Heavy Metals Flashcards
The 2 heavy metals of greatest concern are
lead and mercury
what are 3 problems associated with heavy metals
- associated with particulate matter, easily transported into the atmosphere
- toxic, even in low [ ]
- can bioaccumulate
Facts about mercury:
- extremely ___
- only metal to remain ___ at room temp
- ___ heat conductor
- volatile
- liquid
- poor
mercury is often mined in the form of ____
why?
what is it?
cinnabar
- b/c Hg is rarely found in nature in free form
- it’s mercury sulfide (HgS)
- deep red crystal, used to be used as a pigment & in jewelry
Early Chinese thought that cinnabar could:
Mercury was first mined in Spain over ___ years ago (workers would get sick and die)
prolong life
2000 yrs
Where does “Mad as a Hatter” saying come from?
Hat makers dipped felt hats in mercury to soften it
- caused twitching and dementia
Mercury is not biodegradable, but converts into different forms.
List 3 common forms of Mercury:
Elemental Mercury (Hg)
- can be mixed with other metals –> forms alloys called amalgams
Inorganic Mercury (mostly Hg 2+)
- ionic mercury (elemental form oxidized, precipitated)
Organomercury (mostly MeHg+)
- this is the form of greatest concern
- highly toxic and persistent
- methylmercury and other forms
methylmercury, dimethylmercury, ethylmercury, diethylmercuty, merbromin, and thiomersal are are _____
organomercury
Why is organomercury the most toxic form or mercury?
readily absorbed through the skin, and it’s bioavailable to organisms (unlike elemental and inorganic mercury)
- therefore can bioaccumulate
what is the methylation of mercury and where does it happen often?
give steps
inorganic (Hg2+) to organomercury
happens a lot in lakes & oceans
SO4 2- –> S2-
S2- + Hg 2+ –> HgS (cinnabar)
HgS + ? ___ –> CH3Hg (byproduct of respiration)
mercury is a __toxin and ____, which means it increases ____ ____ in the body, and exposure to mercury in pregnancy can cause severe ___ ____
neurotoxin
teratogen
oxidative damage
birth defects
most instances of mercury poisoning occur due to contact with ___, and particularly ____
organomercury
methylmercury
why is methylmercury so toxic?
- readily absorbed by digestive tract of humans (& other tissues)
- from there it can be easily transported across the blood-brain barrier & placenta
why does methylmercury get absorbed by our tissues so readily compared to other things/ other forms of mercury?
- it binds with the amino acid L-cysteine
- body mistakes this methylmercury-L-cysteine for another amino acid, L-methionine, which is the building block of other protein
- what happens is the methylmercury replaces L-methionine, which becomes very problematic
what’s the difference between methylmercury and other forms such as ethylmercury when it comes to accumulating in tissues?
even though some other forms (like ethylmercury) can cross the blood-brain and placental barrier, they don’t accumulate in tissues the same way
- body can flush out ethylmercury, but accumulates methylmercury
