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Case Study: Mercury Bioaccumulation and Biomagnification

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Emma Chiu

on 11 March 2015

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Transcript of Case Study: Mercury Bioaccumulation and Biomagnification

What is in some fish that caused the EPA and FDA to issue the restriction?
Examples of Biomagnified compounds
Polychlorinated biphenyl
Aldrins
Where in the US are mercury depositions highest? What explains this pattern?
The East coast has the most mercury depositions. It can also be seen that major cities have larger depositions of mercury. This is probably due to an increased industry in these regions than others.

What human actions lead to increased Mercury levels in the environment?

In which samples were mercury concentrations the highest (fish, streams, or sediment)? Why do you think this is?
Case Study: Mercury Bioaccumulation and Biomagnification
Nearly all fish and shellfish contain traces of mercury
Why are there restrictions for pregnant women and young children, but not the rest of the population?
For most people, the risk from mercury is not a health concern. Yet, those fish and shellfish that contain high levels of mercury may harm an unborn baby or a young child’s developing nervous system.
Do pregnant women have to avoid all fish? Explain.
No
they only have to select fish that are known to be very very low on mercury
avoid altogether the ones that are high on it
for example: Shark, Swordfish, Mackerel, or Tilefish. Other than that, be moderate on the consumption of low mercury level fish, limiting to 1 or 2 meals maximum per week.
Should Amanda have avoided the pan-seared tuna for lunch?
Since tuna is a low level mercury containing fish, she could’ve eaten this one meal. However, she couldn’t have consumed any more fish that week.
Case Study: Tuna for Lunch?
Main Ideas of Case
Amanda and Tara are close friends who were meeting for lunch one day.
Amanda is pregnant
Refrains from eating certain types of fish (Tuna) once or twice a week because of doctor's recommendation.
Already cut back on coffee and alcohol
Had doubts; why did she need to cut back on tuna?
Asks Tara for more information about biology
The concern level for piscivorous mammals is 0.1 Hg ug/g.
Which fish species have average mercury concentrations that exceed this limit?

Why is the mercury level for piscivorous mammals lower than the level for human health?
It is estimated that all fish species except for the channel catfish surpass the limit of average mercury concentrations of piscivorous mammals.

The mercury level for piscivorous mammals is lower than in human health because as the animal is less likely to have come into contact with mercury as much as humans, it is more likely for humans to have developed a resistance mechanism that would exceed the level of that of piscivorous mammals in comparison.


Should you be concerned about mercury toxicity if you catch and eat a largemouth bass in a local lake? Why or why not?
You should be concerned about eating a largemouth bass in a local lake, given the circumstances.
Industrial or coal-burning plant
Frequent rain and high levels of precipitation--transportation of mercury
you should be concerned about mercury toxicity.
If the largemouth bass has no possibility of coming into contact with mercury, there is no reason for you to be concerned.
Coal burning plants are the most common source of mercury pollution.
Coal is naturally contaminated with mercury, and when the coal is burned and the mercury is released into the air, the mercury is deposited in rain (wet deposition) or it falls from the sky (dry deposition) onto the ground or water.
How does mercury end up in fish? Draw flowchart
Coal Burning Power Plant->Mercury in Air
->Mercury in Water -> Mercury Absorbed in Water -> Fish take in the water and mercury.


Should you be concerned about mercury toxicity if you catch and eat a largemouth bass in a local lake? Why?
Eating a single fish should not be enough to cause problems within your system, even if the fish is known for having relatively high mercury concentrations. It is a problem, however if they are consumed regularly.
Sediment, because it can be in both ground and water, making it absorb more mercury and it is where it resides before it becomes part of runoff.


The toxin can enter the biosphere by:
residue of products with coolants such as fire retardants and light bulbs.
Bits of plastic, cement (an atmospheric carrier), and paints are also carriers because PCBs are used for their plasticizing properties.
PCBs are organochlorides, so PCBs, like DDTs, can remain in the atmosphere for years.
The side effects of contact with PCBs cause endocrine system disruptions, and thyroid problems.
These problems stem into reproductive system issues, with men producing less semen and women having trouble getting pregnant.

Aldrins are pesticides--low solubility in water
persist in the environment and are extremely toxic for fish, with a lethal dose at 0.006 for trout and bluegill.
This is potentially extremely dangerous for people who live on coasts whose sustenance consists of fish from aldrin-contaminated waters, and toxic for animals who feed on trout and bluegill.
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