The statement that pyrethrin quickly kills fleas, does not build up in the dog's bloodstream, and is biodegradable is considered true.

• A. True
• B. False
• C. It only kills ticks
• D. It is carcinogenic

Answer: (A)

Pyrethrins work by disrupting nerve signals in fleas, causing rapid paralysis and death after contact. In dogs, these compounds are quickly metabolized and excreted, so little residue stays in the bloodstream when the product is used as directed. They also break down relatively fast in the environment, so they don’t persist as environmental pollutants. With those properties—fast flea kill, minimal systemic buildup, and biodegradability—the statement is true.

Note that pyrethrins are not limited to killing only ticks, and they are not considered carcinogenic at normal, labeled use.