Which substance is measured in parts per million (ppm) to indicate acuteness of toxicity?

The substance that is measured in parts per million (ppm) to indicate the acuteness of toxicity is LC50. LC50, or lethal concentration 50, is a standard measure in toxicology used to assess the potency of a substance. It represents the concentration of a toxicant in air, water, or soil required to kill 50% of a test population (often aquatic or terrestrial organisms) within a specified time frame, typically 24 hours.

Using ppm as a measurement unit allows for a standardized way of expressing toxicity levels, indicating the specific concentration at which harmful effects may arise. This measurement is particularly important in environmental assessments and safety regulations, helping stakeholders understand the risk associated with exposure to various chemicals.

Conversely, LD50 refers to the lethal dose of a substance required to kill 50% of a test population and is often expressed in milligrams of a substance per kilogram of body weight (mg/kg), concentrating more on the quantity needed for a toxic response rather than concentration in a medium. Therefore, it is not measured in ppm. Pesticide application rate pertains to how much pesticide is applied per area and does not focus directly on toxicity. Exposure duration involves the time an organism is exposed to a toxicant, which is