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
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
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
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 report.
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
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
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 toxicity
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 specific
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 absent.
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 predisposed.
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
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
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 our society.
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,
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
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 different?
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
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
I'll take a phone question.
OPERATOR: Thank you. Ben Harder with Science News, your line is now open.
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 cadmium.
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 the survey.
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
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 now
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 open.
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 the
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
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
We respect and appreciate the input that the broad cadre of scientists
across the agency have contributed as well as scientists from other agencies.
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
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
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.
Listen to the