chapter 16_fungicides

Fungicides Overview

  • Fungicides: Chemicals used to kill or inhibit the growth of fungi in various applications, including agriculture, home, and industrial settings.

  • Uses:

    1. Protection of seed grain during storage, shipment, and germination.

    2. Protection of crops, berries, seedlings, flowers, and grasses in the field, during storage, and shipment.

    3. Suppression of mildews on painted surfaces.

    4. Control of slime in paper production.

    5. Protection of carpets and fabrics in homes.

  • Global Usage: Approximately 500 million pounds of fungicides are used annually worldwide.

  • Toxicity: Varies among fungicides; many are unlikely to cause severe poisoning due to:

    • Low inherent toxicity in mammals.

    • Inefficient absorption through the skin and gastrointestinal tract.

    • Application methods minimizing exposure to individuals.

  • Common Symptoms: Skin and mucous membrane irritation; some fungicides may cause dermatitis and systemic poisoning.

Classes of Fungicides and Toxic Effects

Substituted Benzenes

  • Chloroneb: Low oral toxicity; slightly irritating to skin and mucous membranes; no reported systemic poisonings.

  • Chlorothalonil: Available in various formulations; causes skin/eye irritation and potential allergic reactions; no systemic poisonings reported.

  • Dicloran (DCNA): Broad-spectrum; low oral toxicity; no reported human poisonings.

  • Hexachlorobenzene (HCB): Canceled registrations in the U.S.; linked to porphyria from long-term exposure, resulting in severe skin and systemic issues.

  • PCNB (Pentachloronitrobenzene): Low toxicity; no cases of systemic poisonings reported.

Strobilurins

  • Discover_date: 1990s; introduced late 1990s-early 2000s.

  • Mechanism: Inhibit mitochondrial respiration.

  • Toxicity: Generally low acute toxicity; few human cases reported with minor effects.

  • Commercial Products: Azoxystrobin, Pyraclostrobin.

  • Symptoms of Exposure: Eye, respiratory irritation; mild systemic effects like headache and dizziness.

Thiocarbamate

  • Products: Thiram, Ziram, Ferbam.

  • Toxicity: Less toxic compared to insecticidal carbamates; causes skin/eye irritation; may result in respiratory distress if inhaled.

  • Symptoms of Exposure: Skin and eye irritation, respiratory issues, potential nausea.

EBDC Compounds

  • Products: Maneb, Zineb, Mancozeb.

  • Toxicity: Low systemic toxicity; skin and respiratory irritation possible.

  • Symptoms of Exposure: Skin irritation, possible neurological symptoms from prolonged exposure.

Thiophthalimides

  • Products: Captan, Captafol, Folpet.

  • Toxicity: Few systemic poisonings recorded; irritating to eyes and skin.

  • Symptoms of Exposure: Similar to other compounds; general irritation.

Triazoles

  • Provided as: Wettable powder and emulsifiable concentrates.

  • Products: Triadimefon, Myclobutanil, Propiconazole, Flutriafol.

  • Toxicity: Moderate acute oral toxicity; irritation risk from skin contact.

  • Symptoms of Exposure: Dizziness, nausea, potential chronic effects.

Copper Compounds

  • Products: Copper sulfate, Copper hydroxide, Copper oxychloride.

  • Toxicity: Generally low systemic toxicity; irritants to skin and mucous membranes.

  • Symptoms of Exposure: Nausea, vomiting, abdominal pain, possible hemolysis.

Organomercury Compounds

  • Products: Methyl mercury compounds, phenylmercuric acetate.

  • Toxicity: High acute and chronic toxicity; well-absorbed through the gut and skin.

  • Symptoms of Exposure: Neurological effects, metallic taste, numbness, headaches.

Organotin Compounds

  • Products: Triphenyl tin, fentin hydroxide.

  • Toxicity: Skin and eye irritant; neurological symptoms possible.

  • Symptoms of Exposure: Headaches, dizziness, possible severe CNS effects.

Cadmium Compounds

  • Products: Cadmium chloride, cadmium sulfate.

  • Toxicity: Discontinued in the U.S.; can cause respiratory and gastrointestinal effects.

  • Symptoms of Exposure: Cough, malaise, nausea, abdominal pain.

Miscellaneous Organic Fungicides

  • Varied products with little reported toxicity to humans. Examples include Anilazine, Benomyl, Dodine.

  • Symptoms of Exposure: Generally low systemic risk; skin irritation common.

  • Confirmation of Poisoning: Laboratory tests for exposure are often limited.

Treatment Guidelines

  • General Treatment:

    1. Skin decontamination with soap and water.

    2. Eye decontamination with copious water flushes.

    3. Consider GI decontamination after substantial ingestion of harmful fungicides.

    4. Supportive care for systemic symptoms.

Conclusion

  • Understanding the types of fungicides, their potential health risks, and treatment options is essential for safety in agricultural and residential environments.