Final answer:
First-generation rodenticides require multiple feedings by rodents to achieve a lethal dose, and the LD50 value, which measures toxicity, varies by exposure method and between species.
Step-by-step explanation:
Yes, first-generation rodenticides often require multiple feedings for rodents to consume a lethal dose. These substances have lower acute toxicity compared to second-generation rodenticides, meaning rats and mice need to ingest the poison over a few days to accumulate a fatal amount. As with any chemical, the toxicity is quantified by the LD50, which stands for lethal dose-50% and refers to the amount of substance required to kill 50% of the test animal population. This measure of toxicity takes into account the animal's method of exposure and varies significantly between species. A low LD50 indicates a highly toxic chemical, while a high LD50 signifies lower toxicity. Understanding these measures is crucial as risk assessments for human exposure are based on this data extrapolated from animal studies, with recognition of the differences evidenced at various doses and in different species.