The planet’s deepest point is in the Pacific Ocean’s Mariana Trench, which lies miles below the sea surface. According to a new study published in Nature Ecology & Evolution, even in this remote locale, creatures cannot escape pollution.
A team of researchers recently sent a remotely operated vehicle into the depths of the Mariana Trench. They found that extraordinarily high levels of forbidden industrial chemicals are contaminating marine life more than 7 miles deep in the trench. The small hard-shelled marine life that the robotic submarine brought to the surface was polluted with toxic chemicals, with toxin levels 50 times greater than those of the most heavily polluted rivers in the world.
These pollution levels were not the only alarming aspect of the discovery. The types of compounds found were all considered “persistent organic pollutants” (POPs), meaning they stick around in the environment for a very long time. Two of the most prevalent types are PCBs and PBDEs. PCBs were once used in many industrial applications, but were outlawed in the United States in the 1970s after being linked to cancer. Similarly, PBDEs were used in a wide range of products — from electronics to couch cushions. Neither chemical breaks down in the environment.
These compounds stick to the surface of materials like plastic. Many creatures mistakenly eat this colorful but toxic material, causing the POPs to build up in their bodies, lurking in their fat tissues. When these sea creatures die, their POP-riddled bodies sink to the ocean floor, where deep-sea marine life eat their remains. POPs are therefore transferred to other creatures along the food chain.
The Mariana Trench is many miles away from any industrial source. This suggests that these pollutants travel over long distances despite having been prohibited worldwide decades ago.
【題組】39( ) According to the passage, which of the following statements is true?
(A) PCBs are often used in making electronic products.
(B) Chemicals washed down to the ocean stay on the surface.
(C) The deepest point of the Mariana Trench is free from pollution.
(D) A robotic vehicle was used to help study pollution in the Mariana Trench.