New SAT Reading Practice Test 58: Mercury in Fish Passage

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Mercury in Fish Passage

Mercury is an unusual element; it is a metal but
is liquid at room temperature. It is also a neurotoxin
and a teratogen, as it causes nerve damage and birth
defects. Mercury can be found just about every-
05where; it is in soil, in air, in household items, and
even in our food. Everyday objects, such as thermometers,
light switches, and fluorescent lightbulbs,
contain mercury in its elemental form. Batteries
can also contain mercury, but they contain it in the
10form of the inorganic compound mercury chloride.
Mercury can also exist as an organic compound,
the most common of which is methylmercury.
While we can take steps to avoid both elemental
and inorganic mercury, it is much harder to avoid
Most of the mercury in the environment
comes from the emissions of coal-burning power
plants; coal contains small amounts of mercury,
which are released into the air when coal burns.
20The concentration of mercury in the air from
power plants is very low, so it is not immediately
dangerous. However, the mercury is then washed
out of the air by rainstorms and eventually ends up
in lakes and oceans.
25The mercury deposited in the water does not
instantaneously get absorbed by fish, as elemental
mercury does not easily diffuse through cell
membranes. However, methylmercury diffuses
into cells easily, and certain anaerobic bacteria
30in the water convert the elemental mercury to
methylmercury as a by-product of their metabolic
processes. Methylmercury released into the water
by the bacteria diffuses into small single-celled
organisms called plankton. Small shrimp and other
35small animals eat the plankton and absorb the
methylmercury in the plankton during digestion.
Small fish eat the shrimp and then larger fish eat the
smaller fish; each time an animal preys on another
animal, the predator absorbs the methylmercury.
40Because each animal excretes the methylmercury
much more slowly than it absorbs it, methylmercury
builds up in the animal over time and is passed on
to whatever animal eats it, resulting in a process
called bioaccumulation.
45As people became aware of the bioaccumulation
of mercury in fish, many reacted by eliminating
seafood from their diet. However, seafood contains
certain omega-3 fatty acids that are important
for good health. People who do not eat enough
50of these fatty acids, especially eicosapentaenoic
acid (EPA) and docosahexaenoic acid (DHA), are
more likely to have heart attacks than people who
have enough EPA and DHA in their diet. Because
fish and shellfish, along with some algae, are the
55only sources of these fatty acids, eliminating them
from our diet might have worse health effects than
consuming small amounts of mercury.
Scientists have studied the effects of mercury by
conducting tests on animals and by studying various
60human populations and recording the amount of
mercury in their blood. By determining the levels of
mercury consumption that cause any of the known
symptoms of mercury poisoning, they were able
to identify a safe level of mercury consumption.
65The current recommendation is for humans to
take in less than 0.1 microgram of mercury for
every kilogram of weight per day. This means that
a 70-kilogram person (about 155 pounds) could
safely consume 7 micrograms of mercury per day.
70Since haddock averages about 0.055 micrograms
of mercury per gram, that person could safely eat
127 grams (about 4.5 ounces) of haddock per day.
On the other hand, swordfish averages about 0.995
micrograms of mercury per gram of fish, so the
7570-kilogram person could safely eat only about 7
grams (about one-quarter of an ounce) of swordfish
per day.
Nutritionists recommend that, rather than elimi-
nate fish from our diet, we try to eat more of the
80low-mercury fish and less of the high-mercury fish.
Low-mercury species tend to be smaller omnivo-
rous fish while high-mercury species tend to be the
largest carnivorous fish. Awareness of the par-
ticulars of this problem, accompanied by mindful
85eating habits, will keep us on the best course for
healthy eating.

1. The author of the passage would most likely agree with which of the following statements?

  • A. Mercury poisoning is only one of many concerns that should be considered when choosing which fish to add to one's diet.
  • B. More should be done by scientists and nutritionists to inform people about the dangers of mercury poisoning.
  • C. Fish is an essential part of a healthy diet and can be eaten safely if recommendations for mercury consumption are kept in mind.
  • D. The mercury present in the air is more dangerous to people than the mercury consumed by eating fish with high mercury levels.

2. Which choice provides the best evidence for the answer to the previous question?

  • A. Lines 16-18 ("Most of … plants")
  • B. Lines 32-35 ("Methylmercury released … plankton")
  • C. Lines 58-61 ("Scientists … their blood")
  • D. Lines 83-86 ("Awareness … eating")

3. In addition to the levels of mercury in a specific species of fish, people should also consider which of the following when determining a safe level of consumption?

  • A. Their own body weight
  • B. Where the fish was caught
  • C. The other meats they are eating
  • D. What they ate the day before

4. As used in line 20, "concentration" most nearly means

  • A. focus.
  • B. application.
  • C. density.
  • D. awareness.

5. The passage most strongly suggests which of the following statements is accurate?

  • A. It is not possible to completely avoid environmental exposure to mercury.
  • B. Inorganic mercury is more dangerous to humans than organic mercury.
  • C. Most of the exposure to mercury experienced by humans comes from fish consumption.
  • D. Mercury is one of the most abundant elements found in nature.

6. Which choice provides the best evidence for the answer to the previous question?

  • A. Lines 1-2 ("Mercury is an unusual … temperature")
  • B. Lines 4-6 ("Mercury … our food")
  • C. Lines 20-22 ("The concentration … dangerous")
  • D. Lines 28-32 ("However, methylmercury … processes")

7. The main purpose of paragraph 3 is to explain

  • A. the reasons why mercury deposited in water is not harmful to fish.
  • B. the relationships between predators and prey in aquatic animals.
  • C. how the largest fish accumulate the greatest amounts of mercury.
  • D. the difference between methylmercury and other types of mercury.

8. Which of the following pieces of evidence would most strengthen the author's line of reasoning?

  • A. More examples in paragraph 1 of places mercury is found
  • B. Details in paragraph 2 about the levels of mercury found in the air
  • C. An explanation in paragraph 4 of how to treat mercury poisoning
  • D. More examples in paragraph 5 of how many micrograms of mercury people of different weights could eat

9. As used in lines 83-84, "particulars" most nearly means

  • A. data.
  • B. specifics.
  • C. points.
  • D. evidence.

10. Based on the information in the passage and the graphic, which of the following statements is true?

  • A. The fish with the lowest average weight is the safest to eat.
  • B. A person can safely eat more marlin than albacore tuna in one day.
  • C. Eating large fish carries a lower risk of mercury poisoning than eating small fish.
  • D. A person can safely eat more Alaskan pollock than black striped bass in one day.