Final Flashcards
(30 cards)
What important expression is Paracelsus credited with?
“Everything is toxic, nothing is toxic; the dose makes the poison.”
Why is Paracelsus’ expression important?
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.
Why is an understanding of modifying factors helpful with reproducibility?
Controlling variables to ensure consistent results.
Why is an understanding of modifying factors helpful with comparability?
techniques that enable cross-study comparisons.
Why is an understanding of modifying factors helpful with applicability?
Assume findings to other scenarios and enhance risk assessment.
Explain how the plant or animal’s health can act as a modifying factor for the effects of contaminant exposure.
- immune system function: health status of an organism influences the efficiency.
- metabolic rate: a healthy organism might metabolize more efficiently than a stressed/diseased one.
- life stage: the overall health of an organism may fluctuate with age, influencing the ability to deal with contaminants.
List the four major classes of chemical interactions that can occur in the environment.
- no interaction: no amplification or reduction of effects.
- strict addition: do not interact to amplify or reduce effects.
- synergistic: amplifies the overall impact.
- antagonistic: counteracts or reduces the overall impact.
Which chemical interaction often applies to chemicals that share a similar mode of toxicity?
Synergistic effects since the combined effect is greater than the sum of them acting independently.
What is hormesis? Include a graph.
Low-dose amounts have a beneficial effect and high-dose amounts are toxic
What chemical property strongly enhances its ability to bioconcentrate?
Lipophilicity: the tendency of a chemical to dissolve in lipids or fats.
What type of biological tissue is involved in bioconcentration?
Fatty tissue due to their affinity for lipid-based environments, anything highly lipophilic.
What is biomagnification? Include a diagram.
The process by which the concentration of certain substances increase at higher trophic levels in a food chain.
What two properties of a chemical strongly increase the potential for it to bioaccumulate?
Lipophilicity: fat-soluble chemicals.
Low metabolic degradation: chemicals that are resistant to breakdown/slow to break down.
Why does the concentration in the environment provide a poor surrogate for exposure?
You can have low concentrations, but because it accumulates over time, you can still end up with very high concentrations in a top predator.
What is ionizing radiation?
A form of radiation that has enough energy to remove tightly bound electrons from atoms.
What part do free radicals play in the mechanism of toxicity displayed by ionizing radiation?
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.
What is a cascade mechanism of free radical propagation and how does water assist?
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.
What is somatic DNA damage?
Damage to enzymes, structural proteins, lipids, cell membranes, organelles, and may result in cell mutations and cancer.
What is genetic DNA damage?
Damage to DNA and chromosomes in reproductive tissue can result in birth defects and organism mutations.
What are the three primary mechanisms of toxicity attributed to metal exposure?
- block essential functional groups on enzymes.
- displace essential metals in enzymes.
- modify conformation of biomolecules.
How can your body develop a tolerance to metal exposure?
Metal halides float around and give metals a place to interact with, having no other function.
What is the mechanism of toxicity associated with narcosis?
Non-specific type of reaction resulting in anesthesia of the organism.
Why is narcosis considered reversible?
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.
What changes were made of pesticides from chlorinated organics to modern botanicals?
“Dilution is the solution to pollution.” Pesticides were developed to be more water soluble, less persistent, and more selective.
