What does a poison refer to in terms of its toxicity?

A substance that has an oral LD50 lower than 50 mg/kg is considered a poison because a lower LD50 value indicates a higher level of toxicity. The LD50 value represents the dose at which 50% of a test population (typically laboratory animals) is expected to die upon exposure. Consequently, if the LD50 is lower than 50 mg/kg, it means that only a small amount of the substance can cause lethal effects, reflecting a significant hazard to health.

In contrast, a substance with an oral LD50 higher than 50 mg/kg is regarded as less toxic, as it requires a larger dose to induce the same lethal outcome. Non-toxic substances or those with no effects on body weight or health fall into a different category altogether, as they do not pose a risk of toxicity at any reasonable exposure level. Understanding these distinctions is vital for assessing risks associated with chemical exposure in various environments, including those encountered by utility arborists.