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Perspective on the Toxicity of Ethylene Glycol: Bushy Run to DART
William Snellings, Union Carbide, CT
DR. DE SESSO: Our first speaker today who will tell us a little bit about the background of this chemical
and how we got to where we are today is Dr. William Snellings.
Bill received his PhD in toxicology from the University of Michigan and Ann Arbor and has spent much of
his career either at Bushy Run or Carnegie Mellon and then at Union Carbide. He is one of the old-time
inhalation toxicologists, and he told me I had to tell you that his age can be indicated by the fact that he used
wooden chambers.
(Laughter.)
DR. DE SESSO: And if that is the kind of introduction he needs, then that is the kind of introduction he
gets, and at this point we will let Bill take over.
DR. SNELLINGS: I am Bill Snellings, and I really am honored to be a part of this group.
I was here about 20 years ago talking on ethylene oxide, and I think John Cleary was probably in the
audience.
We were doing some work, research on ethylene oxide and today we are going to talk on ethylene glycol
with an esteemed panel and a group of researchers, and my job is just really to introduce, just to give you
a quick overview of about 40 years of research and open it up to the true researchers to show you what we
have been doing recently.
With ethylene oxide simply all you have to do is add water, and you have ethylene glycol. So, I haven’t
moved too far from one of the parent compounds, and I have here a list.
I will bring this back to the topic, but these are some lessons to learn, and really I would hope by the end
of the day that you will appreciate or understand the points that I am making here, but as you can see in
1949, actually it was at my second birthday my mother instructed me, “Son, don’t eat too much ice cream
and definitely not too fast.”
You know, you get the pain above the eye, and I must have had a real big issue or problem with ice cream
that year because my father, also said, “Don’t lick the ice cream off your arms and face.”
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I had gotten it all over myself, and another lesson to learn which will be related again back to the research
of today, my best friend at my thesis dissertation when I had an unreasonable professor asking too many
questions, he told me later, “Not everybody is a rat.”
(Laughter.)
DR. SNELLINGS: So, I will hopefully bring all this back to some sense, but I think it is pretty interesting,
and I don’t have much time to go through but ethylene glycol was first really manufactured, I mean it was
made in the 1800s but Union Carbide was the first to produce it on a big scale.
In 1937, the Chemical Hygiene Fellowship was started. Some of you now know the name. It is called
Bushy Run Research Center.
Unfortunately, it is not in existence any longer, but in 1937, Henry Smith, and probably some of you know
him, he was one of the founding fathers of industrial toxicology started the lab, and sure enough the first
report that came out of that laboratory was on ethylene glycol.
It was an acute study, and you can see in the forties and the seventies; I am not going to go through them,
but there were lots of studies, subchronic repetitive exposure studies and it really wasn’t until in the
midseventies that some of the longer-term studies were started.
Industry did one. Government did one, but the reproduction studies, that was a three-generation repro-
duction study and basically at the top level, and now this reproduction study was in the diet. Ethylene glycol
was in the diet and even at the top dose really not too much was found.
In 1978, again at Chemical Hygiene Fellowship Bob Marenpot did a study with ethylene glycol. Again, it is
in the diet, and this is all going to come back, hopefully, in a few minutes so that you can understand a little
bit more about dose rate, and 1983 was the first time that we really were getting some findings.
By the way in 1978, again at the top dose there really wasn’t anything there at 1000 milligrams per
kilogram. Price and Kimmel and Tyle, I believe that is the ones were doing some work on gavage, rat and
mouse, and they found significant effects, many different ones, but the lowest dose was still an effect level.
As you will see we continued to do gavage work, but what was scheduled at that time was to do an
inhalation study, and I will have a couple of slides in just a minute to show you some of the problems that
we had with the inhalation work, but we ran a whole body; that is where you put the animal in the
chamber and by that time it was not wooden chambers, thank you, but we exposed them to an aerosol and
I will tell you why it had to be an aerosol when I get to those slides.
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In 1986 and, also, 7 years later and now another 7
years later we have taken a sort of a break in the
research and tried to come to the scientific com-
munity and share what we have done and ask ques-
tions. How are we; are we going the right way?
So, that was the first time three people, Carol
Kimmel being one of them and Neil Chernof and
Bruce Stewart; Bruce Stewart was the leading in-
halation toxicologist at that time, and their recom-
mendation was to keep on going, but they under-
stood the problems with the whole body. Again, I
am going to explain it in a second but recom-
mended that we do a nose only.
So, sure enough the problems with inhalation test-
ing, ethylene glycol has a very low vapor pressure.
So, to get to a reasonable concentration you have
to cook it quite a bit or you are going to have to
turn it into an aerosol.
If we had a saturated vapor concentration in this
room it is around 200 milligrams per cubic meter,
very difficult, if not impossible to obtain, and we
saw nothing at that level.
You have to go up to 2000 milligrams per kilo-
gram, at least we thought so in the preliminary work
to see any type of biological events in the mothers.
I don’t know if anyone has ever done a limit dose
or a limit concentration test in this room, but I
wish you could see what 2000 milligrams per cu-
bic meter is a limit concentration.
Some regulatory groups say that any concentration
higher than that is considered not to be toxic on an
acute basis, but it is a rainstorm. I am talking a
rain forest rainstorm. You cannot see the animals
at that concentration, but we had to go that high
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because we didn’t think that we could get any bio-
logical response, at least in the mothers.
Another confounding part was ethylene glycol is an
irritant. The government has done work on humans,
20 volunteers. Actually they were prisoners who were
exposed to aerosols of ethylene glycol, and they found
out that at around 300 milligrams per cubic meter
that they could only breathe that concentration for
two breaths, and after that they had to get out of the
exposure. Again, we are eight times higher than
that.
So, you have the physical impaction of aerosols, the
irritant of ethylene glycol. We did the whole body
study anyway, and we saw excessive preening. The
animals were licking their fur left and right. They
were having a good time.
We estimated after the study and when we found as
I told you a minute ago, sure enough we found the
same type of features, the facial features that we will
talk about a little bit later today, but we found those
as we did in the gavage studies, but when we took
the amount of ethylene glycol, eluted it off the fur
we found that indeed it was above a calculated LOEL
if you had ingested the material orally.
So, we said, “Maybe this wasn’t an inhalation study.”
So, we talked with some experts and they said,”If
you are concerned about irritation maybe you had
better do a nose only water study, only water,” but
again, and this is published. It is Shelly Tyle’s work.
I really enjoyed reading this.
We got, at these high concentrations of water, we
got similar effects. We got cleft palate. We got
exencephaly. We got at very lower levels, but we
were getting because of the physical impaction, and
by the way we compared it.
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We had a nose-only water aerosol and a whole body
water aerosol and we thought the restraining
mechanisms from a nose only was causing most of
the problems, but in actuality both the whole body
and the aerosol water ones were having similar type
effects, and it was due to this high concentration,
the physical impaction of the water.
Maternal trauma, everything from swelling of the
face to exudates around the nose and the nares and
the eyes, so, what we decided after talking to con-
sultants don’t use air as the control. Use the water
as the control, and so, we did a nose only ethylene
glycol study, but indeed we did, we still got the
maternal trauma.
They were struggling so much that they broke the
seals, the dam. The nose sticks through a dental
dam and what ended up happening is that some of
the ethylene glycol aerosol actually did get onto the
face of the animals.
So, we were quite concerned and still are that this
study is well done, but part of the problem was we
had contamination. We had an oral study at the same
time.
I will show you at the end of my brief talk just some
of the numbers so you get a better appreciation for
how much the oral ingestion in these studies plays
a part.
So, we continued after doing the nose only, we did
a dermal study, and this one actually was clean, also,
and then in 1988 and 1989, we did the gavage stud-
ies to find a NOEL. Remember I said that Price,
they had not come up with a NOEL, and both rat
and mouse had a similar NOEL for ethylene glycol
by gavage.
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Since we really felt, and this is the key part of today’s
talk that the inhalation was not the way to go to assess
or at least inhalation by nose only was not the way to
go in the routine way of looking at risk assessment for
ethylene glycol.
We knew that we had to get to the higher concentra-
tions. Aerosol was the only way, but we knew the irri-
tation and the high physical impaction problems would
just cause too many variables and make it impossible
to do a good risk assessment.
So, in the late eighties we started doing metabolism
pharmacokinetics and today Ed Carney and Rick Corley
will be talking on these areas and then Shelly when she
left Bushy Run, she still was doing work on ethylene
glycol, and sure enough they did a rabbit gavage study
and lo and behold it was clean even at concentrations
that killed the mothers.
So, we had some species difference then. Chris
Newsome and Otto Grundler will be talking about spe-
cies differences. Then in 1993, 7 years later we, again,
had a data dump so to speak, and with Jack Moore
when they were working on the risk assessments on
developmental and reproductive toxicants ethylene gly-
col was reviewed, and George Daston is here today,
and he was part of that, too.
So, we had a major review and some really good sug-
gestions were given to us for filling data gaps. Mode of
action we really started and Ed is going to be speaking
on that; developing a PBPK, Rick will talk on that, and
as I said the species differences, and here we are at the
year 2000.
So, how does this all come back to what I initially said?
All right, don’t eat too much ice cream and definitely
not too fast.
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We know that at high concentrations that with ethylene glycol you are going to have in animals, at very high
concentrations you are going to have some issues with developmental toxicity.
Dose rate effect is key here. You can take the same dose. Here it is in the diet. This is in the rat, and the
NOEL is 1000, but if you give that quickly as in a gavage that 1000 now turns into an effect level with
significant adverse effects, malformations and variations.
You give the dose slowly dermally because it is a slow absorption and not as well absorbed and again you
are much, much higher in concentration before you get a LOEL.
So, that is my little take on dose rate. Don’t eat it too fast. Don’t lick the ice cream off your arms and face.
That goes back to this whole body exposure.
Remember I told you that they were licking the material off their bodies. The NOEL for that study even
though it was an inhalation study with oral ingestion, it was 150 milligrams per cubic meter, we reduced
dramatically reduced the amount of oral ingestion by going to the nose only.
We still think there was significant oral ingestion, but look at that. It changed the NOEL by an order of
magnitude. So, definitely what is on the fur can affect the inhalation study.
Not everybody is a rat. That goes to the species differences. The rat NOEL is 500 milligrams per kilogram.
The rabbit is greater than 2000. They did not come up with a LOEL.
So, again, I hope by the end of our talk you can appreciate better with the science some of my little funny
stories. So, with that I guess I will entertain any questions, but I didn’t really produce any data.
So, I won’t feel bad if I don’t have questions, but I will be glad to answer any questions along with the
panel, but is there a question before we give it to the scientists giving you all the background data?
All right, let me turn it over to Ed.
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