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NRSC 333 > 5. Organics > Flashcards

5. Organics Flashcards

1
Q

What are organic contaminants?

A

Chemicals that contain carbon and more than one C-H covalent bond

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2
Q

What is the “origin” of organic contaminants

A

Absent from the Earth’s crust; number without limit and increasing
Background concentration approaches 0.

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3
Q

What is a hydrocarbon?

A

A molecule consisting of hydrogen and carbon.

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4
Q

What is an aromatic hydrocarbon?

A

Includes an aromatic group (ring structure)

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5
Q

What are PAHs?

A

Polycyclic Aromatic Hydrocarbons

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6
Q

Characteristics of PAHs (5)

A
  • Two or more fused benzene rings
  • Exists as complex mixtures
    ○ 100s of congeners
    ○ Additive, synergistic, antagonistic effects
  • Persistent (years to decades to break down)
  • Natural and anthropogenic sources
    ○ Natural: burning of organic matter (forest fire, volcanoes)
    ○ Anthropogenic: oil spills, charring your meat on the BBQ
  • Environmentally significant PAHs range from 2 rings (naphthalene) to 7 rings (coronene)
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7
Q

What are congeners

A

Different forms within a class
(dioxins, furans, PAHs, PCBs, all have each some congeners)

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8
Q

Characteristics of low molecular weight (LMW) PAHs? (3)

A
  • water soluble
  • not likely to bioaccumualte
  • can be acutely toxic
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9
Q

Characteristics of high molecular weight (HMW) PAHs? (5)

A
  • Hydrophobic
  • More resistant to oxidation, reduction, and vaporization
  • Can accumulate in sediments and organisms
    ○ Particularly in invertebrates (lack of metabolizing enzymes)
  • Carcinogens
  • More harmful to birds because they bioaccumulate (hazard less, exposure higher, so risk higher)
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10
Q

What are HAHs?

A

Halogenated Aromatic Hydrocarbons

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11
Q

Characteristics of HAHs (2)

A
  • Many congeners, all occur as complex mixtures
    ○ Always these → number of rings
  • Very potent and very persistent
    ○ Very potent → only need a little bit to have an effect
    ○ Longer half life (more than PAHs)
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12
Q

Effects of PAHs (4)

A
  • Development Abnormalities
  • Carcinogenic
  • Endocrine disruption
  • Immune effects
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13
Q

Examples of HAHs (4)

A
  • dioxins
  • furans
  • PCBs
  • some pesticides e.g. DDT
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14
Q

What is the structure of dioxins

A

2 halogenated benzene rings linked together by 2 oxygens

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15
Q

What is the structure of furans?

A

2 halogenated bezene rings linked together with 1 oxygen

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16
Q

What is the source of dioxins and furans

A

Not manufactured: they are products of high temperature incineration (e.g. volcanoes, forest fires, municipal garbage incineration)
* Never produced on purpose, sometimes made by accident when you’re doing things at high temperature
* For instance, agent orange was contaminated with dioxin

17
Q

What is the structure of PCBs

A

2 halogenated benzene rings linked together only by carbon (like its only a line connecting the two rings)

18
Q

What are dioxin like compounds (DLCs)? (4 characteristics)

A
  • Compounds that act like dioxins
  • They form a subset of HAHs
  • All exert toxicity through binding to the AHR
  • Very potent toxicants
19
Q

Examples of DLCs

A
  • dioxins
  • furans
  • some PCBs
20
Q

3 steps of the AHR pathway

A
  1. Contaminant binds to AHR
  2. Induce expression of metabolic enzymes (CYP1A)
  3. CYP1A metabolizes contaminant
21
Q

Issue with DLCs and the AHR pathway

A
  • DLCs turn on the pathway
  • They are not well matabolized by CYP1A
  • So the AHR pathway stays active
  • This is toxic to the cell (the continuous expression of CYP1A)
22
Q

How do PAHs exert toxicity through the AHR pathway?

A
  • PAHs bind to AHR
  • They are well metabolized by CYP1A
  • They are not considered DLCs because their toxicity occurs through a different metabolism
  • It is the product of the metabolism of PAHs by CYP1A that is carcinogenic
23
Q

Characteristics of organic pesticides (3 points)

A
  • A chemical designed and used to kill ‘pests’
    ○ e.g. herbicide, pesticide, rodenticide, fungicide
  • Diverse structures and modes of actions
  • Concerns about the safety of non-target species
24
Q

Categories of pesticides (3)

A
  • organochlorines
  • organophophates
  • neonicitinoids
25
Q

Characteristics of organochlorines (3)

A
  • Persistent, biomagnify
  • Most banned in North America
  • Affective to combat malaria
26
Q

Examples of organochlorines (2)

A
  • DDT
  • chlordane
27
Q

Characteristics of organophosphates (4)

A
  • Less persistent than organochlorines
  • Inhibit acetylcholinesterase (neurotransmitter)
  • Similar receptors in insects, birds and mammals,
    ○ So problematic because if you are targeting insects you might also hurt birds and mammals due to this
  • Extremely toxic to birds at low doses
28
Q

Examples of organophosphates (2)

A
  • monocrotophos
  • chlorpyrifos
29
Q

Characteristics of neonicitinoids (6)

A
  • Neuroactive insecticides
  • Selective: ‘safe’ for mammals and birds
  • Because they target a receptor that is specific to insects
  • Toxic for insects
  • Honey bee collapse disorder
  • More recent evidence suggests that they are toxic to birds
30
Q

Example of neoicitinods (1)

A

imidacloprid

31
Q

Example: Monocrotophos event and issues (5 points)

A
  • Withdrawn form the US market in the 1980s
  • This left a gap in the record and data
  • Still available in other countries (it was the scecond most used organophophate insectisde in the 1990s worldwide)
  • Sprayed on firelds to control grasshoppers in Argentina
  • Resulted in death of approximately 20,000 Swainson’s Hawks
32
Q

Example: Neonicitinoids insectiside event and issues

A
  • Systemic insecticide available since 1992
    ○ Applied to seed coat (not sprayed)
  • Linked to honey bee collapse disorder
    ○ Behavioral effects
    ○ Controversial, because you don’t know how much is being exposed to bees in real life
  • Toxic to birds?
    ○ Toxicity or diminished food supply
    ○ Because it targets the specific insect receptor
33
Q

Endocrine disruption def

A

exogenous substance or mixtures that alters function(s) of the endocrine system and consequently causes adverse health effects

34
Q

What is the endocrine system?

A

A system of glands and hormones that regulates distant organs through chemical signalling

35
Q

Estrogen signalling

A
  • Hypothalamus releases hormone to pituitary
  • Pit releases to ovaries
  • When estradiol (female sex hormone) is released, it travels throughout the body
  • The response to estrogen is analogous to the response of dioxin
  • Estrogen or an estrogen mimic comes into the cell, binds to the receptor, causes transcription changes,
    *Makes vitellogenin (?)
  • Problem is when there is a mimic of estrogen and binds to it not properly, for example in a male
36
Q

What is vitellogin?

A
  • Vitellogenin is a biomarker for exposure to estrogenic compounds
  • Vitellogenin (VTG) is an egg yolk precursor protein
  • Normally only produced in females during oocyte maturation
    ○ Very low background levels in males
  • Effective biomarker for estrogenic chemicals
37
Q

Another endocrine disruptor definiton (reading)

A

“An [ED] needs sufficient molecular similarity, specificity (affinity), and efficacy to achieve a potency that would interfere with the endocrine system by either: (1) mimicking a hormone produced in the body or by (2) interfering with normal binding of the hormone to its receptor and through effects on transport, synthesis, breakdown, or excretion.”
* If it really mimics your body, you are disrupting messaging system in your body that is fundamental to your growth
* That one little tweak sends out crazy signals

NRSC 333 (23 decks)

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