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INTRODUCTION

Pesticides include insecticides, herbicides, and rodenticides.1 Pesticide toxicity results from intentional, accidental, and occupational exposures. More than 150,000 pesticide poisoning deaths occur each year worldwide, with insecticides accounting for the majority of the mortality.2 Pesticides are marketed as multiple formulations, often under shared brand names. Therefore, complex clinical syndromes can result from exposure to both active and other ingredients. Human toxicity can occur from many ingredients in proprietary formulations, including solvents and surfactants. Pesticides have class-specific toxicities, with many having both local and systemic effects. Management often includes consultation with a hazardous materials and toxins database or with a poison control center. Cornerstones of management are meticulous supportive care and early identification of exposures that may benefit from administration of an antidote.

The World Health Organization classifies pesticides according to toxicity based on rodent median lethal oral and dermal exposures. However, human case-fatality rates display large variation for compounds within the same chemical and/or World Health Organization toxicity classification.3 Toxicity classification should not be used to predict severity after human exposure.

INSECTICIDES

Chemical insecticides are toxic to the human nervous system, producing acute and chronic manifestations, as well as delayed sequelae after acute exposure. Six major classes of insecticides are in common use (Table 201-1). Other compounds used to control insects include repellents.

TABLE 201-1Insecticides and Repellents

ORGANOPHOSPHATES

Commonly used organophosphates include diazinon, acephate, malathion, parathion, and chlorpyrifos. Organophosphate and carbamate compounds are the insecticide exposures most commonly resulting in healthcare facility attendance in the United States.4 Potency among organophosphates varies; highly potent compounds, such as parathion, are used primarily in agriculture, whereas those of intermediate potency, including coumaphos and trichlorfon, are used in animal care. Diazinon and chlorpyrifos were phased out from household use in the United States in 2000 due to neurotoxicity, particularly on the developing brains of children, but they continue to be used in many other parts of the world.2 The organophosphate structure can be modified into chemical agents of mass destruction (see Chapter 8, “Chemical Disasters”).

Globally, organophosphate poisoning results most commonly from deliberate self-poisoning.2,5 Accidental exposures occur in agricultural and industrial settings through use of pesticide spray applicators or spills during transport.6 Inadvertent exposure can occur from flea-dip products in pet groomers and children and from contaminated food. Systemic absorption of organophosphates occurs by inhalation and after mucous membrane, transdermal, transconjunctival, or GI exposure.

Consultation with a poison control center or medical toxicologist can be useful to assist in patient management and to collect data for surveillance reports. When consulting, precise communication of the specific product ...

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