Final

Question 1

What important expression is Paracelsus credited with?

Answer 1

“Everything is toxic, nothing is toxic; the dose makes the poison.”

Question 2

Why is Paracelsus’ expression important?

Answer 2

No matter what contaminant you’re exposed to, there will always be a safe concentration/dose that will not pose any harm to the human body.

Question 3

Why is an understanding of modifying factors helpful with reproducibility?

Answer 3

Controlling variables to ensure consistent results.

Question 4

Why is an understanding of modifying factors helpful with comparability?

Answer 4

techniques that enable cross-study comparisons.

Question 5

Why is an understanding of modifying factors helpful with applicability?

Answer 5

Assume findings to other scenarios and enhance risk assessment.

Question 6

Explain how the plant or animal’s health can act as a modifying factor for the effects of contaminant exposure.

Answer 6

1. immune system function: health status of an organism influences the efficiency.
2. metabolic rate: a healthy organism might metabolize more efficiently than a stressed/diseased one.
3. life stage: the overall health of an organism may fluctuate with age, influencing the ability to deal with contaminants.

Question 7

List the four major classes of chemical interactions that can occur in the environment.

Answer 7

1. no interaction: no amplification or reduction of effects.
2. strict addition: do not interact to amplify or reduce effects.
3. synergistic: amplifies the overall impact.
4. antagonistic: counteracts or reduces the overall impact.

Question 8

Which chemical interaction often applies to chemicals that share a similar mode of toxicity?

Answer 8

Synergistic effects since the combined effect is greater than the sum of them acting independently.

Question 9

What is hormesis? Include a graph.

Answer 9

Low-dose amounts have a beneficial effect and high-dose amounts are toxic

Question 10

What chemical property strongly enhances its ability to bioconcentrate?

Answer 10

Lipophilicity: the tendency of a chemical to dissolve in lipids or fats.

Question 11

What type of biological tissue is involved in bioconcentration?

Answer 11

Fatty tissue due to their affinity for lipid-based environments, anything highly lipophilic.

Question 12

What is biomagnification? Include a diagram.

Answer 12

The process by which the concentration of certain substances increase at higher trophic levels in a food chain.

Question 13

What two properties of a chemical strongly increase the potential for it to bioaccumulate?

Answer 13

Lipophilicity: fat-soluble chemicals.

Low metabolic degradation: chemicals that are resistant to breakdown/slow to break down.

Question 14

Why does the concentration in the environment provide a poor surrogate for exposure?

Answer 14

You can have low concentrations, but because it accumulates over time, you can still end up with very high concentrations in a top predator.

Question 15

What is ionizing radiation?

Answer 15

A form of radiation that has enough energy to remove tightly bound electrons from atoms.

Question 16

What part do free radicals play in the mechanism of toxicity displayed by ionizing radiation?

Answer 16

When you knock an electron off, you create a free radical. They are very reactive and unstable due to them wanting to recapture an electron.

Question 17

What is a cascade mechanism of free radical propagation and how does water assist?

Answer 17

A chain reaction of the breaking off electrons which creates a linear reaction.

Water can be disturbed or excited which can easily create a free radical.

Question 18

What is somatic DNA damage?

Answer 18

Damage to enzymes, structural proteins, lipids, cell membranes, organelles, and may result in cell mutations and cancer.

Question 19

What is genetic DNA damage?

Answer 19

Damage to DNA and chromosomes in reproductive tissue can result in birth defects and organism mutations.

Question 20

What are the three primary mechanisms of toxicity attributed to metal exposure?

Answer 20

1. block essential functional groups on enzymes.
2. displace essential metals in enzymes.
3. modify conformation of biomolecules.

Question 21

How can your body develop a tolerance to metal exposure?

Answer 21

Metal halides float around and give metals a place to interact with, having no other function.

Question 22

What is the mechanism of toxicity associated with narcosis?

Answer 22

Non-specific type of reaction resulting in anesthesia of the organism.

Question 23

Why is narcosis considered reversible?

Answer 23

Two mechanisms are fighting each other, chemical trying to break and cell trying to repair. Once the chemical is removed, the cell can repair the damage.

Question 24

What changes were made of pesticides from chlorinated organics to modern botanicals?

Answer 24

“Dilution is the solution to pollution.” Pesticides were developed to be more water soluble, less persistent, and more selective.

Question 25

What are two modes of toxic action for pesticides that target the nervous system?

Answer 25

1. AEase inhibitors: AEase degrades ACh at the synaptic junction.
2. synaptic receptor-site binding: binds to the ACh receptor on the post-synaptic site and then mimics ACh.

Question 26

What are two modes of toxicity associated with herbicides?

Answer 26

1. inhibition of photosynthesis: target the process of photosynthesis by disrupting the energy needed for growth and survival.
2. inhibition of biosynthesis: inhibit key enzymes involved in amino acid or fatty acid biosynthesis.

Question 27

Why is glyphosate the most widely used herbicide and why is it seen as negative?

Answer 27

Can make seeds resistant to glyphosate which allows for farmers to use these plants and then spray the herbicide to kill weeds.

Many dislike it since it’s producing GMO plants and it binds strongly to the soil, polluting it.

Question 28

What is an endocrine disruptor?

Answer 28

A foreign substance or mixture that alters the function of the endocrine system.

Question 29

What is the mechanism of toxicity of an endocrine disruptor?

Answer 29

Mimic the structure of natural hormones, block the binding site of natural hormones to their receptors, and can influence the synthesis or metabolism of hormones.

Question 30

What is an example of an endocrine disruptor?

Answer 30

Bisphenol A:
- used in certain plastics
- can mimic the hormone estrogen
- can bind to estrogen receptors which influences the hormonal signaling pathways