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Pesticide activity

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Outline Lethal dose 50 Lethal concentration 50 Lethal time 50

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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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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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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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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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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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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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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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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.