Chapter 3. Chapter 3: Information Literacy

Interactive Study Guide
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Chapter Three: Information Literacy

Guiding Question 3.4

What kind of scientific studies allow us to assess the potential hazard of a particular chemical? How do we determine “safe” exposures?

Why You Should Care

Determining the safety or danger of a chemical is very challenging. Most chemicals are not lethal at first touch but can accumulate in the body over long periods of time and cause a variety of illnesses with different levels of symptoms. Any research into a chemical’s toxicity will involve studies of the chemical in controlled conditions in cells in the lab (in vitro studies), in animals (in vivo studies), and in humans exposed to the chemical outside the lab.

These studies will reveal different impacts—some minor and maybe some major—of the chemicals on cells, animals, and humans. Toxicologists measure levels where the majority of the study’s populations (cells or animals) die after exposure (this is the LD50 value), review these studies, and conclude the levels that are considered “safe” for exposure to the chemicals.

Determining safe levels of a new chemical is more than the LD50 value. “Safe” has to also account for differences between people’s sensitivity to the chemical, people’s short-term and long-term exposure, and possible interactions that haven’t been discovered yet.

Test Your Vocabulary

Choose the correct term for each of the following definitions:

Term Definition
Research that studies the effects of experimental treatment cells in culture dishes rather than in intact organisms.
A scientist who studies the cause and patterns of disease in human populations.
Scientists who study the specific properties of any given potential toxin.
Research that studies the effects of an experimental treatment in intact organisms.
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Infographic 3.3 BPA studies

Question Sequence

1.

Please examine Infographic 3.3 closely to answer the following questions:

For the in vivo studies on the mice:

A) How much more did the BPA-exposed mice's prostate glands weigh compared to the control mice?

B) What did the researchers believe the BPA was doing in the mice? Did they know this for sure? What did they propose doing in further research on mice?

A) For the mice exposed to BPA at 2 ppb, their prostates weighed 9 mg more (52 vs. 43 mg). For the mice exposed to BPA at 20 ppb, their prostates weighed 12 mg more (55 vs. 43 mg).

B) In mice, it is believed, but not known, that BPA was acting to increase the size or number of prostate cells to make them larger and heavier. More research was needed to clarify exactly how this was happening by examining prostates’ DNA to discover what reactions were occurring.

Question Sequence

4.

Fill in the blank with the correc term for each of the following definitions:

: A graph of the effects of a substance at different concentrations or levels of exposures.

The dose of a substance that would kill 50% of the test population is called .

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