Occupational and Environmental Pesticides

An essential overview of pesticide types, their action, and safety measures, tailored for II MBBS students.

1. Occupational & Environmental Pesticides Dr. Shivankan Kakkar , MD

2. Pesticides – Definition and Uses WHO Definition: Chemical compounds used to kill pests (insects, rodents, fungi, and weeds). Agricultural Use : Controls pests to protect crops and livestock, improving productivity. Public Health Use: Used to kill vectors like mosquitos, flies, and fleas. Household Use: Eliminates domestic pests. Dr. Shivankan Kakkar, MD 2

3. Toxicity and Environmental Impact Potential Toxicity: Harmful to non-target organisms, including humans; must be used with caution. Environmental Impact: Pesticides contribute significantly to environmental toxicity. Dr. Shivankan Kakkar, MD 3

4. Dr. Shivankan Kakkar, MD 4

5. Types of Pesticides Biodegradable Pesticides: Broken down by microbes and organisms into harmless substances. Persistent Pesticides: Remain in the environment, bioaccumulate in animals, and magnify in the food web (e.g., DDT). Dr. Shivankan Kakkar, MD 5

6. Categories of Pesticides Pesticides include: Insecticides Rodenticides Herbicides Fungicides Dr. Shivankan Kakkar, MD 6

7. Insecticides Definition: Insecticides are substances used to kill insects that threaten crops or human health. Types of Insecticides: Anticholinesterases Chlorinated Hydrocarbons Pyrethroids Most Extensively Used Pesticides. Dr. Shivankan Kakkar, MD 7

8. Dr. Shivankan Kakkar, MD 8 Pesticides Insecticides Anticholinesterases Chlorinated hydrocarbons Pyrethroids Rodenticides Herbicides Fungicides

9. Anticholinesterase Insecticides Types: Organophosphate (OP) and Carbamate. Action: Paralysis of insects through persistent depolarization of muscle end-plates. Human Impact: Inhibits cholinesterase, leading to poisoning (occupational, accidental, suicidal). Environmental Impact: Not persistent, no long-term implications. Dr. Shivankan Kakkar, MD 9 Pesticides Insecticides Anticholinesterases Chlorinated hydrocarbons Pyrethroids Rodenticides Herbicides Fungicides

10. Dr. Shivankan Kakkar, MD 10

11. Chlorinated Hydrocarbon Insecticides Example: DDT – widely used, later banned due to environmental impact. Mechanism: Interferes with GABAergic transmission and Na+ channel inactivation. Human Impact: Causes nausea, seizures, and chronic exposure can damage multiple organs; carcinogenic. Environmental Impact: Persistent in nature, bioaccumulation in animals and humans. Dr. Shivankan Kakkar, MD 11 Pesticides Insecticides Anticholinesterases Chlorinated hydrocarbons Pyrethroids Rodenticides Herbicides Fungicides

12. Pyrethroid Insecticides Source: Derived from chrysanthemum flowers; synthetic variants have longer-lasting action. Uses: On crops, pets, livestock, and for mosquito control. Mechanism: Blocks Na+ channels in insect axons, leading to paralysis. Human Impact: Low toxicity, may cause irritation, dizziness, or systemic effects. Environmental Impact: Low hazard, but toxic to aquatic life (fishes, shrimps). Dr. Shivankan Kakkar, MD 12 Pesticides Insecticides Anticholinesterases Chlorinated hydrocarbons Pyrethroids Rodenticides Herbicides Fungicides

13. Rodenticides Definition : Rodenticides are nonspecific pest control chemicals used to kill rats, mice, and other rodents. Toxicity : These chemicals are toxic to all mammals, including dogs, cats, and birds, which may be poisoned secondarily. Major Classes : Anticoagulants Metal Phosphides Dr. Shivankan Kakkar, MD 13

14. Anticoagulant Rodenticides Mechanism : Blocks vitamin K cycle, causing internal bleeding and capillary damage. First-generation : Examples: Warfarin, Coumatetralyl Require repeated doses, less toxic. Second-generation ( Superwarfarins ) : Examples: Brodifacoum, Diphenacoum Single-dose, more toxic, lethal even to resistant rats. Antidote : Vitamin K for human poisoning. Dr. Shivankan Kakkar, MD 14

15. Metal Phosphides Examples : Zinc and Aluminium Phosphides Mechanism : Reacts with stomach acid to release toxic phosphine (PH 3 ) gas. Zinc Phosphide : Used in baits, fast-acting (1–3 days), effective against anticoagulant-resistant rats. Aluminium Phosphide ( Alphos ) : Used for fumigation, releases PH 3 gas upon contact with moisture or acid. No specific antidote; supportive treatment required. Dr. Shivankan Kakkar, MD 15

16. Poisoning & Treatment Symptoms : Nausea, vomiting, abdominal pain, seizures, pulmonary edema . Toxicity : Phosphine gas inhibits mitochondrial function, leading to cell damage. Treatment : Supportive care, acidosis correction, and decontamination for metal phosphide poisoning. Dr. Shivankan Kakkar, MD 16

17. Herbicides Definition : Pesticides used to kill unwanted plants and weeds. Types : Nonselective : Kills all plants, e.g., Paraquat. Selective : Targets specific plants while sparing crops, e.g., Glyphosate, Diclofop -methyl. Contact : Kills only the plant parts it contacts, e.g., Paraquat. Systemic : Travels through plant’s xylem/phloem, affecting the entire plant, e.g., Glyphosate. Dr. Shivankan Kakkar, MD 17

18. Paraquat Type : Nonselective, fast-acting contact herbicide. Uses : Kills emerging weeds, affecting only green parts of plants. Mechanism : Inhibits photosynthesis by generating superoxide free radicals. Toxicity : Highly toxic when ingested, causing organ damage (lungs, liver, kidneys). Management : No antidote; supportive care includes decontamination (gastric lavage, activated charcoal), avoiding oxygen therapy unless necessary. Dr. Shivankan Kakkar, MD 18

19. Diclofop -methyl Type : Selective, post-emergence herbicide. Uses : Controls grassy weeds in crops like wheat, barley, peas, and potatoes. Environmental Impact : Non-persistent in soil but may persist in aquatic systems. Toxicity : Moderately toxic to mammals and aquatic organisms, with concerns over reproductive effects and cancer risk. Approval : Approved in Europe and other countries. Dr. Shivankan Kakkar, MD 19

20. Glyphosate Type : Broad-spectrum systemic herbicide. Uses : Kills broad-leaf weeds and grasses, often used with genetically engineered glyphosate-tolerant crops. Mechanism : Inhibits plant enzyme for aromatic amino acid synthesis. Toxicity : Causes skin irritation; ingestion can lead to corrosive effects and organ damage. Carcinogenicity : Divided opinions, classified by WHO as "probably carcinogenic," but EFSA deems it unlikely to be genotoxic. Dr. Shivankan Kakkar, MD 20

21. Fungicides Definition : Chemicals used to prevent fungal diseases in horticultural and agricultural crops. Action : Primarily fungistatic , inhibiting fungal growth or reproduction rather than killing them. Specificity : Many phytoparasitic fungi are highly host-specific (e.g., wheat stem rust infects only wheat). Dr. Shivankan Kakkar, MD 21

22. Types of Fungicides Inorganic Fungicides : Copper sulfate , Cuprous oxide. Organic Sulfur Fungicides : Mancozeb, Thiram, Propineb. Organophosphorus Fungicides : Isoprothiolene , Iprobenfos. Benzimidazole Fungicide : Carbendazim. Benzenoid Fungicide : Metalaxyl . Azole Fungicides : Hexaconazole, Propiconazole. Dr. Shivankan Kakkar, MD 22