Pesticides Pesticides Aquatic Ecotoxicology Lecture Aquatic Ecotoxicology Lecture November 19, 2003 November 19, 2003 Dr. Matt Moore Dr. Matt Moore USDA Agricultural Research Service USDA Agricultural Research Service National Sedimentation Laboratory National Sedimentation Laboratory Oxford, Mississippi Oxford, Mississippi
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Pesticides Aquatic Ecotoxicology Lecture November 19, 2003 Dr. Matt Moore USDA Agricultural Research Service National Sedimentation Laboratory Oxford,
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1.1. First synthesized in 1874First synthesized in 1874
2.2. Insecticidal properties discovered by Paul MInsecticidal properties discovered by Paul Mller ller (Ciba-Geigy) in 1939; Nobel Prize(Ciba-Geigy) in 1939; Nobel Prize
3.3. Control animal pests, disease vectors (mosquito), Control animal pests, disease vectors (mosquito), ectoparasites on farm animalsectoparasites on farm animals
4.4. Used as emulsifiable concentrate and sprayUsed as emulsifiable concentrate and spray
5.5. Started noticing problem w/ American robins Started noticing problem w/ American robins while spraying for Dutch Elm Diseasewhile spraying for Dutch Elm Disease
1.1. Developed in Germany during WWII as a Developed in Germany during WWII as a substitute for nicotene to control aphidssubstitute for nicotene to control aphids
2.2. Inhibit acetylcholinesteraseInhibit acetylcholinesterase1.1. HOWHOW2.2. WHEREWHERE3.3. Example in bird migrationExample in bird migration
3.3. Produced for warfareProduced for warfare
4.4. Most OPs are lipophilicMost OPs are lipophilic
Chlorpyrifos Chlorpyrifos – use decreased by 62% in last decade– use decreased by 62% in last decade
Diazinon Diazinon (being phased out by EPA); termite & fire ant(being phased out by EPA); termite & fire ant
ParathionParathion - weak inhibitor of cholinesterase; highly - weak inhibitor of cholinesterase; highly toxic in cells due to conversion to paraoxon; toxic in cells due to conversion to paraoxon; promoted by Cpromoted by CP450P450 in endoplasmic reticulum; in endoplasmic reticulum;
9000X more toxic than parathion itself9000X more toxic than parathion itself
MalathionMalathion – degrades to non-toxic OP by mammalian – degrades to non-toxic OP by mammalian carboxyesterases; used in boll weevil eradicationcarboxyesterases; used in boll weevil eradication
Methyl parathionMethyl parathion – 50X more toxic to mammals than – 50X more toxic to mammals than malathion; use has increased 86% over the last malathion; use has increased 86% over the last decadedecade
InsecticidesInsecticidesCARBAMATESCARBAMATES
1.1. Derivatives of carbamic acidDerivatives of carbamic acid
2.2. Developed more recently than OCs and OpsDeveloped more recently than OCs and Ops
1.1. NicotineNicotine1.1. Isolated from leaves of tobacco plantIsolated from leaves of tobacco plant2.2. Uses recorded at least 200 years agoUses recorded at least 200 years ago
• RotenoneRotenone• Derived from roots of Derived from roots of Derris, Lonchocarpus, TephrosiaDerris, Lonchocarpus, Tephrosia• Commercial insecticides in 1930sCommercial insecticides in 1930s• Flavonoid derivative; strongly inhibits mitochondrial Flavonoid derivative; strongly inhibits mitochondrial
respirationrespiration• Highly toxic to fishHighly toxic to fish• Can be used in smaller amounts to paralyze fish for Can be used in smaller amounts to paralyze fish for
consumptionconsumption• Relatively non-toxic in humansRelatively non-toxic in humans• Exempt from requirement of an EPA tolerance when applied Exempt from requirement of an EPA tolerance when applied
3. Led to derivation of synthetic pyrethroids which have 3. Led to derivation of synthetic pyrethroids which have better better photostability and are generally more active than their photostability and are generally more active than their natural counterparts natural counterparts
--when ingested by insects, toxin causes --when ingested by insects, toxin causes paralysis of the gutparalysis of the gut
--or may kill by bacterial growth if endospore --or may kill by bacterial growth if endospore germinatesgerminates
HerbicidesHerbicides
1.1. Comprise ~ 70% of currently applied pesticidesComprise ~ 70% of currently applied pesticides
2.2. Many different classes, but we will focus on 5 brieflyMany different classes, but we will focus on 5 briefly
3.3. Typically Typically characterized as very water soluble, with characterized as very water soluble, with little – no effects on non-targets (especially little – no effects on non-targets (especially vertebrates / invertebrates)vertebrates / invertebrates)
HerbicidesHerbicidesCHLORPHENOXYCHLORPHENOXY
• One of most important groups of herbicidesOne of most important groups of herbicides
• 2,4-D2,4-D
• Disturb growth processes by interfering with Disturb growth processes by interfering with transport of nutrients; similar to natural growth transport of nutrients; similar to natural growth regulator – indole acetic acidregulator – indole acetic acid
• Selectively toxic between monocots and dicotsSelectively toxic between monocots and dicots
• Mainly used to “weed out” dicots in monocot cropsMainly used to “weed out” dicots in monocot crops
• Formerly most applied herbicide in global marketFormerly most applied herbicide in global market
• Primarily two herbicides: Primarily two herbicides: ParaquatParaquat and and DiquatDiquat
3.3. Diquat registered for aquatic usesDiquat registered for aquatic uses
4.4. Paraquat (and diquat) are quick acting; widely usedParaquat (and diquat) are quick acting; widely used
5.5. Target anything green (chlorophyll)Target anything green (chlorophyll)
6.6. Use in cotton for defoliationUse in cotton for defoliation
7.7. Hazardous to humans (lungs)Hazardous to humans (lungs)
HerbicidesHerbicidesACETAMIDESACETAMIDES
• Main example: Main example: PROPANILPROPANIL
• Formerly most applied rice herbicide; 63% decrease Formerly most applied rice herbicide; 63% decrease in usage over last decadein usage over last decade
• Lack of acylamidase enzymes in target plants (e.g. Lack of acylamidase enzymes in target plants (e.g. barnyard grass) causes plant deathbarnyard grass) causes plant death
• Fairly low toxicity to non-target organisms (when Fairly low toxicity to non-target organisms (when compared to expected environmental concentrations compared to expected environmental concentrations – EECs)– EECs)
HerbicidesHerbicidesGLYPHOSATEGLYPHOSATE
• Use increased 93% in last decadeUse increased 93% in last decade
--used as fungicide and wood preservative--used as fungicide and wood preservative since the 1930ssince the 1930s
--35 million lbs / year produced in US (1985)--35 million lbs / year produced in US (1985)
--uncouples oxidative phosphorylation by --uncouples oxidative phosphorylation by inhibition of Nainhibition of Na++ and K and K++ ATPase ATPase
Other PesticidesOther PesticidesRODENTICIDESRODENTICIDES
1.1. WarfarinWarfarin--Vitamin K antagonist (required for blood --Vitamin K antagonist (required for blood clotting)clotting)
--low water solubility--low water solubility
--lipophilic--lipophilic
--Second generation of warfarins: “Super --Second generation of warfarins: “Super Warfarins” are 200x more potent than Warfarins” are 200x more potent than original warfarin; Half-life is 60x longeroriginal warfarin; Half-life is 60x longer
Other PesticidesOther PesticidesRODENTICIDESRODENTICIDES
National pesticide control first attempted by:National pesticide control first attempted by:Insecticide Act of 1910Insecticide Act of 1910
Targeted more to prevention of fraudulent products ratherTargeted more to prevention of fraudulent products ratherthan misuse of poisonsthan misuse of poisons
2 Principle Laws of Pesticides:2 Principle Laws of Pesticides:
1. 1. Federal Insecticide, Fungicide, and Rodenticide Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA)Act (FIFRA)
2. 2. Federal Food Drug and Cosmetic Act (FFDCA)Federal Food Drug and Cosmetic Act (FFDCA)
Pesticide RegulationPesticide Regulation
FIFRAFIFRA
--First enacted in 1947; amended in 1959 & 1961--First enacted in 1947; amended in 1959 & 1961
--Must be registered before being sold or distributed in--Must be registered before being sold or distributed ininterstate commerceinterstate commerce
--Amended again in 1964 thanks to --Amended again in 1964 thanks to Silent SpringSilent Spring
Pesticide RegulationPesticide Regulation
FIFRAFIFRA
--Prior to 1970, USDA controlled approval under FIFRA--Prior to 1970, USDA controlled approval under FIFRA
--Passed responsibility onto US EPA--Passed responsibility onto US EPA
--Major FIFRA overhaul in 1972--Major FIFRA overhaul in 1972a. Registration was more restrictivea. Registration was more restrictiveb. Burden of proof was on manufacturerb. Burden of proof was on manufacturer
Pesticide RegulationPesticide Regulation
FIFRAFIFRA
--1978 further amendments--1978 further amendments
a. Streamline registration w/ generic a. Streamline registration w/ generic reregistration reviews reregistration reviews
b. Added authority to grant conditional b. Added authority to grant conditional registration registration
c. Resolve data issues of propriety and c. Resolve data issues of propriety and compensation compensation
Pesticide RegulationPesticide Regulation
FIFRAFIFRA
--1988 amendments--1988 amendments
a. Require expedited reregistration of a. Require expedited reregistration of existing existing pesticides to ensure that pesticides to ensure that registration are registration are supported by supported by adequate dataadequate data
RegistrationRegistration--Older pesticides which were registered before the --Older pesticides which were registered before the implementation of current regulations and testing implementation of current regulations and testing guidelines have data base reviewed by EPAguidelines have data base reviewed by EPA
--If found unsatisfactory for current requirements, --If found unsatisfactory for current requirements, data must be repeated according to current data must be repeated according to current guidelinesguidelines
--After this, EPA issues a “Registration Standard”--After this, EPA issues a “Registration Standard”
--If deficiencies exist, manufacturer may repeat --If deficiencies exist, manufacturer may repeat studies or must cancel registrationstudies or must cancel registration
Pesticide RegulationPesticide Regulation
FIFRAFIFRA
General ecotoxicology and environmental testingGeneral ecotoxicology and environmental testing 1. Ecotoxicity tests1. Ecotoxicity tests 2. Environmental fate testing2. Environmental fate testing 3. Ecological risk assessments3. Ecological risk assessments
Initial toxicity data used for the following:Initial toxicity data used for the following:
*Define acute toxicity of a.i. to different aquatic and *Define acute toxicity of a.i. to different aquatic and terrestrial speciesterrestrial species
*Compare initial acute toxicity with actual or EEC to *Compare initial acute toxicity with actual or EEC to assess potential impactassess potential impact
*Provide data to determine whether or not need for *Provide data to determine whether or not need for precautionary labelprecautionary label
*Indicate need for further laboratory &/or field studies*Indicate need for further laboratory &/or field studies
Environmental Fate TestingEnvironmental Fate Testing1.1. Significant degradation routesSignificant degradation routes2.2. Primary degradatesPrimary degradates3. 3. Degradation / metabolic pathwayDegradation / metabolic pathway4.4. Potential ½ life and persistence in environmentPotential ½ life and persistence in environment5.5. Dissipation / mobility of chemical, potential EECDissipation / mobility of chemical, potential EEC
Food & Drug Administration (FDA) enforces tolerances Food & Drug Administration (FDA) enforces tolerances (residue limits) for pesticides on food crops(residue limits) for pesticides on food crops
Delaney Clause (1958)Delaney Clause (1958) in the in the Food Additives AmendmentFood Additives Amendment states there shall be NO measurable concentration of states there shall be NO measurable concentration of cancer-causing substance (no matter the true risk)cancer-causing substance (no matter the true risk)
Compare analytical chemistry in 1958 (LOD 20-100 ppm) to Compare analytical chemistry in 1958 (LOD 20-100 ppm) to analytical chemistry in 2003 (LOD ????)analytical chemistry in 2003 (LOD ????)