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
____is used as a preservative in vaccines. Can that be harmful for us?
Thimerosal
can degrade to ethylmercury in the body, so some think it’s harmful.
BUT the body doesn’t accumulate it, and there’s no evidence of adverse health effects from thimerosal so it’s fine
Minamata disease=
How did it get its name?
mercury poisoning
named b/c of a mass mercury poisoning in Minamata Bay, Japan when a corporation dumped wastewater containing methylmercury straight into the Bay
Chisso Corporation dumped methylmercury waste into Minamata Bay from ____-___.
___ (and feral cats!) were most affected, showing signs of _____ damage
___ deaths reported
1932-1959
children
neurological damage
900
how did the people of Minamata Bay accumulate so much mercury?
biomagnification!
They ate lots of fish and other seafood
also drinking water/ swimming
Give an example of a Canadian case similar to Minamata Bay
Grassy Narrows Reserve in Ontario
- pulp and paper plant dumped Hg into the water for over a decade (1960-1976)
- first nations most impacted
- Drs from Minamata Bay were called in to help
The burning of ____for energy is responsible for most of airborne mercury in Canada
coal
stop using coal as energy!
Facts about Lead:
- resistant to ___
- very ___(soft/hard)
- usually mined in the form of _____ ___, found near zinc ore deposits
corrosion
soft
lead sulfide
List 4 things that lead has been used for in history
- makeup powder
- used to make water pipes
- paint additive (speed up drying, more durable)
- additive to gasoline (antiknocking)
Toxicity of Lead:
- ___toxin
- can also cause ___ disorders
- ____ or ingested
- induces ___ stress that can damage ____ and enzyme function
neurotoxin
blood
inhaled or ingested
oxidative stress
DNA
Lead bioaccumulates in several tissues
(List 4)
- blood
- soft tissues
- bone
- teeth
___ is the most sensitive to lead, and ___are at the highest risk
lead exposure correlated with _____ disabilities and reduced __ size
the brain
children
intellectual
brain
The largest lead emissions used to come from ___, but now are from the ___ and ___ of base metals
automobiles (lead gasoline)
smelting and refining of base metals
Why do older people now have a higher [Pb] than younger people ?
More exposure when they were younger and it stayed there `
Lead bioaccumulates, but it doesn’t ____ very well. Why?
biomagnify
it’s in the bones which usually aren’t consumed
What occurred in Flint, Michigan in 2014-2015?
Flint water crisis= lead poisoning in Michigan (Flint river)
- city switched drinking water source from Detroit system to the flint river (to save money)
- chlorine was added, which corroded the lead pipes
- [lead] was extremely high
- finally switched back to Detroit water, but lots of legionnaire’s disease (severe pneumonia) linked to water quality
