Passage 3 | Environmental Science
PCBs in the Environment
Among the harmful substances polluting the environment, perhaps the most well known by activists is a group of chemicals collectively called polychlorinated biphenyls, or PCBs. PCBs are a family of 209 separate compounds. In the past, PCBs were commonly used as fire deterrents and insulation for high- voltage electrical components like capacitors and transformers. [A] This is because one of the characteristics of PCBs is their resistance to extremely high temperatures. [B] They are also known to be very stable and nonreactive and thus are effective insulators. [C] However, due to these qualities, PCBs remain in the environment and are difficult to remove. [D]
Before PCB use was curtailed by legislation in the 1970s, their widespread use created environmental problems that remain current global issues. PCBs persist in the environment and pollute the ecosystem by contaminating water, soil, and air. When PCBs in rivers evaporate into the air, they can be carried great distances on the wind, returning to the food chain through precipitation. As a result, PCBs have been detected all over the world.
PCBs in water and soil build up inside plants and animals, which in turn are consumed by humans. Because the concentration of PCBs increases the higher they move through the food so chain, humans who eat contaminated animals ingest large amounts of the chemicals. When a PCB chemical enters the human body, it is transported throughout the body by the bloodstream and is eventually stored in fatty tissue, where it typically lingers for a long time. Unlike water-soluble substances, these chemicals do not deteriorate easily in water and as a result do not get expelled from the body. Instead they remain and build up over long periods of time—in some cases, many years. During this time, they may reach the dangerous levels to which reproductive irregularities, various types of cancer, conditions affecting the immune system, and other illnesses have been attributed.
Because of the lack of public information about the dangers of PCBs, the use of the chemicals was unregulated for some time. However, throughout the 1970s, research demonstrating the link between PCBs and severe health problems became undeniable. In 1974, the US FDA declared that fish containing PCB quantities higher than five parts per million were unsafe for human consumption. In the same year, a study conducted by the Environmental Protection Agency discovered that the Hudson River contained high levels of PCBs, and soon activist groups were campaigning for bans against the chemicals and calling for cleanup actions from the companies that were responsible for contaminating the environment with such industrial wastes. Epitomizing the kind of corporate negligence that had led to harmful levels of PCBs in the environment. General Electric, one of the United States’ largest corporations, became symbolic of the struggle between environmentalists and the manufacturing industry. It had dumped approximately 1.3 million pounds of PCBs into the Hudson River. Supported by environmental and public health advocates. New York State sued General Electric in 1975 and demanded that the company stop dumping PCBs into the Hudson. Soon after, rising fears regarding the poisonous aspects of PCBs, and their constant exposure to the environment, resulted in congressional intervention in 1976, when the Toxic Substances Control Act (TSCA) was passed, prohibiting the commercial production and distribution of PCBs. By this time, however, decades of PCB dumping had already made a lasting mark on the environment.
In recent times, attempts have been made to develop PCB cleanup methods that involve bacteria that combat the effect of PCBs on the environment and, in turn, animals and humans. Beginning in the early 1990s, researchers conducted studies on ways to eliminate PCBs from the environment using bacteria that exist naturally. The researchers focused their work on the badly contaminated Hudson River, using an inexpensive system involving anaerobic and aerobic bacteria.
This process is a biodégradation method and can treat about 70 percent of the PCBs in a sample. The first phase involves the conversion of PCB substances by the anaerobic bacteria into less-harmful compounds. The remaining PCB material can then be treated with aerobic bacteria, which break down the substances into carbon dioxide and water. Other research has determined that the PCBs that are left after this process has been performed can be completely eliminated using other chemical solutions.
27. The word curtailed in the passage is closest in meaning to
28. The word it in the passage refers to
29. The word expelled in the passage is closest in meaning to
30. In paragraph 3, the author states that PCBs are responsible for all of the following health problems EXCEPT
(A) issues with reproductive abnormalities
(B) conditions related to the immune system
(C) different kinds of cancer
(D) circulatory disorders and heart disease
31. The word negligence in the passage is closest in meaning to
32. Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information.
(A) In the 1970s, new applications for PCBs were discovered, and the government encouraged the chemicals’ production and distribution.
(B) When the TSCA was passed, people began to express their concerns about the hazards associated with PCBs in the environment.
(C) Because of the public’s concern about PCBs, the government placed restrictions on the use of the chemicals.
(D) The TSCA prevented manufacturers from using PCBs to produce or distribute their commercial products.
33. According to paragraph 4, which of the following sentences most accurately reflects the authors opinion about General Electric’s use of PCBs?
(A) Because PCBs were legal, the company should not be punished for its innocent mistake.
(B) The company behaved irresponsibly by dumping PCBs into the Hudson River.
(C) It is justified because the company manufactured products that were useful in everyday life.
(D) It is unfortunate, but those types of mistakes are necessary for technological progress.
34. In paragraph 4, why does the author mention activist groups?
(A) To argue that PCBs are not as harmful as they were once believed to be
(B) To point out that, for some time, PCBs were essential to the manufacturing industry
(C) To explain why most people were not aware of the harmful nature of PCBs
(D) To introduce the efforts that people made to prevent the further use of PCBs
35. According to paragraph 5, how are some researchers attempting to reduce PCB pollution?
(A) By organizing groups of volunteers to clean up local rivers
(B) By encouraging the government to pass laws preventing pollution
(C) By using bacteria to break down the PCBs in water supplies
(D) By performing studies based on past cleanup projects
36. The word conversion in the passage is closest in meaning to
37. Look at the four squares H that indicate where the following sentence could be added to the passage.
If discarded in water or soil, for instance, the chemicals can cause major ecological problems.
Where would the sentence best fit?
38. Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some sentences do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points.
The presence of harmful PCBs in the environment remains a current and global pollution issue.
(A) PCBs are a class of chemicals that were once widely used in manufacturing electrical equipment
(C) Humans may be exposed to PCBs by drinking polluted water, eating contaminated fish, coming in physical contact with the chemicals, or breathing polluted air.
(E) Before the 1970s corporations dumped millions of pounds of PCBs into the environment, but as people became aware of the dangers, the government restricted the chemicals’ use.
(B) PCBs have a stable nature that allows them to remain in the environment for a long time, causing serious health problems to humans and animals.
(D) Because they are not water-soluble, PCBs are especially dangerous in the human body, where they remain in fatty tissues for long periods of time.
(F) Researchers are working on ways to clean up the PCB waste that, though discarded before the 1970s, continues to pollute the environment.