SOURCES & CHEMISTRY OF PESTICIDES

Course No. : VPHA 613Course Title: Toxicology of Pesticides & Other Toxic

Agents

Dr. MD YOUSUF ALI SARKER

Department of PharmacologyFaculty of Veterinary Science, BAU

TALK PLAN

BACKGROUND

FATE OF PESTICIDES

PEST & PESTICIDES

GENERAL SOURCE OF POISONING

CHEMICAL PROPERTIES OF PESTICIDES

REFERENCES

BACKGROUND

Pesticides use in agriculture is dated back to the beginning of agriculture

In Bangladesh pesticides are used vigorously to increase the agricultural production

About 70 % of pesticides are used in rice field in Bangladesh

Worldwide use of pesticides causes toxicity

However toxicity depends on the sources & chemical nature of pesticides

Chowdhury et al., 2012

FATE OF PESTICIDES

PESTICIDES

Atmosphere

Water

Soil

Living individual

Fate of Pesticides

PEST & PESTICIDES

Pest

Any substance or mixture of substances intended for

preventing, destroying, or controlling any pest

Insecticides, rodenticides, herbicides etc.

An organism, usually an insect, regarded as injurious or

unwanted.

Causes damage to agriculture through feeding on crops or

parasitizing livestock

Pesticides

GENERAL SOURCE OF POISONING

Accidental exposure

Intentional exposure and

Occupational exposure

Source of poisoning

Accidental exposure

Ingestion of pesticide sprayed crops, fodder, straw and

drinking water

Aerial spraying of pesticides

Ingestion of contaminated concentrates

Feeding/watering in pesticide contaminated containers

Spraying of interior walls of animal house

Improper storage

Improper and indiscriminate use of pesticides

Ingestion of bait

Intentional exposure

Residues of pesticides in agricultural products(in grain, pulse, vegetable)

Residues of pesticides in animal products(in meat, milk, egg)

Use as feed additives

Occupational exposure

Faulty spray of pesticides by unskilled workers or

inefficient equipments

Satish K. Garg, 2000

Chemodynamic processes depends on inherentphysico-chemical properties

Chemodynamic processes are Oxidation

Reduction

Hydrolysis

Photodegredation and

Biodegredation of pesticides

CHEMICAL PROPERTIES OF PESTICIDES

Zacharia et al.

Water insoluble but soluble in oil & organic solvent

Can enter the neural membrane

Reducing the potassium transport through pores

Inhibiting Na+-K+ and Ca+-Mg+ ATPases

Antagonize GABA

Organochlorines Insecticides

Satish K. Garg, 2000

Chemical properties

Organochlorines Insecticides (Cntd)

DDT

Lindane

Dicofol

Aldrin

Organophosphorous Insecticides

General chemical structure; (RO)2P(A)X R= methyl/ ethyl A= sulfur/ oxygen X= different variables

Stable in water and alkali

Highly lipid soluble

Less volatile

Irreversible inhibition of AChE by alkyl phosphorylation

Chemical properties

Organophosphorous Insecticides (Cntd)

Parathion Malathion

The basic structure of carbamate

R1 = Phenol, naphthalene or other cyclic hydrocarbons R2 & R3 = -H, -CH3, -C2H5 or other short chain alkyl groups

Decarbamylation & hydroxylation is key features

Carbamate Insecticides

Chemical properties

Carbaryl

Synthetic Pyrethroids

Polarizing ability of both type I & II

Type II: Inactivated Na gate

Hydrolytic degradation

Inhibiting Na+-K+ and Ca+-Mg+ ATPases

Inhibit GABA receptors

Chemical properties

Compound/S that has the potential of either killing or damaging

unwanted plants or weeds The biochemical differences

Plants biochemical difference is used to kill weeds

Herbicides

Table: Classification based on chemical structure

Type Example

Dinitro compounds DNOC, DNP

Phenoxyacetic acids 2,4-D, 2,4,5-T

Bipyridinium compounds Diaquat, paraquat

Triazenes Atrazine, propazine

Herbicides (Cntd)

Chemical properties

Little soluble in water

Stable in sterile water

PH labile

Non-volatile

Stable upto 300°C

Herbicides (Cntd)

DNOC 2,4-D

AtrazineParaquat

Chemical used to kill pest rodents, moles, rabbits and

hare, etc

Commonly used rodenticides are alphanapthyl thiourea

(ANTU), warfarins, zinc phosphate, flouroacetate, red

squill etc.

Rodenticide

Colorless, crystalline powder (ANTU, warfarin, Zn3P2)

Slightly soluble in water

Antocoagulant properties (interfere Vit. K) (Warfarin)

Inactivated by CYP450 (Warfarin)

Slowing TCA cycle by inhibiting aconitase enzyme

(Fluoroacetate)

Rodenticide (Cntd)

Chemical properties

Rodenticide (Cntd)

Chemical properties

Red Squill

Obtained from plant Urginea maritima (sea onion)

Contains many types of steroidal cardioactive glycosides

Most common cardiac glycosides are

Scilliroside,

Scillaren,

Proscillaridin,

Glucoscillaridin Garcia Casado, 2000

Rodenticide (Cntd)

ANTU

Zn3P2

Warfarin

REFERENCES

Bhattacharjee, S., Fakhruddin, a. N. M., Chowdhury, M. a Z., Rahman, M. a., & Alam, M. K. (2012). Monitoring of selected pesticides residue levels in water samples of paddy fields and removal of cypermethrin and chlorpyrifos residues from water using rice bran. Bulletin of Environmental Contamination and Toxicology, 89(2), 348–353. http://doi.org/10.1007/s00128-012-0686-8

Balbaa SI, Khafagy SM, Khayyal SE, Girgis AN. TLC-spectophotometric assay of the main glycosides of red squill, a specific rodenticide. J Nat Prod. 1979;42:522-524

FAO. (2004). International Code of Conduct on the Distribution and Use of Pesticides, Rome Italy.

Chowdhury, M. A. Z., Banik, S., Uddin, B., Moniruzzaman, M., Karim, N., & Gan, S. H. (2012). Organophosphorus and carbamate pesticide residues detected in water samples collected from paddy and vegetable fields of the Savar and Dhamrai Upazilas in Bangladesh. International Journal of Environmental Research and Public Health, 9(9), 3318–3329. http://doi.org/10.3390/ijerph9093318

Garcia Casado P , Renedo MJ , Fernandez M , Vega FA . Proscillaridin A yield from squill bulbs. Pharm Acta Helv. 2000;52: 218-221.

Jinde, C. D. (1994). Physic0 -Chemical Properties and Environmental Fate of Pesticides.

REFERENCES (CNTD)

Thank You All