This document discusses lethal dose 50 (LD50), lethal concentration 50 (LC50), and lethal time 50 (LT50) measurements for assessing pesticide toxicity. LD50 refers to the dose in mg/kg body weight that kills 50% of test animals, with a lower value indicating greater toxicity. LC50 measures the concentration in air exposure that kills 50% of test animals. The document provides LD50 examples for the pesticide dichlorvos and explains how LD50, LC50, and LT50 tests are conducted using pure chemicals administered orally, dermally, or by inhalation to determine the dosage or concentration that kills half of the test population.

1. Pesticide activity
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2. Outline
Lethal dose 50
Lethal concentration 50
Lethal time 50
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3. LD50 (Lethal Dose 50)
This is the statistical estimate of the number of mg of toxicant per kg of bodyweight required to
kill 50% of a large population of test animal.
Invented In 1927, J.W. Trevan attempted to find a way to estimate the relative poisoning potency
of drugs and medicines used at that time.
LD50 value is useful when comparing the toxicities of different AI and formulations.
The lower the LD50 the greater the toxicity to human & animal and vice versa.
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4. WHO
class
Toxicity LD50 for the rat (mg/kg) body weight
Oral Dermal
I a Extremely hazardous <5 <50
I b Highly hazardous 5-50 50-200
II Moderately hazardous 50-2000 200-2000
III Slightly hazardous Over 2000 Over 2000
U Unlikely to present acute hazard 5000 or higher
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5. For example, some LD50s for dichlorvos, an insecticide commonly used in household pesticide strips, are listed below.
Oral LD50 (rat): 56 mg/kg
Dermal LD50 (rat): 75 mg/kg
Intraperitoneal LD50: (rat) 15 mg/kg
Inhalation LC50 (rat): 1.7 ppm (15 mg/m3); 4-hour exposure
Oral LD50 (rabbit) 10 mg/kg
Oral LD50 (pigeon:): 23.7 mg/kg
Oral LD50 (rat): 56 mg/kg
Oral (mouse): 61 mg/kg
Oral (dog): 100 mg/kg
Oral (pig): 157 mg/kg
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6. Lethal Concentration LC50
The concentrations of the chemical in air that
kills 50% of the test animals during the
observation period.
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7. Inhalation LC50
Commonly Used Term Exposure of rats for 4 hours ppm
Extremely toxic 10 to less
Highly toxic 10-100
Moderate toxic 100-1000
Slightly toxic 1000-10000
Practically non-toxic 10000-100000
Relatively harmless <100000
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8. How Ld50 and lc50 test are done
All test are performed using pure form of the chemical.
The chemical can be given to the animal through the following means:
Orally
Skin (dermal)
Injection in blood stream, intermuscular, abdominal cavity.
Final value obtained is identified as LD50 or LC50
This research can be tested on different animals such as rats, pigs, hamsters.
LD values are expressed as the weight of chemical administered per kg body weight of the
animal
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9. Example
E.g. LD50 (Oral, rat) 5mg/kg means that 5 milligrams of that
chemical for every 1kg body weight of the rat when
administered in one dose by mouth causes the death of
50% of the test group.
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10. Lethal time LD50
A calculated period of time within which a specific
concentration of a chemical is expected to cause death in
50% of a defined experimental animal population.
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