What are the levels of PFOS in freshwater fish?

• A. 8,000 million parts per trillion.
• B. 70 parts per trillion.
• C. 0.02 parts per trillion.
• D. 0 parts per trillion.

Answer: (A)

PFOS levels in freshwater fish are typically discussed in parts per trillion because these contaminants persist and bioaccumulate in aquatic organisms. Concentrations can range from very low (near detection limits) in clean waters to extremely high in heavily polluted environments, reflecting ongoing exposure and the ability of PFOS to accumulate in tissue over time. The idea being tested is that PFOS can reach large tissue burdens under substantial contamination, so the higher end of the reported range represents the potential extreme. In this context, the largest figure illustrates the possibility of very high PFOS accumulation in fish from polluted sites, which is why it is considered the best answer among the given options.