for years UNPOP Table 7-2 Toxaphene in N. America Figure 7-6

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    21. Env. Chemistry, Baird & Cann 1,2,3,4,5,6-Hexachlorocyclohexane Mixture of eight stereochemical isomers Used to control mosquitoes and in agricultural applications after WWII Use restricted since 1970s, -toxicity & tendency to bioaccumulate Lindane is the active ingredient (isomer) that kills insects; used in medical treatment to rid children of lice and scabies also to treat seeds and seedlings

    22. Env. Chemistry, Baird & Cann Chlorinated Cyclopentadienes First used in 1950s: Aldrin, dieldrin, endrin, chlordan mirex, heptachlor (all POPs: Table 7-2); endosulfan Used to control soil insects, fire ants, cockroaches, termites, grasshoppers, locusts, etc. Persistence, toxicity & bioconcentration led to a ban or severe restictions for most of these pesticides in developed countries; endosulfan still used extensively as an insecticide in domestic & agricultural applications; much lower persistence and bioconcentration

    23. Env. Chemistry, Baird & Cann Preparation of Endosulfan

    24. Env. Chemistry, Baird & Cann Principles of Toxicology Toxicology -study of the harmful effects to living organisms of substances (both natural & synthetic) that are foreign to them Acute -rapid onset of symptoms Chronic exposure over a long period of time (particularly important in environmental toxicology) Substances may exhibit both acute and chronic toxicity e.g. many organochlorines cause chloracne (a skin irritation) while long term many cause skin disease leading to cancer Epidemiology -health history of a group of humans in relationship to substances that they have been accidentally exposed to

    25. Env. Chemistry, Baird & Cann Dose-Response Relationships Most experiments involve acute rather than chronic toxicity (for practical considerations) Dose=(mass of a chemical)/(mass of subject) LD50 dose that is lethal to 50% of the population (Table 7-4) Threshold no animals are effected just below threshold No observable effects level (NOEL) just below threshold Ames Test uses bacteria to test for mutations

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    27. Env. Chemistry, Baird & Cann Risk Assessment Risk Assessment quantitative answers to: What are the likely types of toxicity expected for the human population exposed to this chemical. What is the probability of each effect occurring to the population. To perform a risk assessment need to know: Hazard information: toxicity type (acute, chronic, birth defects, cancer) Dose response relationship from modes of exposure (oral, dermal, inhalation) Potential for exposure

    28. Env. Chemistry, Baird & Cann Risk Assessment For chronic exposure no observable effects level (NOEL) or threshold levels are determined from animal studies, Acceptable daily intake (ADI) (EPA uses toxicity reference dose, RfD) often times are 1/100 of the NOEl

    29. Env. Chemistry, Baird & Cann The Distribution of Environmental Pollutants Fugacity (f) tendency to escape from a given physical phase; can be calculated from the following equation:

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    31. Env. Chemistry, Baird & Cann Organophosphates (OP) Insecticides Non-persistent More acutely toxic than organochlorines; some indication of childhood leukemia & brain cancer from use indoors Main mode of exposure through food Can accumulate in the fatty tissue however they general decompose in a few days or weeks in the environment Use in agriculture Figure 7-9

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    33. Env. Chemistry, Baird & Cann

    34. Env. Chemistry, Baird & Cann Carbamate Insecticides Derived from carbamic acid Short lived (react with water) & decompose to nontoxic substances Carbaryl (1-naphthyl N-methyl carbamate; Sevin); LD50 = 307 mg/kg; lawn & garden insecticide, low toxicity to mammals but highly toxic to honey bees

    35. Env. Chemistry, Baird & Cann Organophosphates & Carbamates Organophosphates and carbamates mode of action is to bind with acetylcholine and interrupt the destruction of neurotransmitters see: http://academic.scranton.edu/faculty/CANNM1/toxicologymodule.html Sickness & deaths: especially in developing countries; usually from misuse Some nerve gases act in the same manner (look up the structure of Sarin and decide how it works chemically)

    36. Env. Chemistry, Baird & Cann Pesticides from Natural Sources Insecticides manufactured by plants (nicotine, rotenone phermones, juvenile hormones) for self protection; extracted from plants or may be synthesized in the lab Pyrethrins isolated from chrysanthemums, same mode of actions as organophosphates; synthetic examples have been produced which do not decompose in sunlight (which the naturally occurring ones do); used to control lice in ancient times, still used in in flea sprays for animals

    37. Env. Chemistry, Baird & Cann Pesticides from Natural Sources Rotenone natural product from roots of certain bean plants crop insecticide for 150 years also used to paralyze and/or kill fish Widely used in many products such as flea and tick powder and sprays for tomato plants Some evidence that chronic exposure may lead to Parkinsons disease

    38. Env. Chemistry, Baird & Cann Integrated Pest Management Combine Best Features of Various Methods Chemical control synthetic & natural pesticides Biological control introduction of predators, parasites & pathogens Cultural control farm practices that prevent pests from flourishing Host-plant resistance genetic engineering Physical control Regulatory control

    39. Env. Chemistry, Baird & Cann Green Chemistry: Insecticides that Target Only Certain Insects Organochlorines, organophosphates and carbamates are broad spectrum pesticides (toxic to a wide array of insects) Confirm Mach 2 and Intrepid target only certain species which molt such as caterpillars (PGCC Award, Rohm&Haas 1998) These insecticides mimic the hormone 20-hydroxyecdysone which triggers the molting process during which the insect ceases eating and drinking; insecticides do not drop back to basal level thus insect never resumes feeding or drinking

    40. Env. Chemistry, Baird & Cann Confirm Mach2 and Intrepid

    41. Env. Chemistry, Baird & Cann Reduced Risk Pesticides Confirm and Intrepid are classified as reduced risk pesticides by the USEPA. This program was started in 1993 and the pesticide must meet one or more of the following requirements. (1) reduces pesticide risks to human health; (2) reduces pesticide risks to non-target organisms; (3) reduces the potential for contamination of valued environmental resources, or (4) broadens adoption of IPM (integrated pest management) or makes it more effective. Rewarded with expedited review

    42. Env. Chemistry, Baird & Cann Green Chemistry: A New Method for Controlling Insects Annual cost of termite control in US is $1.5 billion Annually 1.5 million homes have termite problems in US Traditionally control of subterranean termites was to treat the soil with large volumes of insecticides surrounding the structure to create an impenetrable chemical barrier; can lead to groundwater contamination, worker exposure, harm to beneficial insects

    43. Env. Chemistry, Baird & Cann Green Chemistry: A New Method for Controlling Insects Sentricon system Monitoring for the presence of termites: wooden monitoring stations placed at intervals around structure Baiting infestation of station; Recruit II (hexaflumuron/cellosic) matrix placed in station (interrupts the molting process of termites) Monitoring

    44. Env. Chemistry, Baird & Cann Green Chemistry: A New Method for Controlling Insects Hexaflumaron reduced risk pesticide

    45. Env. Chemistry, Baird & Cann Herbicides Chemicals that destroy plants e.g. kills weeds without destroying valuable plants Most widely used pesticide in N. America Inorganic salts were used first in the first half of the twentieth century sodium arsenite Na3AsO3, sodium chlorate NaClO3, (both kill by dehydrating the plant) copper sulfate CuSO4 Toxic to mammals and persistent in soils Have largely been replaced by organics

    46. Env. Chemistry, Baird & Cann Triazines Most common atrazine Destroy weeds in corn & soybean fields Blocks photosynthesis Concentration too high (dry season) no plants will grow Moderately soluble in water Kow=103 thus some bioconcentration life on the order of years Found in surface waters Carcinogen? Higher rates of cancer in farmers Certain regions of US has been banned

    47. Env. Chemistry, Baird & Cann Atrazine Metabolites enter waterways Not removed in typical treatment of drinking water except C filtration Maximum contaminant level (MCL) 3ppb in US, some agricultural regions it is banned; EU health advisory level 0.05 ppb, several EU countries have banned atrazine

    48. Env. Chemistry, Baird & Cann Herbicides Chloroacetamides Alachlor most well known Glyphosate Inhibits synthesis of amino acids containing an aromatic ring Found in Roundup Decompose? How ? To what? Toxic decomposition products? Persistent/buildup in the environment? Roudup Ready strains of soybeans have developed through biotechnology

    49. Env. Chemistry, Baird & Cann Phenoxy Herbicides 2,4-D Golf courses, lawns, agricultural fields; kills broadleaf weeds 2,4,5-T kills brush along roadside, power lines

    50. Env. Chemistry, Baird & Cann Summary In general no pesticide is completely safe Elimination of all pesticides would lead to increase in disease, more crop loss/higher prices Considerations in elimination: cheap safe alternative if not what are the consequences of action and inaction Precautionary principle -Where there are threats of serious or irreversible damage, lack of full scientific certainty shall not be used as a reason for postponing cost-effective measures to prevent environmental degradation. Opponents of the use of this principle point out that it is impossible to anticipate all possible consequences, positive or negative, of introducing a new substance and that consequently we could become frozen into inaction.

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