pesticides aquatic ecotoxicology lecture november 19, 2003 dr. matt moore usda agricultural research...

PesticidesPesticides

Aquatic Ecotoxicology LectureAquatic Ecotoxicology Lecture

November 19, 2003November 19, 2003

Dr. Matt MooreDr. Matt Moore

USDA Agricultural Research ServiceUSDA Agricultural Research Service

National Sedimentation LaboratoryNational Sedimentation Laboratory

Oxford, MississippiOxford, Mississippi

Suggested ReadingSuggested Reading

Silent Spring Silent Spring (1962; 1994)(1962; 1994)Our Stolen Future Our Stolen Future (1996)(1996)

Aquatic Dialogue Group: Pesticide Risk Aquatic Dialogue Group: Pesticide Risk Assessment and Mitigation Assessment and Mitigation (1994)(1994)

Principles and Methods of Toxicology Principles and Methods of Toxicology (1994)(1994)

USGS book series on pesticidesUSGS book series on pesticides

EVERYTHING IS A EVERYTHING IS A STIMULUS – RESPONSESTIMULUS – RESPONSE REACTION REACTION

3 Types of Stimuli3 Types of Stimuli

A. PhysicalA. Physical

B. BiologicalB. Biological

C. C. ChemicalChemical

What is a pesticide?What is a pesticide?

FIFRA definitionFIFRA definition

What are the types of pesticides?What are the types of pesticides?

Types of pesticidesTypes of pesticides

InsecticidesInsecticides

1. Organochlorines1. Organochlorines

2. Organophosphates2. Organophosphates

3. Carbamates3. Carbamates

4. Biological / botanical / pyrethroids4. Biological / botanical / pyrethroids

5. Pyrrole5. Pyrrole

Types of pesticidesTypes of pesticidesHerbicidesHerbicides

1. Chlorphenoxy1. Chlorphenoxy2. The Quats (para- and di-)2. The Quats (para- and di-)3. Triazine****3. Triazine****4. Acetamides4. Acetamides

FungicidesFungicides1. Pentachlorophenol1. Pentachlorophenol

RodenticidesRodenticides1. Warfarin1. Warfarin2. Strychnine2. Strychnine

Types of pesticidesTypes of pesticidesAcaracidesAcaracides

MolluscicidesMolluscicides

Etc. Etc.

What are some important properties of pesticides?What are some important properties of pesticides?

Water solubilityWater solubility

Photolysis, hydrolysis, volatilizationPhotolysis, hydrolysis, volatilization

““Table 1”Table 1”


-Most work on nervous system-Most work on nervous system

-Toxicity mechanism of -Toxicity mechanism of mostmost insecticides is insecticides is similar in mammals and insectssimilar in mammals and insects

-Selectivity is primarily in the dose-Selectivity is primarily in the dose

-Dose vs. Exposure-Dose vs. Exposure


ORGANOCHLORINESORGANOCHLORINES

3 general classes (focus on just 2)3 general classes (focus on just 2)

1.1. DDT and related compounds DDT and related compounds

2.2. Chlorinated cyclodienesChlorinated cyclodienes1.1. AldrinAldrin

2.2. DieldrinDieldrin

3.3. HeptachlorHeptachlor


ORGANOCHLORINESORGANOCHLORINES

1.1. Limited vapor pressureLimited vapor pressure

2.2. Very low water solubilityVery low water solubility

3.3. High lipophilicity = TROUBLEHigh lipophilicity = TROUBLE

InsecticidesInsecticidesORGANOCHLORINESORGANOCHLORINES

DDTDDT

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


DDTDDT

6.6. MODE OF ACTIONMODE OF ACTION

--within nerve cell action potential, holds --within nerve cell action potential, holds sodium channel open longer than usualsodium channel open longer than usual

--result in delayed repolarization, but still --result in delayed repolarization, but still no no precise understandingprecise understanding

7.7. Banned in US – 1972; still in use elsewhereBanned in US – 1972; still in use elsewhere


Chlorinated CyclodienesChlorinated Cyclodienes(Chlordane, Dieldrin, Aldrin, Endosulfan)(Chlordane, Dieldrin, Aldrin, Endosulfan)

1.1. As a class, they are significantly more toxic than As a class, they are significantly more toxic than DDT-type pesticidesDDT-type pesticides

2.2. Endosulfan still has limited registration for use on Endosulfan still has limited registration for use on foodfood

InsecticidesInsecticidesORGANOPHOSPHATESORGANOPHOSPHATES

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


5.5. Less stable than organochlorines (OCs)Less stable than organochlorines (OCs)

6.6. Largely short-term (acute) toxicityLargely short-term (acute) toxicity

7.7. More polar and water soluble than OCsMore polar and water soluble than OCs

8.8. Largely replaced OCs as pesticides of choiceLargely replaced OCs as pesticides of choice


EXAMPLES:EXAMPLES:

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


EXAMPLES:EXAMPLES:

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

3.3. Acetylcholinesterase inhibitorsAcetylcholinesterase inhibitors

EXAMPLE: EXAMPLE: AldicarbAldicarb (systemic insecticide) (systemic insecticide)

InsecticidesInsecticidesBIOLOGICAL / BOTANICALBIOLOGICAL / BOTANICAL

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

to growing cropsto growing crops


3.3. PyrethroidsPyrethroids

1. Originally derived from chrysanthemum plants1. Originally derived from chrysanthemum plants

2. Significant insecticidal properties 2. Significant insecticidal properties

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

4. Potential benefits?4. Potential benefits?

5. Potential problems?5. Potential problems?

EXAMPLES: EXAMPLES: Permethrin, Cypermethrin, Deltamethrin, Permethrin, Cypermethrin, Deltamethrin, Fenvalerate, Esfenvalerate, Lambda-cyhalothrin, Fenvalerate, Esfenvalerate, Lambda-cyhalothrin, bifenthrinbifenthrin


4.4. BiologicalBiological

Bt Bt ((Bacillus thuringiensis)Bacillus thuringiensis)

----endotoxinendotoxin

--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

• TCDD (dioxin) – Agent Orange (2,4-D & 2,4,5-T)TCDD (dioxin) – Agent Orange (2,4-D & 2,4,5-T)

HerbicidesHerbicidesTHE QUATS (Bipyridyls)THE QUATS (Bipyridyls)

• 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

• Round-UpRound-Up

• Monsanto; Round-Up ready soybeans; cornMonsanto; Round-Up ready soybeans; corn

• Genetic engineering debate……Genetic engineering debate……

HerbicidesHerbicidesTRIAZINESTRIAZINES

• AtrazineAtrazine is most popular type of triazine applied is most popular type of triazine applied

• Commonly found in Midwest groundwater wellsCommonly found in Midwest groundwater wells

• Relatively non-toxic to MOST non-target vertebrate Relatively non-toxic to MOST non-target vertebrate and invertebratesand invertebrates

• Recent arguments…..Recent arguments…..

Other PesticidesOther Pesticides

FUNGICIDESFUNGICIDESPentachlorophenolPentachlorophenol

--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

2.2. StrychnineStrychnine--kills birds, rodents, moles, predatory --kills birds, rodents, moles, predatory animalsanimals

--human effects similar to animals--human effects similar to animals

--blocks neuronal excitability, sensory --blocks neuronal excitability, sensory stimuli produce exaggerated reflex actionsstimuli produce exaggerated reflex actions

--Treatment: DIAZEPAM (anti-depressant)--Treatment: DIAZEPAM (anti-depressant)

Pesticide RegulationPesticide Regulation

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)


FIFRAFIFRA

--First enacted in 1947; amended in 1959 & 1961--First enacted in 1947; amended in 1959 & 1961

--Emphasized consumer protection & product efficacy--Emphasized consumer protection & product efficacy

--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


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


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


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

Pesticide RegulationPesticide RegulationFIFRAFIFRA

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


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

““Tiered ecological testing”Tiered ecological testing”

ACUTE ACUTE → CHRONIC → CHRONIC →→ SIMULATED &/OR FIELD STUDYSIMULATED &/OR FIELD STUDY


MinimumMinimum tests to support registration of outdoor-use tests to support registration of outdoor-use

1. Avian single-dose oral toxicity test1. Avian single-dose oral toxicity test2. Avian dietary toxicity test w/ upland game bird2. Avian dietary toxicity test w/ upland game bird3. Avian dietary toxicity test w/ waterfowl species3. Avian dietary toxicity test w/ waterfowl species4. Freshwater fish acute toxicity test w/ warmwater 4. Freshwater fish acute toxicity test w/ warmwater speciesspecies5. Freshwater fish acute toxicity test w/ coldwater 5. Freshwater fish acute toxicity test w/ coldwater speciesspecies6. Aquatic invertebrate acute toxicity test w/ immature 6. Aquatic invertebrate acute toxicity test w/ immature life stagelife stage

(Other info may be required—estuarine, beneficials, etc.)(Other info may be required—estuarine, beneficials, etc.)


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

Ecological Risk AssessmentsEcological Risk Assessments

Pesticide RegulationPesticide RegulationFFDCAFFDCA

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 ????)

pesticides aquatic ecotoxicology lecture november 19, 2003 dr. matt moore usda agricultural research...

Documents

trouble slide

mississippi slide

exposure slide

food slide

heptachlor slide

lipophilic slide

pyrrole slide

strychnine slide