Third National Report
on Human Exposure to Environmental Chemicals
July 21, 2005
DR. GERBERDING: Hi; good afternoon. Thank you for joining us today. I
have great news to report today. We have just completed and are announcing
the release of the new exposure report for the 148 potentially toxic
chemicals of interest to human health. This report is a breakthrough for
CDC. It is the largest and most comprehensive report of its kind ever
released anywhere by anyone, and it really provides a giant step forward
in our ability to understand the relationship between exposures to various
chemicals and potential human health effects.
We also like to say that many times, CDC is a national treasure.
Certainly our environmental health program is more than a national
treasure. I think in this regard it is an international treasure and the
data in this report are used not only for us to understand what levels of
exposures people are experiencing to various chemicals but, more
importantly, what are the human health consequences of those exposures?
Where do we need to do more research? How are our public health system and
responses affecting the levels of exposure, over time, and where do we
really need to focus the lens in our research to get more data and take
even more action for combating these threats?
What I'm going to do is just highlight some of the most important
components of the report. If I can just draw your attention here to this
graphic, which I think you can see represents the levels of lead in
children over time.
This exposure report is based on a representative population of the
U.S. government, excuse me, of U.S. citizenry. It is compiled from the
experience of our NHANES study which assures us that we do have a
representative population and we can follow the population over time.
What you can see here is among children in the United States, between
the ages of one and five years old, who are included in the sample, the
proportion with blood lead levels above 10 micrograms per deciliter has
dropped precipitously over the past several years, so that in this most
recent exposure report, only 1.6 percent of children had elevated blood
Now of course this doesn't mean that children with any detectable lead
in their blood are safe from the complications of lead and we don't know
what is the safe level, so we continue to strive to assure that all
children are free from lead exposure in their home, in their environment,
but nevertheless, this is an astonishing public health achievement and I
think really speaks to the removal of lead from gasoline, which was one of
the major correlates of this reduction but also the lead abatement
programs and other steps, being able to screen, treat and protect children
from lead exposure.
I'd also like to point out another very, very important public health
These data represent, by age, between 4 to 11 years old, 12 to 19 years
old, and 20 to 74 years old, the concentration of cotinine in the blood.
This is a nicotine byproduct. These blood measurements are based on
representative sample of the United States non-smoking population. So what
this really reflects is exposure to passive tobacco use, and what you can
see for the various age groups, that over the last decade there has been
an astonishing reduction in exposure to tobacco smoke in the environment,
so-called passive or secondhand smoke. For children, for example, there's
been a 50 percent reduction in exposure to these tobacco byproducts, and
even among adults, there's been an astonishing decrease.
While this is very, very good news and I think really addresses the
utility of the tobacco use laws, it does disguise a very important piece
of information that deserves further research, and that is while these
population levels have decreased among African Americans at any age, there
is not this degree of reduction, and so we have a disparity, and the
reductions are being experienced primarily by non-African Americans but
not by African Americans.
This could represent ongoing exposure, tobacco, or possibly some
genetic differences, but I think right now the leading hypothesis is that
there is a disparity in the exposure levels to tobacco and tobacco smoke
and the environment of people represented in the African American
community. So we have work to do in this regard.
Now let me talk about a couple of other, we think very important
findings from the exposure report.
One relates to a chemical called cadmium, c-a-d-m-i-u-m, which is a
chemical that is primarily associated with exposure to cigarettes through
Our exposure report shows that about 5 percent of our population, 20
years and older, had cadmium levels in their urine that were close to the
point at which there was concern for health effects.
We don't know that there is a direct association but certainly finding
cadmium of this level indicates a need for further research, and that
allows me to illustrate one very important concept of this whole exposure
CDC, as I said, is the international treasury for being able to measure
these chemicals in the blood but there are other agencies, including the
Environmental Protection Agency and the National Institute of
Environmental Health, that conduct research. We also work with the FDA and
with academicians in a variety of centers around the country to study the
relationship between these exposure levels and human health effects.
CDC is currently collaborating on 50 to 75 research projects going on
in academic centers around the country to really take what we are focusing
the lens on in the exposure report and delve into more detail do these
situations present a risk to pregnant women? Do they represent a risk to
developing children or infants? Is there additional evidence of disparity
in exposure and health effects?
So knowing the levels that are present in the population has a very
important use in defining the research agenda and helping us explore
further what needs to be done about the problem.
Let me just say a couple of words about mercury because the exposure
report provides information about exposure primarily to methyl mercury and
remember, methyl mercury is the form of mercury that comes from exposure
to shellfish and other food products that contain methyl mercury that's
accumulated from other sources.
Mercury exposure is particularly important to women of child-bearing
age because mercury levels above 58 micrograms are associated with
neurodevelopmental effects in the fetus.
Our exposure reports that no women in the survey had mercury levels
that approached this concentration but we do see that a small percentage
of women, about 5 point--percent--5.7 percent of women had levels within a
factor of ten of what has been defined as the health threshold effect.
So we have no conclusive information of harmful effects associated with
this. Again it shines a light on the need for very specific information,
studying women who have concentrations in this range, and identifying
what, if any, the fetal effect might be.
But in addition, it helps us hone in on areas where we may need to be
doing more measurement and more precise measurement and, hopefully, over
time, the association between very accurate measures of exposure and very
tight studies of the relationship between exposure and potential risk can
help us improve our awareness and the need for additional public health
interventions in this domain.
We've got some good news about pesticide exposure in this report,
particularly the organochlorine pesticides. These are compounds like
Aldrin and Endrin and Dieldrin, which has been used in the United States
in decades past that were largely eliminated from use in the late 1980s,
and what the exposure report shows is that since these chemicals have no
longer been used as pesticides, we have virtually eliminated them from the
human population. So over time there's been a decay, the pesticides have
been eliminated from our environment and people are no longer experiencing
any potential risk from exposure to them.
Let me talk about another chemical that's important, a bit hard to
spell and pronounce, but we're talking about the compounds called
phthalates. Phthalates is spelled p-h-t-h-a-l-a-t-e. These compounds are
associated with plastics and vinyl, they come in a variety of chemical
variations, and in this report our scientists were able to refine the
ability to separate out the various phthalates and to look at them with
much more precision individually than ever before.
The metabolites of these compounds are also measured in the exposure
survey, and I think this is going to really help us refine our ability to
study the relationship, if any, between phthalate exposure and potential
endocrinologic and other toxicities.
One of the most important issues with phthalates has been the
suggestion that they may have antianginal effects, some animal studies
have suggested this, and certainly it's something that bears further
evaluation. With the precision of these estimates now, we will be able to
support those studies in more detail.
The last compound I wanted to mention today was the pyrethroids which
are the insecticides that are found in almost any product that we would
use today when we go to the store to buy an insect agent. We have been
able to measure five of these for the first time ever in the United States
population. What we know is that because they're used so ubiquitously,
there is widespread exposure to them and our exposure report bears this
out. So we have a reason now to look further to see if there are any
health effects from these exposures. We have no evidence of that at this
point in time, but, again, now that we've documented that not only are
they being used in the environment, but they can be measured in the blood
of people in that environment, it's our responsibility to take this to the
next step and to work with our scientific partners to assess what if any
health effects are a consequence of this.
What I can say in summary to all of this is that the third exposure
report is the largest and most comprehensive study of its kind. We think
it is an astonishing opportunity for us to hone in our research to
understand the benefits of the public health interventions that have been
taken, to suggest additional public health interventions, but also
importantly in many cases these data help relieve worry and concern.
For example, if people were concerned about a particular exposure in a
particular environment, we can now go to the exposure report and say, No,
we've measured the levels in the population and we know that your levels
are the same as everybody else's. There is no indication that this
building or this particular environment is a health threat to you, so
that we don't waste our time looking at hypotheses that aren't supported
by the evidence, and we can look further to understand what might be the
causes of a particular set of syndromes or a particular constellation of
findings in people who are concerned about a pesticide set of exposures.
So the value of this report is not just scientific from the standpoint
of research, it also has some very practical uses, and we have seen time
and time again that this has been a great help to individual people, it's
been a help to public health agencies, and we think that it's a tool that
needs to develop and expand over time.
In fact, in 1999 when we first began to measure levels of compounds in
people's blood we were only able to measure 27. In this report, we have
measured 148 chemicals including, I believe, 36 or 38 chemicals that have
never been measured before. We expect the next time the report comes out
that number will have grown to 309, and by the 2005-2006 study time frame,
we will have the ability to look at a total of about 473 different
chemical compounds in the blood of people across our nation.
So it's a wonderful tool, a wonderful testament to the scientists in
our National Center for Environmental Health. Last week we announced that
our center had a new director. Dr. Howie Frumkin from Emory (University)
has taken the lead of our National Environmental Health Center, and I can
see that he's picking up here where Dr. Sinks here in the room today left
off as providing extraordinary scientific leadership. But I also want to
acknowledge Dr. Pirkle who heads the scientific team that conducts this
type of research and is a passionate advocate of getting the data in front
of the decisions to assure that we're doing everything we can to reduce
any harmful effects associated with chemical exposure. So thank you for
your hard work and thank you for your interest, and I'm happy to take any
questions on the exposure report.
MR. WAHLBERG: David Wahlberg from the Atlanta Journal-Constitution. I
know that only some of the 148 chemicals or metabolites in the chemicals
have toxicity levels that are known. Do we know how many have known
And related to that, do we know if they all now have reference ranges?
And related to that, can you explain to the general public the difference
between finding chemicals in the people versus health effects?
DR. GERBERDING: Thank you. Let me answer your question generically
first, and them some of it you can follow back with Dr. Pirkle to get some
It's very important that when we measure exposure, what we're measuring
is the presence or absence of the amount of various chemicals in the
blood. That does not in any way directly correlate with a particular
health effect or set of health effects, but it does provide the foundation
for understanding and predicting who might have those health effects and
how they relate to the data that we've been able to collect from other
more focused research studies and from studies in animals or test tube
conditions. That's why we need to work so carefully with the EPA and the
other research agencies.
Often in the past when the EPA has needed to develop reference
standards or threshold standards for determining above what level was
there likely to be or potentially a serious health effect, it had to rely
on extrapolation from test tube and animal studies. Now that we can
accurately measure these exposures in humans, it sets the stage for us to
get the kind of information that we really need which is what does this
mean for people, what does it mean for me, to know that this is present or
I also think that none of us want to be exposed to unnecessary
chemicals, but it's important that we reassure people that for the vast
majority of compounds measured in this study, we have no evidence of
health effects, but we are committed to being sure that that's generally
applicable to all people in our population and that there aren't specified
circumstances or specified people where the risk is either higher because
their exposure is higher, or the risk is higher because they're uniquely
This research methodology or this study methodology that we're
evaluating can be expanded as we begin to look at the genetic component of
various health effects. We talk about the importance of public health or
health protection research. One of the primary areas that we need to be
investing in at CDC is the public health genomics aspects so that it's not
just a matter of are you exposed to a chemical or not, but how does your
body or your unique genetic composition respond to that chemical and
process it in ways that could increase or decrease your likelihood of
experiencing a complication.
So I think what you'll be seeing over time is the next generation of
work going on will be honing in on the genetic basis of the relationship
between exposure and health outcomes. This is a very exciting tool for us.
I can't emphasize enough how this provides some of the missing data that
we've needed and that the EPA has needed in our commitment to working
collaboratively with them.
One of the great things about having Secretary Mike Leavitt in the
Department of Health and Human Services is that he was previously the
leader of the Environmental Protection Agency and has a real strong sense
of how important it is that CDC and EPA work together to provide even
better science to address these problems. So we're very enthusiastic about
that connection, and I think that what you'll be seeing in the new CDC is
the scaling up and the speeding up of our ability to really focus in on
chemical exposures and to everything we can to assure people are safe.
DR. GERBERDING: Let me take a question from the phone, please.
MR. BORENSTEIN: Seth Borenstein. Thank you, Dr. Gerberding for doing
this. In terms of looking at, you talked about what has gone down,
especially when compared to the first and the second reports, what
chemicals have you seen an increase of and are there any levels at all
while you're talking about the good news that you are particularly worried
about in the findings?
DR. GERBERDING: As I mentioned, the cadmium exposure is one that we are
concerned about and we will be encouraging additional research in this
area. Cadmium levels in urine can be associated with particular
complications in the urinary tract. This is a chemical that the exposure
is predominantly from cigarette smoking, but we do have more work to do to
really understand if that's the only source or if there are other
potential ways in which people could be exposed to cadmium and what does
that really mean. But the levels of cadmium in about 5 percent of the
people in this evaluation were at a level where we do need to look further
and make sure that we're not missing the opportunity to identify a very
serious health threat.
Of course, the obvious major intervention here is smoking cessation or
not starting smoking, so everything in this exposure report emphasizes the
many chemicals that are associated with exposure to tobacco smoke, and
it's a very important validation of the importance of tobacco cessation in
The other chemical that we have some concern about is, of course,
mercury. I mentioned although we did not see levels high enough in
pregnant women or women of child-bearing age to be concerning for
immediate effects on the fetus, we do want to look further and make sure
that we're not seeing anything that would indicate a health effect that we
haven't yet been able to detect through our traditional studies.
I could also mention data for dioxin-like compounds. This report allows
us to look at about 29 different compounds in the family of dioxins. These
estimates are particularly difficult because the technology required to
measure dioxins is extremely difficult and you need extreme sensitivity
and accuracy of the methodology to do it. So from a methodologic
scientific perspective, the fact that we were able to get this degree of
precision in measuring these particular compounds is extraordinary.
But we do know that the dioxin compounds have health effects. We're not
seeing, again, evidence of an association, but enough information to tell
us that there are specific compounds in this family that may require
further investigation. I'll leave Dr. Pirkle to augment that if he has
anything to add on either of these specific compounds of health interest.
Come on up, Jim.
DR. PIRKLE: Yes, I think the main point on the dioxin compounds is that
there's an ongoing risk assessment that is very dependent on accurate
levels determined in people, and this is the first time we've really had
those levels to feed into that risk assessment. It's going to make that
risk assessment a lot more accurate.
When we look at mercury, one of the considerations is, as Dr.
Gerberding said, that we're concerned about levels at 58 where they're 58
micrograms per liter where there are documented health effects. But we're
also concerned about levels that are at or near the levels where we have
documented health effects because people might be more susceptible than
the persons in those studies where we documented health effects.
So the level that's about a factor of 10, say 5.8 up to 58 micrograms
per liter, we want to focus on that level and make sure that we're
confident that the women who have those levels have a very small risk if
any problem occurring in their child. Again, that was about 5.7 percent of
women of child-bearing age.
DR. GERBERDING: I think I can take another phone question.
MR. HAWTHORNE: Michael Hawthorne. Following-up on that, there have been
several studies since your last report regarding mercury. What I
understand is the previous assumption was the mercury blood level in a
mother was roughly the same as in the umbilical cord or in the child. Some
recent studies have suggested that that's different, that it's roughly 1.7
times higher in the umbilical cord than it is in the mother's blood which
would mean that it would take roughly 3.5 parts per billion in the mother
to get to that tenfold safety factor that Dr. Pirkle just talked about.
I was curious, how many women did you find in this recent report that
were above 3.5 parts per billion?
DR. PIRKLE: When we used that safety factor and we actually apply it to
the 58, it comes down to a level of about 37 micrograms per liter using
that safety factor, and the same statistic is true, we didn't find any
woman that was actually above that level of 37, and the level between, 37
and 5.8 was just the same, 5.7 percent. We did not do a calculation that
lowered the 5.8 down to a 3.5, we have not made that estimate, although
with the data that estimate certainly can be made.
DR. GERBERDING: I can take another phone question.
MR. FISCHER: Douglas Fischer. Somewhat related to the last question,
I'm wondering in the phthalates if you could talk a little bit more about
any sort of trends that you're seeing. I recall the last time you had this
report you were somewhat surprised at the levels of some of the
metabolites in women. Are we seeing that same trend? Is there anything
DR. GERBERDING: Do you want to take that question, too?
DR. PIRKLE: What we've done especially different in this survey is
we've added five more metabolites to phthalates and these five additional
metabolites give us better information on the overall exposure. As you
know, there are many kinds of phthalates, and when we talk about them
we're talking broadly now about a family. In the report we have
information on each one individual. There's diethylhexyl phthalate,
diisononyl phthalate, benzylbutylphthalate. There's a whole family here.
What I can say is that if we take a look at the data in the report, we
have a better characterization of the exposure of each one of these
individual members of the family, and it has helped us clarify some
understanding about the relative exposure that are, say, in cosmetics and
personal care products compared to, say, phthalates that are in soft vinyl
plastic products like in toys or in vinyl tubing or things like this.
Without going into much more detail, let me just answer it in short by
saying, yes, there is much greater detail in this report separating out
those different kinds of sources and how those sources relate to different
levels in people.
DR. GERBERDING: I'll take a question here in the room.
MR. WAHLBERG: Regarding mercury, you said that most of the data in the
report is related to methyl mercury, I think. Did you speciate it enough
to say anything about ethyl or phenyl mercury? Related to that, is there
anything that would explain any exposure to thimerosal from vaccines?
DR. GERBERDING: Let me take the thimerosal part of this first. I know
what Dr. Pirkle is going to describe is a much better methodology that we
expect to be available to us in the future for distinguishing them. But
basically what we're measuring here is methyl mercury.
DR. PIRKLE: Yes. Basically, the measurement that we made is, in this
particular report reported, is a total mercury measurement, about 90
percent of that would be methyl mercury, and certainly at the higher
levels a greater percent, like 98 or 99 percent is methyl mercury.
We are at work in our laboratory to develop a method to measure the
ethyl component of mercury, ethyl mercury. That is not done yet but we're
working very hard on it; okay.
When we do finish that, we will add it to this exposure report and we
will have population levels of ethyl mercury that is the kind of mercury
that's in thimerosal for the entire U.S. population.
So if you'll hang on for a while, we'll try to deliver big goods on
that, give us a little time to finish that method up.
DR. GERBERDING: He is very modest but I know this work is
well-advanced, so we're pretty optimistic that we will be able to have
something in the next exposure report.
I'll take a phone question.
OPERATOR: Thank you. Ben Harder with Science News, your line is now
QUESTION: Thank you for holding this.
You mentioned that cotinine is falling and cadmium exposure is rising.
It would seem that tobacco exposure couldn't account for the rise in
DR. GERBERDING: There's an important distinction here because we are
referring in the cotinine levels to people who don't smoke and part of the
NHANES survey specifically segregates people on the basis of their tobacco
So the data about declining tobacco byproducts are limited to those
people in this presentation of the data who don't smoke themselves and so
therefore it's a reflection of exposure to secondhand smoke only. Cadmium
exposures occurred predominantly in the people who do smoke, so those
represent two different views of the population of the people presented in
I hope that's clear because I think it's, again, very, very important
that these data on secondhand smoke are a strong indicator of how
successful our secondhand smoke was, have been in this country,
particularly for children and as I said before, it begs the question, what
can we do to assure that African Americans experience the same reduction
in exposure to secondhand smoke as the rest of our population.
I can take another telephone question, please.
OPERATOR: Thank you. Marla Cone with the Los Angeles Times, your line
is now open.
QUESTION: Thank you very much.
I had some questions. It looks like there's about a 20 percent decline
in the mercury levels in women between the second study and this one. I'm
wondering what you would attribute that to. Is it more awareness of women
about eating fish? Is it better controls? Because we've heard that mercury
emissions are increasing worldwide?
DR. PIRKLE: Between the study for 1999 and 2000, which was the data
reported in the second report, and this new data we're releasing today
which is 2001 and 2002, we are not actually commenting on trends or
changes over that two-year period and the reason for that is that we want
to get more data for multiple two-year sets before we start establishing
what's a trend and what may just be a variation due to differences as we
sample the population in two-year periods.
We have some data on that but we're basically holding back on saying
what has significantly changed between '99, 2000, and 01-02. Until we get
more data to do better statistical testing we think that that's warranted.
I'm told to actually give my name, so you know who's talking. I'm Jim
Pirkle and I'm the deputy director for science of the environmental health
laboratory. My name is spelled P as in Paul, -i-r-k-l-e.
DR. GERBERDING: Thank you. I'll take another telephone question.
OPERATOR: Thank you. Nena Baker with North Point Press, your line is
QUESTION: [inaudible] what you saw in this report regarding atrazine
and atrazine metabolites. Were you able to determine if there are exposure
levels in the population to this herbicide?
DR. PIRKLE: Yes. Well, we do have measurements on atrazine and atrazine
metabolites, and I think we'd probably just have to talk at another time,
the specific details that you want, but if you--the exposure report is now
live on the Web and it's available at www.cdc.gov/exposurereport,
and if you just click on atrazine, it'll take you right to that page and
actually show you the geometric means, the 50th percentile, the 95th
percentile, and I think give you the data that you're interested in
looking at atrazine metabolites.
DR. GERBERDING: I can take two more questions from the phone.
OPERATOR: Thank you. Todd Zwillich with WebMD News, your line is now
QUESTION: Hi. Can you tell us if the report, prior to releasing it
today, was cleared, vetted, or otherwise altered at any other levels of
DR. PIRKLE: Yes. The report was extensively reviewed. Basically when we
do the report, one reason it takes a while to come out is that we send it
to an external peer review, and so this meets OMB requirements for an
external peer review where we have scientists on the outside,
scientifically reviewed and commented.
It then goes up through a CDC review, which is an additional science
review and the report itself is also sent to the department, that is, HHS,
for review, and these people have made comments, and the appropriate
comments and scientific comments have been taken into account, and we
believe it is a more credible product because of that review.
But there has been no other alteration other than a review of the
science at multiple levels.
DR. GERBERDING: I just want to emphasize that this report is a
scientific report and the clearance process is an appropriate and
expected, and I think, essential component of clearing any scientific
document that comes out of this agency.
We respect and appreciate the input that the broad cadre of scientists
across the agency have contributed as well as scientists from other
But I am very confident that nothing in this report has been altered or
changed in any way because of political considerations or other
We're very proud of it for exactly that reason, that we know we can
stand by the science, we believe this represents, absolutely, the
state-of-the-art science in the world, and we are pleased to bring it
forward to the public and to the community of stakeholders so that we can
make good use of it to protect people from potential effects of chemicals.
Let me take the last question, please.
OPERATOR: Thank you. Maggie Fox with Reuters, your line is now open.
QUESTION: Thanks very much. I'm wondering if you guys have taken a look
at things like the lead data and the cotinine data and compared it to
epidemiological evidence of things.
For instance, is IQ up in the U.S. because of the greatly-reduced
exposure to lead?
DR. GERBERDING: I'm not going to make a joke about your last remark but
I will say that it is actually--what you're describing is an important
component of our overall use of these data.
We know that the information about exposure is only one piece and we
need to create opportunities to relate that change in exposure to changes
in health status.
The specific study you're describing has not been done. In fact the
opposite study has been published, which is to show that there is a
correlation between higher lead levels in children and IQ.
So we don't have population-based IQ information but we do know from
the kind of focused research, that one of the harmful effects of lead
exposure is a change in neurodevelopment and that it is a dose response
effect with respect to the specific exposure report in children at the
higher lead level.
So that's another strong motivation for getting the lead out of our
kids and out of our kids' environment and we think that, on a population
basis, over time, lead exposure has significantly attributed to the
development of kids in adverse ways and we're pretty passionate about
getting the lead out.
So let me just thank you for being here and I hope that you'll feel
comfortable going to the Internet and finding the exposure report but also
circling back to our press office if you have any specific questions on
any of the components of the report or the science of the compounds that
are included in the report. Thank you for your interest.
OPERATOR: Thank you. This does conclude today's conference call. We
thank you for your participation.
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