pesticides report
TRANSCRIPT
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PESTICIDES
Any substance or mixture of substancethat is intended to kill pests.
Pests may include any of the following: Insects Mice and/or other animals
Unwanted plants Fungi Microorganisms
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Algicides or algaecides for the control of algaeAvicides for the control of birdsBactericides for the control of bacteria
Fungicides for the control of fungi and oomycetesHerbicides for the control of weeds Insecticides for the control of insects - these can be
ovicides (substances that kill eggs), larvicides(substances that kill larvae)
or adulticides
(substances that kill adults)Miticides or acaricides for the control of mitesMolluscicides for the control of slugs and snailsNematicides for the control of nematodes
Rodenticides for the control of rodentsVirucides for the control of viruses
http://en.wikipedia.org/wiki/Algicidehttp://en.wikipedia.org/wiki/Algaecidehttp://en.wikipedia.org/wiki/Algaehttp://en.wikipedia.org/wiki/Avicidehttp://en.wikipedia.org/wiki/Birdhttp://en.wikipedia.org/wiki/Bactericidehttp://en.wikipedia.org/wiki/Bacteriahttp://en.wikipedia.org/wiki/Fungicidehttp://en.wikipedia.org/wiki/Fungushttp://en.wikipedia.org/wiki/Oomycetehttp://en.wikipedia.org/wiki/Herbicidehttp://en.wikipedia.org/wiki/Insecticidehttp://en.wikipedia.org/wiki/Egg_(biology)http://en.wikipedia.org/wiki/Egg_(biology)http://en.wikipedia.org/wiki/Insecthttp://en.wikipedia.org/wiki/Larvicidehttp://en.wikipedia.org/wiki/Larvicidehttp://en.wikipedia.org/wiki/Larvahttp://en.wikipedia.org/wiki/Egg_(biology)http://en.wikipedia.org/wiki/Larvicidehttp://en.wikipedia.org/wiki/Larvahttp://en.wikipedia.org/wiki/Miticidehttp://en.wikipedia.org/wiki/Acaricidehttp://en.wikipedia.org/wiki/Mitehttp://en.wikipedia.org/wiki/Molluscicidehttp://en.wikipedia.org/wiki/Slughttp://en.wikipedia.org/wiki/Snailhttp://en.wikipedia.org/wiki/Nematicidehttp://en.wikipedia.org/wiki/Nematodehttp://en.wikipedia.org/wiki/Rodenticidehttp://en.wikipedia.org/wiki/Rodenthttp://en.wikipedia.org/wiki/Virucidehttp://en.wikipedia.org/wiki/Virushttp://en.wikipedia.org/wiki/Virushttp://en.wikipedia.org/wiki/Virucidehttp://en.wikipedia.org/wiki/Rodenthttp://en.wikipedia.org/wiki/Rodenticidehttp://en.wikipedia.org/wiki/Nematodehttp://en.wikipedia.org/wiki/Nematicidehttp://en.wikipedia.org/wiki/Snailhttp://en.wikipedia.org/wiki/Slughttp://en.wikipedia.org/wiki/Molluscicidehttp://en.wikipedia.org/wiki/Mitehttp://en.wikipedia.org/wiki/Acaricidehttp://en.wikipedia.org/wiki/Miticidehttp://en.wikipedia.org/wiki/Larvahttp://en.wikipedia.org/wiki/Larvicidehttp://en.wikipedia.org/wiki/Egg_(biology)http://en.wikipedia.org/wiki/Insecthttp://en.wikipedia.org/wiki/Insecticidehttp://en.wikipedia.org/wiki/Herbicidehttp://en.wikipedia.org/wiki/Oomycetehttp://en.wikipedia.org/wiki/Fungushttp://en.wikipedia.org/wiki/Fungicidehttp://en.wikipedia.org/wiki/Bacteriahttp://en.wikipedia.org/wiki/Bactericidehttp://en.wikipedia.org/wiki/Birdhttp://en.wikipedia.org/wiki/Avicidehttp://en.wikipedia.org/wiki/Algaehttp://en.wikipedia.org/wiki/Algaecidehttp://en.wikipedia.org/wiki/Algicide -
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A systemic pesticide moves inside a plant followingabsorption by the plant. With insecticides and mostfungicides, this movement is usually upward (throughthe xylem) and outward. Increased efficiency may bea result. Systemic insecticides which poison pollen and
nectar in the flowers may kill needed pollinators suchas bees.
Pesticides can also be classed as synthetic pesticidesor biological pesticides (biopesticides), although the
distinction can sometimes blur.
http://en.wikipedia.org/wiki/Xylemhttp://en.wikipedia.org/wiki/Pollenhttp://en.wikipedia.org/wiki/Nectarhttp://en.wikipedia.org/wiki/Flowerhttp://en.wikipedia.org/wiki/Pollinatorhttp://en.wikipedia.org/wiki/Beehttp://en.wikipedia.org/wiki/Biological_pesticidehttp://en.wikipedia.org/wiki/Biological_pesticidehttp://en.wikipedia.org/wiki/Beehttp://en.wikipedia.org/wiki/Pollinatorhttp://en.wikipedia.org/wiki/Flowerhttp://en.wikipedia.org/wiki/Nectarhttp://en.wikipedia.org/wiki/Pollenhttp://en.wikipedia.org/wiki/Xylem -
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History of Pesticides
Pesticides use began before 2500BC
First used to protect their crops.
First documented pesticide is sulfurpowder used in Sumeria about 4500years ago.
By 15th Century, toxic chemicals likearsenic, mercury and lead began its wayinto the pesticide industry.
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In 1939, Paul Miller discovered the pesticideDDT and was found very effective.
It became the most widely used pesticide inthe world
In the 1960, it was discovered that DDTprevent fish-eating birds from reproducing.
DDT was then banned under the Stockholm
Convention on Persistent Organic Pollutants
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Exposure and Absorption
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Pesticide Route of Absorption
Organophosphates Usually skin contact; ingestion
Pyrethins, pyrethroids Inhalation; skin contactN-methyl carbamates,
carbamates, chlorophenoxy
compunds,
Ingestion; skin contact
Coumarins and indandiones Primarily by ingestion; skin
contact possible
Dipyridyls Ingestion or contact with broken
skin
Nitrophenoic and nitrocresoic,
organochlorines,
pentachlorophenol
All forms of absorption
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Dermal Exposure
Most common route of exposure
Tissue of the eyes particularly absorbent
Those in close contact with pesticides are commonly at risk
A cut can greatly increase the absorption
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Oral Exposure
Most severe form of exposure
Accidentally happens when transferredin an unlabeled container
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Respiratory Exposure
Exposure due to fumigant inhalation
Formation of small droplets also causesexposure
Common powder form of pesticide may
also be inhaled
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DISTRIBUTION
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DISTRIBUTION
2,4-D (2,4-Dichlorophenoxyacetic acid)
-an herbicide and a plant growth
regulator
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DISTRIBUTION
Does not bio-accumulate
Sub-chronic oral exposure : eyes, kidney, thyroid, adrenal glands,
ovaries/testes
Acute, Chronic and Sub-chronic doses: liver and muscle damage
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DISTRIBUTION
CAPSAICIN
-animal repellant that is also used as
insecticide, rodenticide, and feedingdepressant
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DISTRIBUTION
Intravenous: accumulation in the brain and spinal cord with
low levels in liver and blood (3 mins) greatest concentration found in spinal cord (10mins)
Subcutaneous: greatest concentration found in kidney with
lower concentrations in brain and spinal cord
low concentration in liver due to metabolicbreakdown
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DISTRIBUTION
DDT (Dichlorodiphenyltrichloroethane)
-organochlorine insecticide first
synthesized in 1874
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DISTRIBUTION
tends to accumulate in fatty tissuesbecause it is non polar
breakdown products are released into theblood
toxic to the liver and the nervous system
has the tendency to bio accumulate
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DISTRIBUTION
MALATHION
-non-systemic, broad-spectrum insecticide
belonging to organophosphate group ofpesticides
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DISTRIBUTION
does not bio accumulate
inhibits cholinesterase enzyme thusdisrupting nervous system function
easily excreted out of the body throughurine
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Metabolism
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Primary Metabolism
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Oxidative Transformation
Oxygenation is the most frequent firststep in biotransformation of pesticides
Mediated by oxidative enzymes likeCYP, peroxidases, and polyphenoloxidases
Agrochemicals can modify pesticidesmetabolism by acting as effectors onCYP like fenpropimorph with chemicalsafener naphthalic anhydride.
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RH + O2 + NAD(P)H + H+ ROH + H2O +
NAD(P)+there are many other P450-mediated
reactions including dehydration,
dimerization, deamination,dehydrogenation, heteroatom dealkylation,epoxidation, reduction, and CC or C5Ncleavage
Other oxidative enzymes includeperoxidases, polyphenoloxidases, laccase,tyrosinases as well as oxidative
nitroaromatic transformation
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Hydrolytic Transformation
Hydrolytic enzymes cleave bonds of a
substrate by adding H or OH from H2Oto each product.
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Aromatic Nitroreductive Process
Nitroreductases are flavoproteins thatuse NAD(P)H as reducing equivalents,
require FMN/FAD cofactor and havevarying sensitivities to O2concentrations
Example conversion of acifluorfen toaminoacifluorfen
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Carbon-Phosphorus bond cleavage
Organophosphates have C-P bond whichdo not undergo photochemical,
hydrolytic thermal, or chemicaldegradation
C-P lyase is the enzyme responsible fordirect C-P bond cleavage but themechanism is not known
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Pesticide Conjugation Reaction
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Carbohydrate and Amino Acid
ConjugationMetabolic process whereby an exogenous
or endogenous natural compound is joined
to a pesticide pesticide or its metabolitefacilitating detoxification,compartmentalization, sequencing andmineralization.
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The most common glucose conjugates areO-glucosides because pesticide oxidationreaction form hydroxyl groups which are
suitable site for glucose conjugation.
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Types of Pesticides:
1. Organophosphates
2. Carbamates
3. Organochlorines4. Pyrethroids
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Organophosphate Metabolism
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Metabolic activation from chlorpyrifos to chlorpyrifos-oxon:
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Hydrolysis of organophosphates:
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Mode of Action
Organophosphorus insecticides exerttheir acute effects in both insects and
mammals by inhibitingacetylcholinesterase (AChE) in thenervous system with subsequentaccumulation of toxic levels of
acetylcholine (ACh), which is aneurotransmitter.
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Toxicity is due to the inhibitory effects oncholinesterase enzymes in the nervous
system.
Biotransformation reactions can be divided
into 3 classes:a. Mixed function oxidases (MFOs)b. Hydrolases
c. Transferases
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Hydrolases
Monobasic diesters and theirderivatives are the major urinary
metabolite of OrganophosphatesHydrolysis of the acid anhydride type
ester bond of the leaving group inpesticidal triesters is well known.
A-esterases or phosphoryl phosphatasesare widespread in mamalian tissues.
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Transferases
The only transferase reaction that isknown to deal with the intact pesticidal
organophosphate triesters involvesglutathione
Reactions involving the conjugation ofcarboxylic acids, alcohols, phenols andamino, imino and sulfydryl groups arewell known.
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Carbamates Metabolism
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Mode of Action
Carbamates are effective insecticidesby virtue of their ability to inhibit AChEin the nervous system.AChE catalyses the hydrolysis of the
neurotransmitter acetylcholine (ACh) tocholine and acetic acid.
Inhibit esterases that have serine intheir catalytic centre; these are calledserine- esterases or beta-esterases.
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Oxidation
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Hydrolysis
Carbamates are hydrolysed eitherspontaneously or by esterases yielding,
as final products, an amine, carbondioxide (CO2), and an alcohol or phenol:
R1
HN-C(O)OR2
+ H2O ---> R1
NH2 + CO2 +R2OH
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Organochlorines
Dichlorodiphenyltrichloroethane
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Pyrethroid Metabolism
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Type I and II pyrethroids are believed toslow the activation(opening) and theinactivation (closing) of the sodiumchannels.
These delays inopening and closing of thesodium channel prolong the sodium current.
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FIRST AID
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First Aid
General First Aid stop source of pesticide exposure
have label at hand for further medicaltreatment
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First AidPesticide on Skin
drench skin and clothing with plentyof water
remove personal protective equipment
dry victim and wrap in blanket or anyclean clothing on hand
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First AidPesticide in Mouth:
rinse mouth with plenty of water give victim up to one quart of milk
or water to drink
induce vomiting only ifinstructions to do so are on thepesticide label
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First Aid
Inhaled pesticide: get victim to fresh air
loosen tight clothing that wouldconstrict breathing
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Chlorophenoxy Herbicides
Treatment of Poisoning Administer intravenous saline/dextrose
Forced alkaline diuresis
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Arsenical Herbicides
Signs and Symptoms Acute arsenic poisoning (within 1 hour)
Digestive tractGarlic odor of breath and fecesInflammation of mouth and esophagus
Burning abdominal pain
Thirst
Vomiting
Diarrhea
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Arsenical Herbicides
Chronic arsenic poisoning Dermal manifestations
Overgrowth of the cornea
Scaling off of dead skinExcessive fluids under the skin of the face, eyelids,
and ankles
White streak across nails
Loss of nails/hairBrick red coloration of mucus membranes
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Rodenticides
Rodents are difficult to kill withpoisons because their feeding habitsreflect their place as scavengers. Theywill eat a small bit of something and wait,and if they don't get sick, they continue.
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R d d
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Rodenticides
Anticoagulants Chronic single-dose or multiple-dose
rodenticides, acting by effectively blocking
the Vitamin K cycle, making the organismunable to produce blood-clotting factors:prothrombin, proconvertin, Christmasfactor and Stuart Factor.
In addition to this, massive toxic dosesof indandiones and hydroxycoumarinsdamage tiny blood vessels, increasingpermeability and causing hemorrhage.
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Coumarin
Bromodialone
Warfarin
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R d nti id
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Rodenticides
Hypercalcemic AgentsConsidered to be single-dosed and sub-chronic.
They affect calcium and phosphate homeostasis.These cause hypercalcemia, increasing calciumlevel, by increasing calcium absorption from food,thus, mobilizing the calcium in the bone matrixinto ionized form and goes into circulation withblood plasma. This would then lead to calcificationof organs such as kidneys, stomach and lungs,further leading to heart problems, bleeding andpossible kidney failure.
e.g. Calciferols - Cholecalciferol, Ergocalciferol
Rodenticides
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Rodenticides
Calciferol
Properties:
A.k.a Vitamin D
Non-toxic to humans up to about 250g. In terms of toxicity, cholecalciferol