Fungicides

Widely used in industry, agriculture, home, and garden, fungicides are used for many purposes—protection of seed grain during storage, transport, and germination; protection of crops, seedlings, and grasses in the field, in storage, and during shipment; suppression of mold; control of slime in paper processing, and protection of carpets and fabrics. Fungicides, used properly, rarely cause severe poisonings. Most have inherently low mammalian toxicity and are absorbed poorly (at least partly because they are formulated as suspensions of wettable powders or granules). Most are applied using methods that intensively expose only a few individuals. Irritant injuries to skin and mucous membranes are relatively common in heavily exposed individuals, however (12).

Of the substituted benzene herbicides, only hexachlorobenzene has produced systemic toxicity. This occurred when hexachlorobenzene-treated seed wheat was used instead for human consumption. In 4 years, approximately 3000 persons developed porphyria due to impaired hemoglobin synthesis. Most affected individuals recovered, but some infants nursed by affected mothers died.

Thiocarbamates, unlike the N-methyl carbamates, have little insecticide activity. Instead they are used to protect seeds, turf, ornamentals, vegetables, and fruit from fungi. Bisdithiocarbamates, represented by thiram, are structurally similar to disulfuram. With heavy exposure an Antabuse-like reaction can be produced if alcohol is ingested subsequently. This reaction is characterized by flushing, sweating, headache, tachycardia, and hypotension.

Other thiocarbamates—ziram, ferbam, and metam-sodium—should theoretically predispose to the Antabuse reaction, but no occurrences have been reported. Metam-sodium decomposition in water yields methyl isothio-cyanate, a gas that is extremely irritating to mucous membranes. Inhalation of the gas may cause pulmonary edema. Metam-sodium is considered a fumi-gant and should be used in outdoor settings only. Persons caring for a victim with metam-sodium ingestion should avoid inhalation of evolved gas. Treatment of exposure is with skin and GI decontamination, oxygen supplementation, fluid support, and avoidance of alcohol.

Ethylene bisdithiocarbamates (EBDC compounds) are another group of fungicides that may irritate skin, respiratory tract, and eyes. Maneb, zineb, nabam, and mancozeb represent this class. Treatment of the irritant effects of these chemicals is by decontamination. Thiophthalimides, represented by captan, captafol, and folpet, are agents used to protect seed, field crops, and stored produce. All of these fungicides are moderately irritating to the skin, eyes, and respiratory tract. They may produce skin sensitization. No systemic poisonings have been reported with these chemicals.

Copper compounds, both inorganic and organic, are irritating to skin, respiratory tract, and eyes. Soluble copper salts, such as copper sulfate and acetate, are corrosive to mucous membranes and the cornea. Systemic toxic-ity is low, probably due to limited solubility and absorption. Treatment of poisoning is with GI and skin decontamination. Ophthalmologic consultation should be obtained if eye irritation persists after flushing the eyes with saline. Intentional ingestions of large volumes of these compounds may result in hemolysis with circulatory collapse and shock, with renal and hepatic failure. In these severe cases, fluid replacement, alkalinization of the urine, chelating agents, and hemodialysis may be required.

Organomercury compounds have been used primarily as seed protectants. Toxicity has occurred primarily when methyl mercury-treated grain intended for planting was consumed in food. Poisonings have also occurred from eating meat from animals fed mercury-treated seed. Organic mercury is efficiently absorbed from the gut and is concentrated in the nervous system and red cells. Early symptoms of mercury poisoning are metallic taste, distal paresthesias, tremor, headache, and fatigue. Further symptoms target the CNS with incoordination, slurred speech, spasticity, rigidity, and decline in mental status. Treatment is by skin and GI decontamination and chelation.

Cadmium has been used to treat fungal diseases of turf and bark of orchard trees. Cadmium salts and oxides are very irritating to mucous membranes of the respiratory and GI tracts. Inhaled cadmium dust or fumes can produce a mild, self-limited respiratory illness with fever, cough, and malaise, similar to metal fume fever. More severe symptoms with labored breathing, chest pain, and hemorrhagic pulmonary edema are associated with heavier exposure and resemble chemical pneumonitis. Cadmium ingestion may produce severe nausea, vomiting, diarrhea, abdominal pain, and tenesmus. Chronic obstructive pulmonary disease (COPD), renal and hepatic injury, and pathological fractures have been associated with chronic cadmium exposure. Treatment is skin and GI decontamination, respiratory support, and chelation therapy (for severe, acute poisoning, though the possibility of inducing renal failure with a large load of cadmium exists).

A long list of miscellaneous organic fungicides is in use in many crop, ornamental, and turf applications. Reports of adverse effects on humans are rare or absent entirely. As with all pesticides, following label directions for use is the key to prevention of adverse events, even with these low-risk chemicals.

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