As a pesticide's LD 50 increases, what happens to its toxicity?

When considering the relationship between a pesticide's LD50 (lethal dose for 50% of the population) and its toxicity, it is important to understand what LD50 represents. A higher LD50 value indicates that a larger dose of the pesticide is required to achieve lethality in half of the test organisms. Therefore, as the LD50 increases, it signifies that the substance is less toxic, meaning it poses a lower risk of harm or fatality to organisms at lower exposure levels. This rationale directly correlates with the understanding that a pesticide with a high LD50 is safer for both the environment and humans compared to one with a low LD50, which would require a smaller amount to be lethal. This fundamental principle underpins the correct answer regarding the relationship between LD50 and toxicity.