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Questions and Answers
What is a primary adverse effect of occupational exposure to pyrethroids?
What is a primary adverse effect of occupational exposure to pyrethroids?
Which of the following is a characteristic sign of Type I pyrethroid compounds?
Which of the following is a characteristic sign of Type I pyrethroid compounds?
What type of toxicity is associated with acute high doses of DDT?
What type of toxicity is associated with acute high doses of DDT?
How is DDT principally excreted from the body post-absorption?
How is DDT principally excreted from the body post-absorption?
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Which of the following statements regarding organochlorine compounds is accurate?
Which of the following statements regarding organochlorine compounds is accurate?
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What is a primary effect of Type II pyrethroid compounds?
What is a primary effect of Type II pyrethroid compounds?
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Which organochlorine compound is known for its effectiveness against pests and disease-transmitting insects?
Which organochlorine compound is known for its effectiveness against pests and disease-transmitting insects?
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What is the typical duration for the reversal of symptoms associated with pyrethroid exposure?
What is the typical duration for the reversal of symptoms associated with pyrethroid exposure?
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What is a common sign of poisoning caused by neonicotinoids?
What is a common sign of poisoning caused by neonicotinoids?
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Which insecticide is known to block mitochondrial respiration at complex I?
Which insecticide is known to block mitochondrial respiration at complex I?
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What may result from dermal absorption of nicotine in workers handling tobacco?
What may result from dermal absorption of nicotine in workers handling tobacco?
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Which symptom is characteristic of avermectin intoxication?
Which symptom is characteristic of avermectin intoxication?
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Which statement accurately describes a use of emamectin benzoate?
Which statement accurately describes a use of emamectin benzoate?
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What condition can result after exposure to rotenone?
What condition can result after exposure to rotenone?
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What is one of the specific actions of avermectin in insects and nematodes?
What is one of the specific actions of avermectin in insects and nematodes?
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Which neonicotinoid is not mentioned in the provided information?
Which neonicotinoid is not mentioned in the provided information?
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What is the most common cause of high oral dose pesticide poisoning?
What is the most common cause of high oral dose pesticide poisoning?
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Which agency is responsible for regulating pesticide use under the Federal Insecticide, Fungicide, and Rodenticide Act?
Which agency is responsible for regulating pesticide use under the Federal Insecticide, Fungicide, and Rodenticide Act?
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Chronic low dose exposure to pesticides primarily occurs through:
Chronic low dose exposure to pesticides primarily occurs through:
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What is a requirement for all pesticides sold or distributed in the United States?
What is a requirement for all pesticides sold or distributed in the United States?
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What is one of the topics evaluated during the pesticide registration process?
What is one of the topics evaluated during the pesticide registration process?
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Which type of pesticides are responsible for a significant number of human poisonings and deaths each year?
Which type of pesticides are responsible for a significant number of human poisonings and deaths each year?
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What can happen when pesticides are deposited on clothing?
What can happen when pesticides are deposited on clothing?
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What type of contamination may result in chronic low doses of pesticides in food?
What type of contamination may result in chronic low doses of pesticides in food?
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What concentration of DEET is recommended for children to minimize exposure to neurotoxic effects?
What concentration of DEET is recommended for children to minimize exposure to neurotoxic effects?
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Which of the following insect repellents is effective against mosquitoes, ticks, and flies?
Which of the following insect repellents is effective against mosquitoes, ticks, and flies?
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How does DEET function in repelling insects?
How does DEET function in repelling insects?
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What is the main risk of chlorophenoxy compounds when humans are exposed?
What is the main risk of chlorophenoxy compounds when humans are exposed?
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What type of herbicide is applied to soil before unwanted vegetation appears?
What type of herbicide is applied to soil before unwanted vegetation appears?
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What is the primary method through which humans are unintentionally exposed to chlorophenoxy compounds?
What is the primary method through which humans are unintentionally exposed to chlorophenoxy compounds?
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What is the mode of action of auxin in broad-leaved plants targeted by herbicides like 2,4-D?
What is the mode of action of auxin in broad-leaved plants targeted by herbicides like 2,4-D?
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Which of the following is NOT a type of herbicide mentioned?
Which of the following is NOT a type of herbicide mentioned?
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What primary effect does glufosinate have on plants?
What primary effect does glufosinate have on plants?
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Which of the following symptoms is NOT associated with mild intoxication of phosphonomethyl amino acids?
Which of the following symptoms is NOT associated with mild intoxication of phosphonomethyl amino acids?
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What classification has the US EPA given to Captan and Folpet based on in vitro mutagenicity tests?
What classification has the US EPA given to Captan and Folpet based on in vitro mutagenicity tests?
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What is the common metabolite found in dithiocarbamates that affects thyroid function?
What is the common metabolite found in dithiocarbamates that affects thyroid function?
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Which fungicide is known for having low overall toxicity and is widely used?
Which fungicide is known for having low overall toxicity and is widely used?
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What health issues have been associated with moderate or severe poisoning from phosphonomethyl amino acids in humans?
What health issues have been associated with moderate or severe poisoning from phosphonomethyl amino acids in humans?
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What type of agent is tributyltin primarily classified as?
What type of agent is tributyltin primarily classified as?
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Which of the following compounds is not classified as a dithiocarbamate?
Which of the following compounds is not classified as a dithiocarbamate?
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What are organic mercury compounds, such as methylmercury, primarily used for?
What are organic mercury compounds, such as methylmercury, primarily used for?
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Which of the following is NOT a required criterion for effective and safe rodenticides?
Which of the following is NOT a required criterion for effective and safe rodenticides?
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What is a known consequence of using fluoroacetic acid and its derivatives?
What is a known consequence of using fluoroacetic acid and its derivatives?
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Which of the following anticoagulant drugs is known for using coumarin derivatives?
Which of the following anticoagulant drugs is known for using coumarin derivatives?
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What is a potential risk associated with using metals as fungicides?
What is a potential risk associated with using metals as fungicides?
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Which symptoms can result from the ingestion of fluoroacetic acid?
Which symptoms can result from the ingestion of fluoroacetic acid?
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Why must rodenticides be species-specific?
Why must rodenticides be species-specific?
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Coumarins affect the synthesis of which of the following factors in clotting?
Coumarins affect the synthesis of which of the following factors in clotting?
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Study Notes
Toxic Effects of Pesticides
- Pesticides are substances or mixtures intended to prevent, destroy, repel, or mitigate pests.
- The target organisms' nervous systems get poisoned.
- Herbicides are compounds that kill or severely injure plants.
- Fungicides are chemicals that prevent fungal growth and reproduction.
Pesticide Exposures
- Accidental and/or suicidal poisonings
- Occupational exposure (manufacturing, mixing/loading, application, harvesting, and handling of crops)
- Bystander exposure to off-target drift from spraying operations
- Consumption of food items containing pesticides
Pesticide Classification
- Insecticides (insects)
- Herbicides (weeds)
- Fungicides (fungi and molds)
- Rodenticides (rodents)
- Acaricides (mites)
- Molluscides (snails and other mollusks)
- Miticides (mites)
- Larvicides (larvae)
- Pediculocides (lice)
Pesticides - Economics, Public Health
- DDT undergoes bioaccumulation in the environment.
- Impacts on bird reproduction.
- DDT was banned in many countries by the mid-1970s.
- Significant reduction of malaria cases after banning DDT.
Pesticides - Human Poisoning
- Exposure occurs via oral or dermal routes or by inhalation.
- High oral doses are from pesticide ingestion or suicidal intent or accidental ingestion due to improper storage.
- Chronic low doses result from pesticide residues in food and water contamination.
Pesticide LD50 values
- Class Ia: Extremely hazardous (5 or less mg/kg for solids and 20 or less mg/kg for liquids)
- Class Ib: Highly hazardous; ranging from 5–50 (solids) to 20–200 (liquids).
- Class II: Moderately hazardous; ranging from 50–500 (solids) to 200–2000 (liquids).
- Class III: Slightly hazardous; (solids over 500, liquids over 2000).
Pesticides - Regulatory Mandate
- Environmental Protection Agency (EPA) regulates pesticide use.
- The Food Quality Protection Act mandates risk assessments of pesticides concerning infants and children for the EPA.
- Large number of studies are required (over 140) which take several years.
Pesticides - Regulatory Mandate - Additional Points
- Product and residue chemistry, environmental fate, toxicology; biotransformation, degradation; occupational exposure and reentry protection, spray drift, environmental impact on non-target species, environmental persistence and
- Toxicity testing requirements for pesticide registration.
Organophosphorus- Toxicity
- OP insecticides have high acute toxicity.
- Oral LD50 values in rats often below 50.
- Symptoms: "cholinergic syndrome" (increased sweating, salivation, bronchial secretion)
- Diagnosis: includes bronchoconstriction,miosis, increased gastrointestinal motility, diarrhea, tremors, and muscular twitching.
- Additional symptoms: respiratory failure.
- Overstimulation of muscarinic and nicotinic cholinergic receptors.
Organophosphorus-Intermediate Syndrome
- Manifested in 20% to 50% of acute OP poisoning.
- Symptoms: Weakness of respiratory, neck, and proximal limb muscles.
- Hypothesis: Muscle weakness from nicotinic receptor desensitization due to prolonged cholinergic stimulation.
Organophosphorus-Polyneuropathy
- Organophosphate-induced Delayed Polyneuropathy (OPIDP).
- Rare occurrence in humans.
- Symptoms include tingling of hands and feet, followed by sensory loss, progressive muscle weakness, and flaccidity of distal skeletal muscles of lower and upper extremities, and ataxia.
- Primary lesion: Bilateral degenerative change in distal levels of axons and their terminals.
Organophosphorus-Long-Term and Developmental Toxicity
- Long-term adverse health effects.
- Particular impact on the CNS.
- Dose-dependent effects: no cholinergic signs at lower doses, but long-term effects at higher doses.
- Mechanisms: Effects on cellular processes (e.g., DNA replication,), neuronal survival, and neurite outgrowth, as well as non-cholinergic pathways.
Carbamate Insecticides
- Derivatives of carbamic acid, mostly N-methylcarbamates.
- Toxicity: from low to extremely high, depending on the specific chemical.
- Symptoms:
- Miosis, urination, diarrhea, salivation, and CNS effects.
- Increased by organic solvents and emulsifiers
Pyrethroids
- Derived from Chrysanthemum cinerariifolium.
- High insecticidal potency, low mammalian toxicity.
- Mechanism:
- Change the normal function of insect voltage-sensitive sodium channels. Increase sodium permeability of the nerve membrane.
Organochlorine Compounds
- Chlorinated ethane derivatives (e.g., DDT and its analogs).
- Cyclodienes: (e.g., chlordane, aldrin, dieldrin, heptachlor, endrin, and toxaphene).
- Hexachlorocyclohexanes: (e.g., lindane).
- Mechanism:
- Interfere with sodium channels in axonal membrane.
Neonicotinoids
- Nicotine-based insecticides effective toward a wide range of insects, including aphids, thrips, and whiteflies.
- Mechanism:
- Activation of nAChRs (in the CNS).
- At high doses, parasympathetic stimulation and ganglionic and neuromuscular blockade predominate.
Other Old and New Insecticides
- Rotenoids: Inhibit the mitochondrial complex I, particularly in organic formulations.
- Symptoms:
- Initial increased respiratory and cardiac rates; clonic and tonic spasms; and muscular depression.
- Avermectins: Parasitic control in humans and veterinary medicine; mostly for the control of mites and other kinds of parasites.
- Symptoms: Hyper excitability; tremors; incoordination followed by ataxia and a coma-like sedation.
Fumigants
- Compounds used for fumigation (particularly for soil treatments, and to control a wide range of pests)
- These agents are highly reactive and cytotoxic.
- Agents: Methyl bromide;1,3-Dichloropropene;Sulfur.
- Mechanisms:
- Respiratory and gastrointestinal effects.
- Neurological symptoms (lethargy, headache, seizures; and potentially paresthesias, peripheral, neuropathy, and ataxia).
Herbicides
- Chemicals that kill or harm plants.
- Preplanting herbicides applied to soil before planting; preemergent herbicides applied to soil before the appearance of unwanted vegetation. Postemergent herbicides applied after unwanted vegetation appears.
- Modes of action: Inhibit photosynthesis, respiration, protein/lipid synthesis, specific enzymes (e.g., glutamine synthetase, and acetolactate synthase).
Chlorophenoxy Compounds
- Auxin-like hormones critical to broadleaved plant growth, but not for grasses.
- Suppress the growth of weeds (e.g., dandelions) without directly affecting the targeted grasses
- Mechanism:
- Affect plant growth hormone synthesis; mostly by acting as auxin mimics and inhibitors.
- Symptoms:
- Vomiting; burning of the mouth; abdominal pain; hypotension; and myotonia; CNS involvement including coma.
Bipyridil Compounds
- Paraquat is a fast-acting contact herbicide. It's used to control broadleaf weeds and grasses, in plantations and fruit orchards; for general weed control.
- Mechanisms: Redox cycling leading to lipid peroxidation and a metabolic process.
- Chronic exposure to paraquat leads to serious damage to the alveolar system, and can be irreversible.
- Symptoms: nausea, vomiting; diarrhea; ulceration of mouth and esophagus; decline in renal function; and neurologic effects*.
Chloroacetanilides
- Examples include alachlor, acetochlor, and metolachlor
- Probable human carcinogens.
- Exposure mostly through drinking water or eating contaminated food, can affect the body weight.
Phosphonomethyl Amino Acids
- Herbicides.
- Inhibiting glutamine synthetase.
- Mild intoxication mainly causes transient gastrointestinal symptoms.
- Moderate/severe poisoning leads to gastrointestinal bleeding, hypotension, and pulmonary dysfunction; renal damage.
- Developmental toxic effects observed in rabbits (deliveries, abortions, and dead fetuses).
Fungicides
- Chemicals capable of killing or harm fungi.
- Types:
- Dithiocarbamates (e.g., maneb, zineb, metiram):
- Symptoms: hypertrophy and hyperplasia of thyroid follicular cells.
- Metals (e.g., copper sulfate):
- High usage for the prevention of seed-borne diseases in crops.
- Triphenyltin acetate; tributyltin acetate
- Symptoms: Moderate to high acute toxicity, but may cause reproductive/endocrine disruption.
Rodenticides
- Used to control rodents in structures and farms.
- Types:
- Fluoroacetic acid derivatives:
- Symptoms:
- Initial gastrointestinal symptoms followed by severe cardiovascular effects (ventricular tachycardia, fibrillation, and hypotension), and CNS effects (agitation, convulsions, and coma).
- Coumarin derivatives (e.g., warfarin):
- Symptoms:
- Anticoagulant activity; severe internal bleeding; potentially severe health risks to humans.
Insect Repellents
- DEET and Picaridin are effective at repelling insects; mainly mosquitoes, ticks, and flies.
- Used for topical treatments for scabies and headlice; effective methods to reduce insect bites and insect infestations.
- Mechanisms:
- Interaction with specific olfactory receptors of the arthropods
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Explore the various toxic effects of pesticides, including their classifications and the different types of exposures individuals may face. Understand the implications for public health and the environment, especially concerning bioaccumulation. Test your knowledge about pesticides and their impact on ecosystems.
