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Preliminary Regulatory Determination Support Document for Naphthalene
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Disclaimers
This document is designed to provide supporting information regarding the preliminary regulatory
determination for naphthalene as part of the Contaminant Candidate List (CCL) evaluation process. This
document is not a regulation, and it does not substitute for the Safe Drinking Water Act (SDWA) or the
Environmental Protection Agency's (EPA's) regulations. Thus, it cannot impose legally-binding
requirements on EPA, States, or the regulated community, and may not apply to a particular situation
based upon the circumstances. Mention of trade names or commercial products does not constitute
endorsement or recommendation for use.
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Preliminary Regulatory Determination Stipport Document for Naphthalene
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Acknowledgments
This document was prepared in support of the EPA's Office of Ground Water and Drinking Water
preliminary regulatory determination for naphthalene as part of the Contaminant Candidate List (CCL)
evaluation process. Dan Olson and Karen Wirth served as EPA's team leaders for the CCL regulatory
determination process and James Taft as Standards and Risk Management Division Chief. Tara Cameron
and Karen Wirth served as Work Assignment Managers. The CCL Work Group provided technical
guidance throughout. In particular, Karen Wirth, Dan Olson, and Joyce Donohue provided scientific and
editorial guidance. External expert reviewers and many stakeholders provided valuable advice to improve
the CCL Program and this decument The Cadmus Group, Inc., served as the primary contractor
providing support for this work. The major contributions of Matt Collins, Emily Brott, and Ashton Koo
are gratefully acknowledged. George Hallberg served as Cadmus' Project Manager.
111
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Preliminary Regulatory Determination Support Document for Naphthalene
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USEPA, Office of Water Report: EPA.815-R-01-008, November, 2001
CONTAMINANT CANDIDATE LIST
PRELIMINARY REGULATORY DETERMINATION
SUPPORT DOCUMENT FOR NAPHTHALENE
Executive Summary
Naphthalene is a 1998 Contaminant Candidate List (CCL) regulatory determination priority
contaminant. Naphthalene is one of the contaminants considered by the U.S. Environmental Protection
Agency (EPA) for a regulatory determination. The available data on occurrence, exposure, and other risk
considerations suggest that regulating naphthalene may not present a meaningful opportunity to reduce
health risk. EPA presents preliminary CCL regulatory determinations and further analysis in the Federal
Register Notice.
To make this preliminary regulatory determination for naphthalene, EPA used approaches guided by
the National Drinking Water Advisory Council's (NDWAC) Work Group on CCL and Six-Year Review.
The Safe Drinking Water Act (SDWA) requirements for National Primary Drinking Water Regulation
(NPDWR) promulgation guided protocol development The SDWA Section 1412(b)(l)(A) specifies that
the determination to regulate a contaminant must be based on a finding that each of the following criteria
are met: (i) "the contaminant may have adverse effects on the health of persons"; (ii) "the contaminant is
known to occur or there is substantial likelihood that the contaminant will occur in public water systems ~
with a frequency and at levels of public health concern"; and (iii) "in the sole judgement of the
Administrator, regulation of such contaminant presents a meaningful opportunity for health risk reduction
for persons served by public water systems." Available data were evaluated to address each of the three
statutory criteria.
Naphthalene is a volatile organic compound (VOC) that is naturally present in fossil fuels such as
petroleum and coal, and is produced when wood or tobacco are burned. Naphthalene is primarily used as
an intermediary hi the production of phthalate plasticizers, resins, phthaleins, dyes, Pharmaceuticals, and
insect repellents. Crystalline naphthalene is used as a moth repellent and a solid block deodorizer for
diaper pails and toilets. Naphthalene is also used to make the insecticide carbaryl and synthetic leather
tanning agents. Releases of naphthalene to the environment, reported through the Toxic Release
Inventory (TRI), are widespread. The occurrence of naphthalene hi site samples recorded hi the Agency
for Toxic Substances and Disease Registry's (ATSDR) Hazardous Substance Release and Health Effects
Database (HazDat) and at National Priorities List (NPL) hazardous waste sites provides further evidence
for the widespread use and environmental release of naphthalene.
Naphthalene was monitored from 1987 to 1999 under the SDWA Unregulated Contaminant
Monitoring (UCM) program. Naphthalene is also monitored or regulated by other federal programs
including the Clean Water Act Priority Pollutants list, the Clean Air Act Hazardous Air Pollutant list, the
Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), the Resource
Conservation and Recovery Act (RCRA), the Federal Insecticide, Fungicide, and Rodenticide Act
(FIFRA), and the Toxic Release Inventory (TRI).
. Because of concerns about human health risk, EPA issued a drinking water health advisory for
naphthalene hi 1990 at 100 ug/L and later recommended guidelines for exposure to naphthalene hi
drinking water. Other federal agencies and organizations have issued recommendations for occupational
exposure.
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Preliminary Regulatory Determination Support Document for Naphthalene
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Naphthalene has been detected in ambient ground water as noted by the United States Geological
Survey's (USGS) National Water Quality Assessment (NAWQA) program. Detection frequencies and
concentrations in ground water are relatively low, with naphthalene occurrence considerably higher hi
urban wells than in rural wells. Naphthalene detection frequencies in urban and highway surface runoff
are slightly higher than in ground water, but concentrations are lower. Maximum concentrations in
surface runoff and in ground water, however, are both well below the Health Reference Level (HRL) of
140 ug/L, a preliminary health effect level used for this analysis.
Naphthalene has also been detected in PWS samples collected under SDWA. Occurrence estimates
are low, with less man 0.5% of all samples showing detections for both rounds of UCM monitoring. The
percentages of public water systems (PWSs) with detections are 0.75% and 1.18% for the two rounds of
UCM monitoring. Percentages of PWSs with detections greater than half the Health Reference Level (>
J/i HRL) are considerably lower: approximately 0.01% for both rounds. National estimates for the
population served by PWSs with detections are also low, especially for detections greater man the HRL.
It is estimated, based upon Round 1 data, that less than 0.01% of the national PWS population is served
by systems with detections greater than the HRL (approximately 16,000 people). While detection
frequencies and concentrations are low, the geographic distribution of detections is widespread. Thirty
two out of the 43 States reporting UCM data for naphthalene report detections. Only 1 State reports
detections greater than the HRL.
The available lexicological data indicate that naphthalene has the potential to cause adverse health
effects in humans and animals at high doses. In humans, hemolytic anemia is the most common
manifestation of naphthalene toxicity. There are inadequate data to support a conclusion about the
carcinogenicity of naphthalene by the oral route of exposure.
Monitoring data indicate that naphthalene is infrequently detected in public water supplies.
Furthermore, when naphthalene is detected, it very rarely exceeds the HRL or a value of one-half of the
HRL. Additionally, when average daily intakes from drinking water are compared with intakes from
food, air, and soil, drinking water accounts for a relatively small proportion of total naphthalene intake.
Therefore, regulation of naphthalene in drinking water is unlikely to represent a meaningful opportunity
for health risk reduction.
VI
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Preliminary Regulatory Determination Support Document for Naphthalene
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Table of Contents
Disclaimers .
'' i
Acknowledgments...
Executive Summary
Table of Contents . .:
vii
Listof Tables .
ix
List of Figures
1.0 INTRODUCTION t
1.1 Purpose and Scope : ,
1.2 Statutory Framework/Background i
1.3 Statutory History of Naphthalene ; , " 2
1.4 Regulatory Determination Process 3
1.5 Determination Outcome ' 4
2.0 CONTAMINANT DEFINITION . 4
2.1 Physical and Chemical Properties '.'.'.'.'.'.'.'.'.'.'.'"' 4
2.2 Environmental Fate/Behavior 5
3.0 OCCURRENCE AND EXPOSURE 5
3.1 Use and Environmental Release '.'.'"'
3.1.1 Production and Use fi
3.1.2 Environmental Release 6
3.2 Ambient Occurrence -
3.2.1 Data Sources and Methods ... 8
3.2.2 Results '.['.'.'.'.'.'.'.'.'.'.'.'.'.'.[['.'.'.'. ' g
3.3 Drinking Water Occurrence Q
3.3.1 Data Sources, Data Quality, and Analytical Approaches in
3.3.1.1 UCMRounds 1 and2 '.'.'.'.'.'.'.'.'.'.'.'.'. 10
3.3.1.2 Developing a Nationally Representative Perspective '. '.'.'.'.'. 11
3.3.1.2.1 Cross-Section Development 11
3.3.1.2.2 Cross-Section Evaluation .- ^
3,3.1.3 Data Management and Analysis 13
3.3.1.4 Occurrence Analysis . 14
3.3.2 Results ."."".'!.'!."!!!!!.'.".'."!!!.'.'.".'!! 15
3.3.2.1 Occurrence Estimates i6
3.3.2.2 Regional Patterns jo
3.4 Conclusion »7
4.0 HEALTH EFFECTS : : 22
4.1 Hazard Characterization and Mode of Action ImpKcations '.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'. 22
4.2 Dose-Response Characterization and Implications in Risk Assessment 23
4.3 Relative Source Contribution 25
4.4 Sensitive Populations "
4.5 Exposure and Risk Information ' ^£
''-' 26
vii
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1.0 INTRODUCTION
1.1 Purpose and Scope
This document presents scientific data and summaries of technical information prepared for, and used
in, the Environmental Protection Agency's pPA)reguktory detenmnation for naphthalene. Information
regarding naphthalene's physical and chemical properties, environmental fate, occurrence and exposure,
and health effects is included. Analytical methods and treatment technologies are also discussed.
Furthermore, the regulatory determination process is described to provide the rationale for the decision.
1.2 Statutory Framework/Background
The Safe Drinking WaterAct (SDWA), as amended in 1996, requires the United States
Environmental Protection Agency (EPA) to publish a list of contaminants (referred to as the Contaminant
Candidate List, or CCL) to assist in priority-setting efforts. The contaminants included on the CCL were
not subject to any current or proposed National Primary Drinking Water Regulations (NPDWR), were
known or anticipated to occur in public water systems, and were known or suspected to adversely affect
public health These contaminants therefore may require regulation under SDWA. The first Drinking
Water CCL was published on March 2,1998 (USEPA, 1998b; 63 FR10273), and a new CCL must be
published every five years thereafter.
The 1998 CCL contains 60 contaminants, including 50 chemicals or chemical groups, and 10
microbiological contaminants or microbial groups. The SDWA also requires the Agency to select 5 or
more contaminants from the current CCL and determine whether or not to regulate these contaminants
with an NPDWR. Regulatory determinations for at least 5 contaminants must be completed 3'/2 years
after each new CCL.
Language in SDWA Section 14l2(b)(l)(A) specifies that the determination to regulate a contaminant
must be based on a finding that each of the following criteria are met
Statutory Finding i: .. .the contaminant may have adverse effects on the health of persons;
Statutory Finding ii: the contaminant is known to occur or there is substantial likelihood that
the contaminant will occur in public water systems with a frequency and at levels of public
health concern; and
Statutory Finding Hi: in the sole judgement of the Administrator, regulation of such
contaminant presents a meaningful opportunity for health risk reduction for persons served
by public water systems.
The geographic distribution of the contaminant is another factor evaluated to determine whether it
occurs at the national, regional, or local level. This consideration is important because the Agency is
charged with developing national regulations and it may not be appropriate to develop NPDWRs for
regional or local contamination problems.
EPA must determine if regulating 1his CCL contaminant will present a meaningful opportunity to
reduce health risk based on contaminant occurrence, exposure, and other risk considerations. The Office
of Ground Water and Drinking Water (OGWDW) is charged with garnering and analyzing the
occurrence, exposure, and risk information necessary to support this regulatory decision. The OGWDW
must evaluate when and where this contaminant occurs, and what would be me exposure and risk to
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Preliminary Regulatory Determination Support Document for Naphthalene
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public health. EPA must evaluate the impact of potential regulations as well as determine the appropriate
measure(s) for protecting public health.
For each of the regulatory determinations, EPA must first publish in the Federal Register the draft
determinations for public comment EPA will respond to the public comments received, and will then
finalize regulatory determinations. If the Agency finds that regulations are wan-anted, the regulations
must then be formally proposed withing 24 months, and promulgated eighteen months later. EPA has
determined that there is sufficient information to support a regulatory determination for naphthalene.
1.3 Statutory History of Naphthalene
Naphthalene has been monitored under the SDWA Unregulated Contaminant Monitoring (UCM)
program since 1987. It was among 14 volatile organic compounds (VOCs) included for discretionary
monitoring (USEPA, 1987; 52 FR 25690). Monitoring for naphthalene under UCM continued throughout
the 1990s, but ceased for small public water systems (PWSs) under a direct final rule published January 8,
1999 (USEPA, 1999a; 64 FR 1494). Monitoring ended for large PWSs with promulgation of the new
Unregulated Contaminant Monitoring Regulation (UCMR) issued September 17\ 1999 (USEPA, 1999b;
64 FR 50556) and effective January 1,2001. At the time the UCMR lists were developed, the Agency '
concluded there were adequate monitoring data for a regulatory determination. This obviated the need for
continuing monitoring under the new UCMR list
EPA issued a drinking water health advisory for naphthalene in 1990, and later recommended
guidelines for exposure to naphthalene in drinking water (USEPA, 1990; ATSDR, 1996). As part of the
CCL process, health effects data have been reviewed. These are summarized in section 4.0 of this
document
Naphthalene is regulated or monitored by other federal programs as well. It is included on the Clean
Water Act Priority Pollutants list for which the EPA establishes ambient water quality criteria. It is also
listed as a Hazardous Air Pollutant under the Clean Air Act and subject to Best Available Control
Technology limits. Both the Comprehensive Environmental Response, Compensation, and Liability Act
(CERCLA or "Superfund") and the Resource Conservation and Recovery Act (RCRA) include it as a
hazardous substance and a hazardous constituent, respectively (USEPA, 2000a). CERCLA's listing
requires reporting of releases over a certain "reportable quantity" which, for naphthalene, is 100 pounds
(ATSDR, 1996).
Naphthalene's sale, use, and distribution is controlled under the Federal Insecticide, Fungicide, and
Rodenticide Act (FIFRA). FIFRA was most recently amended hi 1996 under the Food Quality Protection
Act (FQPA). FIFRA requires registration of all pesticides with EPA, and certain labeling, application,
and use restrictions. Moreover, pesticide manufacturing plants must be registered, and the manufacturer
must provide EPA with scientific data regarding the product's efficacy and demonstrating that it does not
pose an unreasonable risk to people or the environment (USEPA, 1998a; USEPA, 2000a). Naphthalene is
also a Toxic Release Inventory (TRI) chemical. The TRI was established by the Emergency Planning and
Community Right-to-Know Act (EPCRA). EPCRA requires certain industrial sectors to publicly report
the environmental release or transfer of chemicals included in this inventory (USEPA, 1996a).
Finally, the Occupational Safety and Health Administration (OSHA) recommends an occupational
exposure limit of 10 parts naphthalene per million in air (10 ppm) for an 8-hour workday over a 40-hour
workweek. The American Conference of Governmental and Industrial Hygienists (ACGIH) and the Mine
Safety and Health Administration (MSHA) recommend the same weekly limit (USDHHS, 1993). The
National Institute for Occupational Safety and Health (NIOSH) considers over 250 ppm of naphthalene hi
air to be life-threatening (ATSDR, 1996).
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Preliminary Regulatory Determination Support Document for Naphthalene
'Ji
1.4 Regulatory Determination Process
In developing a process for the regulatory determinations, EPA sought input from experts and
stakeholders. EPA asked the National Research Council (NRC) for assistance in developing a
scientifically sound approach for deciding whether or not to regulate contaminants on fee current and
future CCLs The NRC's Committee on Drinking Water Contaminants recommended that EPA. (1)
gather and analyze health effects, exposure, treatment, and analytical[methods dato£«ach <*^f
&>
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Preliminary Regulatory Determination Support Document for Naphthalene
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Specifically, EPA characterized the human health effects that may result from exposure to a
contaminant found in drinking water. Based on this characterization, the Agency estimated a health
reference level (HRL) for each contaminant
For each contaminant EPA estimated me number of PWSs with detections >V£HRL and >HRL, the
population served at these benchmark values, and me geographic distribution, using a large number of
occurrence data (approximately seven million analytical points) that broadly reflect national coverage.
Round 1 and Round 2 UCM data, evaluated for quality, completeness, bias, and representativeness, were
the primary data used to develop national occurrence estimates. Use and environmental release
information, additional drinking water data sets (e.g., State drinking water data sets, EPA National
Pesticide Survey, and Environmental Working Group data reviews), and ambient water quality data (e.g.,
NAWQA, State and regional studies, and the EPA Pesticides in Ground Water Database) were also
consulted.
The findings from these evaluations were used to determine if there was adequate information to
evaluate the three SDWA statutory requirements and to make a preliminary determination of whether to
regulate a contaminant.
1.5 Determination Outcome
The Agency has made a preliminary determination not to regulate naphthalene with an NPDWR
because it is not known to occur in public water systems at levels of public health concern. Monitoring
data indicate that naphthalene is infrequently detected in public water supplies. When naphthalene is
detected, it very rarely exceeds the Health Reference Level (HRL) or a value of one-half of the HRL. All
preliminary CCL regulatory determinations will be presented in the Federal Register Notice. The
following sections summarize the data used by the Agency to reach this preliminary decision.
2.0 CONTAMINANT DEFINITION
Naphthalene, a volatile organic compound (VOQ, is a white solid with a strong odor. Common
synonyms for naphthalene include: mothballs, mothflakes, tar camphor, white tar, naphthene, and
albocarbon. Naphthalene is naturally present in fossil fuels such as petroleum and coal, and is produced
when wood or tobacco are burned. Most of naphthalene consumption (60%) is as an intermediary in the
production of phthalate plasticizers, resins, phthaleins, dyes, Pharmaceuticals, and insect repellents.
Crystalline naphthalene is used as a moth repellent and a solid block deodorizer for diaper pails and
toilets. Naphthalene is also used to make the insecticide carbaryl, synthetic leather tanning agents, and
surface active agents (ATSDR, 1995).
2.1 Physical and Chemical Properties
Table 2-1 lists summary information regarding naphthalene's physical and chemical properties. Also
included are its CAS Registry Number and molecular formula.
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Preliminary Regulatory Determination Support Document for Naphthalene
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Table 2-1: Physical and chemical properties
CAS number
Molecular Formula C10H8
91-20-3
Boiling Point
Melting Point
Molecular Weight
LogK
Water Solubility
Vapor Pressure
Henry's Law
Constantf
218°Cat760mmHg
80.5 °C
128.19 g/mol
2.97
3.29
81.7mg/Lat25°C
0.087mmHgat25°C
1.88 x lO'2
source: ATSDR, 1995.
* note: this quantity is expressed in a dimensionlessform.
2.2 Environmental Fate/Behavior
Naphthalene solid ;evaporates easily in air and is readily degraded in the atmosphere by hydroxyl
radicals (half life
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Preliminary Regulatory Determination Support Document for Naphthalene
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(PWSs) collected under SDWA, this report aggregates and analyzes existing State data that have been
screened for quality, completeness, and representativeness. Populations served by PWSs exposed to
naphthalene are estimated, and the occurrence data are examined for regional or other special trends. To
augment the incomplete national drinking water data and aid in the evaluation of occurrence, information
on the use and environmental release, as well as ambient occurrence of naphthalene, is also reviewed. .
3.1 Use and Environmental Release
3.1.1 Production and Use
Naphthalene is naturally present in fossil fuels such as petroleum and coal, and is generated when
wood or tobacco are burned. Naphthalene is produced in commercial quantities from either coal tar or
petroleum. Most of the naphthalene produced in the United States comes from petroleum by the
dealkylation of methyl naphthalenes in the presence of hydrogen at high temperature and pressure.
Another common production method is the distillation and fractionation of coal tar. Most naphthalene
consumption (60%) is through use as an intermediary in the production of phthalate plasticizers, resins.,
phthaleins, dyes, Pharmaceuticals, and insect repellents. Crystalline naphthalene is used as a moth
repellent and a solid block deodorizer for diaper pails and toilets. Naphthalene is also used to make the
insecticide carbaryl, synthetic leather tanning agents, and surface active agents (ATSDR, 1995).
Naphthalene production in the United States dropped from 900 million Ibs/yr in 1968 to 354 million
Ibs/yr in 1982. Approximately 7 million Ibs of naphthalene were imported and 9 million Ibs were
exported in 1978. By 1989, imports had dropped to 4 million Ibs, and exports increased dramatically to
21 million Ibs (ATSDR, 1995).
3.1.2 Environmental Release
Naphthalene is listed as a toxic release inventory chemical. In 1986, the Emergency Planning and
Community Right-to-Knqjv Act (EPCRA) established the Toxic Release Inventory (TRI) of hazardous
chemicals. Created under the Super-fund Amendments and Reauthorization Act (SARA) of 1986, EPCRA
is also sometimes known as SARA Title m. The EPCRA mandates that larger facilities publicly report
when TRI chemicals are released into the environment. This public reporting is required for facilities
with more than 10 full-time employees that annually manufacture or produce more than 25,000 pounds,
or use more than 10,000 pounds, of TRI chemical (USEPA, 1996a; USEPA, 2000e).
Under these conditions, facilities are required to report the pounds per year of naphthalene released
into the environment both on- and off-site. The on-site quantity is subdivided into air emissions, surface
water discharges', underground injections, and releases to land (see Table 3-1). For naphthalene, air
emissions constitute most of the on-site releases. Also, surface water discharges exhibit no obvious trend
over the period for which data is available (1988-1998), but discharges hit a low in 1996 and 1997, and
increase again in 1998. These TRI data for naphthalene were reported from 47 States (excluding ID, NH,
VT) indicating the widespread production or use of this chemical (USEPA, 2000c).
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Preliminary Regulatory Determination Support Document for Naphthalene
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Table 3-1: Environmental releases (in pounds) for naphthalene in the United States (1988-1998)
Year
1998
1997
1996
1995
1994
1993
1992
1991
1990
1989
1988
.,, On-Site Releases
Air
Emissions
3,374,439
2,449,488
2,863,431
2,690,669
2,889,514
2,744,887
2,626,986
2,927,511
3,912,253
3,523,562
5.165,426
Surface Water
; Discharges
34,148
ISjSSS
11,836
43,311
28,557
31,179
28,925
31,508
36,821
146,983
22.518
Underground
Injection
191,677
187,927
296,776
44,318
97,186
79,814
78,227
39,112
28,130
39,552
50,946
Releases
to Land
1,251,040
82,204
301*513
32,085
47,017
49,886
1,667,150
55,278
143,196
118,409
123.697
Off-Site
Releases
827,708
491,124
582,717
474,106
496,501
334,985
667,556
983,371
919,225
1,054,602
1,359,184
Total On- &
Off-site
Releases
5,679,012
3,224,076
4,056,273
3,284,489
3,558,775
3,240,751
5,068,844
4,036,780
5,039,625
4,883,108
6,721.771
source: USEPA 2000c ''.'''
Although the TRI data can be useful in giving a general idea of release trends, it is far from
exhaustive and has significant limitations. For example, only industries which meet TRI criteria (at least
10 full-time employees and manufacture and processing of quantities exceeding 25,000 Ibs/yr, or use of
more than 10,000 Ibs/yr) are required to report releases. These reporting criteria do not account for
releases from smaller industries: Threshold manufacture and processing quantities also changed from
1988-1990 (dropping from 75,000 Ibs/yr in 1988 to 50,000 Ibs/yr in 1989 to its current 25,000 Ibs/yr -in
1990) creating possibly misleading date trends. Finally, the TRI data is meant to reflect releases and
should not be used to estimate general exposure to a chemical (USEPA, 2000d; USEPA, 2000b).
Naphthalene is also included in the Agency for Toxic Substances and Disease Registry's (ATSDR)
Hazardous Substance Release and Health Effects Database (HazDat). This database records detections of
listed chemicals in site samples; naphthalene was detected in 44 States (States without detections are AK,
AZ, HI, NV» ND, UT; ATSDR, 2000). The National Priorities List (NPL) of hazardous waste sites,
created in 1980 by CERCLA, is a listing of some of the most health-threatening waste sites in the United
States. Naphthalene was again detected in all but six States (excluding HI, NE, NV, MM, ND, WV;
USEPA, 1999c).
In summary, most of naphthalene's consumption is through use as an intermediary in the production
of phthalate plasticizers, resins, phthaleins, dyes, Pharmaceuticals, and insect repellents. Its production in
the United States declined from 1968 to 1982, howeverits import decreased and export increased from
1978 to 1989. The widespread use and production of naphthalene in the United States is evidenced by its
presence in hazardous waste sites in at least 44 States (at NPL sites), its presence in site samples in at least
44 States (listed in ATSDR's HazDat), and its direct release into the environment in at least 47 States
(based on TRI data).
3.2 Ambient Occurrence
To understand the presence of a chemical in the environment, an examination of ambient occurrence
is useful. In a drinking water context, ambient water is source water existing in surface waters and
aquifers before treatment. The most comprehensive and nationally consistent data describing ambient
water quality in the United States are being produced through the United States Geological Survey's
(USGS) National Water Quality Assessment (NAWQA) program. (NAWQA, however, is a relatively
young program and complete national data are not yet available from their entire array of sites across the
nation.)
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3.2.1 Data Sources and Methods
To examine water quality status and trends in the United States, the USGS instituted the NAWQA
program in 1991. NAWQA is designed and implemented in such a manner as to allow consistency and
comparison between representative study basins located around the country, facilitating interpretation of
natural and anthropogenic factors affecting water quality (Leahy and Thompson, 1994).
The NAWQA program consists of 59 significant watersheds and aquifers referred to as "study units."
The study units represent approximately two thirds of the overall water usage in the United States and a
similar proportion of the population served by pubh'c water systems. Approximately one half of the
nation's land area is represented (Leahy and Thompson, 1994).
To facilitate management and make the program cost-effective, approximately one third of the study
units at a time engage in intensive assessment for a period of 3 to 5 years. This is followed by a period of
less intensive research and monitoring mat lasts between 5 and 7 years. This way all 59 study units rotate
through intensive assessment over a ten-year period (Leahy and Thompson, 1994). The first round of
intensive monitoring (1991-96) targeted 20 watersheds. This first group was more heavily slanted toward
agricultural basins. A national synthesis of results from these study units and other research initiatives
focusing on pesticides and nutrients is being compiled and analyzed (Kolpinetal, 2000; Larson et al.,
1999).
For VOCs, the national synthesis will compile data from the first and second rounds of intensive
assessments. Study units assessed in the second round represent conditions in more urbanized basins, but
initial results are not yet available. However, VOCs were analyzed in the first round of intensive
monitoring and data are available for these study units (Squillace etal., 1999). The minimum reporting
level (MRL) for most VOCs, including naphthalene, was 0;2 ug/L (Squillace et al., 1999).
Furthermore, the NAWQA program has compiled, by study unit, data collected from local, State, and
other Federal agencies to augment its own data. The data set provides an assessment of VOCs in
untreated ambient ground water of the coterminous United States for the period 1985-1995 (Squillace et
al., 1999). Data were included in the compilation if they met certain criteria for collection, analysis, well
network design, and well construction (Lapham et al., 1997). They represent both rural and urban areas,
but should be viewed as a progress report as NAWQA data continue to be collected that may influence
conclusions regarding occurrence and distribution of VOCs (Squillace et al., 1999).
The National Highway Runoff Data and Methodology Synthesis has reviewed 44 highway and urban
runoff studies implemented since 1970 (Lopes and Dionne, 1998). Two national studies were included hi
this review: the National Urban Runoff Program (NURP) and studies associated with the EPA National
Pollution Discharge Elimination System (NPDES) municipal stormwater permits.
NURP, conducted in the 1970s and early 1980s, had the most extensive geographic distribution. The
NPDES studies took place in the early to mid- 1990s (Lopes and Dionne, 1998). Naphthalene was an
analyte in both studies.
3.2.2 Results
Naphthalene was detected in both rural and urban wells of the local, State, and federal data set
compiled by NAWQA (Table 3-2). The data represent untreated ambient ground water of the
conterminous United States for the years 1985-1995 (Squillace etaL, 1999). Detection frequencies and
median concentrations are low, especially for rural areas. Occurrence of naphthalene hi rural areas is an
order of magnitude lower than hi urban areas, a trend generally observed for VQCs throughout the United
States (Miller, 2000). The exception to this trend for naphthalene is the maximum concentration, a
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parameter more likely to be influenced by extreme values (outliers) that do not well represent the overall
data.
i*
Table 3-2: Naphthalene detections and concentrations in ground water
Detection frequency
(% of sampled wefts >MRt*)
urban 3.0%
rural 0.2%
Concentrations
(of detections; ug/L)
median maximum
3.9 43
0.4 70
Percent exceeding HAL**
(20 ug/L)
drinking water
all wells wells
0.4 0
0.1 0
after Squillaceetal.,1999
* MRLfor naphthalene in water: 0.2 fig/L
**VSEPA,1996b;ATSDR,i996
The NURP and NPDES studies analyzing urban and highway runoff also found naphthalene (Lopes
andDionne, 1998). Naphthalene was detected in 11% of NURP samples making it among the 3 most
detected VOCs in the study. Its detection frequency was 7% in theNPDES studies. The maximum
concentration was 2.3 ug/L in NURP samples andS.l ug/L in NPDES samples.
The maximum values for urban and highway runoff are well below the Health Advisory Level (HAL)
of 20 jig/L cited by Lopes-and DSonne (1998), the HAL in effect at the time (USEPA, 1996b). The
ground water studies also reported few exceedances of the 20 ug/L HAL (Squillace et al., 1999). The
maximum values for runoff and ground water are considerably less than the current HAL of 100 ug/L
(USEPA, 2000f) and even more so for the Health Reference Level (HRL) of 140 ug/L used as a
preliminary health effects level for the drinking water data analysis presented below.
3.3 Drinking Water Occurrence
The SDWA, as amended in 1986, required PWSs to monitor for specified "unregulated"
contaminants, on a five year cycle, and to report the monitoring results to the States. Unregulated
contaminants do not have an established or proposed NPDWR, but they are contaminants that were
formally listed and required for monitoring under federal regulations. The intent was to gather scientific
information on the occurrence of these contaminants to enable a decision as to whether or not regulations
were needed. All non-purchased community water systems (CWSs) and non-purchased non-transient
non-community water systems (NTNCWSs), with greater than 150 service connections, were required to
conduct this unregulated contaminant monitoring. Smaller systems were not required to conduct this
monitoring under federal regulations, but were required to be available to monitor if the State decided
such monitoring was necessary. Many States collected data from smaller systems. Additional
contaminants were added to the UCM program in 1991 (USEPA, 1991; 56 FR 3526) for required
monitoring that began in 1993 (USEPA, 1992; 57 FR 31776).
Naphthalene has been monitored under the SDWA UCM program since 1987 (USEPA, 1987; 52 FR
25690). Monitoring for naphthalene under UCM continued throughout the 1990s, but ceased for small
PWSs under a direct finaf rule published January 8,1999 (USEPA, 1999a; 64 FR 1494). Monitoring
ended for large PWSs with promulgation of the new Unregulated Contaminant Monitoring Regulation
(UCMR) issued September 17,1999 (USEPA, 1999b; 64 FR 50556) and effective January 1,2001. At
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the time the UCMR lists were developed, the Agency concluded there were adequate monitoring data for
a regulatory determination. This obviated the need for continued monitoring under the new UCMR list.
33.1 Data Sources, Data Quality, and Analytical Approaches
Currently, there is no complete national record of unregulated or regulated contaminants in drinking
water from public water systems collected under SDWA. Many States have submitted their unregulated
contaminant PWS monitoring data to EPA databases, but there are issues of data quality, completeness,
and representativeness. Nonetheless, a significant amount of State data are available for UCM
contaminants that can provide estimates of national occurrence. The contaminant occurrence analyses
findings presented in this report are based on a national cross-section of aggregated state data (i.e., a
representative subset of available state data) derived from the Safe Drinking Water Information System
(Federal version; SDWIS^ED) database.
The National Contaminant Occurrence Database (NCOD) is an interface to the actual occurrence data
stored in the SDWIS/FED and can be queried to provide a summary of the data hi SDWIS/FED for a
particular contaminant The data used in this report were derived from me data in SDWIS/FED and
another database called the Unregulated Contaminant Information System (URCIS). Note, however, that
the SDWIS/FED data used in this report have been reviewed, edited, and filtered to meet various data
quality objectives for the purposes of this analysis. Hence, not all data from a particular source were
used, only data meeting the quality objectives described below. The sources of these data, their quality
and national aggregation, and the analytical methods used to estimate a given contaminant's national
occurrence (from these data) are discussed in this section (for further details see USEPA, 2001a, 2001c).
33.1.1 UCM Rounds 1 and 2
The 1987 UCM contaminants include 34 VOCs, divided into two groups: one with 20 VOCs for
mandatory monitoring, and the other with 14 VOCs for discretionary monitoring (USEPA, 1987; 52 FR
25690). Naphthalene was among me 14 VOCs included for discretionary monitoring. The UCM (1987)
contaminants were first monitored coincident with the Phase I regulated contaminants, during the 1988-
1992 period. This period is often referred to as "Round 1" monitoring. The monitoring data collected by
the PWSs were reported to the States (as primacy agents), but there was no protocol in place to report
these data to EPA.. These data from Round 1 were collected by EPA from many States over time.
The Round 1 data were put into a database called the Unregulated Contaminant Information System,
or URCIS. Most of the Phase 1 regulated contaminants were also VOCs. Both the unregulated and
regulated VOCs are analyzed using the same sample and the same laboratory methods. Hence, the
URCIS database includes data on all of these 62 contaminants: the 34 UCM (1987) VOCs; the 21
regulated Phase 1 VOCs; 2 regulated synthetic organic contaminants (SOCs); and 5 miscellaneous
contaminants that were voluntarily reported by some States (e.g., isomers of other organic contaminants).
The 1993 UCM contaminants include 13 SOCs and 1 inorganic contaminant (IOC) (USEPA, 1992;
57 FR 31776). Monitoring for the UCM (1993) contaminants began coincident with the Phase n/V
regulated contaminants in 1993 through 1998. This is often referred to as "Round 2" monitoring. The
UCM (1987) contaminants were also included in the Round 2 monitoring. As with other monitoring data,
PWSs reported these results to the States. EPA, during the past several years, requested that the States
submit these historic data to EPA.
The details of the actual individual monitoring periods are complex. The timing of required
monitoring was staggered related to different size classes of PWSs, and the program was implemented
somewhat differently by different States. While Round 1 includes the period from 1988-1992, it also
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includes results from samples analyzedprior to 1988 that were "grandfathered" into the database (for
further details see USEPA, 2001a, 2001c).
33.1.2 Developing a Nationally Representative Perspective
The Round 1 and Round 2 databases contain contaminant occurrence data from a total of 40 and 35
primacy entities (largely States), respectively. However, data from some States are incomplete and
biased. Furthermore, the national representativeness of the data is problematic because the data were not
collected in a systematic or random statistical framework. These State data could be heavily skewed to
low-occurrence or high-occurrence settings. Hence, the State data were evaluated based on pollution-
potential indicators and the spatial/hydrologic diversity of the nation. This evaluation enabled the
construction of a cross-section from the available State data sets that provides a reasonable representation
of national occurrence. .._« .
A national cross-section comprised of the Round 2 state contaminant occurrence databases was ,
established using the approach developed for the EPA report A Review of Contaminant Occurrence in
Public Water Systems (USEPA, 1999d). This approach was developed to support occurrence analyses for
EPA's Chemical Monitoring Reform (CMR) evaluation, and was supported by peer reviewers and
stakeholders. The approach cannot provide a "statistically representative" sample because the original
monitoring date were not collected or reported hi an appropriate fashion. However, the resultant
"national cross-section" of states should provide a clear indication of the central tendency of the national
data. The remainder of this section provides a summary description of how the national cross-section
from the SDWIS/FED (Round 2) database was developed. The details of the approach are presented in
other documents (USEPA, 2001a, 2001b); readers are referred to these for more specific information.
3.3.1.2.1 Cross-Section Development
As a first step in developing the cross-section, the State data contained hi the URCIS database (that
contains the Round 1 monitoring results) and SDWIS/FED database (that contains the Round 2
monitoring results) were evaluated for completeness and quality. For both the URCIS (Round 1) and
SDWIS/FED (Round 2) databases, some State data were unusable for a variety of reasons. Some States
reported only detections, or the data were recorded with incorrect units. Data sets only including
detections are obviously biased, over-representing high-occurrence settings. Other problems included
substantially incomplete data sets without all PWSs reporting. Also, data from Washington, D.C. and the
Virgin Islands were excluded from this analysis because it was difficult to evaluate them for the current
purposes in relation to complete State data (USEPA, 2001a Sections n and ID).
The balance of the States remaining after the data quality screening were then examined to establish a
national cross-section. This step was based on evaluating the States' pollution potential and geographic
coverage in relation to all States. Pollution potential is considered to ensure a selection of States that
represent the range of likely contaminant occurrence and a balance with regard to likely high and low
occurrence. Geographic consideration is included so that the wide range of climatic and hydrogeologic
conditions across-the United States are represented, again balancing the varied conditions that affect
transport and fate of contaminants, as well as conditions that affect naturally occurring contaminants
(USEPA, 2001c Sections HI.A. and ffl.B.).
The cross-section States were selected to represent a variety of pollution potential conditions. Two
primary pollution potential indicators were used. The first factor selected indicates pollution potential
from manufacturing/population density and serves as an indicator of the potential for VOC contamination
within a State. Agriculture was selected as the second pollution potential indicator because the majority
of SOCs of concern are pesticides (USEPA, 2001c Section m. A.). The 50 individual States were ranked
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from highest to lowest based on the pollution potential indicator data. For example, the State with the
highest ranking for pollution potential from manufacturing received a ranking of 1 for this factor and the
State with the lowest value was ranked as number SO. States were ranked for their agricultural chemical
use status in a similar fashion.
The States' pollution potential rankings for each factor were subdivided into four quartiles (from
highest to lowest pollution potential). The cross-section States were chosen equally from all quartiles for
both pollution potential factors to ensure representation, for example, from: States with high agrichemical
pollution potential rankings and high manufacturing pollution potential rankings; States with high
agrichemical pollution potential rankings and low manufacturing pollution potential rankings; States with
low agrichemical pollution potential rankings and high manufacturing pollution potential rankings; and
States with low agrichemical pollution potential rankings and low manufacturing pollution potential
rankings (USEPA, 2001c Section m.B.). In addition, some secondary pollution potential indicators were
considered to further ensure that the cross-section States included the spectrum of pollution potential
conditions (high to low). At the same time, States within the specific quartiles were considered
collectively across all quartiles to attempt to provide a geographic coverage across all regions of the
United States.
The data quality screening, pollution potential rankings, and geographic coverage analysis established
national cross-sections of 24 Round 1 (URCIS) States and 20 Round 2 (SDWIS/FED) States. In each
cross-section, the States provide good representation of the nation's varied climatic arid hydrogeologic
regimes and the breadth of pollution potential for the contaminant groups (Table 3-3 and Figure 3-1).
3.3.1.2.2 Cross-Section Evaluation
To evaluate and validate the method for creating the national cross-sections, the method was used to
create smaller State subsets from the 24-State, Round 1 cross-section. Again, States were chosen to
achieve a balance from the quartiles describing pollution potential, and a balanced geographic
distribution, to incrementally build subset cross-sections of various sizes. For example, the Round 1
cross-section was tested with subsets of 4, 8 (the first 4 State subset plus 4 more States), and 13 (8 State
subset plus 5) States. Two additional cross-sections were included hi the analysis for comparison; a
cross-section composed of 16 States with biased data sets eliminated from the 24 State cross-section for
data quality reasons and a cross-section composed of all 40 Round 1 States (USEPA, 2001 c Section
These Round 1 incremental cross-sections were then used to evaluate occurrence for an array of both
high and low occurrence contaminants. The comparative results illustrate several points. The results are
quite stable and consistent for the 8, 13 and 24 State cross-sections. They are much less so for the 4 State,
16 State (biased), and 40 State (all Round 1 States) cross-sections. The 4 State cross-section is apparently
too small to provide balance both geographically and with pollution potential, a finding that concurs with
past work (USEPA, 1999d). The CMR analysis suggested that a minimum of 6-7 States was needed to
provide balance both geographically and with pollution potential, and the CMR report used 8 States out
of the available data for its nationally representative cross-section. The 16 State and 40 State cross-
sections, both including biased States, provided occurrence results that were unstable and inconsistent for
a variety of reasons associated with their data quality problems (USEPA, 2001 c Section ffi.B.1)
The 8, 13, and 24 State cross-sections provide very comparable results, are consistent, and are usable
as national cross-sections to provide estimates of contaminant occurrence. Including greater data from
more States improves the national representation and the confidence hi the results-as long as the States
are balanced related to pollution potential and spatial coverage. The 24 and 20 State cross-sections
provide the most nationally representative cross-sections for the Round 1 and Round 2 data.
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Table 3-3: Cross-section States for Round 1 (24 States) and Round 2 (20 States)
Round 1 (URCIS)
Alabama
Alaska*
Arizona
California
Florida
Georgia
Hawaii
Illinois
Indiana
Iowa
Kentucky*
Maryland*
Minnesota*
Montana
New Jersey
New Mexico*
North Carolina*
Ohio*
South Dakota
Tennessee
Utah
Washington*
West Virginia
Wyoming
Round 2 (SDWIS/FED) |
Alaska*
Arkansas
Colorado
Kentucky*
Maine
Maryland*
Massachusetts
Michigan
Minnesota*
Missouri
New Hampshire
New Mexico*
North Carolina:*
North Dakota
Ohio*
Oklahoma
Oregon
Rhode Island
Texas
Washington*
* cross-section State in both Round 1 and Round 2
Figure 3-1: Geographic distribution of cross-section States for Round 1 (left) and Round 2 (right).
3.3.1.3 Data Management and Analysis
The cross-section analyses focused on occurrence at the water system level; i.e., the summary data
presented discuss the percentage of public water systems with detections, not the percentage of samples
with detections. By normalizing the analytical data to the system level, skewness inherent in the sample
data, particularly over the multi-year period covered in the URCIS data, is avoided. System level analysis
was used since a PWS with a known contaminant problem usually has to sample more frequently than a
PWS that has never detected the contaminant. Obviously, the results of a simple computation of the
percentage of samples with detections (or other statistics) can be skewed by the more frequent sampling
results reported by the contaminated site. This level of analysis is conservative. For example, a system
need only have a single sample with an analytical result greater than the MRL, i.e., a detection, to be
counted as a system with a result "greater than the MRL."
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Also, the data used in the analyses were limited to only those data with confirmed water source and
sampling type information. Only standard SDWA compliance samples were used; "special" samples, or
'Investigation" samples (investigating a contaminant problem that would bias results), or samples of
unknown type were not used in the analyses. Various quality control and review checks were made of the
results, including follow-up questions to the States providing the data. Many of the most intractable data
quality problems encountered occurred with older data. These problematic data were, in some cases,
simply eliminated from the analysis. For example, when the number of data with problems were
insignificant relative to the total number of observations they were dropped from the analysis (For further
details see Cadmus, 2000). .
As indicated above, New Hampshire generally is included in the 20-State, Round 2 national cross-
section. Naphthalene occurrence data from the State of New Hampshire, however, are biased. New
Hampshire reports only 5 samples from three systems for Naphthalene with each system showing a
detection. Though these results are simple detections not violating a health effect standard, and inclusion
of the data does not significantly affect overall summary statistics, to maintain a. consistent method for
managing biased data, New Hampshire's naphthalene data were omitted from Round 2 cross-section
occurrence analyses and summaries presented in this report
33.1.4 Occurrence Analysis
To evaluate national contaminant occurrence, a two-stage analytical approach has been developed.
The first stage of analysis provides a straightforward, conservative, non-parametric evaluation of
occurrence of the CCL regulatory determination priority contaminants as described above. These Stage 1
descriptive statistics are summarized here. Based in part on the findings of the Stage 1 Analysis, EPA
will determine whether more rigorous parametric statistical evaluations, the Stage 2 Analysis, may be
warranted to generate national probability estimates of contaminant occurrence and exposure for priority
contaminants (for details on this two stage analytical approach see Cadmus, 2DOO, 2001).
The summary descriptive statistics presented in Table 3-4 for naphthalene are a result of the Stage 1
analysis and include data from both Round 1 (URCIS, 1987-1992) and Round 2 (SDWIS/FED, 1993-
1997) cross-section States (minus New Hampshire). Included are the total number of samples, the percent
samples with detections, the 99th percentile concentration of all samples, the 99th percentile concentration
of samples with detections, and the median concentration of samples with detections. The percentages of
PWSs and population served indicate the proportion of PWSs whose analytical results showed a
detections) of the contaminant (simple detection, > MRL) at any time during the monitoring period; or a
detections) greater than half the Health Reference Level (HRL); or a detections) greater than the Health
Reference Level.
Naphthalene is not considered to be a linear carcinogen by the oral route of exposure. Accordingly,
the Maximum Contaminant Level Goal (MCLG) is derived using a Reference Dose (RED) approach. The
value used as the Health Reference Level (HRL) for this occurrence evaluation is derived from the RfD
using the following equation:
HRL = RfD x Body Weight x
Drinking Water Intake
Relative Source Contribution
The body weight used in the calculation is an average adult body weight (70 Kg) and the value for daily
water intake is 2 L. In the calculation of the HRL, the relative source contribution is 20%. A different
relative source fector might be used to calculate the MCLG if a determination is made to regulate
naphthalene. .*'
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The 99th percentile concentration is used here as a summary statistic to indicate the upper bound of
occurrence values because maximum values can be extreme values (outliers) that sometimes result from
sampling or reporting error. The 99* percentile concentration is presented for both the samples with only
detections and all of the samples because the value for Ihe 99th percentile concentration of all samples is
below the MRL (denoted by "<" in Table 3^4). For the same reason, summary statistics such as the 95
percentile concentration of all samples or the median (or mean) concentration of all samples are omitted
because these also are all "<" values. This is the case because only 0.43% and 0.23% of all samples
recorded detections of naphthalene in Round 1 and Round 2, respectively.
As a simplifying assumption, a value of half the MRL is often used as an estimate of the
concentration of a contaminant in samples/systems whose results are less man the MRL. With a
contaminant with relatively low occurrence such as naphthalene in drinking water occurrence databases,
the median or mean value of occurrence using this assumption would be half the MRL (0.5 * MRL).
However, for these occurrence data this is not straightforward. For Round 1 and Round 2, States have
reported a wide range of values for me MRLs, This is in part related to State data management
differences as well as real differences in analytical methods, laboratories, and other fectors.
The situation can cause confusion when examining descriptive statistics for occurrence. For example,
for Round 2 most States reported non-detections as zeros resulting in a modal MRL value of zero. By
definition the MRL cannot be zero. This is an artifact of State data management systems. Because a
simple meaningful summary statistic is not available to describe the various reported MRLs, and to avoid
confusion, MRLs are not reported in the summary table (Table 3-4).
In Table 3-4, national occurrence is estimated by extrapolating the summary statistics for the 24 and
20 State cross-sections (minus New Hampshire) to national numbers for systems, and population served
by systems, from the Water Industry Baseline Handbook, Second Edition (USEPA, 2000g). From the
handbook, the total number of CWSs plus NTNCWSs is 65,030, and the total population served by CWSs
plus NTNCWSs is 213,008,182 persons (see Table 3-4). To generate the estimate of national occurrence
based on the cross-section occurrence findings, the national number of PWSs (or population served by
le g inenanonai esuiuaie im tuc ujun-uuuws* i/i * ITU>» »»*m »»w»~»«~ \- , *
number of PWSs (65,030) and the percentage of PWSs with detections (1.18%) and the national estimate
for the total number of PWSs (65,030)].
Because the State data used for the cross-section are not a strict statistical sample, national
extrapolations of these Stage 1 analytical results can be problematic, especially for contaminants with
very low occurrence like naphthalene and other CCL regulatory determination priority contaminants. For
this reason, the nationally extrapolated estimates of occurrence based on Stage 1 results are not presented
in the Federal Register Notice. The presentation in the Federal Register Notice of only the actual results
of the cross-section analysis maintains a straight-forward presentation, and the integrity of the data, for
stakeholder review. The nationally extrapolated Stage 1 occurrence values are presented here, however,
to provide additional perspective. A more rigorous statistical modeling effort, the Stage 2 analysis, could
be conducted on the cross-section data (Cadmus, 2001). The Stage 2 results would be more statistically
robust and more suitable to national extrapolation. This approach would provide a probability estimate
and would also allow for better quantification of estimation error.
Round 1(1987-1992) and Round 2 (1993-1997) data were not merged because they represent
different time periods, different States (only eight States are represented in both rounds), and each round
has different data management and data quality problems. The two rounds are only merged for the simple
spatial analysis overview presented in Section 3.3.2.2 and Figures 3-2 and 3-4.
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33.2 Results
-( . .
33.2.1 Occurrence Estimates
While States with detections of naphthalene are widespread (Figure 3-2), the percentages of PWSs by
State with detections are modest (Table 3-4). In aggregate, the cross-sections show approximately 0.8%
to 1.2% of PWSs in both rounds experienced detections (> MRL), affecting 3.0% to 4.8% of the
population served (approximately 6-10 million people). Percentages of PWSs with detections greater
than half the Health Reference Level (> J4 HRL) are much lower for both rounds: 0.01%. The percentage
of PWSs exceeding the Health Reference Level (> HRL) is also very small (see also Figure 3-4).
Detections greater than the HRL were only reported in Round 1:0.01% of PWSs, affecting a population
of approximately 16;000.
Note that for the Round 1 cross-section, the total number of PWSs (and the total population served by
the PWSs) is not the sum of the number of ground water and surface water systems (or me populations
served by those systems). Because some public water systems are seasonally classified as either surface
or ground water, some systems may be counted in both categories. The population numbers for the
Round 1 cross-section are also incomplete. Not all of the PWSs for which occurrence data was submitted
reported the population they served. (However, the population numbers presented in Table 3-4 for the
Round 1 cross-section are reported from approximately 95% of the systems.)
The national estimates extrapolated from Round 1 and Round 2 PWS numbers and populations are
not additive either. In addition to the Round 1 classification and reporting issues outlined above, the
proportions of surface water and ground water PWSs, and populations served by them, are different
between the Round 1 and 2 cross-sections and the national estimates. For example, approximately 63%
of the population served by PWSs in the Round 2 cross-section States are served by surface water PWSs
(Table 3-4). Nationally, however, that proportion changes to 60%.
Both Round 1 and Round 2 national cross-sections show a proportionate balance in PWS source
waters compared to the national inventory. Nationally, 91% of PWSs use ground water (and 9% of
surface water): Round 1 shows 89% and Round 2 shows 90% of systems using ground water. The
relative populations served are not as closely comparable. Nationally, about 40% of the population is
served by PWSs using ground water (and 60% by surface water). Round 2 data is most representative
with 37% of the cross-section population served by ground water; Round 1 shows about 55%.
There are differences in the occurrence results between Round 1 and Round 2, as should be expected.
The differences are not great, however, particularly when comparing the proportions of systems affected
The results range from 0.8% to 1.2% of PWSs with detections of naphthalene and range from 0.00% to
0.01% of PWSs with detections greater man the HRL of 140 ug/L. These are not substantively different,
given the data sources. The differences in the population extrapolations appear greater, but still constitute
relatively small proportions of the population. Less than 5.0% of the population served by PWSs in either
round are served by systems with detections and only 0.01% of the population served by Round 1 PWSs
were served by systems with detections greater than the HRL.
The Round 2 cross-section provides a better proportional balance related to the national population of
PWSs and may have fewer reporting problems than Round 1. The non-zero estimate of the national
population served by PWSs with detections greater than the HRL using Round 1 data can also provide an
upper bound estimate in considering the data.
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Preliminary Regulatory Determination Support Document for Naphthalene
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Table 3-4: Summary occurrence statistics for naphthalene
Total Number of Samples ,
Percent of Samples With Detections
99tt Percentile Concentration (all samples)
Health Reference Level
Minimum Reporting Level (MRL)
99th Percentile Concentration of Detections
Median Concentration of Detections
Total Number of PWSs
Number of GW PWSs
Number of SW PWSs
Total Population
Population of GW PWSs
Pnrtnlfltinn of SW PWSs
% PWSs with detections (:> MRL)
Range of Cross-Section States
GW PWSs with detections
SW PWSs with detections
% PWSs > 1/2 Health Reference Level (HRL)
Range of Cross-Section States
GW PWSs > \n Health Reference Level
SW PWSs > 1/2 Health Reference Level
% PWSs > Health Reference Level
Range of Cross-Section States
GW PWSs > Health Reference Level
SW PWSs > Health Reference Level
Occurrence bv Population Served :
% PWS Population Served with detections
Range of Cross-Section States
GW PWS Population with detections
SW PWS Population with detections
% PWS Population Served > 1/2 Health Reference Level
Range of Cross-Section States
GW PWS Population > 1/2 Health Reference Level
SW PWS Population > 1/2 Health Reference Level
% PWS Population Served > Health Reference Level
Range of Cross-Section States
GW PWS Population > Health Reference Level
SW PWS Population > Health Reference Level
24 State
Cross-Section
(Round!)
45,567
0.43%
< (Non-detect)
140ug/L
Variable
900 ue/L
l,Oug/L
13,452
12,034
1,502
77,209,916
42,218,746
41.987.0UL_
20 State
Cross-Section
fRound 2)
94,910
0.23%
< (Non-detect)
140ug/L
Variable4
73 ue/L
0.73 ug/L
22,923
20,524
2,399
67,498,059
25,185,032
42.313.027
1.18%
0 - 28.24%
1.08%
1.93%
0.01%
0 - 1.53%
0.02%
0.00%
0.01%
0 - 1.53%
0.02%
0.00%
2.910%
0 - 37.22%
4.005%
1.323%
0.007%
0 - 0.23%
0.013%
0.000%
0.007%
0-0.23%
0.013%
0.000%
0.75%
Or 4.48%
0.62%
1.92%
0.01%
0 - 0.06%
0.01%
0.00%
0.00%
0.00%
0.00%
0.00%
4.790%
0-31.41%
1.162%
6.950%
0.002%
0 - 0.01%
0.007%
0.000%
0.000%
0.000%
0.000%
0.000%
National System &
Population Numbers
~
65,030
59,440
5,590
213,008,182
85,681,696
127.326.486
National Extrapolation
Round 1 Round 2
.769 491
N/A N/A
642 368
10 6
N/A N/A
10 6
0 0
10 0
N/A- N/A
10 0
6,198,000 10,204,000
N/A N/A
3,431,000 995,000
1,685,000 8,849,000
16,000 5,000
N/A N/A
11,000 6,000
0 0
16,000 0
N/A N/A
11,000 0
0 0
; Simmon Results based on data from 244tate Cross-Section, from VRCIS.VCM (1987) Bound 1.
2. £^ Rente based on data frcn 20^^
3.
5 Akto**
-P^PuKKcWaterSystems; GW- Ground Water; SW^Sacec^^.mumeporng
.HRL-HealthReferer&Level,
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Preliminary Regulatory Determination Support Document for Naphthalene
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3.3.2.2 Regional Patterns .
Occurrence results are displayed graphically by State in Figures 3-2,3-3, and 3-4 to assess whether
any distinct regional patterns of occurrence are present. Combining Round 1 and Round 2 data (Figure 3-
2), there are forty-seven States reporting. Four of those States have no data for naphthalene, while
another 11 have no detections of the chemical. The remaining 32 States have detected naphthalene in
drinking water and are well distributed throughout the United States. In contrast to the summary
statistical data presented in the previous section, this simple spatial analysis includes the biased New
Hampshire data.
The simple spatial analysis presented in Figures 3-2,3-3, and 3-4 suggests that special regional
analyses are not warranted because naphthalene occurrence at concentrations below the HRL is
widespread. While no clear geographical patterns of occurrence are apparent, comparisons with
environmental use and release information are useful (see also Section 3.1.2). The 47 TRI States
reporting releases of naphthalene to the environment include all of the States that detected it in drinking
water except New Hampshire. Also, four of the six States that have not detected naphthalene in site
samples reported to ATSDR's HazDat database, and three of the six States where it was not detected at
CERCLA NPL sites, have detected it in drinking water.
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Preliminary Regulatory Determination Support Document for Naphthalene
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Figure 3-2: States with PWSs with detections of naphthalene for all States with data in URCIS
(Round 1) and SDWIS/FED (Round 2)
All States
Naphthalene Detections
in Round 1 and Round 2
B States not in Round 1 or Round 2
No data for Naphthalene
States with No Detections (No PWSs > MRL)
States with Detections (Any PWS > MRL)
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Preliminary Regulatory Determination Support Document for Naphthalene
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Figure 3-3: States with PWSs with detections of naphthalene (any PWSs with results greater than
the Minimum Reporting Level [MRL]) for Round 1 (above) and Round 2 (below) cross-section
States
Oatlicn: State of Alabama at 2S.3X; State ofFbrida at 7.0K
Naphthalene Occurrence IB Ronnd 1
B States not in Cross-Section
No data for Naphthalene
0.00% PWSs> MRL
0.01 - 1.0054 PWSs > MRL
1.00 - 4.00% PWSs > MRL*
"Stale of New Hampshire h an outlier a 100%
Ntpkthalene Occurrence la Round 2
BStates not in Cross-Section
No data for Naphthalene
0.00% PWSs > MRL
0.01 - 1.00% PWSs > MRL
1.00 - 4.00% PWSs > MRL«
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Preliminary Regulatory Determination Support Document for Naphthalene
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Figure 3-4: Cross-section States (Round 1 and Round 2 combined) with PWSs with detections of
naphthalene (above) and concentrations greater than the Health Reference Level (below)
* Outliers: Stale of Alabama at28.3fi; Stale of Florida at 7.0%; State of New Hampshire at 10OX
NapbthaleBC Occurrence
la Romnd 1 »ad Round 2
I 1 States not in Cross-Section
[jTjfjo data for Naphthalene
9 0.00% PWSs > MRL
IH 0.01 - 1.00% PWSs > MRL
IB 1.00 - 4.00% PWSs > MRL*
Naphthalene Occurrence
IB Round 1 aid Ro»d 2
S States not in Cross-Section
No .data for Naphthalene
0.00% PWSs > HRL
0.01 - 1.00% PWSs > HRL
1.00 - 4.00% PWSs > HRL
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Preliminary Regulatory Determination Support Document for Naphthalene
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3.4 Conclusion
Naphthalene has been detected in untreated ambient ground water samples reviewed and/or analyzed
by the USGS NAWQA program. Detection frequencies and concentrations for all wells are relatively
low; however, occurrence is considerably higher for urban wells when compared to rural wells.
Naphthalene has been detected at slightly higher frequencies hi urban and highway runoff.
Concentrations in runoff are low, with maximum concentrations well below the current HAL of 100 ug/L.
Naphthalene has also been found at ATSDR HazDat and CERCLA NPL sites across the country and
releases have been reported through the Toxic Release Inventory.
Naphthalene has also been detected hi PWS samples collected under SDWA. Occurrence estimates
are low for Round 1 and Round 2 monitoring with only 0.43% and 0.23% of all samples showing
detections, respectively. Significantly, the values for the 99th percentile and median concentrations of all
samples are less than the MRL. For Round 1 samples with detections, the median concentration is 1.0
ug/L and the 99th percentile concentration is 900 jig/L. Median and 99 percentile concentrations for
Round 2 detections are 0.73 ug/L and 73 ug/L, respectively. Systems with detections constitute only
1.2% of Round 1 systems and 0.8% of Round 2 systems (an estimate of 769 (Round 1) and 491 (Round 2)
systems nationally). National estimates for the population served by PWSs with detections are also low,
especially for detections greater than the HRL. It is estimated that less than 0.01% of the national PWS
population is served by systems with detections greater than the HRL (approximately 16,000 people).
In summary, the occurrence data indicate that naphthalene is infrequently detected in ambient waters
or public water systems in the United States. Furthermore, when naphthalene is detected, it very rarely
exceeds the HRL or a value of one-half of the HRL. Therefore, hi relation to the key determination
criterion the occurrence data indicate that naphthalene does not occur hi public water systems with a
frequency, or at levels, of public health concern.
4.0 HEALTH EFFECTS
A full description of the health effects and the dose-response information for threshold and non-
threshold effects associated with exposure to naphthalene are presented in Chapters 7 and 8 of the Health
Effects Support Document for Naphthalene (USEPA, 2001b). A summary of the pertinent findings are
presented below.
4.1 Hazard Characterisation and Mode of Action Implications
Data for the human health effects of naphthalene are limited. Medical case reports of accidental and
intentional ingestion identify hemolytic anemia (breakdown of red-blood cells) and cataracts as
significant outcomes of oral exposure hi humans. Case reports of individuals (primarily infants) exposed
to naphthalene via dermal contact, inhalation, or a combination of both exposure routes point to hemolytic
anemia and its consequences such as jaundice and enlargement of the spleen as the most commonly
manifested toxic effects hi humans following exposure at concentrations that exceed average
environmental levels. There are no reliable human toxicity data for subchronic or chronic exposure to
naphthalene.
In animals, acute or subchronic exposure to relatively high oral doses (200 to 700 mg/kg or greater)
of naphthalene resulted hi hemolytic anemia (dogs only) and cataracts (rats and rabbits). Lower oral
doses of naphthalene (less than 200 to 400 mg/kg) administered to rats and mice hi three subchronic
studies resulted hi decreased body weight, central nervous system depression, and altered organ weights,
but did not result hi hemolytic anemia or cataracts. No treatment-related lesions were observed in studies
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Preliminary Regulatory Determination Support Document for Naphthalene
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reporting histopathology.,, A limitation of the health effects database for naphthalene is the lack of
adequately designed chronic oral exposure studies in animals.
There is no evidence of developmental effects in animals after exposure to naphthalene doses of 120
mg/kg or less. Developmental studies at higher doses produced inconsistent results with regard to
maternal and fetal effects.
The available data for mode of action indicate that Oxidative metabolism of naphthalene following
oral or inhalation exposure produces a variety of reactive metabolites. These metabolites subsequently
react with cellular macromolecules such as those in cell membranes or enzymes to elicit toxicity in target
tissues such as the blood, eye, and (in animal inhalation studies) nose and lung. Direct exposure of the
cells lining the respiratory tract causes inflamation, tissue damage, and reparative cell division. Although
naphthalene does not appear to be directly genotoxic, long term inhalation exposure of mice and rats has
caused development of adenomas (benign tumors) and carcinomas in the nasal cavity (rats) and lungs
(female mice). Naphthalene does not appear to be carcinogenic by the oral route.
People with impaired cellular defense capabilities may be more susceptible to naphthalene toxicity.
The finding that individuals deficient in the enzyme glucose-6-phosphate dehydrogenase (G6PD) are
more likely to develop hemofytic anemia following exposure to naphthalene confirms this prediction and
identifies this group as a potentially susceptible population. Individuals with this deficiency have lower
levels of reduced glutathione, a compound which normally protects red blood cells against oxidative
damage. G6PD-deficient neonates, infants, and the fetus are particularly sensitive to naphthalene toxicity
because the metabolic pathways responsible for detoxification of reactive naphthalene metabolites are not
yet well developed. In addition, these groups have low levels of methemoglobin reductase, increasing
their vulnerability in the period immediately after birth. Methemoglobin is a form of hemoglobin hi
which the iron has been changed so that the red blood cell can no longer carry oxygen. Naphthalene and
other chemicals can change the iron in hemoglobin from its +2 to its +3 state causing
methemoglobinemia. The enzyme methemoglobin reductase is responsible for returning the iron in
hemoglobin to its normal +2 state and restoring the ability to bind with oxygen.
4.2 Dose-Response Characterization and Implications in Risk Assessment
Information on the human health effects of naphthalene has been obtained from medical case reports
of intentional or accidental ingestion. The usefulness of case study data for assessing risk from drinking
water ingestion are limited by one or more of the following factors: quantitative exposure data are not
available in most case reports; the toxicokinetics of a single large dose may differ from those of chronic
low-level exposure; and/or the low aqueous solubility of naphthalene may prevent the occurrence of
concentrations in drinking water that are comparable to the doses that require medical attention. The
limited human exposure data from case reports suggest that cataracts occurred following a single dose of
approximately 71 mg/kg consumed over 13 hours (Lezenius, 1902). Indications of hemolytic1 anemia
resulted after a single oral dose of approximately 109 mg/kg (Gidron and Leurer, 1956).
All available dose-response information for naphthalene toxicity hi animals is extensively
summarized in Table 7-7 in the Health Effects Support Document for Naphthalene (USEPA, 2001b).
Five key studies are summarized below. These five studies currently provide the most reliable
information on threshold ^levels for naphthalene toxicity in animals exposed via the oral route. Included
in this group are two short-term studies and three subchronic studies. There are presently no adequately
designed chronic oral exposure studies.
In short-term studies, a Lowest Observed Adverse Effect Level (LOAEL) of 50 mg/kg-day (the
lowest dose tested) was identified for transient signs of neurotoxicity (i.e. slowed respiration and
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Preliminary Regulatory Determination Support Document for Naphthalene
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movement) in pregnant rats administered naphthalene on gestation days 6-15 (NTP, 1991). A No
Observed Adverse Effect Level (NOAEL) of 53 mg/kg-day and LOAEL of 267 mg/kg-day were
identified for effects on body weight and organ weight observed in a 14-day study conducted in mice
(Shopp et al., 1984). In subchronic studies, NOAEL and LOAEL values of 100 mg/kg-day and 200
mg/kg-day, respectively, were identified in 13-week studies conducted in rats and mice (BCL, 1980a, b).
The corresponding duration-adjusted values are 71 mg/kg-day and 143 mg/kg-day, respectively. The
LOAEL in rats was identified on the basis of decreased terminal body weight, while the LOAEL in mice
was identified on the basis of transient clinical signs of toxicity observed during weeks 3 to 5 of the study.
In the third subchronic study, NOAEL and LOAEL values of 53 mg/kg-day and 133 mg/kg-day,
respectively, were identified on the basis of changes in organ weights and data suggestive of changes in
enzyme activity observed in mice administered naphthalene, for 90 days (Shopp et al., 1984).
For hemorytic anemia and cataracts (the endpoints of greatest relevance to humans), the available
animal data are limited by deficiencies in study design, including the use of a single high dose (typically
500 to 2,000 mg/kg-day) and/or an inadequate number of test animals. NOAEL and LOAEL values
therefore cannot be identified in these studies. Holmen et al. (1999) identified a LOAEL of 500 mg/kg-
day for ocular changes in a multidose study where rats were dosed twice weekly for 10 weeks.
To place short-term and subchronic dose-response information in perspective, a high-end estimate of
naphthalene intake can be calculated. The solubility of naphthalene in water is 31 mg/L. Assuming that
naphthalene is present at the limit of solubility, the dose to a 70 kg adult consuming 2 L of drinking water
per day would be 0.9 mg/kg-day. The dose to a 10 kg child consuming 1 L of drinking water per day
would be 3.1 mg/kg-day. Comparison of these doses to the threshold levels for naphthalene toxicity
indicates that the human LOAEL values are at least an order of magnitude greater than the estimated
high-end dose.
The Reference Dose (RfD) for naphthalene is 2 x 10'2 mg/kg-day (USEPA, I998c). The RfD is an
estimate (with uncertainty spanning perhaps an order of magnitude) of a daily oral exposure to the human
population (including sensitive subgroups) that is likely to be without an appreciable risk of deleterious
effects during a lifetime. Because there are no adequate chronic oral exposure studies for naphthalene,
the RfD is based on a NOAEL of 71 mg/kg-day identified for lack of effect on terminal body weight in
male rats orally exposed to naphthalene for 13 weeks (BCL, 1980a). An uncertainty factor of 3,000 was
used in the derivation of the RfD to account for use of a subchronic study (factor of 10), extrapolation
from humans to animals (factor of 10), variability in human populations (factor of 10), and lack of
multidose studies in species that are sensitive to hemolytic anemia and cataracts (factor of 3). The
derivation of the RfD for naphthalene is discussed in Section 8.1.1 of the Drinking Water Support
Document for Naphthalene (USEPA, 2001b).
The Reference Concentration (RfC) for naphthalene is 3 x Hf3 mg/m3 (USEPA, 1998c). The RfC is
an estimate (with uncertainty spanning perhaps an order of magnitude) of a continuous inhalation dose to
the human population (including sensitive subgroups) that is likely to be without appreciable risk of
adverse effects over a lifetime of exposure. The RfC for naphthalene is based on lesions of the nose
observed in a chronic inhalation study of naphthalene in mice (NTP, 1992). Details of the RfC derivation
are provided in Section 8.1.6 of the Health Effects Support Document for Naphthalene (USEPA, 2001b).
Comparison of inhalation doses to the RfC can be useful in the risk assessment of contaminants that
readily volatilize from drinking water during household activities. In the case of naphthalene,
volatilization from water is expected to be minimal.
No quantitative dose-response analysis (including dose-conversion, extrapolation methods, oral slope
factor or inhalation unit risk) for cancer is presented at this time due to the weakness of evidence that
naphthalene may be carcinogenic in humans.
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Preliminary Regulatory Determination Support Document for Ncphthalene
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43 Relative Source Contribution
Relative source contribution analysis compares the magnitude of exposure expected via drinking
water to the magnitude of exposure from intake of naphthalene in other media such as food, air, and soil.
To perform mis analysis, intake of naphthalene from drinking water must be estimated. Drinking water
occurrence data for naphthalene are presented in Section 3.3. The median and 99th percentile
concentrations for naphthalene were below the MRL when all samples (i.e., those with detectable and
nondetectable levels of naphthalene) from either Round I or Round 2 were analyzed.
As a simplifying assumption, a value of one-half of the MRL is often used as an estimate of the
concentration of a contaminant when me results are less man the MRL. Becausea single estimate of the
MRL for naphmalene was unavailable [see Section 5.4;i of foe Health Effects Support Document for
Naphthalene (USEPA, 2001b)], two alternative approaches were used to estimate average daily intakes
from drinking water. The reported detection limits for naphthalene i^ge from 0.01 ug/L for the most
sensitive to 3.3 jig/Lfor the least sensitive methods (ATSDR, 1995). If a value of one-half the detection
limit is used as a rough estimate of the concentration of naphthalene, this equates to a range of 0.005 to
1.65 |ig/L. Assuming intake of 2 L/day of drinking water by a 70 kg adult, the average daily dose would
be 1 4 x 10"3 to 47.1 x 10* |ig/kg-day (1.4 to 47.1 ng/kg-day). The corresponding dose for a 10 kg child
consuming 1 L/day of drinking water would be 0.5 x W* to 165 * 10'3 fig/kg-day (0.5 to 165 ng/kg-day).
Alternatively, if the median concentration for naphthalene in samples with detectable levels
(approximately 1 ug/L) is used, the average daily doses.to an adult and child would be 28.6 x 10" and
100 x 10'3 ng/kg-day (28.6 and 100 ng/kg-day), respectively.
Collectively, available data indicate that intake from drinking water will often be relatively low when
compared to intake from other media. The estimated average daily intakes of naphthalene from drinking
water (based on median detected concentrations) and other media were used to calculate estimated ratios
of the exposure from each medium to the exposure from water. The estimated food:drinking water
exposure ratio ranges from 1 to 8 for an adult and from 2 to 9 for a child. The estimated aindrinking
water exposure ratio is 39 for an adult and 45 for a child. The range of estimated naphthalene intake from
soil is very broad for both children and adults; thus the soil water intake ratio will be highly scenario-
dependent. For an adult, the estimated soilrdrinking water exposure ratio ranges from less than 1 to 103.
For a child, the estimated soihdrinking water exposure ratio ranges from 2 to 430.
4.4 Sensitive Populations
The sensitive populations identified for naphthalene include individuals (including infents, neonates
and the fetus) deficient in the enzyme glucose-6-phosphate dehydrogenase (G6PD). This enzyme helps
protect red blood cells from oxidative damage. The enzyme deficiency makes red blood cells more
sensitive to a variety of toxins, including naphthalene. Thus, the hemolytic response to naphthalene is
enhanced in G6PD-deficient individuals. Higher rates of inherited G6PD deficiency are found among the
people of Asia, Greece, Italy, the Middle East, and Africa. In the United States, an estimated 5.2% to
11.5% of the population has an inherited G6PD deficiency (Luzzatto and Mehta, 1989). Because this
defect is linked to the X-chromosome, males are more likely to be affected than females.
New-bom infante are'generally considered to be more sensitive to naphthalene toxicity because the
metabolic pathways for conjugation of naphthalene are not well developed. New-born infants also have
low levels of methemoglobin reductase, which may compound and prolong some effects of hemolytic
anemia.
Calculation of medium-specific exposure ratios indicates that naphthalene intake from air is about 40-
fold greater than intake from water. Naphthalene intakes from food and soil may also be significantly
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Preliminary Regulatory Determination Support Document for Naphthal
ene
November, 2001
aid greater for a child, respectively) than from water, depending on
ion of naphthalene in drinking water would be unnkery to
dgnfficantly reduce the risk to sensitive populations.
4.5 Exposure and Risk Information
Approximately 6 to 10 million people are served by systems with J**^'?^.^^'1^
eXed^oflteK
the SE2£dT*«md.2 monitoring data, but exposures above ihe ffi^wo* *£££*
Prevalence data for G6PD deficiency in the United States indicate that 5.2% to 11.5/» ofthe exposed
SdS may have reduced activity of G6PD and, thus, have an increasedmkformethemoglobinemia
andirossiblyhemolvticanenuaifexposedtomwierate-to-highdosesofnaphthalene.
MeSSSris a precursor event to hemolysis induced by naphthalene, as weH as by* variety of
Sctemical agents. Hemolytic anemia is an acute effect that is precipitated when the oxidatove
damage to the red blood cell is sufficient to cause breakdown of toe cell membrane. ^l a ***"**
hTe reducedprotection against methemoglobinemia due to developmental delays in me activity of
methemoglobin reductase, a protective enzyme,
Hemolytic anemia is an acute effect that occurs at mod«ate-to-high doses of naphthalene, jvhen
average daily intakes from drinking water are compared with intakes1
water accounts for a relatively small proportion of total naphthalene m
observations, the impact of regulating naphthalene concentrations in drinking'
likely to be small. " ..
4.6 Conclusion
In conclusion, while there is evidence that naphthalene may have adverse bealtheffects m tomans.at
high doses it is unlikely that it will occur in drinking water at frequencies or concentrations that are of
publiSth Lcern. There are inadequate data to support a conclusion about the c^inogenicity_ of
mpSene by me oral route of exposure. All preliminary CCL regulatory determinations and further
analysis will be presented in the Federal Re&ster Notice.
5.0 TECHNOLOGY ASSESSMENT
If a determination has been made to regulate a contaminant, SDWArequires development of
proposed regulations within 2 years of making the decision. It is critical to have suitable momtonng
SeSSdtreatment technologies to support regulation development accordmg to Ihe schedules defined
inmeSDWA.
5.1 Analytical Methods
The availability of analytical methods does not influence EPA's determination of whether or not a
CCL contaminant should be regulated. However, before EPA actually regulates a contaminant and
SSL a Maximum Contact Level (MCL), there must be an analytocal method suitable.for
Suttoemonitoring. Therefore, EPA needs to have approved metfxodsavailabkdfor any CCL reguktory
determination contaminant before it is regulated with an NPDWR. These methods must be suitable for
compliance monitoring and should be cost effective, rapid, and easy to use.
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Preliminary Regulatory Determination Styport Document for N^^^ November, 2001
detectors (PID and ELCD in series), has a method detection limit of 0.02 ug/L.
5.2 Treatment Technology
(GAC) and air stripping.
greater sorption potential.
by ak stripping.
reasonable cost ' s-
OAcN»s^
undergo effective air stripping procedures under certaui concentration conditions.
6.0 SUMMARY AND CONCLUSIONS - DETERMINATION OUTCOME
a are used to guide the determination of whether regulation of a CCL
: 1) the contanSant may adversely affect the health of persons; 2) the
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Preliminary Regulatory Determination Support Document for Naphthalene
November, 2001
contaminant is known or is likely to occur in public water systems with a ^q^cy, and at levels, of
public health concern; and 3) regulation of the contaminant presents ameaningfiil °»2^ *£
risk reduction forpersons served by public water systems. As required by SDWA ^decision to regulate
a contaminant commits the EPA to propose a Maximum Contaminant Level Goal (MCLG) and
promulgate aNational Primary Drinking Water Regulation CNPDWR) for Ae corrfarr^t^ decision
not to regulate a contaminant is considered a final Agency action and is subject to judicial review^ The
Agency can choose to publish a Health Advisory (a nonregulatory action) or other guidance for any
contaminant on the CCL that does not meet the criteria for regulation.
The available toxicological data indicate that naphthalene has the potential to cause adverse health
effects in humans and animals at high doses. In humans, hemolytic anemia is the most common
manifestation of naphthalene toxicity. There are inadequate data to support a conclusion about the
carcinogenicily of naphthalene by the oral route of exposure.
Momtoringd^tamdicatematnaphthaleneismfiequently detected m puHic water supplies en _
naphSene is detected, it very rarely exceeds the Health Reference Level (HRL) or a vatae of one-hatf of
theHRL The available data for naphthalene production show downward trends. The physiochemical
properties of naphthalene, and the available data for environmental fate, indicate that naphthalene in
Sk* water is likely to be rapidly degraded by biotic and abiotic processes and that rt has httle potential
for bioaccumulation. Based on these data, it is unlikely that naphthalene will occur in public water
systems at frequencies or concentration levels that are of public health concern.
EPA considers exposure to both the general public and sensitive populations, including the fetus,
infants, and children, in making its regulatory determination. Approximately 6 to 10 miflion people are
served by PWSs with detections greater man the Minimum Reporting Level. Based on Round 1
monitoring, an estimated 16,000 individuals (about 0.007% of the populationserved by PWSs) _ ^
Sed to naphthalene at levels that exceed both one-half the HRL and the HRL. However, mis estimate
wTheavily influenced by results from samples collected at two ground water systems in one of the cross-
section States that can be.eonsidered to be outlier values. The Round 2-based estimate of 5,000
individuals (approximately 0.002% of the population served) exposed to concentrations greater Jan /, fte
HRL with no exposures at concentrations greater than the HRL appears to be a better estimate of possible
national exposure.
Infants and neonates (approximately 1.3% of the national population) and the fetus (approximately
2.4% of the national population) may experience greater sensitivity to n^thalene toxicity than the
general population. Individuals deficient in the G6PD enzyme (approximately 5.2%-11.5/oofthe
nationalWdation) are also believed to be more sensitive to development of hemolytic anemia than me
general population. When average daily intakes from drinking water are compared with intakes from
food, air and soil, drinking water accounts for a relatively small proportion of total naphthalene intake
These observations suggest that naphthalene regulation in drinking water would not present a meaningful
opportunity for health risk reduction.
While there is evidence that naphthalene may have adverse health effects in humans at high doses, it
is unlikely that it will occur in drinking water at frequencies or concentrations mat are of public health
concern or that regulation of naphthalene represents a meaningful opportunity for health risk reduction in
persons served by public water systems. Preliminary CCL regulatory determinations and further analysis
will be presented in the Federal Register Notice.
28
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Preliminary Regulatory Determination Support Document for Naphthalene
November, 2001
References
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76-34-106002.
<*
BCL 1980b Unpublished subchronic toxicity study: naphthalene (C52904) B6C3F, mice. Report to
the US Department of Health and Human Services, National Toxicology Program, Research Triangle
Park, NC, by BCL, Columbus, OH, under Subcontract No. 76-34-106002.
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Holmen,J.B.,B.EkestenandB.Lundgren. 1999. Naphthalene-induced cataract model in rats: A
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1992-1996. Ground Water. 38(6):858-863.
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Larson, S J R.J. Gffliom, and P.D. Capel. 1999. Pesticides in streams of the United States-Initial
results from the National Water-Quality Assessment Program. US Geological Survey
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Preliminary Regulatory Determination Support Document for Naphthalene
November, 2001
Water-Resources Investigations Report 98-4222. 99 pp. Available on the Internet at:
http://water.w.usgs.gov/pnsp/rep/wrir984222/ Last modified May 6,1999.
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1998c).
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30
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Preliminary Regulatory Determination Support Document for Naphthalene
November, 2001
USEPA 1991 National Primary Drinking Water Regulations- SyntheticOrgaruc Chemicals and
inorganic Chemicals; Monitoring for Unregulated Contaminants; National Primary Drinking Water
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45 pp. Available on the Internet at: http^/www.epa.gov/tri/chemls2.pdf Last modified March 23,
2000. Link to site at: http://www.epa.gov/tri/chemical.htm
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information on the Integrated Risk Information System (IRIS). Washington, D.C.: USEPA. 124 pp.
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http://www.epa.gov/iris/subs1/0436.htm
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f
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http://www epa.gov/triexplorer/trends.htm Last modified May 5,2000.
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Preliminary Regulatory Determination Support Document for Naphthalene
November, 2001
USEPA. 2000d. The Toxic Release Inventory (TRI) and Factors to Consider when Using TR1Data.
Washington, D.C.: USEPA. Available on the Internet afc http://www.epa.gov/tri/tri98/98over.pdf
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assessment. Office of Water. EPA report 815-P-00-001. 50pp.
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Preliminary Regulatory Determination Support Document for Naphthalene
November, 2001
ACGIH
ATSDR
CAS
CCL
CERCLA
CMR
CWS
BCD
ELCD
EPA
EPCRA
FDA
FIFRA
FQPA
FR
G6PD
GAC
GC
g/mol
GW
HAL
HazDat
HRL
IOC
IRIS
L
LOAEL
MCL
MCLG
MDL
mg
mg/kg-day
mmHg
MRL
MS
MSHA
NAWQA
NCOD
NDWAC
NIOSH
MRS
urn
NOAEL
NPDES
NPDWR
NPL
Appendix A: Abbreviations and Acronyms
- American Conference of Governmental Industrial Hygienists
- Agency for Toxic Substances and Disease Registry
Chemical Abstract Service
- Contaminant Candidate List
- Comprehensive Environmental Response, Compensation & Liability Act
Chemical Monitoring Reform
- community water system
- electron capture detectors
- electrolytic conductivity detector
- Environmental Protection Agency
- Emergency Planning and Community Right-to-Know Act
- Food and Drug Administration
- Federal Insecticide, Fungicide, and Rodenticide Act
- Food Quality Protection Act
- federal register
- gIucose-6-phosphate dehydrogenase
- granular activated carbon (treatment technology for organic compounds)
- gas chromatography (a laboratory method)
- grams per mole
- ground water ,
- Health Advisory level
- Hazardous Substance Release and Health Effects Database
- Health Reference Level
- inorganic compound
- Integrated Risk Information System
- organic carbon partition coefficient
- octanol-water partitioning coefficient
- liter
- lowest observed adverse effect level
- maximum contaminant level
- maximum contaminant level goal
- method detection limit
- milligram
- milligram per kilogram per day
- millimeter mercury
- minimum reporting level
- mass spectrometry (a laboratory method)
- Mine Safety and Health Administration
- National Water Quality Assessment Program
- National Drinking Water Contaminant Occurrence Database
- National Drinking Water Advisory Council
- National Institute for Occupational Safety and Health
- National Inorganic and Radionuclide Survey
- nanometer
- no observed adverse effect level
- National Pollution Discharge Elimination System
- National Primary Drinking Water Regulation
- National Priorities List
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Preliminary Regulatory Determination Support Document for Naphthalene
November, 2001
NFS
NTNCWS
NTP
NURP
OGWDW
ORD
OSHA
PID
ppm
PWS
RCRA
RfD
SARA Titie m
SDWA
SDWIS/FED
SOC
SW
TRI
UCM
UCMR
imas
USDHHS
USEPA
USGS
voc
ug
>MCL
>MRL
- National Pesticide Survey
- non-transient non-community water system
- National Toxicology Program
- National Urban Runoff Program
- Office of Ground Water and Drinking Water
- Office of Research and Development
- Occupational Safety and Health Administration
- photoionization detector
-part per million
- public water system
- Resource Conservation and Recovery Act
- reference dose
- Superfund Amendments and Reauthorization Act
- Safe Drinking Water Act
- Federal Safe Drinking Water Information System
- synthetic organic compound
- surface water
- Toxic Release Inventory
- Unregulated Contaminant Monitoring
- Unregulated Contaminant Monitoring Regulation/Rule
- Unregulated Contaminant Monitoring Information System
United States Department of Health and Human Services
- United States Environmental Protection Agency
United States Geological Survey
- volatile organic compound
micrograms
- percentage of systems with exceedances
- percentage of systems with detections
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