Standards for the Use or Disposal of Sewage Sludge: Decision Not To Regulate Dioxins in Land-Applied Sewage Sludge

[Federal Register: October 24, 2003 (Volume 68, Number 206)]
[Notices]
[Page 61083-61096]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr24oc03-153]

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ENVIRONMENTAL PROTECTION AGENCY
[FRL-7577-9]

Standards for the Use or Disposal of Sewage Sludge: Decision Not
To Regulate Dioxins in Land-Applied Sewage Sludge

AGENCY: Environmental Protection Agency.
ACTION: Notice.

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SUMMARY: The U.S. Environmental Protection Agency (EPA or Agency) is
giving final notice of its determination that neither numerical
limitations nor requirements for management practices are currently
needed to protect human health and the environment from reasonably
anticipated adverse effects from dioxin and dioxin-like compounds in
land-applied sewage sludge.

DATES: In accordance with 40 CFR 23.2, this final decision is
promulgated for purposes of judicial review as of 1 p.m. Eastern Time
on November 7, 2003. Under section 509(b)(1) of the Clean Water Act,
judicial review of this final action can be obtained only by filing a
petition for review in the United States Court of Appeals within 120
days after the final action is considered promulgated for purposes of
judicial review.

FOR FURTHER INFORMATION CONTACT: Robert Cantilli, U.S. Environmental
Protection Agency, Office of Water, Office of Science and Technology,
Health and Ecological Criteria Division (4304T), 1200 Pennsylvania
Avenue, NW., Washington, DC 20460 (202) 566-1091. cantilli.robert@epa.gov.

SUPPLEMENTARY INFORMATION:

A. Interested Entities

Entities typically regulated by Standards for the Use or Disposal
of Sewage Sludge are those that prepare sewage sludge (also called
``biosolids'') and/or use or dispose of the sewage sludge through
application to the land, placement in a surface disposal unit, or
incineration in a sewage sludge incinerator. Entities potentially
interested by today's notice include those that prepare and/or use
sewage sludge for land-application purposes. Categories and entities
interested in today's action include:

------------------------------------------------------------------------
Category Examples of affected entities
------------------------------------------------------------------------
State/Local/Tribal Government.......... Publicly owned treatment works
and other treatment works that
treat domestic sewage, prepare
sewage sludge, and/or apply
sewage sludge to the land.
Federal Government..................... Federal Agencies with treatment
works that treat domestic
sewage, prepare sewage sludge,
and/or apply sewage sludge to
the land.
Farmers and ranchers................... Individuals who apply sewage
sludge to land.
Industry............................... Privately-owned treatment works
that treat domestic sewage,
and persons who receive sewage
sludge and change the quality
of the sewage sludge before it
is applied to the land.
------------------------------------------------------------------------

This table is not intended to be exhaustive, but rather provides a
guide for readers regarding entities likely to be interested in this
action. This table lists the types of entities that EPA is now aware
could potentially be interested in this action. Other types of entities
not listed in the table could also be interested. To determine whether
your facility is affected by this action, you should carefully examine
today's notice. If you have questions regarding the applicability of
this action to a particular entity, consult the person listed in the
preceding FOR FURTHER INFORMATION CONTACT section.

B. How Can I Get Copies of This Document and Other Related Information?

1. Docket. EPA has established an official public docket for this
action under Docket ID No. OW-2002-0019. The official public docket
consists of the documents specifically referenced in this action, any
public comments received, and other information related to this action.
Although a part of the official docket, the public docket does not
include Confidential Business Information (CBI) or other information
whose disclosure is restricted by statute. The official docket is the
collection of materials that are available for public viewing at the
Water Docket in the EPA Docket Center, (EPA/DC) EPA West, Room B102,
1301 Constitution Ave., NW., Washington, DC. The EPA Docket Center
Public Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday through
Friday, excluding legal holidays. The telephone number for the Public
Reading Room is (202) 566-1744, and the telephone number for the Water
Docket is (202) 566-2426.
2. Electronic Access. You may access this Federal Register document
electronically through the EPA Internet under the ``Federal Register''
listings at http://www.epa.gov/fedrgstr/.
An electronic version of the public docket is available through
EPA's electronic public docket and comment system, EPA Dockets. You may
use EPA Dockets at http://www.epa.gov/edocket/ to view public comments,
access the index listing of the contents of the official public docket,
and to access those documents in the public docket that are available
electronically. Once in the system, select ``search,'' then key in the
appropriate docket identification number. Although not all docket
materials may be available electronically, you may still access any of
the publicly available docket materials through the docket facility
identified in section B.1.

C. Table of Contents

I. Abbreviations and Acronyms Used
II. What Is the Legal History of the Standards for the Use and
Disposal of Sewage Sludge?
III. What Did EPA Propose for Dioxins in Land-Applied Sewage Sludge?
A. Proposed Rule
B. Notice of Data Availability (NODA)
IV. What Final Action Is EPA Taking Today?
V. What is the Basis for This Final Action for Dioxins in Land-
Applied Sewage Sludge?
A. Overview
B. Assessment of Cancer Risk From Dioxins in Land-Applied Sewage
Sludge
C. Findings Concerning Ecological Effects
D. Indications From the 2001 Survey of Dioxins in Sewage Sludge
VI. Environmental Justice
VII. Discussion of Scientific Information Presented in the NODA
A. Assessing Cancer Risk
B. Assessing Non-Cancer Risk
VIII. Public Comments and Other Considerations
A. Definition of ``Dioxins''
B. The Need for Regulating Dioxins in Land-Applied Sewage Sludge
C. Groundwater Exposure
D. Synergistic Effects
E. Voluntary Program
IX. List of References

I. Abbreviations and Acronyms Used

AMSA--Association of Metropolitan Sewerage Agencies
CFR--Code of Federal Regulations

[[Page 61085]]

CWA--Clean Water Act
DMT--dry metric tons
EFH--Exposure Factors Handbook
EMS--Environmental Management System
EPA--U.S. Environmental Protection Agency
HQ--hazard quotient
HEI--highly exposed individual
LADD--lifetime average daily dose
MGD--million gallons per day
NBP--National Biosolids Partnership
ng TEQ/kg--nanograms toxic equivalence per kilogram body weight
NODA--Notice of Data Availability
NSSS--National Sewage Sludge Survey
PCBs--polychlorinated biphenyls
PCDDs--polychlorinated dibenzo-p-dioxins
PCDFs--polychlorinated dibenzofurans
pg TEQ/day--picograms toxic equivalence per day
pg TEQ/kg-d--picograms toxic equivalence per kilogram body weight per
day
POTWs--Publicly Owned Treatment Works
ppt--parts per trillion
Q1*--cancer slope factor
RfD--reference dose
SAB--Science Advisory Board
SERA--screening ecological risk analysis
TBD--Technical Background Document
TCDD--2,3,7,8-tetrachlorodibenzo-p-dioxin
TEF--toxicity equivalency factor
TEQ--toxic equivalence
WHO--World Health Organization

II. What Is the Legal History of the Standards for the Use or Disposal
of Sewage Sludge?

EPA promulgated Standards for the Use or Disposal of Sewage Sludge
(40 CFR part 503) under section 405(d) and (e) of the Clean Water Act
(CWA), 33 U.S.C. 1345(d), (e), as amended by the Water Quality Act of
1987. In these amendments to section 405 of the CWA, Congress, for the
first time, set forth a comprehensive program for reducing the
potential environmental risks and maximizing the beneficial use of
sewage sludge. As amended, section 405(d) of the CWA requires EPA to
establish numerical limitations and management practices, when
appropriate, that protect public health and the environment from the
reasonably anticipated adverse effects of toxic pollutants in sewage
sludge. Section 405(e) prohibits any person from disposing of sewage
sludge from a publicly owned treatment works (POTWs) or other treatment
works treating domestic sewage for any use except in compliance with
regulations promulgated under section 405.
Section 405(d) calls for two rounds of sewage sludge regulations
and sets deadlines for promulgation. In the first round, EPA was to
establish numerical limits and management practices for those toxic
pollutants which, based on ``available information on their toxicity,
persistence, concentration, mobility, or potential for exposure, may be
present in sewage sludge in concentrations which may adversely affect
public health or the environment.'' CWA section 405(d)(2)(A). The
second round is to address toxic pollutants not regulated in the first
round ``which may adversely affect public health or the environment.''
CWA section 405(d)(2)(B).
EPA did not meet the timetable in section 405(d) for promulgating
the first round of regulations, and a citizen's suit was filed to
require EPA to fulfill this mandate, (Gearhart v. Reilly, Civ. No. 89-
6266-HO (D. Ore.)). A consent decree was entered by the court in that
case, establishing schedules for both rounds of sewage sludge rules.
EPA promulgated the first rule, codified at 40 CFR part 503, in 1993 at
58 FR 9248 (February 19, 1993) (``Round One''). For the second round
(``Round Two''), EPA identified 31 pollutants and pollutant categories
not regulated in Round One that EPA was considering for regulation. In
November 1995, EPA narrowed the original list of 31 pollutants to
polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated
dibenzofurans (PCDFs) and dioxin-like coplanar polychlorinated
biphenyls (PCBs) for the second round of rulemaking (USEPA, 1996). The
consent decree required the Administrator to sign a notice for
publication proposing Round Two regulations no later than December 15,
1999, and to sign a notice taking final action on the proposal no later
than December 15, 2001.
On December 15, 1999, the Administrator signed a proposal to
establish numerical limits for dioxins, dibenzofurans, and co-planar
PCBs (``dioxins'') in sewage sludge that is applied to the land and
proposed not to regulate dioxins in sewage sludge that is disposed of
in a surface disposal unit or fired in a sewage sludge incinerator
(December 23, 1999, 64 FR 72045). On December 15, 2001, the
Administrator signed a final notice of EPA's determination that
numerical limitations or management practices are not warranted for
dioxins in sewage sludge that are disposed of in a surface disposal
unit or incinerated in a sewage sludge incinerator (66 FR 66228). In
that notice, EPA also announced that a final action on the Round Two
proposal to amend the Standards for the Use or Disposal of Sewage
Sludge for sewage sludge that is applied to the land would be published
at a later date. The consent decree in Gearhart was amended to extend
the deadline for final action on the land application Round Two
rulemaking from the original date of December 15, 2001, to a new date
of October 17, 2003.
On June 12, 2002, EPA published a Notice of Data Availability
(NODA) containing new information relating to dioxins in land-applied
sewage sludge and requested public comments (67 FR 40554). The NODA
provided a revised cancer risk assessment for dioxins in land-applied
sewage sludge, newly collected data regarding concentration of dioxins
in sewage sludge, and a new ecological screening risk analysis and
solicited public comments.

III. What Did EPA Propose for Dioxins in Land-Applied Sewage Sludge?

A. Proposed Rule

EPA proposed a numeric limitation of 300 part per trillion (ppt)
for ``dioxins'' measured as toxic equivalence (TEQ) in land-applied
sewage sludge, and related monitoring, record-keeping and reporting
requirements. EPA proposed a definition of ``dioxins'' to mean 29
specific congeners of PCDDs, PCDFs, and coplanar PCBs that have been
found in sewage sludge. The proposed definition of ``dioxins''
specified seven 2,3,7,8-substituted congeners of PCDDs, ten 2,3,7,8-
substituted congeners of PCDFs, and twelve coplanar PCB congeners.
The December 1999 proposal included a monitoring schedule for
dioxins in land-applied sewage sludge that would have required
wastewater treatment plants to monitor for dioxins in their sewage
sludge for two consecutive years. EPA also proposed a modified
frequency of monitoring based on analytical results from the first two
years of monitoring.
EPA also proposed to exclude from the proposed numeric limit and
monitoring requirements those treatment works having a flow rate equal
to or less than one million gallons per day (MGD) and certain sewage
sludge-only entities that receive sewage sludge for further processing
prior to land application. This proposed exclusion was based on the
relatively small amount of sewage sludge that is prepared by these
facilities and entities and, therefore, the low probability that land
application of these materials could significantly increase risk from
dioxins to human health or the environment.
EPA's proposal was based on a deterministic risk assessment and
data regarding dioxins in sewage sludge

[[Page 61086]]

collected in the 1988-1989 National Sewage Sludge Survey (NSSS). See 64
FR 72045, 72048-72051 (December 23, 1999) and the National Sewage
Sludge Survey (USEPA, 1990) for a full discussion of the proposed rule
and supporting documentation.
In addition, unrelated to dioxins in sewage sludge, EPA proposed
technical amendments to the frequency of monitoring requirements for
pollutants other than dioxins. These amendments were intended to
clarify but, with one exception, not alter the monitoring schedule in
the existing sewage sludge rule. The one exception would require
preparers of material derived from sewage sludge to determine the
appropriate monitoring schedule based on quantity of material derived
rather than quantity of sewage sludge received for processing.

B. Notice of Data Availability (NODA)

Based on comments critical of both the proposal's use of a
deterministic risk assessment and its use of more than decade-old data
on dioxins concentrations in sewage sludge, in 2001 EPA collected and
analyzed samples of sewage sludge nationwide in order to obtain new
information on the levels of dioxins in sewage sludge. EPA also
substantially revised the cancer risk assessment for dioxins associated
with land application of sewage sludge. EPA used new dioxins
concentration data in the revised risk assessment and conducted
statistical analyses to better understand the fluctuation of dioxins
concentrations in sewage sludge samples over time. In the NODA, EPA
summarized the new sewage sludge data, the revised risk assessment, and
presented an approach to assess potential non-cancer health effects of
exposure to dioxins associated with land application of sewage sludge.
EPA also presented a screening ecological risk analysis (SERA) of the
effects of dioxins in land-applied sewage sludge on ecological species.
EPA requested comments on the new data and risk analyses, additional
dioxins exposure information, and comments on any impact the data and
information might have on the 1999 proposed rule with respect to land
application of sewage sludge. EPA also requested comment on whether
monitoring requirements to measure dioxins in land-applied sewage
sludge should be promulgated in lieu of a numerical limitation.
In the NODA, EPA also presented information from EPA's draft dioxin
reassessment document, Exposure and Human Health Reassessment of
2,3,7,8-Tetrachlorodibenzo-p-Dioxin (TCDD) and Related Compounds. EPA
described implications of the draft dioxin reassessment for the final
determination regarding regulation of dioxins in land-applied sewage
sludge and requested public comment. EPA included this information in
the NODA in order to be in a position to fulfill its obligations under
the Gearhart v. Whitman consent decree. The consent decree requires EPA
to take final action on or before October 17, 2003, regardless of
whether EPA issues a final dioxin reassessment document, with some
schedule adjustment allowed depending on the timing of EPA's issuance
of a final dioxin reassessment document prior to October 17, 2003. EPA
has not issued a final dioxin reassessment document; thus, the October
17, 2003 deadline applies. Regarding the draft dioxin reassessment
documents discussed in the NODA, EPA has continued to revise these
documents, and the science continues to be under review. Review by the
National Academy of Sciences is the next review to be undertaken, as
specified by Congress in the Conference Report accompanying EPA's
fiscal year 2003 appropriation. H.R. Conf. Rep. No. 108-10, at 1445-46
(2003).

IV. What Final Action Is EPA Taking Today?

EPA has determined that no further regulation of land-applied
sewage sludge is needed to protect public health and the environment
from reasonably anticipated adverse effects from exposure to dioxins in
land-applied sewage sludge. Therefore, no numeric limitations,
monitoring, operational standards, or management practices are being
established in 40 CFR part 503 for dioxins in land-applied sewage
sludge.
While monitoring data could be useful to a local community to
discover whether a significant increase is occurring in the dioxin
concentration and assist in identifying the source of any such
significant increase (see later discussion), the data indicate that
such increases are short-term in nature, and the risk assessment
showing low risk to the HEI takes these spikes into account. Therefore,
EPA has determined that monitoring in lieu of a numerical limit is not
warranted.
With respect to revisions to the existing requirements pertaining
to frequency of monitoring of pollutants other than dioxins in land-
applied sewage sludge, EPA is not taking final action at this time.
Therefore, any comments on the proposed amendment to the footnote to
Table 1 in 40 CFR 503.16 are not being addressed today. EPA may take
final action on this proposed amendment in a subsequent rulemaking.

V. What Is the Basis for This Final Action for Dioxins in Land-Applied
Sewage Sludge?

A. Overview

Sewage sludge is a residual mixture of solids and water as a result
of wastewater treatment. Generally, sewage sludge consists of 2 to 28
percent solids in a water matrix. The solids component of sewage sludge
typically contains microbial residue, microbes and trace quantities of
chemicals such as metals and organic compounds, including dioxin and
dioxin-like compounds. In the United States, approximately 8 million
dry metric tons (DMT) of sewage sludge are produced annually by 16,000
wastewater treatment plants. Approximately 54 percent (4.32 million
DMT) are applied to land to fertilize and condition soils; 28 percent
(2.24 million DMT) are disposed of at municipal solid waste landfills;
17 percent (1.36 million DMT) are incinerated; and 1 percent (0.08
million DMT) is disposed of in lagoons or sewage sludge-only landfills.
Of the total amount land-applied, an estimated 85 percent (3.7 million
DMT) are applied to agricultural lands used to raise crops for human or
animal consumption. Sewage sludge is applied to some 0.1 percent of
available agricultural land in the United States. Other land
application sites include forests, reclamation sites such as strip
mines, and public-contact sites, such as parks, golf courses, highway
median strips, and lawns.
EPA has decided not to regulate dioxins in land-applied sewage
sludge because EPA considers the predicted risks to human health and
the environment from dioxin and dioxin-like compounds in land-applied
sewage sludge to be low. Based on recently collected data and
assessment of risk, EPA has concluded that the existing regulation of
sewage sludge in 40 CFR part 503 is adequate to protect human health
and the environment from the reasonably anticipated adverse effects of
dioxins in land-applied sewage sludge.
Risk is determined based on both toxicity and exposure. Regarding
toxicity, dioxins have been shown to elicit both cancer and a variety
of non-cancer effects in animals, and there is strong evidence to
indicate that humans are susceptible to the same toxic effects.
Although dioxins are found in extremely small quantities in water and
soil, they persist in the environment and accumulate in the food chain.
However, regarding exposure, EPA's evaluation of the effects on human
health due to

[[Page 61087]]

exposure to dioxins in land-applied sewage sludge shows the risks to be
minimal.
This evaluation looked at the segment of the U.S. population that
EPA identified as the most exposed to dioxins in land-applied sewage
sludge: farmers (and their families) who apply sewage sludge to their
land and consume a high percentage of their own products. This
population was selected in part because of their proximity to the land
where sewage sludge is applied and, more importantly, because of the
portion of their diet grown on land where sewage sludge is applied.
EPA's risk assessment shows that even these ``highly exposed
individuals'' (HEI) are at low risk of cancer from dioxins in land-
applied sewage sludge.
The risk assessment analyzed cancer risk from exposure to dioxins
in land-applied sewage sludge. The risk assessment predicted an excess
lifetime cancer risk to members of the highly exposed farm family that
is in the range of cancer risks that does not warrant additional
regulation of land-applied sewage sludge. Indeed, the number of cancer
cases for this farm family population is extremely low, less than one
cancer case per year.
Because the general population of the U.S. has lower exposure to
dioxins from land-applied sewage sludge than the modeled farm family,
the incremental cancer risk from exposure to dioxins in land-applied
sewage sludge for the general population (i.e., those not members of a
highly exposed farm family) is lower than the risk to the HEI.
Therefore, having found that the existing sewage sludge land-
application regulations (e.g., grazing restrictions, agronomic rate
application limitation) are adequate to protect the highly exposed
population from the cancer risks due to dioxins in land applied sewage
sludge, EPA concludes that the existing regulations are adequate to
protect the general population, which is subject to lower exposures.
With respect to non-cancer effects, EPA does not yet have a method
to calculate the non-cancer risks that may occur to either the highly
exposed modeled population or the general population. EPA used a model
to predict the increased dioxin body burden over prolonged exposure to
dioxins in land-applied sewages sludge. However, in the absence of an
acceptable daily dose for dioxins (also referred to also as a reference
dose, or RfD) or other measurement, EPA is not able to estimate the
potential development of non-cancer effects in the modeled HEI
population from the increases in dioxins body burdens. See section
VII.B. for a discussion of the evolving science with respect to
assessing non-cancer health risks from exposure to dioxins.
EPA also performed a Screening Ecological Risk Analysis (SERA) on
the risks to wildlife due to exposure to dioxins from land-applied
sewage sludge. The screen calculated the ratio of estimated doses of
dioxins to wildlife as a result of the land application of sewage
sludge to acceptable dioxin doses to wildlife (dioxin wildlife
benchmarks). While not definitive risk estimates, the results of the
SERA indicate that wildlife species should not be significantly
impacted by dioxins in land-applied sewage sludge.
In addition, the results of EPA's 2001 Dioxin Update to the
National Sewage Sludge Survey (USEPA, 2002b) indicate that dioxin
levels in sewage sludge have declined since 1988, the last time that
dioxins in sewage sludge were surveyed by EPA. There is reason to
believe that this downward trend in dioxin concentration in sewage
sludge will continue as additional regulatory controls are placed on
additional sources of dioxin creation, especially on various types of
combustion practices and their emissions, as well as effluent
limitation guidelines for the pulp, paper, and paperboard point source
category, 40 CFR part 430.
In summary, the information available today on dioxin exposures,
toxicity and assessed cancer risks supports EPA's determination that no
additional numeric limits or management practices are required to
adequately protect human health and the environment from the adverse
effects of dioxins in land-applied sewage sludge.

B. Assessment of Cancer Risk From Dioxins in Land-Applied Sewage Sludge

As EPA stated in the proposal and the NODA, EPA is basing its
decision with respect to human health impacts on an assessment of the
risk of cancer due to exposure to dioxins in land-applied sewage
sludge. Both the risk assessment for the proposed rule and the revised
risk assessment presented in the NODA were based on EPA's
identification of cancer as the hazard to be assessed.
1. Redefinition of the HEI and Assumptions Regarding the HEI: For
the December 1999 proposal, EPA modeled a ``rural family'' as the
Highly Exposed Individual (HEI) population. In the 1999 risk
assessment, EPA assumed that the modeled rural family's risk of adverse
health effects resulting from exposure to dioxins in land-applied
sewage sludge is greater than that of the general population because a
higher percentage of the family's diet consists of food grown on sewage
sludge-amended soil. At proposal, the rural family was assumed to
consume 10 percent of their beef, beef liver, and lamb diet, three
percent of their dairy diet, and 43-59 percent of their produce diet
from crops raised on sewage sludge-amended soil (64 FR 72053).
In contrast, the revised risk assessment conducted in support of
the final decision used a probabilistic method (Monte Carlo) to produce
an estimate of the distribution of risk to the HEI. In general, the
probabilistic risk assessment approach better characterizes the range
of potential risks, and better accounts for uncertainty and
variability. For the revised risk assessment, EPA retained the basic
assumption from the proposal that the modeled HEI population is at
greater risk than the general population. However, EPA revised a number
of the exposure assumptions with respect to the modeled HEI population.
In the revised risk assessment, EPA assumed that members of the
highly exposed farm family live on farms where sewage sludge is land-
applied as fertilizer or a soil amendment on pasture land as well as
crop land. In addition, in the revised risk assessment EPA assumed that
a higher percentage of the farm family's diet consists of food grown on
sewage sludge-amended soil. Specifically, EPA assumed that the farm
family consumes 49 percent of the beef and 25.4 percent of the dairy
products in their diet from products of their own farms. EPA also
assumed, for the first time, that the adults on the farm consume fish
caught from a nearby waterbody (stream) pond. As in the deterministic
risk assessment, the revised risk assessment assumed that the farm
family also raised a significant portion of its fruit and vegetable
diet on sewage sludge amended soils. A description of the modeled HEI
population and how its risk was estimated is presented in the
Background Document, Standards for Use or Disposal for Sewage Sludge,
Final Action (USEPA, 2003b).
In the NODA, EPA requested comments on the Agency's use of the farm
family scenario described for the revised risk assessment. A few
commenters agreed with EPA's definition of the HEI population as the
farm family. Most commenters believed that EPA's hypothetical farm
family risk scenario was unrealistic and would overestimate risk. They
argued that no family would farm its land in the manner described, nor
consume such a high percentage of food (up to 50 percent) grown on
sewage sludge-amended land. They also believed it

[[Page 61088]]

unlikely that every farm in America has a fish pond receiving dioxins
runoff from land-applied sewage sludge. A few other commenters believe
that EPA's assumptions were not sufficiently conservative, for example,
that the percentage of home grown food in the diet was too low.
Comments concerning the HEI also said that the risk assessment did not
consider the possibility that farmland would be developed and that
houses or schools could be built on farmland.
EPA disagrees with comments that assumptions for the modeled HEI
population are too conservative and should be changed. Regarding the
comment that the amount of food grown on sludge-amended land consumed
by farm families as modeled in the revised risk assessment is too
conservative, EPA disagrees. The values that EPA used to estimate the
proportion of the farmer's diet that is home produced were taken from
Table 13-71 (Fraction of Food Intake that is Home Produced) of the
Exposure Factors Handbook (USEPA, 1997), a peer reviewed source of data
for use in risk assessments. For similar reasons, EPA also disagrees
with comments that EPA's estimates of home grown food consumption are
not sufficiently conservative. In addition, as some commenters pointed
out, the risk assessment should model the ``reasonably maximum
exposed'' individual. EPA believes that the HEI modeled in the risk
assessment meets this description, and that ``reasonably maximum
exposed'' is not equivalent to ``maximum exposed.'' Although one could
conceive of the possibility that someone may consume up to100% percent
of their diet from home grown products, EPA does not believe it is
reasonable to use this assumption in the risk assessment.
One commenter stated that houses could be built on farmland in the
future and that EPA should factor this in (presumably to address
families living on sewage sludge amended soil). However, because the
risks associated with the scenario that EPA evaluated (the farm family
as the highly exposed population) are greater than the risks EPA would
estimate for a residential land use scenario, there is no need for EPA
to evaluate residential exposure. In addition, the Agency evaluated the
risks associated with a child's ingestion of sewage sludge amended
soil, which could be typical of a residential scenario. Those risks are
lower than those for a child's ingestion of contaminated beef and dairy
products as in the modeled farm family described herein. (USEPA,
2003a).
Another commenter stated that it is unreasonable to assume that
every farm has a fish pond receiving dioxins from runoff of land-
applied sewage sludge. Fish consumption by an adult recreational fisher
on the farm was one of the pathways used in the exposure model. EPA
agrees that while it is unlikely that every farm will have a waterbody
from which fish are caught and consumed, it is a possible scenario and
a valid one to include in the analysis. In any case, the risk
assessment indicates that the consumption of fish from a stream
receiving dioxins runoff in land-applied sewage sludge results in
minimal influence on the risk estimate.
2. Other Assumptions in the Risk Assessment: In addition to the
revised modeled HEI population assumptions (USEPA, 2003a), other
assumptions were used in the revised risk assessment. Again, these
assumptions, to the extent possible, are presented as a range of
values, which were modeled using a Monte Carlo probabilistic method. A
number of assumptions concern farming practices and sewage sludge
application rates. For sewage sludge application rates, EPA assumed a
distribution ranging from 5 to 10 metric tons of sludge per hectare
applied every other year for a period of time ranging from once to 40
years (that is, EPA assumed that there would be from one to 20
applications of sewage sludge). Half the acreage on the modeled farm
was assumed to be in tilled crop production and half permanently in
untilled pasture. EPA assumed that row crops are tilled three times per
year, and that tilling incorporates sewage sludge into the top 20 cm of
soil. EPA assumed that sewage sludge that is applied to pasture is not
tilled. We used these assumptions because they are typical of
agricultural application situations for soil amendment products by
convention.
Many of the assumptions and values used in the revised risk
assessment differed from those in the 1999 risk assessment for the
proposed rule. The revised risk assessment includes new exposure
pathways and mechanisms to more accurately portray farm conditions for
the modeled HEI population. For example, the 1999 risk assessment
assumed that pastured animals only eat sewage sludge-amended soil
containing dioxins; this was assumed to be the animals' only route of
exposure. In contrast, the revised risk assessment assumed that cattle
ingest dioxins from several sources: leaf surfaces containing dioxins
volatilized from the top two centimeters of soil; sewage sludge
particles that remain on the leaf surfaces; and direct ingestion of
sewage sludge-containing soil. The revised risk assessment also
included chickens and assumed that they ingest soil from a buffer area
that receives dioxins through erosion of surface soils from adjacent
sewage sludge-amended pasture and crop.
EPA requested comments on the specific assumptions outlined in the
revised risk assessment, and received a variety of public comments.
Some commenters believed that these assumptions, like those concerning
the HEI, were too conservative and reflected a worst-case scenario.
Others wanted EPA to evaluate additional exposure pathways and
scenarios (i.e., dermal exposure, risks for breast-fed infants combined
with risks for child and adult receptors, and soil ingestion rates that
reflect potentially different soil contact behavior for crops and
pasture). Other commenters believed EPA underestimated risk of cancer
from exposure to dioxins in land-applied sewage sludge. EPA received
several comments on the conceptual site models and exposure scenarios.
These comments included statements that the risk assessment did not
account for harvesting and land-use restrictions, or variation in
sludge application rates among different crops and regions. Other
commenters stated that modeling assumptions such as the HEI modeled
farm family being exposed to dioxins from multiple pathways were
questionable (uncertainty inherent in application of models and use of
many ``average'' values imbedded in the assessment) and the vapor
dispersion model may underestimate vapor concentration.
The revised risk assessment for dioxins in land-applied sewage
sludge does not include additional exposure pathways, however, EPA has
summed the risk from all pathways to estimate the overall risk to a
given receptor. As explained later in this notice, EPA evaluated the
risks to the adult, child, and nursing infant in the farm family. In
addition to ingestion of breast milk for the infant, the risk
assessment evaluated up to six additional exposure pathways and
exposure routes: (1) Inhalation of ambient air; (2) incidental
ingestion of soil in the buffer; (3) ingestion of above- and below-
ground produce grown on the crop land; (4) ingestion of beef and dairy
products from the pasture; (5) ingestion of home produced poultry and
eggs from the buffer; and (6) ingestion of fish from the nearby
waterbody. More detailed descriptions of the revised risk assessment
assumptions and methodologies are presented in the TBD, Section 5.

[[Page 61089]]

No data were available on the variation in sludge application rates
for specific crops or regions. Had these data been available, they
could have been considered in the analysis. In the revised
probabilistic risk assessment, however, EPA placed the conceptual farm
scenario in 41 different meteorological and agricultural soil regions
in the U.S. to account for variations in different crop harvesting and
land use restrictions. The analysis as conducted is conservative and
the risks estimated using these conservative use assumptions for the
crops requiring the greatest fertilizer application still demonstrate
low risks to even the HEI (members of a farm family that apply sewage
sludge to their own land and consume products from their land).
EPA disagrees with comments that the risk assessment does not
appropriately consider volatilization of dioxins from sewage sludge.
First, the equations that EPA used (USEPA, 2003a) to represent the
sewage sludge's environmental fate and transport in soil included
volatilization as a fate and transport mechanism. While EPA assessed
volatilization as a dioxin transport mechanism for several exposure
pathways, volatilization is an important component only for the
critical pathway of the contamination of forage crops grown on the
agricultural field with subsequent ingestion of these crops by beef and
dairy cattle. This is so because volatilization is the main mechanism
of dioxin transport from the sewage sludge soil mixture to the
receiving surfaces of the forage crop, which is a component of the
mechanism of dioxin exposure to grazing animals. Volatilization of
dioxins via other exposure pathways does not significantly contribute
to the exposure of dioxins to the HEI.
To address the vapor concentration question (i.e., dioxins
concentrations on the surfaces of forage crops), the mixing height
values used in this analysis are contained in the Industrial Source
Complex Short-Term Model, Version 3 (ISCST3), the air model used in
this analysis. This is an approved method for modeling area sources
such as agricultural fields. This model has been validated with
measurement data and is less conservative than the box model used in
the proposed rule, which did not include dispersion and deposition of
sewage sludge. A conservative modeling assumption is that land applied
sewage sludge remains in the top two centimeters (cm) of the receiving
soil for the pasture where the animals are grazed. This is an unlikely
assumption since weathering and natural soil organism (e.g. earthworms)
activity would naturally incorporate the sewage sludge into the soil at
greater depths. This assumption creates an upper end dioxin transport
from the sewage sludge soil mixture to the surface of the forage crop.
3. Cancer Slope Factor (Q1*): The cancer slope factor is used to
calculate the incremental cancer risk attributable to the exposure to a
pollutant. The cancer slope factor (also referred to as Q1*) is a
numeric value which relates the incremental probability of developing
cancer from exposure to a particular substance. The cancer slope factor
is expressed as excess lifetime cancer risk per unit exposure, and is
usually quantified in terms of milligrams or picograms toxic
equivalents of substance per kilogram of body weight/day ((pg TEQ/kg-
d)-\1\). The greater the numeric value of the cancer slope,
the greater the carcinogenic potency of the substance. For example, 1 x
10-\5\ is greater than the numeric value 1 x
10-\6\. The same slope factor is used to estimate cancer
risk for both children and adults. The cancer slope factor represents
the upper bound 95th percentile confidence limit of the excess cancer
risk from a lifetime exposure to a pollutant (i.e., the dose for which
increased risk of cancer is predicted for the most sensitive five
percent of the population).
For calculating cancer risk from exposure to dioxins, in the
revised risk assessment EPA used a cancer slope factor for TCDD of 1.56
x 10-\4\ picrograms toxic equivalence/kilogram body weight/
day ((pg TEQ/kg-d)-\1\) (USEPA, 1985). Thus, the estimate
for the 95th percentile excess lifetime cancer risk to the modeled HEI
population (i.e., the five percent of the HEI population that is most
exposed) is 2 x 10-\5\, or 2 in 100,000.
Cancer risk can also be expressed in terms of the number of
additional cases of cancer annually attributable to exposure to dioxins
in land-applied sewage sludge. This requires an estimation of the
number of people in the United States that fall into the farm family
scenario that EPA modeled. As explained in the NODA (67 FR 40554)
population could be no more than some 11,000 people. By assuming that
all sewage sludge produced in the U.S. is land-applied, and by
including all farm families whose diets consist of 50 percent of
products produced on their farms, EPA took the approach of calculating
a very high estimate of the size of the highly exposed population. A
more realistic estimate of the HEI population takes into account the
fact that only about half of the sewage sludge produced in the U.S. is
land applied, and that the number of individuals who consume both home-
grown dairy and beef can, by definition, be no greater than the smaller
of the number of individuals who consume either home-produced dairy or
home-produced beef. This approach results in an estimate of 1,600
persons in the HEI population, which is number of persons estimated to
consume home-produced diary products. Because it is unlikely that all
of those who consume home-produced dairy products also graze their
dairy cows on sewage sludge-amended pastures, even this number may
overestimate the size of the highly exposed population. See Background
Document, USEPA, 2003b for a detailed explanation of calculating the
HEI population. In order to present both the more realistic evaluation
as well as a high estimate of the number of excess cancer cases in this
population attributable to exposure to dioxins in land-applied sewage
sludge, EPA calculated these estimates as a range.
Using this range of 1,600 to 11,200 individuals in the HEI
population, EPA estimates that there could be between 0.002 to 0.01
total excess cancer cases in the HEI populations attributable to land
application of sewage sludge. This corresponds to additional annual
cancer cases of between 0.00003 and 0.0001 that would be attributable
to land application of sewage sludge. Thus, whether the HEI population
in the U.S. is estimated to be some 1,600 individuals or 11,200
individuals, or whether the maximum 95th percentile or more accurate
50th percentile risk is used, the number of excess lifetime cancer
cases attributable to dioxins in land-applied sewage sludge approaches
zero. EPA's methodology for reaching this estimate is explained as
follows:
EPA estimates individual excess lifetime cancer risk as the product
of an individual's lifetime average daily dose (LADD) of dioxins
(expressed as a TEQ) and the cancer slope factor for TCDD (see Table
1). EPA summed individual exposure and subsequent cancer risks from all
pathways relevant to an exposed individual to estimate the total
individual lifetime cancer risk from all pathways. The estimate of the
total number of lifetime cancer cases expected within a population is
the product of the individual excess lifetime cancer risk estimates for
all individuals in the population and the number of individuals in the
population. Because this estimate looks at the HEI population as a
whole, it is more accurate to apply the 50th percentile risk (1 x
10-\6\) than the 95th percentile risk, which actually
overestimates the predicted number of cancer cases for this population
group. The estimate of

[[Page 61090]]

annual cancer cases within a population is the total number of excess
lifetime cancer cases divided by a 70-year lifetime.
EPA used this procedure to derive the results of the revised risk
assessment. Specifically, in the exposure assessment EPA estimated the
HEI's dose of each 29 dioxin-like congeners detected in sewage sludge.
The dose of each congener was converted to a TEQ dose by multiplying
the congener's dose by the congener's toxicity equivalency factor
(TEF). The TEQ doses for each of the 29 congeners were then summed to
yield an overall TEQ dose to the individual for each exposure pathway
(e.g., inhalation, ingestion). Finally, the TEQ dose was multiplied by
the cancer slope factor (Q1*) to estimate the excess lifetime cancer
risk to the individual for each pathway of exposure. EPA estimated
total lifetime average daily dioxins exposure and excess lifetime risk
to the HEI by summing lifetime average daily dioxins exposures and
excess lifetime cancer risks across all of the exposure pathways
relevant to each modeled individual (adult, child, infant).
Many commenters questioned EPA's use of the 1985 guidance Q1*
rather than the slope factor presented for TCDD in the September 2000
Draft Dioxin Reassessment (USEPA, 2000). They argued that it made no
sense to assess cancer risk based on the 1985 cancer slope factor when
EPA itself had developed an alternate value. Another commenter said
that given the uncertainties in the assessment of the carcinogenicity
of dioxin and dioxin-like compounds, quantifying a cancer slope factor
and adopting a linear extrapolation model only magnified the
uncertainty. EPA conducted its risk assessment utilizing the cancer
slope factor from the 1985 guidance. Because of the terms of the
Consent Decree, in the NODA we also evaluated the cancer risks to the
modeled population by considering the cancer slope factor for dioxins
in the Draft Dioxin Reassessment (USEPA, 2000). EPA's final decision
not to regulate dioxins in land applied sewage sludge is in harmony
with either cancer slope. One commenter believed EPA's existing slope
factor was outdated and that the ongoing dioxin reassessment, or
perhaps the Great Lakes Initiative (GLI) cancer slope factor (USEPA,
1995) reflected more current science.
EPA believes that use of the 1985 guidance Q1* is reasonable. While
alternative cancer slope factor calculations have been under review,
there remains sufficient uncertainty as to whether a different Q1*
should be used for assessing cancer risk from dioxins exposure and what
the new Q1* should be. EPA reevaluated the 1985 cancer slope in 1990 in
the GLI (USEPA, 1995), by examining the pathological data from the
study upon which the cancer slope factor was derived. From this
reevaluation, both new tumor incidences and a new scaling factor were
employed to produce a new cancer slope factor. The GLI cancer slope is
approximately one half the value of the 1985 cancer slope factor. The
GLI cancer slope factor was used to establish water quality standards
for those water bodies. The Agency never officially adopted the GLI
cancer slope factor in its risk assessments for other programs because
by 1995 the Dioxin Reassessment was underway and additional science on
the carcinogenic mechanism for 2,3,7,8-TCDD was evolving. In addition,
the difference between the cancer risk estimate using the 1985 guidance
Q1* and other proposals (e.g., the GLI, alternate Q1* used in the NODA)
would not lead EPA to reach a different conclusion with respect to
whether the predicted adverse health effects (cancer) from dioxins in
land-applied sewage sludge requires EPA to regulate dioxins in land-
applied sewage sludge. A more detailed discussion of the cancer slope
factor is provided in section VII (``Discussion of Scientific
Information Presented in the NODA'').
4. Method of Calculating Risk to the Modeled HEI Population: As
explained previously, using the results of all samples from the EPA
2001 dioxin update survey, EPA modeled all 29 dioxin and dioxin-like
congeners individually, and then summed the results for all congeners
to arrive at the risk for dioxins expressed as TEQ. EPA estimated
excess lifetime cancer risks and corresponding average lifetime daily
exposure to dioxins for a highly exposed farm adult and child (see
section V.D. for a discussion of the EPA 2001 dioxins update survey).
As described in the NODA, the revised risk includes an analysis of
exposures to individuals using 3,000 iterations of the Monte Carlo
analysis. Individuals were subdivided into two exposure scenarios,
those whose exposures begin during childhood and those whose exposures
begin in adulthood. To account for the fact that children's intake
rates vary with age, the analysis used separate sets of exposure
parameters for four age cohorts: ages 1-5, ages 6-11, ages 12-19, and
ages 20-70. To capture the higher intake-rate-to-body weight ratio of
children, a start age between the ages of 1 and 6 was randomly selected
for all children for each iteration in the probabilistic analysis.
Children (defined as between one year and six years of age) are an
important sensitive population in risk assessment because they may be
more highly exposed than adults. This age range was selected because
this represents the highest consumption rate (intake/body weight) for
most of the exposure pathways evaluated in this risk assessment.
Compared to adults, children may eat more food and drink more fluids
per unit of body weight. This higher intake-rate-to-body weight ratio
can result in a higher average daily dioxins dose per body weight for
children as compared to adults. The estimated excess lifetime cancer
risk for individuals whose exposure begins in childhood is less than or
equal to the estimated excess lifetime cancer risk for adults whose
exposure begins later in life. The reason for this is that children's
mobility generally is greater than that of adults. That is, overall,
the period of time that a child will occupy a given residence is
shorter than the period of time an adult will occupy a given residence.
Therefore, individuals whose exposures to dioxins from land-applied
sewage sludge in home-produced foods begins in childhood are, in
general, assumed to be exposed for a shorter duration than those whose
exposure begins in adulthood (USEPA, 2003a).
Infants are also an important sensitive population considered in
the revised risk assessment. Infants may be exposed to dioxin-like
compounds via the ingestion of breast milk. The characterization of
risks to infants of farmers and home gardeners was considered
separately from the characterization of risks to older children (i.e.,
aged 1 year or older). While risks to children and adults were
integrated to assess individuals for whom exposure first occurs during
childhood but continues into adulthood, the lifetime risks to infants
were calculated separately from the risks to older children (i.e., ages
1 year or older) and adults. For infants, exposure during the first
year of life was averaged over an expected lifetime of seventy years to
derive a LADD that was then used to calculate risk. The ``lifetime''
risk to infants thus should be thought of as the contribution to an
individual's lifetime risk that is due to ingestion of breast milk from
a mother exposed to dioxins in home-produced foods derived from land-
applied sewage sludge.
Table 1 below provides percentiles of the distribution of estimated
excess lifetime cancer risk to a farm family adult and child who
consume home-

[[Page 61091]]

produced foods derived from land on which sewage sludge has been
applied.

Table 1.--Risks and Daily Exposure for Highly Exposed Individuals for All Exposure Pathways
[Q1*=1.56 x 10-4 (pg TEQ/kg-d-1]
----------------------------------------------------------------------------------------------------------------
Adult * Child **
---------------------------------------------------------------
Percentile Daily Daily
Risk exposure, pg Risk exposure, pg
TEQ/kg-d TEQ/kg-d
----------------------------------------------------------------------------------------------------------------
50th............................................ 1 x 10-6 0.0086 1 x 10-6 0.0094
75th............................................ 4 x 10-6 0.026 3 x 10-6 0.021
90th............................................ 1 x 10-5 0.064 7 x 10-6 0.042
95th............................................ 2 x 10-5 0.11 1 x 10-5 0.062
----------------------------------------------------------------------------------------------------------------
* Initial exposure begins in adulthood.
* Initial exposure begins during childhood.

As Table 1 shows, the median exposed HEI (at the 50th exposure
percentile), even with the conservative assumptions built into the
definition of the HEI, has a one in a million excess lifetime risk of
cancer. An HEI at the high end of the exposure distribution (i.e., one
at the upper 5 percent exposed or the 95th percentile) has a 2 in
100,000 excess lifetime cancer risk from exposure to dioxins in land-
applied sewage sludge. Both the lifetime and annual excess cases of
cancer are considered conservative based on the assumptions used to
model the HEI. EPA's reference to the 95th percentile exposure scenario
and risk estimate is accompanied by the understanding that only five
percent of the total number of individuals modeled in the HEI
population (estimated to be 80 to 560 individuals nationwide) has an
estimated lifetime cancer risk of 2 in 100,000 or greater. This risk
estimate is considered to be unlikely based on the conservative
assumptions used in constructing the HEI in a farm family. The
remainder of the modeled HEI population will have a lower potential
cancer risk because they are less exposed to dioxins than at the 95th
percentile exposure scenario.
Certain commenters expressed concern that the 1999 human health
risk assessment was limited to characterization of cancer risks,
stating that the non-cancer health effects of dioxins may be a more
serious concern than cancer because non-cancer health effects may occur
at lower doses and may affect more body systems. Commenters recommended
that non-cancer endpoints be considered in Round 2 or that draft
reference doses be used to evaluate non-cancer endpoints.
EPA based the revised risk assessment for dioxin-like constituents
in sewage sludge applied to agricultural land and its decision not to
regulate dioxins in land-applied sewage sludge on the cancer endpoint
because it is the most scientifically well-established and well-
supported endpoint. Although EPA and others have been studying non-
cancer human health effects from exposure to dioxins, a methodology to
adequately assess those risks has not yet been established. Details of
this assessment and developments in the study of assessing non-cancer
risks are discussed further in section VII. Discussion of Scientific
Information Presented in the NODA.

C. Findings Concerning Ecological Effects

In response to public and peer review comments received on the 1999
proposal, EPA performed a screening ecological risk analysis (SERA)
(USEPA, 2003a). The SERA used a two-phased approach that includes: (1)
an initial screening assessment to determine whether the dioxins
concentrations in land-applied sewage sludge warranted further
assessment. This effort was an initial bounding estimate to assess the
upper bound potential for ecological effects at the high end of
exposure, and (2) a more refined assessment using a combination of
higher end central tendency exposure assumptions regarding
environmental media concentrations, receptor-specific dietary
preferences, and ecological benchmarks. EPA used a hazard quotient (HQ)
approach to assess the potential for adverse ecological effects. For
the SERA, the HQ was the ratio of the modeled exposure and an exposure
(an ecological benchmark) that is expected to be without adverse
ecological effects. When HQs are greater than one, exposures exceed
ecological benchmarks, suggesting the potential exists for adverse
ecological effects. When HQs are less than one, exposures are less than
ecological benchmarks, suggesting that there is minimal potential for
adverse ecological effects. In the SERA, EPA determined that all HQs
were less than one.
In the NODA, EPA discussed the SERA and requested comments on the
methodology, the data used, and the results derived from the SERA. As
with the revised cancer risk assessment, the SERA used the
concentrations of dioxins obtained from new sampling data in the 2001
Dioxin Update (USEPA, 2002b) of the National Sewage Sludge Survey
(NSSS). As explained in section V.D., the 2001 dioxin update survey
data consist of sewage sludge samples obtained from 94 municipal
wastewater treatment facilities, and are considered a nationally
representative sample.
The SERA addresses risks to mammals and birds, the receptors that
are expected to have the highest exposure to dioxins. The assessment
does not address risks to other receptor groups such as invertebrates
and plants. The potential for dioxins to bioaccumulate in wildlife
receptors is specifically addressed through analysis of the ingestion
pathway. The analysis includes receptors exposed through ingestion of
both aquatic and terrestrial food items and thus addresses the
potential for bioaccumulation of dioxins from soil, surface water, and
sediment.
The bioaccumulation factors (BAFs) for terrestrial invertebrates
used in the analysis were derived from empirical data and assume a
linear relationship between the concentrations of dioxins in soil and
in food items. However, the BAFs are relatively conservative, and EPA
considers them adequate for a screening level analysis.
There was disagreement among commenters concerning the adequacy of
the SERA and whether dioxins in land-applied sewage sludge posed a risk
to wildlife. Some commenters agreed with EPA's conclusion that there
was no serious ecological risk, while others said that the uncertainty
in the model's applications, and the many ``average''

[[Page 61092]]

values in the assessment, made the low HQs questionable. Other
commenters indicated there was a potential for bioaccumulation in
several forms of wildlife.
EPA believes the SERA is adequate to predict hazards to wildlife
species from dioxins in land-applied sewage sludge. The SERA was
designed to be consistent with EPA's Guidelines for Ecological Risk
Assessment (USEPA, 1998). See the Technical Background Document (TBD)
for a discussion of the SERA (USEPA, 2003a). Because the ecological
analysis was a screening analysis intended only to indicate the
potential for adverse ecological effects, EPA considers the qualitative
uncertainty analysis to be adequate. The uncertainty discussion
identifies sources of uncertainty, discusses their implications for the
outcome of the analysis, and, where possible, indicates whether the
uncertainty is likely to cause an over or underestimation of risk.
Screening-level ecological risk assessments are designed to provide,
for those chemicals and receptors that pass the screen (as in dioxins),
a high level of confidence that there is a low probability of adverse
effects to ecological receptors.
The SERA provides insight into the potential for ecological effects
from dioxins in land-applied sewage sludge. The approach used shows
that the exposures to animals in terrestrial and water body margin
habitats do not exceed protective ecological benchmarks (that is HQs do
not exceed one), suggesting that dioxins in land-applied sewage sludge
do not pose a high potential for adverse ecological effects.

D. Indications From the 2001 Survey of Dioxins in Sewage Sludge

In response to comments on the proposal that EPA needed data more
current than the 1988 National Sewage Sludge Survey (NSSS) data, EPA
conducted a national sampling and analysis effort to measure dioxins in
sewage sludge in 2001 (USEPA, 2002b). The EPA 2001 Dioxin Update of the
NSSS provides data that support the calculation of unbiased national
estimates (i.e., based on a stratified random selection of publicly
owned treatment works) for dioxin and dioxin-like compounds in sewage
sludge. In addition to being more recent, the 2001 data also include
concentrations of coplanar PCB congeners, along with dioxin and furan
congeners. Coplanar PCB congeners were not analyzed in the 1988 NSSS.
EPA sampled sewage sludge from a stratified random sample of 94
POTWs selected from the sample of 174 POTWs surveyed in the 1988 NSSS,
stratified into four size categories: those with a daily flow of less
than one million gallons per day (MGD), 1-10 MGD, 10-100 MGD, and
greater than 100 MGD. The 174 POTWs selected in 1988 had been selected
from the approximately 11,000 POTWs in existence at that time that had
secondary treatment. The 11,000 were sampled according to stratified
probability design (i.e., by size based on wastewater design flow). The
sample for the 2001 Dioxin Update to the National Sewage Sludge Survey
was a subset of the sample for the 1988 NSSS and thus resulted in a
statistically valid national estimate of dioxin congener concentrations
in the Nation's sewage sludge. EPA considers dioxin and dioxin-like
congener concentrations used in the revised risk assessment to be
representative of dioxins congener concentrations in sewage sludge
nationwide because of the sample design. See Section III, Statistical
Support Document for the Development of Round 2 Biosolids Use or
Disposal Regulations (USEPA 2002b).
The sewage sludge samples were processed to produce a single
representative sample for each facility. In addition, the data reflect
probability-based survey weights based on the numbers of POTWs in the
four strata defined on the basis of quantity of flow. Since the few
POTWs in the flow group receiving more than 100 MGD of influent
wastewater produce the largest amounts of sewage sludge, the
probability-based sample design incorporated an over-sampling of large
POTWs. The survey weights reflect this feature.
The 2001 dioxins update survey was designed based on the 1988 NSSS
in order to allow comparability of statistically valid national
estimates, although, as explained later, a number of factors limit the
degree of comparison that is possible. A comparison of results for
dioxin and furan congeners obtained in the 1988 and 2001 surveys is
presented in Table 2. This table summarizes the results using
alternative methods for handling non-detect measurements. These
comparisons do not include coplanar PCB congeners because the 1988 NSSS
did not collect coplanar PCB congener data.

Table 2.--National Estimates (nanograms/kilogram dry matter basis) for Dioxin and Furan Congeners in the EPA 2001 Dioxin Update Survey and 1988 NSSS
--------------------------------------------------------------------------------------------------------------------------------------------------------
Zero for nondetects \1/2\ minimum level of ML for nondetects
-------------------------------- quantitation (ML) for -------------------------------
Method for handling nondetects (estimate) nondetects
2001 1988 -------------------------------- 2001 1988
2001 1988
--------------------------------------------------------------------------------------------------------------------------------------------------------
Mean.................................................... 21.70 46.50 21.70 67.30 21.80 88.20
Std. dev................................................ 47.5 153.0 47.5 153.0 47.5 157.00
Maximum................................................. 682.00 1870.00 682.00 1870.00 682.00 1870.00
99th%................................................... 100.00 450.00 100.00 453.00 100.00 466.00
98th%................................................... 54.40 402.00 54.40 404.00 54.40 455.00
95th%................................................... 33.30 301.00 33.30 303.00 33.30 340.00
90th%................................................... 31.40 56.70 31.60 152.00 31.70 226.00
50th%................................................... 15.50 5.68 15.50 34.20 15.50 52.40
--------------------------------------------------------------------------------------------------------------------------------------------------------

The EPA 2001 dioxin survey suggests that dioxins levels in sewage
sludge have decreased from 1988 to 2001. In addition, the upper
percentile values obtained in the EPA 2001 dioxins update survey are
lower than those obtained in the 1988 NSSS. See Statistical Support
Document for the Development of Round 2 Biosolids Use or Disposal
Regulations (USEPA, 2002b) for a full discussion of the 2001 updated
dioxins survey.
It is not possible to draw firm conclusions with regard to changes
in dioxin concentrations in sewage sludge nationally, due to
differences in the two surveys caused by changed circumstances since
1988 (13 years between surveys). During this time, changes may have
occurred at POTWs, and there have been changes and improvements in
analytical methods. Nevertheless, as discussed in the NODA, EPA has
made a number of

[[Page 61093]]

observations regarding changes in dioxins concentrations in sewage
sludge based on a comparison of the data in the two surveys. As
mentioned previously, the 94 POTWs participating in the EPA 2001 dioxin
update survey also participated in the original 1988 NSSS. Samples from
14 of the POTWs showed dioxins concentrations (dioxins and furans only)
equal to or greater than 93 ppt TEQ from at least one of the surveys.
These same 14 POTWs exhibited the greatest differences in the dioxins
and furans concentrations when comparing the results of the 1988 and
2001 EPA surveys. The other 80 POTWs participating in both surveys have
substantially smaller differences, as well as lower dioxins levels
measured in both surveys. Of the 14 POTWs with the greatest differences
between the two surveys, four had large increases in sewage sludge
dioxins concentrations and ten had large decreases in sewage sludge
dioxins concentrations from 1988 to 2001.
No sampled POTW with high levels of dioxins in sewage sludge in the
1988 NSSS showed high levels in the 2001 update survey. Based on these
data, EPA infers that POTWs with higher concentrations of dioxins in
their sewage sludge may experience a greater variability in dioxins
concentrations over time, and that higher dioxins levels may not remain
high for a significant period of time. It is possible that POTWs with
higher concentrations of dioxins in their sewage sludge intermittently
receive dioxins from unidentified but specific sources via the sewer
system. Likewise, POTWs with moderate or low levels of dioxins in their
sewage sludge may experience much less variability in dioxins
concentrations over time. This second group of POTWs appears to be
experiencing typical environmental background variation of dioxins
levels.
EPA requested comments on the significance of the differences in
dioxins concentrations in sewage sludge measured in the EPA 2001 dioxin
update survey compared to dioxins concentrations in sewage sludge
measured in the 1988 NSSS. Several commenters noted that dioxin levels
had decreased between the 1988 survey and the 2001 survey. One
commenter was unsure of the implications of the finding, because
analytical methods have improved and PCBs were not analyzed in earlier
surveys, but felt that both dioxin and PCB levels have most likely
declined because of changes in their use.
Three commenters said that the results indicated that attendant
risks were also decreasing; one went on to say that EPA should use the
findings to promote public confidence in land application of sewage
sludge and dioxins regulatory limits. Another respondent said that the
decrease made stringent regulatory requirements for sewage sludge
unnecessary and that existing dioxins controls are having a noticeable
effect on environmental releases. One commenter said that the findings
should give regulatory agencies and the public confidence that
decisions based on current data sets will provide adequate protection
under reasonably anticipated future conditions.
One commenter endorsed EPA's response to previous public comments
by obtaining new data in the 2001 dioxins update survey to the 1988
NSSS, saying that the initiative demonstrated EPA's commitment to use
reliable data to provide accurate risk assessments of sewage sludge.
Another commenter felt that EPA had inappropriately weighted data from
the NSSS by giving greater weight to samples from small-production
POTWs and thereby understating risk estimates. Another commenter was
unsure whether the study was designed to test the hypothesis that there
might be differences in dioxins concentrations between small and large
facilities. Finally, some commenters felt that the survey data support
taking no action for dioxins in land-applied sewage sludge.
EPA believes that appropriate consideration of data from small
POTWs was made in the design of the sample for the survey. A simple
random sample of POTWs, without regard to the amount of influent
wastewater, would not have provided adequate representation of the
POTWs receiving the larger amounts of influent wastewater. In fact, a
simple random sample, drawn without regard to size, would have been
dominated by POTWs in the less than 1 million gallons per day (MGD)
flow group.
Regarding indications from the data, EPA believes that the data
suggest an overall decrease in dioxins. New or revised pretreatment
requirements and pollution prevention measures adopted since 1988 would
be expected to have reduced dioxins in the influent to POTWs. The
decrease of dioxins in sewage sludge observed in the two surveys
supports the Agency's conclusion that new regulatory requirements for
dioxins in land-applied sewage sludge are unnecessary.

VI. Environmental Justice

Environmental justice and equity concerns involve consideration of
the potential for minorities and people of lower economic status to be
impacted by dioxins exposures to a greater degree than the rest of the
general population. EPA believes the HEI analysis addresses reasonable
high end exposures that could represent a subsistence low income farm
family. The HEI analysis addresses exposure regardless of minority or
economic status.

VII. Discussion of Scientific Information Presented in the NODA

For the past 12 years, EPA has been conducting a reassessment of
the human health risks associated with dioxin and dioxin-like
compounds. This reassessment is not a final document. In this decision
the Agency continued its practice of using the best available data
published from a variety of sources that meet the Information Quality
Guidelines. The Agency considered all such data and associated
uncertainty to determine the strength of the evidence in finalizing
this regulatory action related to dioxin and dioxin-like compounds.

A. Assessing Cancer Risk

1. Incremental Cancer Risk
As explained in section V.A. of this Notice, the revised risk
assessment for dioxins in land-applied sewage sludge supporting today's
final action uses the 1985 Q1* of 1.56 x 10-4 (pg TEQ/kg-
d)-1. The estimated upper bound lifetime risks for highly
exposed farm family adults using this Q1* range from 2 x
10-5 at the 95th percentile exposure to 1 x 10-6
at the 50th percentile exposure for multi-pathway exposure to dioxins
through land-applied sewage sludge (see Table 1). There are two
exposure scenarios for adults living in the farm family exposed to
dioxins in land-applied sewage sludge: (1) Individuals whose exposure
begins in adulthood referred to as ``Adult'' in Table 1, and (2)
individuals whose exposure begins in childhood referred to as ``Child''
in Table 1. As explained in section V.A., the estimated lifetime cancer
risks for the child are less than or equal to the estimated lifetime
cancer risks for the adult. These risks correspond to estimated daily
exposures for the latter group of adults ranging from 0.11 at the 95th
exposure percentile to 0.0086 pg TEQ/kg-d at the 50th exposure
percentile.
Use of the alternative Q1* of 1 x 10-3 (pg TEQ/kg-
d)-1 that was considered in the NODA would result in
estimated high-end multi-pathway excess lifetime cancer risks for the
latter group of adults in the highly exposed farm family ranging from 1
x 10-4 at the 95th exposure percentile to 6 x
10-6 at the 50th exposure percentile. These estimated risks
in the NODA are based on the same daily exposures indicated

[[Page 61094]]

in Table 1. Again, the estimated excess lifetime cancer risks expressed
for individuals born on the farm (see discussion above and in USEPA,
2003b) would be less than or equal to the estimated risks for
individuals exposed to dioxins on the farm starting some years after
birth (i.e., the corresponding values are 6 x 10-5 at the
95th exposure percentile and 6 x 10-6 at the 50th exposure
percentile).
2. Background Cancer Risk
The significance of the exposure and cancer risk due to a specific
source such as dioxins in land-applied sewage sludge can be understood
in the context of general population background exposure to dioxins
from all sources. In other words, the exposure attributed to a
particular source can be considered in the context of its contribution
to the overall risk.
The background lifetime cancer risk to the general population from
exposure to dioxins (all sources) is approximately 2 x 10-4
using the 1985 Q1* of 1.56 x 10-4 (pg TEQ/kg-
d)-1. The background risk to the HEI is identical to the
background risk to the general population, since it is the risk
associated with exposure to dioxins from all sources.
As previously explained, the estimated cancer risk for the HEI from
exposure to dioxins in land-applied sewage sludge is 2 x
10-5 using the 1985 Q1*. However, excess lifetime cancer
risk associated with dioxins in land-applied sewage sludge is very low
compared to the background lifetime cancer risk from dioxins. At the
95th percentile, the increase in risk of the HEI (farm family estimated
to be no more than 11,200 persons in the US) is about 10 percent of
their background risk. As previously explained, excess cancer cases for
this modeled population from exposure to dioxins in land-applied sewage
sludge are estimated to be 0.002 to 0.01, again depending on the HEI
analysis chosen (USEPA, 2003b), using the 1985 Q1*. Further, EPA
estimates that the excess lifetime cancer risk to the overall U.S.
general population from exposure to dioxins in land-applied sewage
sludge is likely to be much lower than the excess lifetime cancer risk
to the HEI, and as such, correspondingly lower relative to the general
population's background risk from dioxins. This is because the general
population's exposure to dioxins from dietary items grown on farms that
use sewage sludge as a fertilizer or soil conditioner is significantly
lower than the modeled HEI farm family's exposure to dioxins from the
crops that they consume from their farms that use sewage sludge.
(USEPA, 2003b).
Note that actual risks for individuals are a function of dietary
habits, as well as a particular individual's susceptibility to develop
cancer, and may be higher or lower. Thus, high-end incremental excess
lifetime cancer risk estimates for highly exposed farm families from
dioxins in land-applied sewage sludge are approximately an order of
magnitude (i.e., ten times) lower than background risks.
Based on this evaluation of the range of cancer risks to the
modeled HEI , EPA believes the projected cancer risks to the HEI from
dioxins in land-applied sewage sludge are reasonable.

B. Assessing Non-Cancer Risk

EPA generally uses a reference dose (RfD) for evaluating the
potential for non-cancer effects for an incremental exposure that
results from a specific source of contamination. The RfD is an estimate
of a daily oral exposure to the human population that is unlikely to
cause an appreciable risk of deleterious non-cancer effects over a
lifetime. RfDs for particular contaminants are useful health benchmarks
when background exposures are low or nonexistent.
As discussed in section VII of the NODA, background exposures for
dioxin-like compounds have been quantified by EPA as being in the range
of 1 pg TEQ/kg/d for adults. On a body burden basis, the background
body burden for dioxin TEQs for adults in the U.S. has been estimated
to be 5 nanograms toxic equivalence per kilogram body weight (ng TEQ/
kg), on a whole body weight basis (USEPA, 2002a). As the NODA
suggested, conventional approaches to calculating an RfD for dioxins
would result in an RfD that is likely to be substantially below current
background intakes. For this reason, EPA believes that establishment of
an RfD that is below typical background exposures is uninformative in
judging the significance of incremental dioxins exposures on human
health and therefore not useful for subsequent risk management
decisions for dioxins. Consequently, EPA has not developed an RfD for
dioxins.

VIII. Public Comments and Other Considerations

EPA received over 200 comments on the 1999 proposed amendments to
the Standards for the Use and Disposal of Sewage Sludge and 27 comments
on the 2002 June 12, 2002 NODA regarding the land application of sewage
sludge. The majority of the comments were addressed by the NODA or are
addressed earlier in this Notice. A summary of other major comments is
presented below, along with a summary of EPA's responses. A complete
copy of all public comments and EPA's response to comments can be found
in the Response to Comments Document in the docket (USEPA, 2003c).

A. Definition of ``Dioxins''

Several comments were received concerning the proposed definition
of dioxins. Commenters indicated a preference for two separate and
distinct definitions for ``dioxin'' and ``coplanar PCBs'' (i.e.,
dioxins would mean tetra through octa chlorinated dibenzo-p-dioxin and
furan congeners; and coplanar PCBs would mean the 12 coplanar PCB
congeners).
EPA Response: As previously mentioned, EPA defined ``dioxins'' in
the proposed rule as 29 specific congeners of PCDDs, PCDFs, and
coplanar PCBs that have been found in sewage sludge. The proposed
definition of ``dioxins'' specifies seven 2,3,7,8,-substituted
congeners of PCDDs, ten 2,3,7,8-substituted congeners of PCDFs, and
twelve coplanar PCB congeners. EPA had proposed a definition of dioxins
using TEF values for dibenzo-p-dioxins and furans described in USEPA
1989 and the WHO 98 TEF scheme for coplanar PCBs. As explained in the
NODA (67 FR 40556), EPA now uses the WHO 98 system of TEFs to account
for the overall toxicity of complex mixtures of all 29 congeners. The
TEF system is accepted worldwide as the most scientifically defensible
and most easily implemented method to assess these mixtures in risk
assessments.

B. The Need for Regulating Dioxins in Land-Applied Sewage Sludge

EPA received a number of comments regarding the need, or lack of
need, to regulate dioxins in land-applied sewage sludge. There was
disagreement among the comments premised on dioxins levels in the
environment and perceived or real risks. Comments in favor of
regulation (including setting numerical limits) included suggestions
that: (1) A regulatory program is needed to ensure that dioxins are not
land-applied, (2) it is illogical not to have a regulatory limit for
dioxins when EPA regulated various metals in sewage sludge, (3) a risk-
based limit is necessary, (4) sewage sludge is a significant source of
dioxins and should therefore be regulated, (5) EPA should establish a
risk-based limit and not a limit based on the 95th percentile
concentration of dioxins measured in the 2001 dioxins update survey,
and (6) EPA has traditionally used a one-in-one-million risk as
acceptable for regulation,

[[Page 61095]]

and that there is no justification for setting less stringent standards
for sewage sludge.
Commenters in favor of not regulating dioxins in sewage sludge felt
that there was no need for numeric limits or other requirements,
because the overall risks were well within EPA acceptable limits, that
the data supported no further regulation, and that EPA failed to
address the issue of whether further reductions in exposure were
necessary or cost-effective.
EPA Response: For the reasons discussed elsewhere in this Federal
Register notice, EPA has decided not to regulate dioxins in sewage
sludge that is land applied. These decisions are based on the revised
cancer risk assessment, the SERA, and 2001 Dioxin Update Survey data.
Weighing risks using the collective body of scientific information, EPA
has concluded that the increased risks of humans developing cancer from
exposure to dioxins in land-applied sewage sludge, as well as effects
to the environment, are reasonable, and that no further regulation is
warranted. Therefore, neither numeric limitations nor management
practices for dioxins in land-applied sewage sludge are being imposed.
Since the general population consumes only a small fraction of
their diets from products grown on farms with land-applied sewage
sludge, EPA assumed that a regulatory decision that is protective of
the highly exposed farm family is also protective of the general
population. EPA's risk analysis has shown that when dioxins TEQ
concentrations in sewage sludge are modeled, only five percent of the
population was at a risk level of 2 x 10-5. EPA believes
that the actual risk is likely to be lower, due to the many
conservative assumptions used in constructing the HEI risk
characterization.
Regarding comments that there is no justification for setting less
stringent standards for sewage sludge than one-in-one-million risk, the
revised risk assessment for dioxins in land-applied sewage sludge
indicates that an individual in the highly exposed modeled population
(estimated to be between approximately 1,600 and 11,200 people) has an
estimated excess lifetime cancer risk ranging from 1 x 10-6
to 4 x 10-5 (50th to the 99th percentile exposure) for
exposure by multiple pathways. EPA further notes that the lifetime
cancer risk ranging from 1 x 10-6 to 4 x 10-5 may
be overestimates due to the substantial number of conservative
assumptions used in the revised risk assessment. As a result, the
Agency does not agree that the risks discussed here warrant further
regulation.

C. Groundwater Exposure

Certain commenters stated that EPA did not take into consideration
the potential exposure to groundwater impacted by dioxins in land-
applied sewage sludge.
EPA Response: The Agency did not analyze a groundwater
contamination pathway because dioxins are hydrophobic and they bind
very tightly to the sewage sludge/soil matrix. Our analysis found that
transport of dioxins through the soil to groundwater, in the subsurface
environment, was minimal. Details are provided in the TBD (USEPA,
2003).

D. Synergistic Effects

Some public comments indicated that EPA did not consider
synergistic effects. They asserted, for example, that dioxins can be
mobilized by solvents and surfactants, which are common in sewage
sludge. Commenters also asserted that exposure to dioxins may increase
susceptibility to other carcinogens and that this dimension should be
analyzed.
EPA Response: There are no models or data available to address
synergistic effects with respect to the fate and transport of diverse
types of pollutants. Therefore, EPA could not assess such effects from
other pollutants acting in combination with the 29 dioxin,
dibenzofuran, and coplanar PCB congeners modeled by EPA. While such
effects are always possible, EPA is not aware of scientific evidence to
date suggesting that any such effects are likely to be significant for
dioxins interacting with other pollutants in sewage sludge. The TEF/TEQ
approach as outlined in today's notice allows EPA to assess the toxic
effects from exposure to the sum of all 29 dioxin and dioxin-like
congeners.

E. Voluntary Program

EPA received a wide variety of comments on methodologies to reduce
dioxins sources and contamination. Two commenters agreed with EPA's
suggested methodology for identifying dioxins sources (i.e.,
identifying dioxins sources by tracing their congener
``fingerprints''). Some supported the use of voluntary programs in
combination with regulatory standards and monitoring programs. Others
suggested that a voluntary program only is sufficient, but that EPA
should develop guidance to provide additional details and explain how
communities can utilize the voluntary methodology. There was concern
about who would define ``high'' concentrations of dioxins in sewage
sludge or ensure that adequate steps would be taken to reduce high
dioxins concentrations if such a program were voluntary. Some
commenters asserted that EPA should positively encourage facilities
with a history or likelihood of elevated dioxins levels in sewage
sludge to monitor and investigate possible sources contributing to high
dioxins levels. One commenter noted that the suggested EPA methods
would be expensive and perhaps beyond the means of POTWs.
Another commenter said that EPA should require management practices
to lessen human exposure to sewage sludge in which dioxins are below
the numeric limit and should require POTWs to develop pretreatment
programs to reduce dioxins in sewage sludge and minimize dioxins
discharges into sewer systems.
EPA Response: With today's final notice EPA is imposing no
regulatory requirements on small or large facilities, including
monitoring. However, EPA believes that there may be local benefits from
establishing a voluntary monitoring and source investigation and
identification program for dioxins in land-applied sewage sludge for
some POTWs.
EPA believes that voluntary monitoring for dioxins in sewage
sludge, combined with a source identification program when high
concentrations of dioxins in sewage sludge are encountered, could
identify dioxins sources that contribute to any elevated levels of
dioxins in sewage sludge. Mixtures of the 29 dioxin congeners have
distinct patterns (i.e., profiles or fingerprints) depending on the
dioxins source. For example, a congener profile that is dominated by
chlorinated dibenzofurans is often characteristic of a chemical
manufacturing source. Voluntary monitoring and source identification,
and perhaps a follow-up source reduction program, utilizing these
fingerprints, could assist in the identification and subsequent
mitigation or elimination of dioxins sources when relatively high
dioxins concentrations in sewage sludge are detected.
EPA encourages POTWs to consider implementing a voluntary sewage
sludge dioxins monitoring and dioxins source identification program
through an Environmental Management System (EMS) approach. An EMS for a
wastewater utility that generates sewage sludge is a voluntary program
that encourages a utility to perform above and beyond mandatory Federal
and State sewage sludge requirements and, thereby, improve their
environmental

[[Page 61096]]

performance in all areas of wastewater management including the use or
disposal of sewage sludge. EMS participants involve citizens in their
communities to assist in defining improved environmental performance.
EMS status is awarded to participating utilities only after a rigorous
review and subsequent certification by a third party. A voluntary
dioxins monitoring and source investigation program, and suggestions
for reducing and eliminating sources of dioxins in sewer service areas,
could help contribute to reducing concentrations of dioxins in the
community's sewage sludge.
The biosolids industry most likely will be implementing an EMS
through the National Biosolids Partnership (NBP). The NBP is a
partnership formed in 1997 with AMSA (Association of Metropolitan
Sewerage Agencies), WEF (Water Environment Federation), and EPA (U.S.
Environmental Protection Agency). Through partnering with sewage sludge
producers, sewage sludge service contractors such as sewage sludge land
application companies, sewage sludge users, regulatory agencies,
universities, the farming community, and environmental organizations,
the goal of the NBP is to advance environmentally sound and accepted
biosolids management practices.
Through a voluntary EMS, being developed for biosolids by the NBP,
EPA continues to provide the public with educational information, based
on the best science, about the recycling and disposal of biosolids. EPA
strongly supports the ongoing efforts of the NBP to develop the EMS and
to provide correct and timely information and community-friendly
practices that could be followed via its new communications system. The
EMS program supports local authorities to find ways to meet and go
beyond what is required in State and Federal regulations. About 54
municipalities are now pilot-testing their biosolids EMS programs based
upon a blueprint developed by the NBP.
In 2003, the first two municipal wastewater treatment authorities,
Orange County (CA) Sanitation District and the Department of Public
Works from the City of Los Angeles, CA were awarded entry into the EMS
Program by certification from an independent third party auditor.
Several additional municipalities will be ready to undergo an
independent third party audit of the EMS program later this year
(2003). Municipalities involved in the voluntary EMS program are
reporting benefits they have achieved. They report that their
participation in the EMS program has resulted in more efficient
operation, reduced odors from biosolids, less intrusive transport of
the sewage sludge to land application sites, better communication, and
meaningful involvement of the public. The Agency plans to continue
supporting NBP activities and working with municipalities on expanding
the use of EMS programs in biosolids management. Two NBP Web site
addresses that present relevant biosolids information are
http://www.biosolids.org and http://biosolids.policy.net/
emsguide/manual/

IX. List of References

Lorber, M.N. 2002. Evaluating Non-Cancer Risk from Land Application
of Sewage Sludge Using an Increment Over Background Approach.
Memorandum from Matthew Lorber, National Center for Environmental
Assessment, Office of Research and Development, USEPA, Washington,
DC to Alan B. Hais, Health and Ecological Criteria Division, Office
of Science and Technology, Office of Water, USEPA, Washington, DC,
April 2002.
USEPA, 1985. Health Assessment Document for Polychlorinated Dibenzo-
p-Dioxins. EPA/600/8-84/014F. Final Report. Office of Health and
Environmental Assessment. Washington, DC. September, 1985.
USEPA, 1990. National Sewage Sludge Survey; Availability of
Information and Data, and Anticipated Impacts on Proposed
Regulations; Proposed Rule. Federal Register 55 (218): 47210-47283.
USEPA. 1995. Great Lakes Water Quality Initiative Criteria Documents
for the Protection of Human Health. Washington, D.C. EPA-820-B-95-
006. Office of Water.
USEPA. 1996. Technical Support Document for the Round Two Sewage
Sludge Pollutants. EPA-822-R-96-003. Office of Water. Washington,
DC. August 1996.
USEPA. 1997. Exposure Factors Handbook. National Center for
Environmental Assessment. Washington, DC. EPA/600/P-95/002F(a-c).
Vol. I: 208 pp. Vol. II: 336 pp. Vol. III: 340 pp. Also available at
NTIS (Vol. I PB98-124225, Vol. II PB98-124233, Vol. III PB98-124241,
The Set PB98-124217). See also http://www.epa.gov/ncea/exposfac.htm.
USEPA. 1998. Guidelines for Ecological Assessment (Final). EPA/630/
R-95/002F. Risk Assessment Forum. Washington, DC.
USEPA. 2000. Exposure and Human Health Reassessment of 2,3,7,8-
Tetrachlorodibenzo-p-Dioxin (TCDD) and Related Compounds. Part III:
Integrated Summary and Risk Characterization for 2,3,7,8-
Tetrachorodibenzo-p-Dioxin (TCDD) and Related Compounds (SAB Review
Draft). EPA/600/P-00/001Bg. Prepared by the National Center for
Environmental Assessment, Office of Research and Development,
Washington, DC. September 2000. Available online at http://www.epa.gov/ncea.
USEPA. 2002a. Notice of Data Availability, 67 FR 40554, June 12,
2002.
USEPA. 2002b. Statistical Support Document for the Development of
Round 2 Biosolids Use or Disposal Regulations, Office of Science and
Technology, Washington, DC.
USEPA, 2003a. Exposure Analysis for Dioxins, Dibenzofurans, and
Coplanar Polychlorinated Biphenyls in Sewage Sludge, Technical
Background Document, The Office of Water, Washington, DC.
USEPA, 2003b. Highly Exposed Population Background Document, Office
of Water, Office of Science and Technology. Washington, DC.
USEPA, 2003c. Response to Public Comments. Office of Science and
Technology. Washington, DC.
Van den Berg M, et al. 1998. Toxic Equivalency Factors (TEFs) for
PCBs, PCDDs, and PCDFs for Humans and Wildlife. Environ. Health
Perspect. 106(12): 775-792.

Dated: October 17, 2003.
Marianne Lamont Horinko,
Acting Administrator.
[FR Doc. 03-26923 Filed 10-23-03; 8:45 am]
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