[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]
BILLING CODE 4163-18-P