Lecture 4 Flashcards
Name 2 examples of metals:
- Arsenic
- Mercury
T or F: Metals are found on the periodic table, cannot be created / cannot be destroyed - the amount on the planet is relatively constant
T
Give some general principles about metals:
- They are ubiquitous because of countless uses in industry and commercial and consumer products
- They are elemental because they do not breakdown
- They can be inhaled, ingested; some are absorbed through the skin
- Many bioaccumulate in the ecosystem, increasing exposure to people
- Many bioaccumulate in our bodies
T or F: Some metals are essential for nutrition but even these are toxic at high quantities
T
What types of toxicity is caused by a high quantity of metals?
- neurotoxicity
- kidney toxicity
How can you treat metal toxicity ?
With chelators, they suck the metals out but the danger is that the chelators with chelate other things out and create deficiencies.
T or F: Chelators are good for treating chronic metal toxicity?
F
Name the 3 general toxic mechanisms of metals:
1- Promoter of oxidation
2- Competition for divalent cation binding sites (ex: calcium or iron-dependent systems)
3- Binding of sulfhydryl groups (methionine and cysteine can become targets and cause misfolding of proteins)
Why do we care about metals?
Because they persist, accumulate, they are ubiquitous (local to global) and toxic
CCA:
Chromated copper arsenate
Industrial exposure of Arsenic =
exposure from use in wood preservation (CCA) and in the microelectronics industry
Environmental exposure of Arsenic =
exposure from fallout from smelters and arsenic pesticide spraying
Natural exposure of Arsenic =
deep-water well ingestion
There are hot spots of Arsenic worldwide because:
- arsenic mining is all over the world
- drinking water from aquifers contaminated with arsenic is more common
Why do some countries have a higher national standard for the level of Arsenic in drinking water?
Because these countries do not have the money necessary to treat contaminated water
____% of mercury comes from natural sources
30-40% (emissions from oceans, volcanoes, precipitation events, soils)
Coal-fired power plants, oil industry, mining (gold) =
mercury
Mercury uses:
- Small-scale gold mining
- Chlorine industry (Chlor-Alkali)
- Batteries
Explain the mercury cycle:
1) Hg-S (metals bind to sulphur)
2) Burning coal = releases Hg0
(burn that really hot - what happens is that you split that mercury-sulfate bond Hg-S and you release mercury to a 0 valence state (Hg0) 0 valence means gas/vapour form)
3) Atmospheric mercury can stay up into the air, atmospheric deposition, mercury gets oxidized Hg2+ (deposition)
4) Biomethylation (MeHg)
SRB converts Hg2+ to MeHg (increases with decrease in pH and O2 and increase in DOC)
T or F: MeHg can effectively cross membranes (BBB and placenta) and binds strongly to protein thiols
T
MethylHg is a ________________
neurodevelopmental threat
Minamata disease is linked with an increase exposure to ___________
methylmercury
Methylmercury toxicity in fish is linked with _________________
reproductive and behavioral damages
Organisms, often animals, used to detect risks to humans by providing advance warning of a danger. The terms primarily apply in the context of environmental hazards than those from other sources :
Sentinel species
Name other contaminants that we can find in fish other than mercury:
- PCBs
- Chlordane
- Dioxins
- DDT
T or F: the benefits of fish intake exceed the potential risks
T
