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
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