4. Metals Flashcards
What are POPs?
Persistent Organic Pollutants
Where do POPs circulate and accumulate?
- Circulate globally, move through the atmosphere
- Accumulate in cold climates
What is the dirty dozen?
12 POPs:
- Aldrin, chlordane, DDT, dieldrin, endrin, heptachlor, mirex, toxaphene, hexachlorobenze,
- PCBs, PCDDs (dioxins), PCDFs (furans)
- pesticides
- can occur naturally
What are examples of POPs (4)
- the dirty dozen
- PAHs
- flame retardants
- TBT (tributylin)
What are PBTs?
PBTs are chemicals that are persistent, bioaccumulative and toxic
What is “persistent” related to in terms of risk = exposure x hazard?
exposure
What is “toxic” related to in terms of risk = exposure x hazard?
hazard
What is most concerning?
A chemical that is very hazardous but not persistent
or
A chemical that is persistent but not hazardous?
A chemical that is persistent but not hazardous
A chemical that isn’t persistent but is hazardous becomes concerning when the contaminant is everywhere, for example, flame retardant → you are exposed constantly even though it is not persistent
Characteristics of metals (8)
- High electrical conductivity
- Luster (shine)
- Generally cations (positive)
- Naturally occurring (they are elements)
○ Become contaminants when measured levels > background levels - Not created or destroyed
- Human activities alter availability, speciation, and distribution
- Essential nutrients AND toxicants (U-shaped dose response)
○ You need a little bit, but too much becomes bad for you - Complex chemistries → difficult to study
What is AEF?
Anthropogenic Enrichment Factor
→ The percentage that humans are responsible to having released into the environment VS what was already there
→ If humans hadn’t released any, the AEF would be 0%
What are PVALs?
Protective values for aquatic life
→ numeric levels that are considered acceptable for metals in a body of water
What is ISQGs
Interim sediment quality guidelines (a PVAL)
What are PELs?
Probable effect levels (a PVAL)
What are the general mechanisms of toxicity of metals? (3)
- Promote formation of oxyradicals
- Competition for divalent cation binding sites
- Binding of sulfhydryl
What are oxyradicals?
Reactive oxygen molecules that can cause damage to DNA.
(they can potentially lead to cancerous cells)
What does it mean “Competition for divalent cation binding sites”?
Metals often have a +2 charge and will compete with other metals with that same charge:
* e.g. calcium, iron-dependent systems
- Mercury could come in and take the place of calcium
- Metals can come in and displace iron, causes issues (e.g. hemoglobin)
What does it mean for metals to bind to sulfyhydryl
○ Sulfur containing group (also called ‘thiol’)
○ 2 sulfur containing amino acids (methionine and cysteine)
i.e. metals can bind to proteins (amino acids are what make up proteins)
What are organometallic compounds?
Organic compouds with a metal element
Characteristics of organometallic compounds (2ish)
- Can be manufactured or formed naturally
- Behave differently than the pure element
○ Propensity to biomagnify
○ May exhibit different toxicities
What are non essential metals (3)
- cadmium
- lead
- mercury
Example of an essential metal
Iron (Fe)
* it is in hemoglobin
* hemoglobin = iron containing oxygen transport metalloprotein in red blood cells
3 forms of mercury
- Elemental mercury - Hg(0)
- Inorganic mercury - Hg(II)
- Organic mercury - e.g. HgCH3 (methylmercury)
Characteristics of elemental mercury (3)
- Liquid at room temperature (e.g. in old thermometers)
- Released as a vapor when coal or other fossil fuels are burned
- Human exposure: inhalation
Characteristics of inorganic mercury (3)
- Formed when elemental mercury combines to other elements (e.g. HgCl2, Hg(OH)2, HgO)
- Can be manmade or occur naturally in environment
- Human exposure: workplace
Characteristics of organic mercury (3)
- Formed when elemental mercury combines with carbon (e.g. methylmercury)
- Biomagnifies
- Human exposure: diet, through placenta
Which form of mercury is the most concerning?
Methylmercury, because it biomagnifies
What is mercury (effect-wise)
A potent neurotoxicant
What species can mercury be found in?
Fish
Characteristics of Lead (Pb) (3 points)
- Complex chemistry: Pb2+, Pb4+, up to 4 Pb-C bonds
○ All have different fates (how they move around in the environment) toxicities - Legacy sources (banned in the 1970s)
○ Antiknock gas, paint pigment - Current source
○ Lead shot/sinkers
§ Impact on waterfowl
○ Storage batteries
Consequences of led poisonning (2)
- low IQ
- motor deficits
Examples of anions (2)
Nitrates and phosphates
Consequence of nitrates and phophates
Eutrophication → algal blooms → hypoxia
Characteristics of nitrates and phosphates
Less toxic (hazard) but released in large quantities (exposure) and can be persistent (exposure)
