Pesticides Report

7/28/2019 Pesticides Report

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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

Documents

Pesticides Report