The element lead is a heavy, soft metal that has been known since ancient times to be poisonous in large quantities. More recently, it has been recognized that even low exposure to lead causes biological damage over long periods of time. For decades in the twentieth century, however, nearly every automobile produced exhaust laced with lead.
In the body, lead causes widespread damage by interfering with many enzymes (proteins that enable biological processes). The typical ion, or charged atomic form, of lead easily replaces calcium, iron, and zinc ions, which are necessary components of these enzymes. Lead ions are imperfect replacements, so the enzymes fail to function properly. Lead particularly damages the central nervous system, impeding the proper growth and working of brain cells. The element also displaces calcium in bone tissue, providing a reservoir for lead to reenter the rest of the body even when outside sources are removed. Children are particularly vulnerable to harm from lead exposure and can be impaired cognitively and behaviorally for life.
Easy to find, mine, and refine, lead has been in use for thousands of years. The word “plumbing” comes from plumbum, the Latin word for lead, because the ancient Romans ran drinking water through pipes made of the metal. Lead is now a crucial component of car batteries, radiation shields, and ammunition. The two forms of lead that have contributed the most to human exposure, however, are lead paint and tetraethyl lead (TEL), a gasoline additive that prevents a problem called engine knock.
Internal combustion engines depend upon the smooth burning of mixtures of fuel and air, so that the pistons inside the engines are driven in a steady way. When these mixtures ignite prematurely, however, unintended shock waves damage the pistons and other engine parts. This phenomenon is labeled “engine knock” for the loud metallic pinging that accompanies the shock waves. Engine knock is suppressed by changing the composition of the fuel itself or by adding other chemicals. Early automobile engines that ran on petroleum-based fuel suffered greatly from engine knock, because it was difficult and expensive to alter the makeup of the fuel itself to eliminate this issue.
Without the discovery of TEL’s “antiknock” capabilities, automobiles may have had to run on non-petroleum-based fuel, such as ethanol. However, in 1919, TEL was identified as a potent additive to gasoline that eliminated knock and further lubricated engine valves. The United States oil industry quickly began to manufacture TEL and promote it as a means of improving both power and fuel economy in automobiles. Rapid expansion of industrial production of the additive resulted in several lethal accidents, as unprotected chemical plant workers were poisoned by contact with TEL. After a conference called by the chief United States health official, however, TEL was approved for countrywide use. Soon, automobiles in the United States and elsewhere were running almost exclusively on leaded gasoline.
In the late 1940s, geologist Clair Patterson analyzed the radioactive decay of uranium into lead in terrestrial rocks, as well as in meteorites, in order to determine the age of the Earth. In these investigations, however, Patterson had to overcome contamination resulting from lead pollution. The focus of his subsequent research was to show how widespread this contamination was and to advocate for restrictions on the use of TEL. His advocacy, as well as that of other scientists, was resisted by supporters of the lead and automobile industries. Under pressure to reduce general air pollution created by automobiles, however, manufacturers announced in the early 1970s that antipollution devices called catalytic converters would be installed on new cars. Since these devices would be ruined by lead, the use of TEL was to be phased out.
By 1986, the use of lead gasoline additives in the United States was prohibited. Since then, sharp reductions in blood-lead levels in the population have been observed, along with other improvements in public health. Nevertheless, TEL is still used in automobiles in a few countries, as well as in “avgas” (aviation gasoline) that fuels propeller airplanes around the world. In addition, the blanket of lead particles deposited globally by prior combustion of leaded gasoline will pose an environmental hazard for many years to come.
Now answer the questions.
| P1 | Paragraph 1 |
| S1 | The element lead is a heavy, soft metal that has been known since ancient times to be poisonous in large quantities. |
| 2 | More recently, it has been recognized that even low exposure to lead causes biological damage over long periods of time. |
| 3 | For decades in the twentieth century, however, nearly every automobile produced exhaust laced with lead. |
The phrase “laced with” in the passage is closest in meaning to
| P2 | Paragraph 2 |
| S1 | In the body, lead causes widespread damage by interfering with many enzymes (proteins that enable biological processes). |
| 2 | The typical ion, or charged atomic form, of lead easily replaces calcium, iron, and zinc ions, which are necessary components of these enzymes. |
| 3 | Lead ions are imperfect replacements, so the enzymes fail to function properly. |
| 4 | Lead particularly damages the central nervous system, impeding the proper growth and working of brain cells. |
| 5 | The element also displaces calcium in bone tissue, providing a reservoir for lead to reenter the rest of the body even when outside sources are removed. |
| 6 | Children are particularly vulnerable to harm from lead exposure and can be impaired cognitively and behaviorally for life. |
In paragraph 2, the author indicates that enzymes in the body do not work correctly when they contain lead ions because
Why does the author mention a “reservoir” in paragraph 2?
| P3 | Paragraph 3 |
| S1 | Easy to find, mine, and refine, lead has been in use for thousands of years. |
| 2 | The word “plumbing” comes from plumbum, the Latin word for lead, because the ancient Romans ran drinking water through pipes made of the metal. |
| 3 | Lead is now a crucial component of car batteries, radiation shields, and ammunition. |
| 4 | The two forms of lead that have contributed the most to human exposure, however, are lead paint and tetraethyl lead (TEL), a gasoline additive that prevents a problem called engine knock. |
Which of the sentences below best expresses the essential information in the highlighted sentence in paragraph 3? Incorrect choices change the meaning in important ways or leave out essential information.
| P4 | Paragraph 4 |
| S1 | Internal combustion engines depend upon the smooth burning of mixtures of fuel and air, so that the pistons inside the engines are driven in a steady way. |
| 2 | When these mixtures ignite prematurely, however, unintended shock waves damage the pistons and other engine parts. |
| 3 | This phenomenon is labeled “engine knock” for the loud metallic pinging that accompanies the shock waves. |
| 4 | Engine knock is suppressed by changing the composition of the fuel itself or by adding other chemicals. |
| 5 | Early automobile engines that ran on petroleum-based fuel suffered greatly from engine knock, because it was difficult and expensive to alter the makeup of the fuel itself to eliminate this issue. |
The word “prematurely” in the passage is closest in meaning to
It can be inferred from paragraph 4 that the primary reason to suppress engine knock is to
The phrase “this issue” in the passage refers to
| P5 | Paragraph 5 |
| S1 | Without the discovery of TEL’s “antiknock” capabilities, automobiles may have had to run on non-petroleum-based fuel, such as ethanol. |
| 2 | However, in 1919, TEL was identified as a potent additive to gasoline that eliminated knock and further lubricated engine valves. |
| 3 | The United States oil industry quickly began to manufacture TEL and promote it as a means of improving both power and fuel economy in automobiles. |
| 4 | Rapid expansion of industrial production of the additive resulted in several lethal accidents, as unprotected chemical plant workers were poisoned by contact with TEL. |
| 5 | After a conference called by the chief United States health official, however, TEL was approved for countrywide use. |
| 6 | Soon, automobiles in the United States and elsewhere were running almost exclusively on leaded gasoline. |
When does paragraph 5 indicate that lethal accidents occurred in relation to other events described?
The phrase “almost exclusively” in the passage is closest in meaning to
| P6 | Paragraph 6 |
| S1 | In the late 1940s, geologist Clair Patterson analyzed the radioactive decay of uranium into lead in terrestrial rocks, as well as in meteorites, in order to determine the age of the Earth. |
| 2 | In these investigations, however, Patterson had to overcome contamination resulting from lead pollution. |
| 3 | The focus of his subsequent research was to show how widespread this contamination was and to advocate for restrictions on the use of TEL. |
| 4 | His advocacy, as well as that of other scientists, was resisted by supporters of the lead and automobile industries. |
| 5 | Under pressure to reduce general air pollution created by automobiles, however, manufacturers announced in the early 1970s that antipollution devices called catalytic converters would be installed on new cars. |
| 6 | Since these devices would be ruined by lead, the use of TEL was to be phased out. |
The word “subsequent” in the passage is closest in meaning to
Paragraph 6 mentions all of the following as true of the activities of geologist Clair Patterson EXCEPT:
| P7 | Paragraph 7 |
| S1 | By 1986, the use of lead gasoline additives in the United States was prohibited. |
| 2 | Since then, sharp reductions in blood-lead levels in the population have been observed, along with other improvements in public health. |
| 3 | Nevertheless, TEL is still used in automobiles in a few countries, as well as in “avgas” (aviation gasoline) that fuels propeller airplanes around the world. |
| 4 | In addition, the blanket of lead particles deposited globally by prior combustion of leaded gasoline will pose an environmental hazard for many years to come. |
Which of the following statements is best supported by the reports on the current use of TEL described in paragraph 7?
| Paragraphs 2-3 | |
| P2 S4–6 | Lead particularly damages the central nervous system, impeding the proper growth and working of brain cells. The element also displaces calcium in bone tissue, providing a reservoir for lead to reenter the rest of the body even when outside sources are removed. Children are particularly vulnerable to harm from lead exposure and can be impaired cognitively and behaviorally for life. |
| P3 S1 | A Easy to find, mine, and refine, lead has been in use for thousands of years. |
| 2 | B The word “plumbing” comes from plumbum, the Latin word for lead, because the ancient Romans ran drinking water through pipes made of the metal. |
| 3 | C Lead is now a crucial component of car batteries, radiation shields, and ammunition. |
| 4 | D The two forms of lead that have contributed the most to human exposure, however, are lead paint and tetraethyl lead (TEL), a gasoline additive that prevents a problem called engine knock. |
Look at the part of the passage that is displayed above. The letters [A], [B], [C], and [D] indicate where the following sentence could be added.
Despite this potential for injury, the utilization of lead is widespread.
Where would the sentence best fit?
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 poisonous metal lead was released by most cars for decades.