PESTICIDES

ORGANOCHLORINES

AS A GROUP, LOW TOXICITY

BUT CYCLODIEENES!!

DDT

CYCLODIENES

CHLORINE COMPONENT - HEPATOXIC!

NA POTASIUM CHANNELS, HYPEREXCITABILITY, TREMORS, ANXIETY

DDT - POOR SKIN ABSORPTION - RISK INGESTION!

SLOW SOIL DEGRADATION, BIOACCUMULATES

CYCLODIENES - ACUTE TOXIC, SKIN ABSORPTION, CARCINOGEN, BANNED

EXAMPLES OF ORGANOSPHOSPHATES

PARATHION

MALATHION

CHLORPIRFOS

REMEMBER IRRERVESRIBLE PHOSPHORYLATION VS REVERSIBLE OF CARBAMATES

DEGREE OF TOXICITY IS BASED ON:

1. LD50

2. ROUTES

3. DURATION

4. DOSE

5. VULNERABILITY

CARBAMATES

 

Carbamylation of acetylcholinesterase enzyme

                        

IN contrast to organophosphates, process can be
                           reversed spontaneously by hydrolysis

          Clin. Picture -  Short duration

                               -    Not that severe

          Pralidoxime R not indicated

 

PYRETHRIN

Derived from Crysanthemum flowers

          Light instability + high production costs      development of synthetic pyrethroïed derivatives

   

Delay sodium channel inactivation – leads to repeated
                                    nerve impulse discharge

Little absorption through intact skin/rapidly metabolised in liver

 

PARAQUAT

MORTALITY 60% POST INGESTION!

ACCUMULATES IN LUNG, PARAQUAT LUNG FIBROSIS

MECHANISM: REACTIVE OXYGEN SPECIES, FREE RADICALS

RAPIDLY INACTIVATED IN SOIL

LUNG FIBROSIS, ADULT RESPIRATORY DISTRESS SYNDROME AND SKIN ULCERS AND BLISTERS

FUMIGANTS

Methylbromide          -           Pulm. oed, CNS depress

          Ethylenedibromide -  Suspected carcinogen

                                           -    Nefro, hepato, neuro toxic

CONTROL OF PESTICIDES IN SOUTH AFRICA

1.         Pesticide poisoning is notifiable – National Health Act

2.         It must be registered – Fertilizers, Farmfeeds, Agricultural Remedies and Stock Remedies Act, No. 36 of 1947.

3.         Product residue level is determined by – Foodstuffs, Cosmetics and Disinfectants Act, No 54 of 1972.

Storage and disposal of extremely toxic pesticides as prescribed by – Hazardous Substances Act, No.15 of 1973