This is the story of Dr. Karen
Wetterhahn. She was an internationally
respected chemistry professor at
Dartmouth College in New Hampshire. She
performed research on the effects of
heavy metals on living systems,
especially their role in causing cancer.
She was also the victim of heavy metal
poisoning, specifically dimethylmercury
poisoning.
Her story is one of the most powerful
and sobering examples of why lab safety
is not optional. Now, she was a research
advisor with people working under her.
She didn't ever need to handle chemicals
directly herself. In fact, most research
advisors don't handle day-to-day work
directly themselves. But, on August
14th, 1996,
she was handling dimethylmercury.
Why? Because she knew how toxic it was
and didn't want anyone else to have to
handle it.
She had a reputation for being
meticulous about safety, and on that
day, she was being meticulously safe and
following all of the recommended safety
precautions for handling
dimethylmercury.
Now, mercury is a neurotoxin, meaning a
toxin that affects the nervous system,
including the brain.
Think of the English idiom mad as a
hatter.
The phrase originated because a lot of
hat makers in 18th and 19th century
England had mercury poisoning. This is
because mercury compounds were used to
make felt, and then the felt was used to
make hats.
Dimethylmercury
is a lot more toxic than other mercury
compounds.
One reason is that it has a high vapor
pressure, meaning it vaporizes easily
and can be inhaled.
It also has two methyl groups and the
methyl groups make the molecule nonpolar
and therefore much more fat-soluble
than just regular mercury. So, it can
pass straight through the skin, cross
the blood-brain barrier, and get into
the brain. Now, the human brain is about
60% fat
and dimethyl mercury is fat-soluble.
So, a lot of it ends up in the brain.
Dr. Wetterhahn later recalled that on
that day that she was handling the
dimethyl mercury, just a couple of drops
spilled from the end of the pipette and
onto her glove.
She didn't panic. The drops just touched
her glove, which should protect her
skin.
She was using a fume hood, so she
shouldn't have to worry about the high
vapor pressure or inhaling the vapor.
She was doing everything that she was
supposed to be doing to stay safe.
She didn't think she was in any
immediate danger. So, she cleaned up the
area before removing her gloves.
What Dr. Wetterhahn didn't know at the
time was that dimethyl mercury also goes
right through latex gloves.
So, those drops that hit her glove and
the time she took to clean up the spill
properly were a huge problem.
Dimethyl mercury can actually permeate a
lot of plastic and rubber compounds. So,
later tests showed that it can actually
permeate latex gloves and enter the skin
in about 15 seconds.
And if the gloves aren't an effective
barrier,
that means that this extremely toxic
form of mercury actually touched her
skin,
passed straight through her skin, and
into her bloodstream. And from there, it
could go through the blood-brain barrier
and find its way into the brain without
her even knowing.
There was no pain,
no burning, no sign that anything was
wrong.
About 3 months later, she started having
brief episodes of abdominal pain
and noticed significant weight loss.
5 months after the initial incident, she
started having the more distinct
neurological symptoms of mercury
poisoning, like loss of balance and
slurred speech.
Around this time is when she sought
medical attention.
At this point, tests showed that she had
severe mercury poisoning. Her blood
mercury content was about 4,000
micrograms per liter with a toxicity
threshold of only 200 micrograms per
liter.
Her urinary mercury content was 234
micrograms per liter with a toxicity
threshold of only 50 micrograms per
liter. And normal ranges for those are
both much, much lower, and preferably
zero.
But,
the problem with these tests is that
blood and urine are both water-based.
And dimethyl mercury is highly
fat-soluble.
So, it had to have been in much higher
concentrations
in bodily organs that were fatty, like
the brain.
She had aggressive chelation therapy,
which is when you use a large molecule
called a chelating agent that binds to
the mercury and leaves the body through,
in this case, urine.
The treatment was reducing the amount of
mercury in her body because more mercury
started passing out through her urine.
But, her condition deteriorated rapidly.
Why?
At this point in time, a lot of the
dimethylmercury had time to make its way
into the fatty parts of her body.
The chelating agent was predominantly
removing mercury from the water-soluble
tissues like the blood and urine.
It was too late. She was still getting
worse.
About 3 weeks after the first
neurological symptoms appeared,
she was in a vegetative state
punctuated by periods of extreme
agitation.
She died
on June 8th, 1997,
about 10 months after her initial
exposure.
Her exposure timeline was confirmed by
analysis of her hair, which showed a
huge jump in mercury levels 17 days
after the lab incident with a peak at 39
days,
followed by a gradual decline. So, this
wasn't long-term accumulated exposure
over the course of her career.
It was one specific incident.
Her story showed that standard safety
precautions, which she was following,
were completely inadequate for super
toxic chemicals like dimethylmercury.
Her story shook the scientific world. It
rewrote lab protocols. It led to
research about glove compatibility and
the creation of glove compatibility
charts, stricter fume hood guidelines,
and a giant rethinking of how we handle
toxic substances.
OSHA, the Occupational Safety and Health
Administration in the United States,
noticed.
They now recommend the use of
dimethylmercury be completely avoided
unless absolutely necessary. And they've
mandated the use of these plastic
laminate gloves called silver shield
when handling the compound.
Dr. Wetterhahn wanted her story to be
shared.
Her legacy includes significant and
lasting improvements to lab safety.
If you ever spend time in a lab, I'm not
trying to scare you. This isn't about
instilling fear of all chemicals.
Statistically, being in a chemistry lab
is safer than driving a car or being on
a sports field.
But, it is your job to keep it that way.
Every lab safety rule has a reason.
Every one of them was written based on
someone's experience. Some of them even
have someone's life behind them.
Please take the lab safety rules that
you are supposed to be following
seriously.
Thanks for watching chemistry in a
nutshell.
This is the story of Dr. Karen
Wetterhahn. She was an internationally
respected chemistry professor at
Dartmouth College in New Hampshire. She
performed research on the effects of
heavy metals on living systems,
especially their role in causing cancer.
She was also the victim of heavy metal
poisoning, specifically dimethylmercury
poisoning.
Her story is one of the most powerful
and sobering examples of why lab safety
is not optional. Now, she was a research
advisor with people working under her.
She didn't ever need to handle chemicals
directly herself. In fact, most research
advisors don't handle day-to-day work
directly themselves. But, on August
14th, 1996,
she was handling dimethylmercury.
Why? Because she knew how toxic it was
and didn't want anyone else to have to
handle it.
She had a reputation for being
meticulous about safety, and on that
day, she was being meticulously safe and
following all of the recommended safety
precautions for handling
dimethylmercury.
Now, mercury is a neurotoxin, meaning a
toxin that affects the nervous system,
including the brain.
Think of the English idiom mad as a
hatter.
The phrase originated because a lot of
hat makers in 18th and 19th century
England had mercury poisoning. This is
because mercury compounds were used to
make felt, and then the felt was used to
make hats.
Dimethylmercury
is a lot more toxic than other mercury
compounds.
One reason is that it has a high vapor
pressure, meaning it vaporizes easily
and can be inhaled.
It also has two methyl groups and the
methyl groups make the molecule nonpolar
and therefore much more fat-soluble
than just regular mercury. So, it can
pass straight through the skin, cross
the blood-brain barrier, and get into
the brain. Now, the human brain is about
60% fat
and dimethyl mercury is fat-soluble.
So, a lot of it ends up in the brain.
Dr. Wetterhahn later recalled that on
that day that she was handling the
dimethyl mercury, just a couple of drops
spilled from the end of the pipette and
onto her glove.
She didn't panic. The drops just touched
her glove, which should protect her
skin.
She was using a fume hood, so she
shouldn't have to worry about the high
vapor pressure or inhaling the vapor.
She was doing everything that she was
supposed to be doing to stay safe.
She didn't think she was in any
immediate danger. So, she cleaned up the
area before removing her gloves.
What Dr. Wetterhahn didn't know at the
time was that dimethyl mercury also goes
right through latex gloves.
So, those drops that hit her glove and
the time she took to clean up the spill
properly were a huge problem.
Dimethyl mercury can actually permeate a
lot of plastic and rubber compounds. So,
later tests showed that it can actually
permeate latex gloves and enter the skin
in about 15 seconds.
And if the gloves aren't an effective
barrier,
that means that this extremely toxic
form of mercury actually touched her
skin,
passed straight through her skin, and
into her bloodstream. And from there, it
could go through the blood-brain barrier
and find its way into the brain without
her even knowing.
There was no pain,
no burning, no sign that anything was
wrong.
About 3 months later, she started having
brief episodes of abdominal pain
and noticed significant weight loss.
5 months after the initial incident, she
started having the more distinct
neurological symptoms of mercury
poisoning, like loss of balance and
slurred speech.
Around this time is when she sought
medical attention.
At this point, tests showed that she had
severe mercury poisoning. Her blood
mercury content was about 4,000
micrograms per liter with a toxicity
threshold of only 200 micrograms per
liter.
Her urinary mercury content was 234
micrograms per liter with a toxicity
threshold of only 50 micrograms per
liter. And normal ranges for those are
both much, much lower, and preferably
zero.
But,
the problem with these tests is that
blood and urine are both water-based.
And dimethyl mercury is highly
fat-soluble.
So, it had to have been in much higher
concentrations
in bodily organs that were fatty, like
the brain.
She had aggressive chelation therapy,
which is when you use a large molecule
called a chelating agent that binds to
the mercury and leaves the body through,
in this case, urine.
The treatment was reducing the amount of
mercury in her body because more mercury
started passing out through her urine.
But, her condition deteriorated rapidly.
Why?
At this point in time, a lot of the
dimethylmercury had time to make its way
into the fatty parts of her body.
The chelating agent was predominantly
removing mercury from the water-soluble
tissues like the blood and urine.
It was too late. She was still getting
worse.
About 3 weeks after the first
neurological symptoms appeared,
she was in a vegetative state
punctuated by periods of extreme
agitation.
She died
on June 8th, 1997,
about 10 months after her initial
exposure.
Her exposure timeline was confirmed by
analysis of her hair, which showed a
huge jump in mercury levels 17 days
after the lab incident with a peak at 39
days,
followed by a gradual decline. So, this
wasn't long-term accumulated exposure
over the course of her career.
It was one specific incident.
Her story showed that standard safety
precautions, which she was following,
were completely inadequate for super
toxic chemicals like dimethylmercury.
Her story shook the scientific world. It
rewrote lab protocols. It led to
research about glove compatibility and
the creation of glove compatibility
charts, stricter fume hood guidelines,
and a giant rethinking of how we handle
toxic substances.
OSHA, the Occupational Safety and Health
Administration in the United States,
noticed.
They now recommend the use of
dimethylmercury be completely avoided
unless absolutely necessary. And they've
mandated the use of these plastic
laminate gloves called silver shield
when handling the compound.
Dr. Wetterhahn wanted her story to be
shared.
Her legacy includes significant and
lasting improvements to lab safety.
If you ever spend time in a lab, I'm not
trying to scare you. This isn't about
instilling fear of all chemicals.
Statistically, being in a chemistry lab
is safer than driving a car or being on
a sports field.
But, it is your job to keep it that way.
Every lab safety rule has a reason.
Every one of them was written based on
someone's experience. Some of them even
have someone's life behind them.
Please take the lab safety rules that
you are supposed to be following
seriously.
Thanks for watching chemistry in a
nutshell.