Which description best explains why PCBs are dangerous?

Which description best explains why PCBs are dangerous?

• A. They are highly reactive in air
• B. They are toxic, persistent, and bioaccumulative
• C. They readily biodegrade in soil
• D. They dissolve quickly in water

Answer: (B)

PCBs are dangerous mainly because they are toxic, persistent, and bioaccumulative. They resist natural degradation, so they linger in the environment for long periods. Their lipophilic nature causes them to concentrate in the fatty tissues of organisms, and as these organisms are eaten by predators higher in the food chain, PCB levels magnify—a process that can reach humans who consume contaminated fish or meat. This combination explains why they pose long-term health and ecological risks. The other statements don’t fit: PCBs are not highly reactive in air; they are chemically very stable and not readily oxidized. They do not biodegrade readily in soil—degradation is extremely slow and often incomplete. They do not dissolve quickly in water; they are poorly soluble in water and tend to partition into sediments and organisms.

PCBs are dangerous mainly because they are toxic, persistent, and bioaccumulative. They resist natural degradation, so they linger in the environment for long periods. Their lipophilic nature causes them to concentrate in the fatty tissues of organisms, and as these organisms are eaten by predators higher in the food chain, PCB levels magnify—a process that can reach humans who consume contaminated fish or meat. This combination explains why they pose long-term health and ecological risks.

The other statements don’t fit: PCBs are not highly reactive in air; they are chemically very stable and not readily oxidized. They do not biodegrade readily in soil—degradation is extremely slow and often incomplete. They do not dissolve quickly in water; they are poorly soluble in water and tend to partition into sediments and organisms.