Which statement concerning pyrethroids is false?

The statement that pyrethroids tend to build up in food chains is false. Pyrethroids are synthetic chemicals modeled after natural pyrethrins, which are derived from chrysanthemum flowers. One of the key characteristics of pyrethroids is that they generally do not bioaccumulate in the same way some other pesticides do, such as organochlorines. This means that while they have the potential to be toxic to non-target organisms, especially aquatic life, they do not significantly accumulate in organisms in a food chain context.

In contrast, the other statements regarding pyrethroids are true. They are known for their high toxicity to fish and other aquatic organisms due to their high lipophilicity, which increases their toxicity in aquatic environments. Pyrethroids are also designed to break down relatively quickly in the environment, which can minimize their long-term ecological impact. The synthetic nature of pyrethroids means they have a more controlled environmental persistence relative to their natural counterparts, alongside their origin from chrysanthemum flowers, confirming their relationship with pyrethrins.