What is the oral LD50 level that represents a highly toxic pesticide?

The oral LD50 level is a key measure used to assess the toxicity of a substance, specifically indicating the dose required to kill 50% of a test population (typically laboratory animals) through oral ingestion. A lower LD50 value signifies higher toxicity, meaning that less of the substance is needed to achieve lethal effects.

In the context of the provided options, a level of 46 mg/kg indicates a significant degree of toxicity; it demonstrates that just 46 milligrams of the pesticide per kilogram of body weight can be lethal to half of the test subjects. This threshold categorizes it as highly toxic, as many regulatory frameworks define substances with an LD50 of less than 50 mg/kg as highly toxic.

By comparison, while 380 mg/kg and 5800 mg/kg also present numerical values, they indicate lower levels of toxicity, meaning larger doses are required to produce lethal effects. The value of 640 ng/kg, represented as nanograms per kilogram, is an incomprehensibly lower quantity, placing it in an exceedingly high toxicity range, but in terms of the measured LD50 levels, 46 mg/kg stands out for its more practical application in determining the toxicity of pesticides in typical contexts.

Therefore, the correct answer effectively captures the