[Federal Register Volume 73, Number 61 (Friday, March 28, 2008)]
[Notices]
[Pages 16685-16688]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E8-6350]
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DEPARTMENT OF HEALTH AND HUMAN SERVICES
Centers for Disease Control and Prevention
[ATSDR-241]
Public Comments and Revised Final Criteria for Removing Chemicals
From Future Editions of CDC's National Report on Human Exposure to
Environmental Chemicals
AGENCY: Centers for Disease Control and Prevention (CDC), Department of
Health and Human Services (HHS).
SUMMARY: On Tuesday, May 16, 2006, CDC published draft criteria for
removing chemicals from future releases of CDC's National Report on
Human Exposure to Environmental Chemicals (the ``Report'') (See FR,
Vol. 71, No. 94, p. 28346-7). This and previous notices related to the
``Report'' are at http://www.cdc.gov/exposurereport/chemical_nominations.htm. The proposed criteria provided that a chemical may be
removed from the ``Report'' if (1) a new replacement chemical (i.e., a
metabolite) is more representative of exposure than is the chemical
currently measured; or (2) after three survey periods (or not less than
6 years), detection rates for all chemicals within a methodological and
chemically related group are less than 5 percent for all population
subgroups (i.e., two sexes, three race/ethnicity groups, and three age
groups); or (3) after three survey periods (or not less than 6 years),
levels of chemicals within a methodological and chemically related
group are unchanged or declining in all the specific subgroups as
documented in the ``Report.''
Using these criteria, CDC would have continued to measure the
chemical and not remove it from the ``Report'' if it met either of two
proposed exceptions to these criteria: (a) It is a chemical for which
there is an established biomonitoring threshold (e.g., CDC's level of
concern for blood lead levels in children) or any chemical for which
there is widespread public health concern (e.g., mercury) or (b) three
survey periods (or not less than 6 years) have passed, constituting the
minimum time before a chemical could be removed; a longer period may be
necessary to account for the half-life of a particular chemical or to
account for a recent change (e.g., the removal of a chemical from
commerce) that would necessitate monitoring of the population. In that
notice, CDC pointed out that the criteria for removing a chemical from
the ``Report'' are not corollaries of the criteria for adding chemicals
to the ``Report.''
Summary of Public Comments
CDC received 31 public comments on the criteria cited above and
describes below the comments received and CDC's responses to those
comments. Comments are grouped in the following categories: Removal
process, criterion 1, criterion 2, criterion 3, and exceptions ``a''
and ``b.''
General Informational Comments Related to Process and Procedure
CDC received several public comments about how the process of
removing chemicals from the ``Report'' would be implemented. These
generally pertained to (1) concurrence on the scientific basis for
exposure assessment; (2) analytical cost considerations as secondary;
(3) description of the policy basis for the process; (4) consideration
of and suggestions for alternative approaches to limited sample
volumes; and (5) affirmation of decision procedures, transparency, and
public notification.
CDC responses to general informational comments:
Understanding exposures through biomonitoring can help scientists
focus research on those chemicals found in people's bodies and target
the appropriate levels of exposure. The ``Report'' provides unique
exposure assessment information and not assessment of health risk.
However, the biomonitoring data in the ``Report'' can facilitate and
complement the risk-assessment process. For some chemicals, such as
lead and mercury, risks have become better characterized when
biomonitoring levels have become the benchmark to which the risks are
tied. CDC considers the public health utility and quality of
biomonitoring information to be the primary consideration, with cost of
analysis as an important, but secondary, consideration (See Federal
Register Vol. 67, No. 34 March 20, 2002, pages 12996-7).
The policy basis for the development of criteria for removing
chemicals from the ``Report'' was developed in consideration of sound
science and resource utilization. With guidance from a Work Group that
was convened at the direction of the Board of Scientific Counselors of
the National Center for Environmental Health and the Agency for Toxic
Substances and Disease Registry (NCEH/ATSDR), the proposed criteria
were established, and comments from the public were solicited through
the Federal Register notice published in May 2006 (Vol. 71, No. 94, p.
28346-7).
As currently described, only one of the three criteria needs to
apply to delist a chemical. That is, the three criteria apply
independently--no combinations of criteria are necessary to qualify a
chemical for removal from the ``Report.'' When chemicals published in
the ``Report'' meet a criterion for removal, they will be deleted from
future reports. The Division of Laboratory Sciences (DLS) at NCEH will
make these decisions using the finalized criteria only and will post
the names of the removed chemicals on its Web site: http://www.cdc.gov/exposurereport.
Two commenters provided helpful suggestions for maintaining
flexibility in applying the removal process and suggested alternative
plans for optimal use of samples. For those chemicals requiring large
amounts of sample volume to detect the chemicals, alternatives such as
less frequent sampling or pooled analyses are appropriate alternatives.
CDC has actively researched these alternatives and will continue to
weigh the relative cost-benefit of other approaches in addressing the
issue of limited sample volume. Such approaches could include less
frequent sampling, pooling of samples, and development of more
sensitive analytical methods. For difficult decisions, the NCEH/ATSDR
[[Page 16686]]
Board of Scientific Counselors will be consulted for advice on the use
of alternative approaches.
This process of announcing draft criteria and requesting comment on
the criteria was the first step in ensuring transparency. Commenters'
involvement in this process is evidence of CDC's efforts to involve
multiple groups with varied viewpoints. CDC will announce the process
for both nominating and removing chemicals from the ``Report'' in a
future Federal Register notice. When chemicals are removed through this
process, announcements will be made on CDC's Web site (http://www.cdc.gov/exposurereport). Descriptions of ongoing activities related
to the ``Report'' have been provided in public meetings with advisory
groups, in regional and national conferences, through publication of
introductory material in the ``Report'' itself, in previous Federal
Register announcements, and in postings of these materials on the CDC
Web site.
Specific comments related to Criterion 1: If a new replacement
chemical (i.e., a metabolite) is more representative of exposure than
the chemical currently being measured.
Two specific comments and one general comment were received.
CDC Responses related to Criterion 1:
The first comment recommends a phased overlap in the analysis of
the previously measured chemical with the replacement chemical. CDC
agrees with this recommendation, which would occur naturally in the
course of the scientific accrual of knowledge and measurements about
the new replacement chemical. Both old and replacement chemicals may
exist in the ``Report'' simultaneously until such knowledge and
experience are accrued.
The second comment requested a wording change in criterion 1 from
``(i.e., a metabolite)'' to ``(i.e., a metabolite or other chemical).''
The wording change is accepted.
A general comment was made that the meaning of the phrase ``is more
representative of exposure'' can be inferred. CDC notes that a
replacement chemical is more representative of exposure when the
measured concentration of the replacement chemical accounts for a
greater fraction of the dose or has pharmacokinetic characteristics
that decrease the variability in exposure estimation (such as longer
persistence in the body).
Revised draft Criterion 1: If a new replacement chemical (i.e., a
metabolite or other chemical) is more representative of exposure than
the chemical currently being measured.
Specific comments related to Criterion 2: If after three survey
periods (or not less than 6 years), detection rates for all chemicals
within a methodologically and chemically related group are less than 5
percent for all population subgroups (e.g., two sexes, three race/
ethnicity groups, and three age groups).
CDC received six overlapping comments from different commenters on
the description or discussion of the following: (1) The requirement of
a 5% detection rate for all population subgroups to meet the criterion;
(2) the adequate number of survey periods applicable to the criterion;
(3) the definition of ``methodological and chemically related group'';
and (4) the application of the criterion to the entire group versus
individual chemicals in the group to achieve cost savings.
CDC Responses Related to Criterion 2
(1) The requirement of a 5% detection rate. Not removing a chemical
from the ``Report'' until all reported subgroups have fallen below the
5% detection rate is a conservative approach, allowing continued
population monitoring even though some subgroups would no longer meet
that criterion. A 5% detection rate allows an estimate of the 95th
percentile for a population group. The 95th percentile is extremely
useful for characterizing levels of unusual exposure in a population.
If removal of a chemical from the ``Report'' resulted by meeting this
criterion, but there were known exposures to special groups that are of
public health interest, targeted monitoring studies could be
recommended. CDC may be able to assist some states or other agencies in
biomonitoring of special groups with unusual potential for exposure or
who potentially may be at more risk for adverse health effects.
(2) The adequate number of survey periods applicable to the
criterion. No absolute guide governs the number of survey periods
necessary for inclusion in this criterion. CDC considered three survey
periods because this number was the minimum number of survey point
estimates from which trends might be calculated. Still, environmental
conditions and releases of chemicals may change human exposures over
time, and for some persistent chemicals--that is, persistent either in
the body or in the environment--the 6-year period would be too short to
measure a meaningful change. Thus, to accommodate these situations, CDC
added exemption ``b.'' CDC has also rephrased the following statement
to address reassessment of a chemical removed from the ``Report'' under
either criterion 2 or 3: ``For a chemical that meets criterion 2 or 3,
the chemical would be removed from the `Report' for two future survey
periods (4 years) and then measured again in the following survey
period (2 years). If either criterion 2 or 3 is still satisfied for
this 12-year period (i.e., three initial 2-year survey periods, two
intervening 2-year survey periods, final 2-year survey period), then
the chemical would be removed from the `Report' and not reinstated
unless the chemical once again met the criteria for inclusion in the
`Report.' ''
(3) The definition of ``methodologically and chemically related
group.'' Often, many similar chemicals are measured together in the
same analytical procedure on a single preparation of an individual
specimen. This is possible because the chemicals share similar
physical/chemical properties and because of recent advances in
separation and detection technologies (e.g., chromatography followed by
mass spectrometry). Such chemicals were previously referred to as
belonging to a ``methodologically and chemically related group.''
Because of issues in the following discussion, the terminology and
definition have been changed to the following: A ``method-related
group'' is defined as a group of chemicals that are (1) measured
together using a single analytical method; (2) structurally similar;
(3) typically generated together from exposure sources (e.g., dioxin
congeners, furan congeners, polyaromatic hydrocarbons); and (4)
typically assessed for health risk together as a group.
Commenters asked whether a chemical satisfying this criterion
should be measured in subsequent reports (as CDC intends) only because
other chemicals in the ``methodologically and chemically related
group'' were being reported. CDC seeks to balance both the scientific
importance and cost of measuring specific chemicals. In regard to
scientific importance, scientists who consider the aggregate effect of
certain chemical groups (e.g., molar sums or toxic equivalents [TEQs])
may need to know whether a component chemical of a group was not
detected and noncontributory as opposed to not measured. CDC would
continue to measure a chemical in a method-related group that met this
criterion for removal where it would be helpful for risk assessment of
the entire group of chemicals (e.g., dioxins).
(4) The application of the criterion to the entire group versus
individual chemicals in the group to achieve cost savings.
Commenters asked whether there would not be some cost savings by
not
[[Page 16687]]
measuring a chemical that met a criterion for removal among the
multiple chemicals measured in such an assay. Removing one of a group
of related chemicals (e.g., PCBs) from the ``Report'' although it alone
meets a criterion, would generate little additional savings. The
relative cost savings are in direct proportion to the number of
chemicals in a multichemical analysis. Removing 1 of 26 chemicals
(e.g., PCB congeners) would save only about 4% of the post-instrumental
analysis labor and cost of standards but would result in little or no
savings in all other costs such as labor, supplies, sample preparation,
and instrument analysis. Thus, if cost impact were minimal, CDC would
continue to measure a chemical in a method-related group that met this
removal criterion.
A commenter requested the addition of ``mode of action'' to the
definition of a chemically and methodologically related group. Because
``mode of action'' may involve chemicals of different structural
classes and different analytical methods, CDC chose not to add this
descriptor to the current definition of a method-related group.
Revised draft Criterion 2: If, after three survey periods (a period
of not less than 6 years), detection rates for all chemicals within a
method-related group are less than 5 percent for all population
subgroups (e.g., two sexes, three race/ethnicity groups, and the age
groups used in the ``Report'').
Specific comments related to Criterion 3: If, after three survey
periods ( or not less than 6 years), levels of chemicals within a
methodologically and chemically related group are unchanged or
declining in all the specific subgroups as documented in the
``Report.''
Comments addressed the following: (1) No change or declining levels
over three survey periods is not synonymous with lessened health
concerns, (2) the criterion does not address unforeseen increases in
chemicals after their removal from the ``Report,'' (3) whether new
demographic groups might be added in the future and whether criterion 3
would also apply to these new demographic groups (e.g., people aged 60
years and older), and (4) further definition of unchanged or declining
levels is required.
CDC Responses related to Criterion 3:
(1) No change or declining levels over three survey periods is not
synonymous with lessened health concerns. CDC agrees that the phrase
``no change over a 6-year period'' is not synonymous with a lessened
concern for certain chemicals with possible heath risks. If, however,
there is public health concern about a particular chemical, exception
``a'' would apply. If 6 years or three survey periods is not long
enough to evaluate a persistent chemical, exception ``b'' would apply.
In addition, a chemical previously removed from the ``Report'' could
reappear in the ``Report'' if that chemical again met the inclusion
criteria for selecting chemicals for the ``Report.'' (see Federal
Register, Vol. 71, No. 94, May 16, 2006, pages 28346-7).
(2) The criterion does not address unforeseen increases in levels
of chemicals after their removal from the ``Report.'' CDC agrees that
criterion 3 would not address situations involving an unforeseen rise
in the level of a chemical after its removal from future monitoring by
the ``Report.'' As it did for criterion 2 (stated above), CDC will
include the following language: ``For a chemical that meets criterion 2
or 3, the chemical would be removed from the `Report' for two future
survey periods (4 years) and then measured again in the following
survey period (2 years). If either criterion 2 or 3 is still satisfied
for this 12-year period (i.e., three initial 2-year survey periods, two
intervening 2-year survey periods, final 2-year survey period), then
the chemical would be removed from the `Report' and not reinstated
unless the chemical once again met the criteria for inclusion in the
`Report.'''
(3) Whether new demographic groups might be added in the future and
whether criterion 3 would also apply to these new demographic groups
(e.g., people aged 60 years and older). As is also stated above for
Criterion 2, Criterion 3 would apply to all subgroups--listed age
groups, both sexes, and three race/ethnicities-for which statistically
sufficient data are reported. In other words, if all but one subgroup
satisfied the criterion, it would be important to continue measuring
the chemical. In answer to the possibility of additional subgroups in a
future ``Report,'' CDC does intend to divide the 20 and older age group
into two groups: 20-59 years and 60 years and older. If past and
additional (new) demographic groups all satisfy the criterion, the
chemical could be removed. Other than this older age group, NHANES
sampling design and statistical considerations make it unlikely that
demographic groups will be added.
(4) Further definition of unchanged or declining levels is
required. CDC agrees that the phrase ``unchanged or declining'' needs
further definition. CDC has revised the wording of this criterion by
adding the following: ``Evidence that chemical levels are unchanged or
declining would be the absence of a statistically significant (p <
0.05) positive slope of mean (or geometric mean) levels of the chemical
over the time period.''
Revised draft Criterion 3: If after three survey periods (a period
of not less than 6 years), levels of chemicals within a method-related
group are unchanged or declining in all the demographic subgroups
documented in the ``Report.'' Evidence that chemical levels are
unchanged or declining would be the absence of a statistically
significant (p < 0.05) positive slope of mean (or geometric mean)
levels of the chemical over the time period.
Specific comments related to Exceptions ``a'' and ``b'': (a) It is
a chemical for which there is an established biomonitoring health
threshold (e.g., CDC's level of concern for blood lead levels in
children) or any chemical for which there is widespread public health
concern (e.g., mercury), or (b) three survey periods (or not less than
6 years) have passed, which constitute the minimum time before a
chemical could be removed; a longer period may be necessary to account
for the half-life of a particular chemical or to account for a recent
change (e.g., the removal of a chemical from commerce) that would
necessitate monitoring of the population.
Comments addressed the following: (1) the meaning of the phrase
``widespread public health concern'' in exception ``a,'' and (2) the
rationale for exception ``b.''
CDC Responses related to Exceptions ``a'' and ``b'':
(1) The meaning of the phrase ``widespread public health concern'':
A commenter stated that ``widespread health concern'' was broad and
vague and wished to know what constituted ``widespread concern'' as
well as the process used to determine ``widespread concern.'' CDC will
change the sentence in exception ``a'' that contains the phrase
``widespread public health concern'' to ``The chemical has an
established federal biomonitoring health threshold (e.g., CDC's level
of concern for blood lead levels in children) or after consultation
with relevant federal agencies, CDC learns that a federal agency
considers the chemical of sufficient priority to warrant continued
monitoring.''
(2) The rationale for exception ``b.'' A commenter stated that ``*
* * this exception appears to provide the CDC with a sensible amount of
flexibility; the commenter urges CDC to provide the rationale for
applying this exception.'' To better explain exception ``b,'' CDC will
use the following wording: ``The chemical has a long half-life (e.g.,
DDE),
[[Page 16688]]
which would require additional time to track changes reliably in
population levels, or recent changes in exposure sources indicate that
future levels are likely to increase.'' Chemicals with long half-lives
in the body or persistence in the environment may not decline
appreciably within shorter time frames such as 6 years, and longer
periods of monitoring may be necessary to assess whether exposure
levels are changing.
Revised draft exceptions: (a) The chemical has an established
federal biomonitoring health threshold (e.g., CDC's level of concern
for blood lead levels in children) or after consultation with relevant
federal agencies, CDC learns that a federal agency considers the
chemical of sufficient priority to warrant continued monitoring; or (b)
the chemical has a long half-life (e.g., DDE), which would require
additional time to track changes reliably in population levels, or
recent changes in exposure sources indicate that future levels are
likely to increase.
Summary of Revised Draft Criteria
As stated, CDC now publicly announces the final criteria for
removing chemicals from future releases of the ``Report.'' These
criteria will become part of a combined process for nominating
candidate chemicals for inclusion in or removal from the ``Report.''
The process will include (a) nominations from the public of candidate
chemicals to include in or remove from the ``Report,'' (b) an external
scoring of nominations in accordance with the published nomination and
removal criteria, and (c) assistance from the Board of Scientific
Counselors of CDC's National Center for Environmental Health/Agency for
Toxic Substances and Disease Registry in reviewing plans for including
or removing chemicals and identifying alternatives for monitoring
specific at-risk population subgroups. This combined process will occur
periodically (e.g., every 6 years). Note that the criteria for
selecting and removing chemicals apply only to chemicals published in
the ``Report''--not to those merely nominated.
The final removal criteria are as follows: A chemical will be
removed from the ``Report'' if it meets any one of the following three
criteria and does not meet either of the exceptions to those criteria.
Accordingly, a chemical will be removed if (1) a new replacement
chemical (i.e., a metabolite or other chemical) is more representative
of exposure than the chemical currently measured; or (2) if after three
survey periods (a period of not less than 6 years), detection rates for
all chemicals within a method-related group are less than 5 percent for
all population subgroups (i.e., two sexes, three race/ethnicity groups,
and the age groups used in the ``Report'') or; (3) if after three
survey periods (a period of not less than 6 years), levels of chemicals
within a method-related group are unchanged or declining in all the
demographic subgroups documented in the ``Report.'' Evidence that
chemical levels are unchanged or declining would be the absence of a
statistically significant (p < 0.05) positive slope of mean (or
geometric mean) levels of the chemical over the time period.
For a chemical that meets criterion 1, the chemical would be
removed from future reports and would be replaced with the new chemical
that better reflects exposure.
For a chemical that meets criterion 2 or 3, the chemical would be
removed from the ``Report'' for two future survey periods (4 years)
then measured again in the following survey period (2 years). If either
criterion 2 or 3 is still satisfied for this 12-year period (three
initial 2-year survey periods, two intervening 2-year survey periods,
final 2-year survey period), then the chemical would be removed from
the ``Report'' and not reinstated unless the chemical once again met
the criteria for inclusion in the ``Report.''
A chemical would continue to be measured and not be removed from
the ``Report'' if it met either of two exceptions to the above-cited
revised draft criteria: (a) The chemical has an established federal
biomonitoring health threshold (e.g., CDC's level of concern for blood
lead levels in children) or after consultation with relevant federal
agencies CDC learns that a federal agency considers the chemical of
sufficient priority to warrant continued monitoring; or (b) the
chemical has a long half-life (e.g., DDE), which would require
additional time to track changes reliably in population levels, or
recent changes in exposure sources indicate that future levels are
likely to increase.
FOR FURTHER INFORMATION CONTACT: Dorothy Sussman, Telephone 770-488-
7950.
SUPPLEMENTARY INFORMATION: CDC publishes the ``Report'' under
authorities 42 U.S.C. 241 and 42 U.S.C. 242k. The ``Report'' provides
ongoing assessment using biomonitoring of the exposure of the
noninstitutionalized, civilian population to environmental chemicals.
Biomonitoring assesses human exposure to chemicals by measuring the
chemicals or their metabolites in human specimens such as blood or
urine. For the ``Report,'' the term environmental chemical means a
chemical compound or chemical element present in air, water, soil,
dust, food, or other environmental medium. The ``Report'' provides
exposure information about participants in an ongoing national survey
known as the National Health and Nutrition Examination Survey (NHANES).
This survey is conducted by CDC's National Center for Health
Statistics; measurements are conducted by CDC's National Center for
Environmental Health. The first ``Report,'' published in March 2001,
gave information about levels of 27 chemicals found in the U.S.
population; the second ``Report'' was published in January 2003, and it
contained exposure information on 116 chemicals, including the 27
chemicals in the first ``Report.'' The third ``Report'' was published
in July 2005, and it contained exposure information on 148 chemicals,
including data on the chemicals published in the second ``Report.''
Copies of the third ``Report'' can be obtained in the following ways:
Access http://www.cdc.gov/exposurereport, send an e-mail to
[email protected], or telephone 1-800-CDC-INFO.
Dated: March 25, 2008.
Kenneth Rose,
Director, Office of Policy, Planning, and Evaluation, National Center
for Environmental Health/Agency for Toxic Substances and Disease
Registry.
[FR Doc. E8-6350 Filed 3-27-08; 8:45 am]
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