5. Organics

Question 1

What are organic contaminants?

Answer 1

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

Question 2

What is the “origin” of organic contaminants

Answer 2

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

Question 3

What is a hydrocarbon?

Answer 3

A molecule consisting of hydrogen and carbon.

Question 4

What is an aromatic hydrocarbon?

Answer 4

Includes an aromatic group (ring structure)

Question 5

What are PAHs?

Answer 5

Polycyclic Aromatic Hydrocarbons

Question 6

Characteristics of PAHs (5)

Answer 6

• 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)

Question 7

What are congeners

Answer 7

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

Question 8

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

Answer 8

• water soluble
• not likely to bioaccumualte
• can be acutely toxic

Question 9

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

Answer 9

• 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)

Question 10

What are HAHs?

Answer 10

Halogenated Aromatic Hydrocarbons

Question 11

Characteristics of HAHs (2)

Answer 11

• 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)

Question 12

Effects of PAHs (4)

Answer 12

• Development Abnormalities
• Carcinogenic
• Endocrine disruption
• Immune effects

Question 13

Examples of HAHs (4)

Answer 13

• dioxins
• furans
• PCBs
• some pesticides e.g. DDT

Question 14

What is the structure of dioxins

Answer 14

2 halogenated benzene rings linked together by 2 oxygens

Question 15

What is the structure of furans?

Answer 15

2 halogenated bezene rings linked together with 1 oxygen

Question 16

What is the source of dioxins and furans

Answer 16

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

Question 17

What is the structure of PCBs

Answer 17

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

Question 18

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

Answer 18

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

Question 19

Examples of DLCs

Answer 19

• dioxins
• furans
• some PCBs

Question 20

3 steps of the AHR pathway

Answer 20

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

Question 21

Issue with DLCs and the AHR pathway

Answer 21

• 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)

Question 22

How do PAHs exert toxicity through the AHR pathway?

Answer 22

• 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

Question 23

Characteristics of organic pesticides (3 points)

Answer 23

• 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

Question 24

Categories of pesticides (3)

Answer 24

• organochlorines
• organophophates
• neonicitinoids

Question 25

Characteristics of organochlorines (3)

Answer 25

* Persistent, biomagnify * Most banned in North America * Affective to combat malaria

Question 26

Examples of organochlorines (2)

Answer 26

* DDT * chlordane

Question 27

Characteristics of organophosphates (4)

Answer 27

* 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

Question 28

Examples of organophosphates (2)

Answer 28

* monocrotophos * chlorpyrifos

Question 29

Characteristics of neonicitinoids (6)

Answer 29

* 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

Question 30

Example of neoicitinods (1)

Answer 30

imidacloprid

Question 31

Example: Monocrotophos event and issues (5 points)

Answer 31

* 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

Question 32

Example: Neonicitinoids insectiside event and issues

Answer 32

* 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

Question 33

Endocrine disruption def

Answer 33

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

Question 34

What is the endocrine system?

Answer 34

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

Question 35

Estrogen signalling

Answer 35

* 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

Question 36

What is vitellogin?

Answer 36

* 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

Question 37

Another endocrine disruptor definiton (reading)

Answer 37

"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