Chapter 3. Chapter 3: Information Literacy

Interactive Study Guide
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Chapter Three: Information Literacy

Guiding Question 3.3

What factors influence whether or not a particular chemical is toxic and how toxic it is?

Why You Should Care

We know that molecules interact with one another. Consider your choices for dinner—by adding different herbs and spices you can make food spicier (hot sauce!), fragrant (curry powder), or blander (sugar or cream can mute flavors). Salt is the chef’s best friend because it heightens other flavors, as it changes how our taste buds work.

These examples all point at ways that molecules interact, and toxins follow the same rules. Watch how vitamin Z (a fake molecule) could influence DDT’s effect in the body.

  • Additive effects increase linearly. (Adding DDT to vitamin Z has the same risk.)
  • Antagonistic effects decrease one another. (Adding vitamin Z decreases DDT’s risk.)
  • Synergistic effects produce a much greater effect. (Vitamin Z greatly increases DDT’s risk because DDT is much more persistent.)

Test Your Vocabulary

Choose the correct term for each of the following definitions:

Term Definition
The ability of a substance to dissolve in a liquid or gas.
Exposure to two or more chemicals has an effect equivalent to the sum of their individual effects.
The buildup of fat-soluble substances in the tissue of an organism over the course of its lifetime.
Exposure to two or more chemicals has a lesser effect than the sum of their individual effects would predict.
The length of time it takes a substance to break down in the environment.
The increased levels of fat-soluble substances in the tissue of predatory animals that have consumed organisms that have bioaccumulated toxins.
Chemicals that cause direct damage upon exposure.
Chemicals that don't readily degrade over time.
Exposure to two or more chemicals has a greater effect than the sum of their individual effects would predict.
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Question Sequence

1.

Humans eat fruits and vegetables for calories, fiber, and vitamins. Common vitamins found in broccoli include vitamins A and C and various B vitamins.

A) Vitamin C is a water-soluble vitamin, so we excrete it hours after it’s been consumed, and we cannot overdose on it because we cannot store it. Which does this demonstrate: bioaccumulation, biomagnification, or neither? Explain.

B) Vitamin A is a fat-soluble vitamin that we can store, and a vitamin-A overdose is rare but shows up as digestive and skin issues. Which does this demonstrate: bioaccumulation, biomagnification, or neither? Explain.
A) Vitamin C demonstrates neither bioaccumulation nor biomagnifications because we do not store it and excrete it soon after we consume it. If we could store it, it would reflect bioaccumulation. If we ate plants and animals that also bioaccumulated it, then our consumption and storage would reflect biomagnification.

B) Vitamin A shows bioaccumulation because we are storing the chemical in our bodies. It does not show biomagnification because we are not eating plants or animals that are also biomagnifying it (the production of it by plants and animals for their own use is bioaccumulation).
Infographic 3.4 Factors that Affect Toxicity

Question Sequence

4.

For the following statements, determine if there are additive, antagonistic, or synergistic effects of the two chemicals:

A) Piperonyl butoxide (PBO) is a pesticide additive that significantly increases the effectiveness of other pesticides by stopping their breakdown.

B) Ammonia and hydrochloric acid are both water pollutants, but when released together, they have lower effects than when released separately.

C) Arsenic is a bioaccumulator in drinking water that doesn’t mix with or affect any other known water pollutant.

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