EPA
United States Office of Water
Environmental Protection 4607
Agency
ERA815-R-O1-O14
November 2OO1
Contaminant Candidate List
1 ' , « • -it V I , . > ' /
Preliminary Regulatory
Determinajipn Support
Document for Sodium
I , H
. , f „ I i
' i
Printed on Recycled Paper
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CCL Preliminary Regulatory Determination Support Document for Sodium
November, 2001
Disclaimers
This document is designed to provide supporting information regarding the regulatory determination
for sodium 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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CCL Preliminary Regulatory Determination Support Document for Sodium
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Acknowledgments
This document was prepared in support of the EPA's Office of Ground Water and Drinking Water
regulatory determination for sodium 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 Tail 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 document. 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.
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CCL Preliminary Regulatory Determination Support Document for Sodium
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USEPA, Office of Wats-Report: EPA 815-R-01-014, November, 2001
CONTAMINANT CANDIDATE LIST
PRELIMINARY REGUliATORY DETERMINATION SUPPORT
TOCUMENT FOR SODIUM
Executive Summary
Sodium is a 1998 Contaminant Candidate List (CCL) regulatory determination priority contaminant
Sodium 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 sodium 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 sodium, 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 arid 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.
Sodium (Na)is a naturally occurring element ubiquitous in the environment. It is the sixth most
abundant element in the Earth's crust and the most abundant anion in the hydrosphere. Sodium in the
ocean is associated with chlorine in the form of sea salt In the lithosphere, most sodium minerals exist as
soluble salts found primarily in evaporite deposits and silicate minerals, and more rarely as halides or
aluminohalides. The sodium cation (Na4) is necessary for a number of biochemical processes in many
living organisms.
Sodium chloride (NaCI) is the most economically and industrially important form of sodium with
thousands of uses. Among other things, salt is used as a flavor enhancer or food preservative, as a road
deicer, in water softening treatment, in powdered soaps and detergents, as the electrolyte in saline
solutions, in rubber manufacture, and as a pesticide. Sodium chloride is also used in oil and gas
exploration, textile and dyeing industries, metal processing, pulp and paper production, tanning and
leather treatment, and in the chemical industry to manufacture other chemicals. Widespread
environmental releases of five other sodium compounds reported through the Toxic Release Inventory
(TRI) underscore the heavy use and release of sodium in the environment.
A Health Advisory (HA) has until now never been issued for sodium, though a Drinking Water
Equivalent Level (DWEL) is available. The DWEL of 20 mg/L is a non-enforceable guidance level
considered protective against non-carcinogenic adverse health effects and is based on an American Heart
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CCL Preliminary Regulatory Determination Svppon Document for Sodium
November, 2001
Association recommendation issued in 1965. Also, EPA has issued a non-enforceable guidance of 250
mg/L for salinity and dissolved solids in ambient waters (USEPA, 1997; 62 FR 52194).
Hie sale, use, and distribution of pesticide products containing sodium chloride and sodium bromide
are controlled under the Federal Insecticide, Fungicide, and Rodenticide Act (FLPKA). The
Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA, or "Superfund")
also includes sodium and many of its compounds on its list of hazardous substances. A number of
sodium compounds are also listed as hazardous constituents under the Resource Conservation and
Recovery Act (RCRA).
Sodium occurrence in ambient waters and stream bed sediments monitored by the United States
Geological Survey's (USGS) National Water Quality Assessment (NAWQA) program is ubiquitous,
approaching 100% of water and sediment sampling sites for all land use categories. Although sodium
detection frequencies are high, sodium occurrence at levels of public health concern is low. Less than 6%
of all surface water sites and less than 8% of all ground water sites report detections greater than 120
mg/L, a benchmark concentration level used for this analysis.
Sodium has been detected in ground water PWS samples collected through the National Inorganic
and Radiomiclide Survey (NIRS) study. Occurrence estimates are high with 100% of samples showing
detections, affecting 100% of the national population served. The 99th percentile concentration of all
samples is 517 mg/L. About 13.2% of the NIRS systems exceeded the 120 mg/L benchmark level,
affecting approximately 7.1 million people nationally. Additional data, including both ground water and
surface water PWSs from select States, were examined through independent analyses and also show
substantial sodium occurrence.
The weight of evidence favors the conclusion that high sodium intakes can have an adverse effect on
blood pressure, especially for sodium-hypertensives. Hypertension affects almost 50 million people in
the United States, and along with factors such as body weight, alcohol intake, and cholesterol, is a risk
factor for heart disease. However, hyptertension is influenced more by lifestyle, behavior, and other
nutrient intake than by sodium intake.
Sodium is known to occur in public water systems and in a few cases at levels of public health
concern, particularly for salt-sensitive hypertensives. However, at these same concentrations, taste is
generally affected and would likely lead consumers to decrease consumption. In addition, when
compared with other intake routes, sodium from drinking water has a minor impact. For these reasons,
regulation of sodium is unlikely to present a meaningful opportunity for health risk reduction for persons
served by public water systems. However, EPA may choose to issue a non-enforceable Drinking Water
Advisory, based on current health effects, taste effects, and occurrence data, to provide guidance to
communities that may be exposed to elevated concentrations of sodium chloride or other sodium salts in
their drinking water. In addition, under EPA-required sodium monitoring, test results must be reported to
State and local public health authorities, who may advise sensitive populations of any risk they may face.
VI
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CCL Preliminary Regulatory Determination Support Document for Sodium
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Table of Contents
Disclaimers i
Acknowledgments ... iii
Executive Summary ..... .. v
Table of Contents vii
List of Tables .... ix
List of Figures xi
1.0 INTRODUCTION 1
1.1 Purpose and Scope 1
1.2 Statutory Framework/Background 1
1.3 Statutory History of Sodium, : 2
1.4 Regulatory Determination Process 3,
1.5 Determination Outcome 4
2.0. CONTAMINANT DEFINITION 4
2.1 Physical and Chemical Properties 5
2.2 Environmental Fate and Transport 5
3.0 OCCURRENCE AND EXPOSURE .6
3.1 Use and Environmental Release 6
3.1.1 Production and Use 6
3.1.2 Environmental Release 10
3.2 Ambient Occurrence 11
3.2.1 Data Sources and Methods 12
3.2.2 Results 12
3.3 Drinking Water Occurrence 14
3.3.1 Analytical Approach "... 14
3.3.1.1 National Inorganic and Radionuclide Survey (NIRS) 14
3.3.1.2 Supplemental IOC Data .... 15
3.3.1.3 Data Management and Analysis . 15
3.3.1.4 Occurrence Analysis 16
3.3.2 Results 17
3.4 Conclusion 21
4.0 HEALTH EFFECTS 21
4.1 Hazard Characterization and Mode of Action Implications 21
4.2 Dose-Response Characterization and Implications in Risk Assessment 23
4.3 Relative Source Contribution 23
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CCL Preliminary Regulatory Determination Support Document for Sodium
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1.0 INTRODUCTION
1.1 Pay-pose arid Scope
This document presents scientific data and summaries of technical information prepared for, and used
in, me U.S. Environmental Protection Agency's (EPA) regulatory determination for sodium. Information
regarding sodium'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 Water Act (SDWA), as amended in 1996, requires the 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,
1998c; 63 FR 10273), 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 micfobial 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 31A years
after each new CCL.
Language in SDWA Section 1412(b)(l)(A) specifies that the determination to regulate a contaminant
must be based on a rinding 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 this CCL contaminant will present a meaningful opportunity to
reduce health risk based on contaminant occurrence, exposure, and other risk considerations. The Office
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CCL Preliminary Regulatory Determination Support Document for Sodium
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of Ground Water and Drinking Water (OGWDW) is charged with gathering 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 the exposure and risk to
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 hi the Federal Register the draft
determinations for public comment EPA is required to 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 within twenty-four months, and promulgated eighteen months
later. EPA has determined that mere is sufficient information to support a preliminary regulatory
determination for sodium.
13 Statutory History of Sodium
Sodium chloride (NaCl), otherwise known as halite, salt, sea salt, or table salt, is the most
economically and industrially important form of sodium, with an estimated 14,000 direct and indirect
uses. Among other things, salt is used as a flavor enhancer or preservative in food, as a road deicer, in
water softening treatment, in powdered soaps and detergents, as the electrolyte in saline solutions, in
rubber manufacturing, and as a pesticide. Sodium chloride is also used in oil and gas exploration, textile
and dyeing industries, metal processing, pulp and paper production, tanning and leather treatment, and in
the chemical industry (Kostick, 1993; Gornitz, 1972). Because salt has so many human end uses and is
abundant in the ocean, sodium is ubiquitous hi the environment.
A Health Advisory (HA) for sodium has never been issued, though a Drinking Water Equivalent
Level (DWEL) is available. The DWEL of 20 mg/L is a non-enforceable guidance level considered
protective against non-carcinogenic adverse health effects and is based on an American Heart Association
recommendation issued in 1965. Also, EPA has issued a non-enforceable guidance of 250 mg/L for
salinity and dissolved solids in ambient waters (USEPA, 1997; 62 FR 52194).
The sale, use, and distribution of pesticides, including those containing sodium, is controlled under
the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). FIFRA was most recently amended in
1996 under the Food Quality Protection Act (FQPA). FIFRA requires registration of all pesticides with
EPA, as well as 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).
Pesticide products containing sodium chloride and sodium bromide have been registered under
FIFRA since 1954 and 1975, respectively. Currently, thirty-two sodium bromide pesticide products and
two pesticide products containing sodium chloride are registered in the United States (USEPA, 1993).
The Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA, or
"Superfund") includes sodium and many of its compounds on its list of hazardous substances.
CERCLA's listing requires reporting of releases over a certain "reportable quantity" which, for elemental
sodium, is ten pounds (USEPA, 1998b). A number of sodium compounds are also listed as hazardous
constituents under the Resource Conservation and Recovery Act (RCRA) (USEPA, 1998b). Furthermore,
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CCL Preliminary Regulatory Determination Sitpport Document for Sodium
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data are available for five sodium compounds through the Toxic Release Inventory (TRT). The TRI was
established by the Emergency Planning and Community Right-to-Know Act (EPCRA). EPCRA requires
certain industrial sectors to publically report the environmental release or transfer of chemicals included
in this inventory (USEPAi 2000a).
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 the 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 data for each contaminant;
(2) conduct a preliminary risk assessment for each contaminant based on the available data; and (3) issue
a decision document for each contaminant describing the outcome of the preliminary risk assessment
The NRC noted that in using this decision framework, EPA should keep in mind the importance of
involving all interested parties.
One of the formal means by which EPA works with its stakeholders is through the National Drinking
Water Advisory Council (NDWAC). The NDWAC comprises members of the general public, State and
local agencies, and private groups concerned with safe drinking water, and advises the EPA Administrator
on key aspects of the Agency's drinking water program. The NDWAC provided specific
recommendations to EPA on a protocol to assist the Agency in making regulatory determinations for
current and future CCL contaminants. Separate but similar protocols were developed for chemical and
microbial contaminants. These protocols are intended to provide a consistent approach to evaluating
contaminants for regulatory determination, and to be a tool that will organize information in a manner that
will communicate the rationale for each determination to stakeholders. The possible outcomes of the
regulatory determination process are: a decision to regulate, a decision not to regulate, or a decision that
some other action is needed (e.g., issuance of guidance).
The NDWAC protocol uses the three statutory requirements of SDWA Section 1412(b)(l)(A)(i)-(iii)
• (specified in section 1.2) as the foundation for guiding EPA in making regulatory determination
decisions. For each statutory requirement, evaluation criteria were developed and are summarized below.
To address whether a contaminant may have adverse effects on the health of persons (statutory
requirement (i)), the NDWAC recommended that EPA characterize the health risk and estimate a health
reference level (or, in the case of sodium, a benchmark) for evaluating the occurrence data for each .
contaminant
Regarding whether a contaminant is known to occur, or whether there is substantial likelihood that
the contaminant will occur, in public water systems with a frequency, and at levels, of public health
concern (statutory requirement (ii)), the NDWAC recommended that EPA consider (1) the actual and
estimated national percent of public water systems (PWSs) reporting detections above half the health
reference level (or benchmark); (2) the actual and estimated national percent of PWSs with detections
above the health reference level (or benchmark); and (3) the geographic distribution of the contaminant
To address whether regulation of a contaminant presents a meaningfulopportunity for health risk
reduction for persons served by public water systems (statutory requirement (iii)) the NDWAC
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CCL Preliminary Regulatory Determination Support Document for Sodium
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recommended that EPA consider estimating the national population exposed above half the health
reference level (or benchmark) and the national population exposed above me health reference level (or
benchmark).
The approach EPA used to make preliminary regulatory determinations followed the general format
recommended by the NRC and the NDWAC to satisfy the three SDWA requirements under section
1412(b)(l)(AXi)-(iii)- The process was independent of many of the more detailed and comprehensive
risk management factors that will influence the ultimate regulatory decision making process. Thus, a
decision to regulate is the beginning of the Agency regulatory development process, not the end.
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 la the case of sodium, a benchmark was chosen based on
taste effects, which occur at lower concentrations man health effects.
For each contaminant EPA estimated the number of PWSs with detections >V£HRL (or benchmark)
and >HRL (or benchmark), the population served at these values, and the 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
After reviewing the best available public health and occurrence information, EPA has made a
preliminary determination not to regulate sodium with an NPDWR. This preliminary determination is
based on the finding that regulation of sodium may not present a meaningful opportunity for health risk
reduction for persons served by public water systems. However, EPA may issue an advisory to provide
guidance to communities that may be exposed to drinking water contaminated with sodium chloride or
other sodium salts. All preliminary CCL regulatory determinations are presented in the Federal Register
Notice. The following sections summarize the data used to reach this preliminary decision.
2.0. CONTAMINANT DEFINITION
Sodium (Na) is a naturally occurring element ubiquitous in the environment It is the sixth most
abundant element in the Earth's crust and the most abundant anion in the hydrosphere (the hydrosphere is
all water, including atmospheric and oceanic water, on earth; Gornitz, 1972). The sodium cation (Na4) is
necessary for biochemical processes like sodium pumps and concentration gradients in many living
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CCL Preliminary Regulatory Determination Support Document for Sodium
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organisms (Madigan et al., 1997). Theiearth's oceans contain roughly 18.4 quadrillion short tons (1 short
ton = 2000 Ibs) of sodium associated with chlorine in the form of sea salt (Kostick, 1993). In the
lithosphere, most sodium minerals exist as soluble salts found primarily in evaporite deposits, as intricate
rock-formingsilicates, orasrarehalidesoraluminohalides(Gornitz, 1972).
Sodium chloride (Nad), otherwise known as halite, salt, sea salt, or table salt, is the most
economically and industrially important form of sodium, with an estimated 14,000 direct and indirect
uses. Among other things, salt is used as a flavor enhancer or preservative in food, as a road deicer, hi
water softening treatment, in powdered soaps and detergents, as the electrolyte in saline solutions, in
rubber manufacturing, and as a pesticide. Sodium chloride is also used in oil and gas exploration, textile
and dyeing industries, metal processing, pulp and paper production, tanning and leather treatment, and in
the chemical industry to manufacture such chemicals as chlorine, sodium metal, sodium hydroxide,
sodium carbonate, and sodium sulfate (Kostick, 1993; Gornitz,1972).
2.1 Physical and Chemical Properties
Sodium is an alkali metal located hi group 1A of the periodic table, and has an atomic weight of
22,99 g/mol, melting point of 97.82 °C, and boiling point of 892 °C. Sodium metal is a soft solid with a
shiny metallic luster and is an excellent conductor of electricity. Sodium does not occur in nature hi its
pure form because the metal readily gives up its single valence electron, making it highly reactive (Brown
et al., 1994). Elemental sodium reacts violently with water to form sodium hydroxide and hydrogen gas,
and oxidizes in the presence of oxygen to sodium monoxide. Sodium commonly occurs as sodium
halides (NaCl, NaBr), sodium carbonates (NaaCC^ NaHCO3), sodium sulfetes (NaaSO,,, NaHSO4),
sodium hydride (NaH), or sodium nitrate (NaNO3) (Gornitz, 1972).
2.2 Environmental Fate and Transport
. '*•• .- • .. ... ., - ,.'•:.-
A sodium salt is formed when the sodium cation replaces some or all of the hydrogen cations in an
acid. Sodium salts that occur hi seawater can be classified as "cyclic" salts because they traverse different
atmospheric, terrestrial, and aquatic environments before returning to the ocean. More specifically, cyclic
salts are conveyed from the ocean into the atmosphere by spray and then transported inland dissolved hi
suspended water droplets. The salts are transferred to the soil through precipitation or dry deposition and
eventually leach to freshwater streams and ground water. From these freshwater reservoirs, the salts
return to the ocean, thus completing the cycle (Fairbridge, 1972). Sodium chloride that has been used hi
industry and released into the environment either directly or by means of landfills is also expected to
cycle back to the ocean (Kostick, 1993).
Sodium salts can occur on earth as evaporite deposits, formed when the rate of evaporation exceeds
the rate of precipitation plus runoff. Ancient deposits were formed chiefly by the evaporation of
retreating seas (Kostick, 1993; Feldman and Cruft, 1972). Recent evaporite deposits are predominantly
non-marine hi origin and occur hi hot, arid climates or hi windy, restricted basins (Feldman and Cruft,
1972). Evaporite deposits of halite (NaCl) can become deformed under increasing temperatures and
pressures, disrupting surrounding sediment layers and forming salt domes. Salt domes can extend
vertically downward more than 20,000 feet and are common hi the Gulf Coast region of the United States
(Gornitz, 1972; Kostick, f993).
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CCL Preliminary Regulatory Determination Support Document for Sodium
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Sodium salts are water soluble and can leach to freshwater (Fairbridge, 1972). Sodium does not
adsorb strongly to clay, and therefore can be leached from clay sedimentary rock (Creasey, 1972).
Sodium salts are natural constituents of ground water because of the abundance of evaporite minerals in
the earth's crust Ground water sodium levels may be increased in areas where salt is used to deice
highways (Hackett, 1972).
3.0 OCCURRENCE AND EXPOSURE
TMs section exammes the occurrence of sodium in drinking water. While no complete national
database exists of unregulated or regulated contaminants in drinking water from public water systems
(PWSs) collected under SDWA, this report aggregates and analyzes existing federal and State data that
have been screened for quality, completeness, and representativeness. Populations served by PWSs
exposed to sodium 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 sodium, is also
reviewed.
3.1 Use and Environmental Release
3.1.1 Production and Use
The earth's oceans contain approximately 46 quadrillion short tons (I short ton = 2,000 Ibs) of
sodium chloride, or 18.4 quadrillion short tons of sodium (sodium chloride is 40% sodium by weight)
(Figure 3-1). Sodium chloride is also known as salt, sea salt, halite, or table salt.
Sodium is transported from the ocean to the atmosphere by spray and is suspended in water droplets
until it is either precipitated or introduced to the soil by dry deposition (Fairbridge, 1972). Sodium levels
in precipitation are higher near coastal areas and decrease further inland (Figure 3-2).
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CCL Preliminary Regulatory Determination Support Document for Sodium
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Figure 3-1: Abundance of sodium chloride (salt) in the ocean
World oeaan volum*
of 829 million cubic mites has
48
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CCL Preliminary Regulatory Determination Support Document for Sodium
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Table 3-1; End uses of sodium chloride in 1990 (in thousands of short tons)
Sectors and subsectors
Chemicals:
••* »»•»>«**•••• .Chlorine STKi sodium hydroxide manuiactufc
.»««.»«*.« .Manufacture of other chemicals, ?ikg sodium carbonate and sodium metal
.HHHH«.«»..HH»»MH».»H.Total chemicals ' ,
Ice control/stabilization:
................... Government
......... ......... Commercial
...»»«.»»*.».»»»»H.»».»Tot&] ice control
Food processing
».»««.«H»..^f eat packers
...................Dairy
•«.*.»».»..». »Bakmg
.MK*..«»».M*.C^rai& mill processing
«.„..„... — ...Other food processing
...««.....«.....Gtocery wholesale
.»««».»..». »H..«.«..H«.Tota] food processing
General Industrial
......MH«...»..Textiles and dyeing
............... ....Metal processing
......Rubber
.....»...™.....oa
.-„.«„«..... J*ulp and paper
...«»...«..M...Tanning and leather
.»«»...«»»,»Other industrial
...... ........................... ....Total general industries
Agricultural
.. ....... „....„.. Feed retailers and/or dealers-mixers
«.««-,«».„. Jced manu&cturers
,»«..«.w. — Direct-buying and user
.« ,....,. ^.....Distributors
*....„»»».......»....,».».... Xotal agricultural
Distributors
.»»«...»».M..Grocery wholesale and/or retailers
...».«».»»«. Jnstitutional wholesalers and end users
...................U.S. Government resale
...... ....... ......Other wholesale and/or retailers
............................ ...... Total distributors
Water treatment
..»».«..„..... .Government
............... ...ComracTcial
.„ ^»...»» .... .Distributors
•»HHt***it.*.*.t..***..»..*HH.*Tota] water treatment
Other
.HH«..HH.H«»»»».....H»»Grand total
qfterKastick 1993
P— <™
19,182
2,046
21^28 47
10,757
545
11,302 25
598 '
140
171
97
298
671
2^93 5
227
346
45
793
283
109
288
2,091 5
1,101
546
55
619
2,321 5
223
Q£
yo
9
1,851
2,030 5
297
198
1,123
1,618 4
2,030 . 4
100
Sodium chloride is the most economically and industrially important form of sodium, with an
estimated 14,000 direct and indirect uses (Kostick, 1993). As depicted in Table 3-1, sodium chloride use
can be broken down into eight major categories: chemical (47%), ice control (25%), food processing
(5%), general industrial (5%), agricultural (5%), distributors (5%), water treatment (4%), and
miscellaneous (4%).
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CCL Preliminary Regulatory Determination Support Document for Sodium
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Two sodium end uses with the most probable immediate effect on drinking water quality are water
treatment and road deicing. Jn water treatment, sodium is used as a softener by substituting the sodium
cation, Na% for calcium (Ca2*) and magnesium (Mg2*), both of which make water "hard." Water is
considered"hard" when calcium and magnesium ions occur in high concentrations and leave caked
mineral deposits m household and commercial equipment. Various softening processes exchange sodium
cations for calcium and magnesium cations and release sodium directly into the drinking water supply
(Kostick, 1993). Many sodium salts are used for water treatment, for example sodium chloride, sodium
hydroxide, sodium bicarbonate, and sodium carbonate. ;
Sodium chloride that has been used to deice roads can also be a problem for drinking water systems.
The salt and ice mixture creates a brine with a lower freezing point than water, effectively melting ice
(Kostick, 1993). Sodium chloride is a cheap and effective solution to frozen roads, but can become an
environmental concern when run-off affects local vegetation and soil quality, as well as ground water and
surface water supplies. In one study, sodium levels eight times the norm were detected forty-five feet
from the highway in areas where deicing salt had been used for 18 years (USEPA, 1990). A different
study, undertaken by the Federal Government and University researchers, found that highway deicing
with sodium chloride made a significant impact on the salinity of the nation's streams between the years
1974-1981. Data for the investigation came from the National Water Quality Surveillance System and
from United States Geological Survey (USGS) National Stream Quality Accounting Network sampling
stations (Smith etal., 1987).
Table 3-2: U.S. sodium chloride statistics, 1990-1998 (in thousands of metric tons)
1998
1997
1996
1995
1994
1993
1992
1991
1990
Production
41,200
41,400
42,200
42,100
40,100
39,200
36,000
36,300
36,800
Exports
731
748
869
670
742
688
992
1,780
2,270
Imports
8,770
9,160
10,600
7,090
9,630
5,870
5,390
6,190
5,970 .
Consumption, reported*
44,200
49,500
52,800
46,500
47,200
44,400
39,700
40,600
no data
after Kostick.1994 and Kastick, 1998
*Reported consumption is sales or use as reported by the salt companies including their imports and exports.
The United States produces more sodium chloride than any other country in the world, with other
major producers including Russia, England, Germany, Canada, and France (Gornitz, 1972; Kostick,
1993). From 1990 to 1998, United States NaCl consumption was between three to ten million metric tons
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CCL Preliminary Regulatory Determination Support Document for Sodium
November, 2001
greater than its production (1 metric ton = 2,205 Ibs), with imports three to thirteen times higher than
exports (Table 3-2).
Although these figures suggest that the U.S. relies on foreign sources to meet consumption needs,
most imports were supplied by foreign subsidiaries of major U.S. sodium chloride producers (Kostick,
1998). For the years 1994-1998, United States salt statistics analyzed by State indicate that Louisiana
sold, or used, the most sodium (35%), followed by Texas (23%), New York (11%), Kansas (7%), and
Utah (4%) (Kostick, 1994; Kostick 1995; Kostick, 1996; Kostick, 1997; Kostick, 1998).
3.1.2 Environmental Release
Beyond raw production and use data, the disposal and release of sodium products to the environment
is of special concern to drinking water systems. The end use of some sodium products involves direct
environmental application, as with pesticides like sodium chloride or sodium bromide (USEPA, 1993).
Other sodium products are dispersed post-consumption to the environment or are disposed of in landfills.
Table 3-3 outlines the environmental fate of products from general sodium chloride use categories.
Table 3-3; Environmental fate of post-consumer sodium chloride, 1990 (in millions of short tons)
Dispersive Lasses
Chemicals-as waste effluent, sewage
Food-through excretion, assimilation
Industrial-as waste effluent, sewage
Agriculture-through excretion,
assimilation
Water treatment-through sewage
Deicing-runoff
Other
Total
12.5
2.1
1-7
2.3
1.6
11.3
3.2
34.7
Disposed to Landfill and Incineration
Chemicals-plastics, glass, paper
Food-discarded waste food
Industrial-rubber, textiles
Agricultural
Water treatment
Deicing
Other
Total
8.7
0.2
0.4
0
0
0
1.0
10.3
aflerKasttck, 1993
Dispersive losses of sodium chloride are those released to the environment directly after
consumption. Examples include salt in run-off following highway deicing, effluents in industrial sewage,
or salt released into the drinking water supply following water softening treatment. Sodium chloride can
also be dispersed to the environment through use hi dry cleaning compounds, perfume, gasoline additives,
Pharmaceuticals, and cosmetics. Products disposed of in landfills include those products brought to
municipal sanitary landfills or toxic/hazardous landfills (Kostick, 1993).
The environmental release of some potentially toxic sodium compounds, including sodium azide,
sodium dicamba, sodium dirnethyldithiocarbamate, sodium hydroxide, and sodium nitrite, is regulated by
10
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CCL Preliminary Regulatory Determination Support Document for Sodium
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the Toxic Release Inventory (TRI) (USEPA, 2000b). The Toxic Release Inventory of hazardous
chemicals was established by the Emergency Planning and Community Right-to-Know Act (EPCRA) in
1986. EPGRA is also sometimes known as SARA Tifle DJ. 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 man 10,000 pounds, of a TRI chemical (USEPA, 1996; USEPA, 2000a).
Facilities are required to report the pounds per year of TRI chemicals released into the environment
both on- and off-site. Forty-two States reported releases of sodium azide, sodium dicamba, sodium
dimethyldithiocarbamate, or sodium nitrite (1995-1998). Only AK, ffi, ID, MT, NV, NM, ND, and VT
reported no releases of any of these compounds. In 1988, all fifty States^ Puerto Rico, the Virgin Islands,
and American Samoa reported releases of sodium hydroxide (USEPA, 2000c). Sodium hydroxide, also
known as caustic soda or lye, is used in such industries as pulp and paper, organic and inorganic chemical
production, petroleum, soaps and detergents, water treatment, and textiles (Kostick, 1993). The
compound is important because of its myriad of uses audits toxichy. In 1988, the TRI reported on- and
off-site releases of sodium hydroxide totaling approximately 108 million pounds. The on-site quantity is
subdivided into air emissions, surface water discharges, underground injections, and releases to land.
Approximately thirteen million pounds of sodium hydroxide, or roughly 20% of total on-site releases,
were discharged directly to surface water in 1988. The chemical was taken off of the TRI list in 1989
(USEPA, 2000c).
In conclusion, because sodium has so many human end uses and is abundant in the ocean, sodium is
ubiquitous in the environment Two sodium uses of particular significance to drinking water supplies are
salt for highway deicing and salt for Water softening treatment. Sodium chloride is the most economically
and industrially important form of sodium, with an estimated 14,000 direct and indirect uses. The United
States is the largest sodium chloride producing country in the world, with production quantities averaging
40 million metric tons from 1990-1998.
The disposal and release of sodium products to the environment is of great concern to drinking water
supplies. Approximately 34.7 million short tons of sodium chloride were dispersed to the environment
post-consumption in 1990,' while roughly 10.3 million short tons were disposed of in landfills. The Toxic
Release Inventory has reported releases of toxic sodium compounds like sodium azide, sodium dicamba,
sodium dimethyldithiocarbamate, or sodium nitrite in 42 States. Sodium hydroxide, though listed as a
TRI chemical only for reporting year 1988, had documented releases in all 50 States as well as Puerto
Rico, the Virgin Islands, and American Samoa.
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 USGS's National Water Quality
Assessment (NAWQA) program. NAWQA, however, is a relatively young program and complete
nationd data are not yet available from their entire array of sites across the nation.
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CCL Preliminary Regulatory Determination Support Document for Sodium
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3.2.1 Date Sources and Methods
The USGS instituted the NAWQA program in 1991 to examine water quality status and trends in the
United States. 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 "stady units."
The study units represent approximately two thirds of the overall water usage in the United States and a
similar proportion of the total population served by public 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 are engaged in intensive assessment for a period of 3 to 5 years. This is followed by a
period of less intensive research and monitoring that lasts between 5 and 7 years. In 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 study units and the second round monitored another
16 beginning in 1994.
Sodium is an analyte for both surface and ground water NAWQA studies, with a Minimum Reporting
Level (MRL) of 0.2 mg/L. Sodium occurrence in bed sediments is also assessed (MRL = 0.005%).
Sodium data from the first two rounds of intensive NAWQA monitoring have undergone USGS
quality assurance checks and are available to the public through their NAWQA Data Warehouse (USGS,
2001). Occurrence results are presented below. The descriptive statistics generated from the sodium
NAWQA data broadly characterize the frequency of sodium detections by sample and by site.
Furthermore, detection frequencies above a benchmark level of 120 mg/L are also presented for all
samples, and by site (see Section 3.3.1.4 for further discussion of this benchmark level and its
development). The median and 99th percentile concentrations are included as well to characterize the
spread of sodium concentration values in ambient waters sampled by the NAWQA program.
3.2.2 Results
Typical of many inorganic contaminants, sodium occurrence in ambient surface and ground waters is
high (Table 3-4). This is not surprising, considering that sodium is the sixth most abundant element in the
Earth's crust, the most abundant anion in the hydrosphere, and is used in many products. Surface and
ground water detection frequencies are similar, between 90% and 100% in all cases, though ground water
detections are somewhat lower. Median sodium concentrations and benchmark exceedances are also
similar between surface and ground water, but ground water benchmark exceedances are generally higher
than surface water exceedances, while median concentrations are lower for ground water. The 99th
percentile concentrations are variable but are generally higher for ground water.
Table 3-4 illustrates that low-level sodium occurrence is ubiquitous. Surface water detection
frequencies are 100% for all land use categories. Detection frequencies > 120 mg/L (by site) are similar
for urban, mixed, and agricultural areas, while forest/rangeland areas show extremely low frequencies of
benchmark exceedances. »These results are understandable because forest/rangeland basins are not as
affected by anthropogenic inputs of sodium (like agrochemical applications) as other land use categories.
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CCL Preliminary Regulatory Determination Support Document for Sodium
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Median concentrations for sodium in surface waters range from 4.7 mg/L in forest/rangeland areas to
21.9 mg/L in urban areas. The median level in urban basins is substantially higher than in other land use
categories and may reflect the effects of road salt applications, more prevalent in areas with greater
population densities. The 99th percentile concentrations are similar for all land use categories except for
forest/rangeland areas, with a lower 99th percentile concentration. Simple detections and detections
exceeding the benchmark by site, for all sites, are approximately 100% and 5.5%, respectively. These
figures indicate that although sodium is -ubiquitous hi surface water, detection frequencies at levels
exceeding the benchmark concentration level are relatively low.
For ground water, detections approach 100% of sites for all land use categories. Urban areas show
the greatest median concentration and frequency of benchmark exceedances. Forest/rangeland areas show
no detections greater than the benchmark, and exhibit the lowest median and 99th percentile values. These
results suggest that urban and agricultural releases of sodium can leach to ground water, as
forest/rangeland areas have such consistently low detection values. Detection frequencies above the MRL
and the benchmark level for all sites are approximately 99.9% of sites and 7.5% of sites, respectively.
Again, sodium detection frequencies in ground water at levels exceeding the benchmark concentration
level are low compared to sodium occurrence.
Similar to surface and ground water, 100% of bed sediment sampling sites showed detections hi all
land use categories. Sodium concentrations hi bed sediments are measured by the percent of sodium by
weight in the sediment sample analyzed. The median concentrations range from 0.4% (forest/rangeland
basins) to 0.8% (urban basins) and the 99th percentile concentrations range from 1.8% (forest/rangeland
and agricultural) to 2.0% (urban). Again, similar to surface and ground waters, urban basins and
forest/rangeland basins occupy the extremes of the concentration percentile spectrum. However, bed
sediment concentration percentiles are generally comparable across land use types. The occurrence of
sodium hi stream sediments is pertinent to drinking water concerns because some desorption of the
compound from sediments into water will occur through equilibrium reactions, although at very low rates.
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CCL Preliminary Regulatory Determination Support Document far Sodium
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Table 3-4: Sodium detections and concentrations in streams and ground water
Detection frequency Detection frequency
>MRL* >120mg/L**
Concentration
(all samples; rag/L)
surface -water
urban
mixed
agricultural
forest/rangeland
all sites
ground water
urban
mixed
agricultural
forest/rangeland
all sites
% samples
100%
100%
100%
100%
100%
90.7 %
V '
93.1 %
93.1 %
s
94.9 %
93.0 %
% sites
100%
100%
100%
100 %
100 %
99.7%
100.0%
99.9 %
100.0 %
99.9 %
% samples
4.4%
2.9%
4.6 %
0.1 %
3.6%
9.3%
6.4%
6.4 %
0.0%
6.6%
%sites
6.2 %
6.6%
6.0%
0.5 %
5.5 %
11.0%
6.8 %
6.8%
0.0 %
7.5 %
median
21.9
12.2
11.0
4.7
11.0
13.2
9.7
8.1
2.9
8.8
percentile
310
270
330
97
298
410
502
788
33
480
* The Minimum Reporting Level (MRL) for sodium in -water is 0.2 mgfL.
* * Sec Section 3.3.1.4for a discussion of this benchmark level used to evaluate the occurrence data for sodium.
33 Drinking Water Occurrence
33.1 Analytical Approach
33.1.1 National Inorganic and Radionuclide Survey (MRS)
In the mid-1980s, EPA designed and conducted the National Inorganic and Radionuclide Survey
(NIRS) to collect national occurrence data on a select set of radionuclides and inorganic chemicals being
considered for National Primary Drinking Water Regulations. The NIRS database includes 36 inorganic
compounds (lOCs) (including 10 regulated lOCs), 2 regulated radionuclides, and 4 unregulated
radionuclides. Sodium was one of the 36 lOCs monitored.
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CCL Preliminary Regulatory Determination Support Document for Sodium
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The MRS provides contaminant occurrence data from 989 community PWSs served by ground water.
The MRS does not include surface water systems. The selection of this group of PWSs was designed so
mat the contaminant occurrence results are statistically representative of national occurrence. Most of the
MRS data are from smaller systems (based on population served by the PWS) and each of these
statistically randomly selected PWSs was sampled a single time between 1984 and 1986.
The MRS data were collected from PWSs in 49 States. Data were not available for the State of
Hawaii. In addition to being statistically representative of national occurrence, NBRS data are designed to
be divisible into strata based on system size (population served by the PWS). Uniform detection limits
were employed, thus avoiding computational (statistical) problems mat sometimes result from multiple
laboratory analytical detection limits. Therefpre, the MRS data can be used directly for national
contaminant occurrence analyses with very few, if any, data quality, completeness, or representativeness
issues. .
33.1.2 Supplemental IOC Data
One limitation of the MRS study is a lack of occurrence data for surface water systems. To provide
perspective on the occurrence of sodium in surface water PWSs relative to ground water PWSs, SDWA
compliance monitoring date that were available to EPA were reviewed from States with occurrence data
for both ground and surface water.
The State ground water and surface water PWS occurrence data for sodium used in this analysis were
submitted by States for an independent review of the occurrence of regulated contaminants in PWSs at
various times for different programs (USEPA, 1999). In the USEPA (1999) review, occurrence data from
a total of 14 States were noted. However, because several States contained data that were incomplete or
unusable for various reasons, only 12 of the 14 States were used for a general overview analysis. From
these 12 States, 8 were selected for use in a national analysis because they provided the best data quality
and completeness and a balanced national cross-section of occurrence data. These eight were Alabama,
California, Illinois, Michigan, Montana, New Jersey, New Mexico, and Oregon.
Only the Alabama, California, Illinois, New Jersey, and Oregon State data sets contained occurrence
data for sodium. The data' represent approximately 36,000 analytical results from more than 5,500 PWSs
mostly during the period from!993 to 1997, though some earlier data are also included. The number of
sample results and PWSs vary by State.
3.3.1.3 Data Management and Analysis
The data used in the State analyses were limited to only those data with confirmed water source and
sampling type information. Only standard SDWA compliance samples were used; "special" samples,
"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 that provided 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 problematic data were
insignificant relative to the total number of observations they were dropped from the analysis (for further
details see USEPA, 1999).
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CCL Preliminary Regulatory Determination Support Document for Sodium
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33.1.4 Occurrence Analysis
The summary descriptive statistics presented in Table 3-5 for sodium are derived from analysis of the
MRS data. Included are the total number of samples, the 99thpercentile concentration of all samples, and
the median concentration of all samples. The percentages of PWSs and population served indicate the
proportion of PWSs and PWS population served 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 benchmark level; or a detection(s) greater than the benchmark level.
The benchmark level used to evaluate the occurrence information for sodium is 120 mg/L, which was
derived from the National Research Council's dietary guideline (NRC, 1989a) for adults of 2.4 g/day for
sodium from sodium chloride (table salt). The Drinking Water Equivalent concentration is 1.2 g/L given
a drinking water intake of 2 L/day. A Relative Source Contribution (RSC) of 10% was applied, giving
rise to the benchmark of 120 mg/L ([2400mg/2L]* 0.10).
In Table 3-5, national occurrence is estimated by extrapolating the summary statistics for sodium to
national numbers for systems, and population served by systems, from the Water Industry Baseline
Handbook, Second Edition (USEPA, 2000d). From the handbook, me total number of ground water
community water systems (CWSs) plus ground water non-transient, non-community water systems
(NTNCWSs) is 59,440, and the total population served by ground water CWSs plus ground water
NTNCWSs is approximately 85.6 million persons (see Table 3-5). To arrive at the national occurrence
estimates, the national estimate for ground water PWSs (or population served by ground water PWSs) is
simply multiplied by the percentage for the given summary statistic (e.g., the national estimate for the
total number of ground water PWSs with detections (i.e., > MRL; 59,440) is the product of the percentage
of ground water PWSs with detections (100%) and the national estimate for the total number of ground
water PWSs (59,440)).
The nationally extrapolated occurrence estimates for sodium are not presented in the Federal Register
Notice. While the MRS data were collected in a statistically appropriate fashion suitable for
extrapolation, the data available for many CCL regulatory determination priority contaminants were not a
strict statistical sample. National extrapolations of these data can be problematic. Also, the MRS data
only represent ground water PWSs. Thus, national extrapolations from MRS data do not represent
national occurrence for all PWSs. Therefore, to maintain consistency across all CCL regulatory
determination priority contaminants, a straight-forward presentation, and data integrity, only the actual
occurrence results for all CCL regulatory determination priorities are presented in the Federal Register;
Notice for stakeholder review. The nationally extrapolated occurrence values for sodium are presented
here, however, to provide additional perspective.
In Table 3-6, occurrence data on sodium directly submitted by the States of Alabama, California,
Illinois, New Jersey, and Oregon for A Review of Contaminant Occurrence in Public Water Systems
(USEPA, 1999) were used to augment the MRS study .which lacked surface water data. Included in the
table are the same summary statistics as Table 3-5, with additional information describing the relative
distribution of sodium occurrence between ground water and surface water PWSs in the 5 States.
The State data analysis was focused on occurrence at the system level because a PWS with a known
contaminant problem usually has to sample more frequently than a PWS that has never detected the
contaminant The results of a simple computation of the percentage of samples with detections (or other
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CCL Preliminary Regulatory Determination Support Document for Sodium
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statistics) can be skewed by the more frequent sampling results reported by the contaminated site. The
system 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
thantheMRL."
When computing basic occurrence statistics, such as the number, or percent, of samples, or systems,
with detections of a given contaminant, the value (or concentration) of the MRL can have important
consequences. For example, the lower the reporting limit, the greater the number of detections (Ryker
and Williamson, 1999). 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 than the MRL.
However, for these occurrence data this is not straightforward. This is in part related to State data
management differences as well as real differences in analytical methods, laboratories, and other factors.
The situation can cause confusion when examining descriptive statistics for occurrence. Because a
simple meaningful summary statistic is not available to describe the various reported MRLs, and to avoid
confusion, MRLs are not reported hi the summary table (Table 3-6).
33.2 Results
The NIRS data in Table 3-5 show that approximately 100% of ground water PWSs (this extrapolates
to all 59,440 systems nationally) had detections of sodium, affecting about 100% of the ground water
PWS population served (approximately 85.6 million people nationally). Approximately 23% of the NIRS
PWSs had detections greater than Vz the benchmark level of 120 mg/L (about 13,500 ground water PWSs
nationally), affecting approximately 18.5% of the population served (estimated at 15.9 million people
nationally). The percentage of NIRS PWSs with detections greater than the benchmark level of 120 mg/L
was approximately 13% (about 8,000 ground water PWSs nationally), affecting 8.3% of the population
served (estimated at approximately 7.1 million people nationally)
Drinking water data for sodium from the supplemental individual States vary among States (Table 3-
6). Sodium monitoring has not been required under SDWA, though these States had obviously conducted
some monitoring. Alabama, California, New Jersey, and Oregon have substantial amounts of data and
PWSs represented. However, the number of systems with sodium data for Illinois is far less than the
number of PWSs in this State. Hence, it is not clear how representative these data are. Because the NIRS
data only represent sodium occurrence in ground'water PWSs, the supplemental State data sets provide
some perspective on surface water PWS occurrence.
For simple detections, the supplemental State data show a range from 99.3% to 100% of ground water
PWSs (Table 3-6). These figures are comparable to the NIRS ground water PWS results: 100% greater
than the MRL (Table 3-5). The supplemental State data show 100% simple detections for surface water
PWSs. Comparisons made between data for simple detections need to be viewed with caution because of
differences in MRLs between the State data sets and the NIRS study, and among the States themselves
(see Section 3.3.1.4), though these numbers for sodium are very comparable. For further perspective, the
median concentration of all samples for the NIRS data (16.4 mg/L) is bracketed by the range of median
concentrations from the States' data (5.26 mg/L to 31 mg/L).
/
The supplemental State data sets indicate that ground water PWS detections greater than the
benchmark level of 120 mg/L are between 3% and 15% (Table 3-6). The NIRS national average is within
1
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CCL Preliminary Regulatory Determination Support Document for Sodium
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this range at 13.2% of PWS greater than the benchmark level of 120 mgfL (Table 3-5). As might be
expected, surface water PWSs showed slightly fewer exceedances of the benchmark level than ground
water PWSs, ranging from 0% - 3%.
Reviewing sodium occurrence by PWS population served shows that from 0.5% - 50% of the States'
ground water PWS populations were served by systems with detections greater than the benchmark level
of 120 mg/L (Table 3-6). However, the figure of 50% is the maximum among the supplementary States.
Three of the 5 States show ground water PWS populations receiving more than 120 mg/L at percentages
lower than that for MRS, which is 8.3%. Populations served by surface water PWSs with detections
greater than 120 mg/L ranged from 0% - 1.4% among the five supplemental Slates. Population figures
for the supplemental States are incomplete and are only reported for those systems in the database that
have reported their population data. For sodium, approximately 82% of the PWSs reporting occurrence
data for these 5 States also reported population data.
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CCL Preliminary Regulatory Determination Support Document for Sodium
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Table 3-5: Sodium occurrence in ground water systems (NCRS survey)
: *.
;. •.-....• - .„• ' .., .. - -. :.. •
Frequency Factors
Total Number of Samples/Systems
99th Percentile Concentration fall samtjles)
Median Concentration (all samples)
Minimum Reporting Level (MRL)
Total Population
Occurrence hy Samples/System
% Ground Water PWSs with detections (> MRL)
Range of Cross-Section States
% Ground Water PWSs > 60 mg/L (1/2 benchmark level)
Range of Cross-Section States
% Ground Water PWSs > 120 mg/L (benchmark level)
Range of Cross-Section States
Occurrence hy Population Served
% Ground Water PWS Population Served with detections
Range of Cross-Section States
% Ground Water PWS Population Served > 60 mg/L
Range of Cross-Section States
% Ground Water PWS Population Served > 120 mg/L
Ranpeof Cross-Section States
Benchmark Level
= 120 mg/L
989
517ms/L
16.4 mg/L
0.91 me/L2
1.48?.rm
100%
100%
22.6%
0-100%
13.2%
0 - 73.7%
100%
100%
18.5%
0 - 100%
8.3%
0 - 89.5%
National System &
Population Numbers1
59,440
—
. _
—
85.681.696
National Extrapolation
. .
59,440
N/A
13,463
N/A
7,873
N/A
85,682,000
N/A
15,859,000
N/A
7,147,000 -
N/A
' Total PWS and population numbers are from EPA's March 2000 Water Industry Baseline Handbook.
2 Because all data reported for sodium were detections, the minimum value is presented here instead of the MRL for sodium.
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CCL Preliminary Regulatory Determination Support Document for Sodium
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Table 3-6: Occurrence summary of ground and surface water systems by State for sodium
Frwrnencv Factors
Total Number of Samples
Number of Ground Water Samples
Number of Surface Water Samples
Percent of Samples with Detections
Percent of Ground Water Samples with Detections ,
Percent of Surface Water Samples with Detections
99 Perccntile Concentration Call samples)
Median Concentration (all samples)
Minimum Reporting Level (MRL)
Total Number of PWSs
Number of Ground Water PWSs
Number of Surface Water PWSs
Total Population Served
Ground Water PWS Population Served
Surface Water PWS Population Served
Occurrence bv Svstem
% PWSs with detections (> MRL)
Ground Water PWSs with detections
Surface Water PWSs with detections
Benchmark Level = 120me/L
% PWSs > 1/2 Benchmark Level
Ground Water PWSs > 1/2 Benchmark Level
Surface Water PWSs > 1/2 Benchmark Level
V» PWSs > Benchmark Level
Ground Water PWSs > Benchmark Level
Surface Water PWSs > Benchmark Level
Occurrence bvPoDnl»tion Served
'/» PWS Population Served with detections
Ground Water PWS Population with detections
Surface Water PWS Population with detections
Benchmark Level '= 120me/L
% PWS Population Served > 1/2 Benchmark Level
Ground Water PWS Population > 1/2 Benchmark
Surface Water PWS Population > 1/2 Benchmark
% PWS Population Served > Benchmark Level
Ground Water PWS Population > Benchmark Level '
Surface Water PWS Pomilation > Benchmark Level
Alabama
1327
917
410
99.3%
99.0%
99.8%
260mjc/L
5.26 mg/L
Variable1
435
366
69
3,662,222
1,820,214
1,837,743
100%
100%
100%
223%
26.2%
1.5%
9.7%
11.5%
0.0%
100%
100%
100%
17.5%
33.2%
0.0%
5.0%
8.1%
0.0%
California
27,494
25,111
2,383
99.5%
99.6%
99.5%
209ms/L
31 mg/L
Variable1
2,433
2,214
219
45375,106
27,791,117
30,740,138
99.8%
99.8%
100%
29.4%
30.5%
18.3% '
11.4%
12.2%
2.7%
100%
100%
100%
76.5%
69.4%
77.2%
33.3%
49.4%
1.4%
Illinois
383
313
70
100%
100%
100%
370ms/L
25 mg/L
Variable1
227
160
67
1,995,394
724,635
1,270,179
100%
100%
100%
19.4%
263%
3.0%
10.6%
15.0%
0.0%
100%
100%
100%
11.2%
30.2%
0.3%
8.7%
24.0%
0.0%
New Jersey
4,417
3,941
476
99.0%
99.1%
98.1%
150 mg/L
14 mg/L
Variable1
1,444
1,411
33
6,350,025
2,478,067
3,871,958
99.4%
99.4%
100%
11.0%
11.0%
12.1%
3.6%
3.6%
3.0%
100.0%
99.9%
100%
13.7%
21.2%
8.9%
1.8%
4.3%
0.2%
Orecon
2319
1,506
813
98.8%
98.8%
100%
166mg/L
9.78 mg/L
Variable1
1,032
863
169
2,101,401
1,261,661
1,497,224
99.4%
993%
100%
10.5%
11.7%
4.1%
2.8%
3.1%
1.2%
100.0%
99.9%
100%
3.5%
4.6%
1.1%
0.4%
0.5%
0.1%
' See Section 3.3.1.4 for details
20
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CCLPreliminary Regulatory Determination Support Document for Sodium
November, 2001
3.4 Conclusion ;
The Toxic Release Inventory has reported releases of toxic sodium compounds like sodium azide,
sodium dicamba, sodium dimethyldithiocarbamate, or sodium nitrite in 42 States. Sodium hydroxide,
though only listed as a TRI chemical for reporting year 1988, had documented releases in all 50 States as
well as Puerto Rico, the Virgin Islands, and American Samoa.
Low-level sodium occurrence in ambient waters and stream bed sediments monitored by the USGS
NAWQA program is ubiquitous, approaching 100% of water and sediment sampling sites for all land use
categories. Forest/rangeland basins show the lowest frequency of benchmark level exceedances,* median
concentrations, and 99th percentile concentrations across all land use categories for ambient waters and
bed sediments. Benchmark level exceedances, median, and 99th percentile concentrations are generally
similar for all other land use categories, although urban and agricultural basins sometimes exhibit higher
levels. Although sodium detection frequencies are high in ambient waters and stream bed sediments,
sodium occurrence at levels of public health concern is low.
Sodium has been detected in ground water PWS samples collected through the MRS study.
Occurrence estimates are high with 100% of samples showing detections affecting 100% of the national
population served. The 99th percentile concentration of all samples is 517 mg/L. At the benchmark level
of 120 mg/L, 13.2% of thfe NIRS systems showed exceedances, affecting approximately 7.1 million
people nationally.
Additional SDWA data from the States of Alabama, California, Illinois, New Jersey, and Oregon,
including both ground water and surface water PWSs, were examined through independent analyses and
also show substantial levels of sodium occurrence. These data provide perspective on the NIRS estimates
that only includ&data for ground water systems. The supplemental State data show that all five States
reported almost 100% detections in both ground water and surface water systems. At detections above
the benchmark level of 120 mg/L, surface water PWS detection frequencies are generally lower than
those for ground water. If national data for surface water systems were available, the occurrence and
exposure estimates would be substantially greater than from NIRS alone.
4.0 HEALTH EFFECTS
A full description of the health effects associated with exposure to sodium are presented in
Drinking Water Advisory: Consumer Acceptability Advice and Health Effects Analysis on Sodium
(USEPA, 2001). A summary of the pertinent findings are presented below.
4.1 Hazard Characterization and Mode of Action Implications
Sodium is physiologically necessary for maintaining normal body fluid volume, blood pressure, and
cell function. The major source of sodium generally comes from the intake of food, with only a small
contribution from drinking water. Normal sodium level in the blood is about 154 mEq/L.
According to the National Research Council, the estimated minimum daily requirements for sodium
are 120-225 rag for infants (0 months-1 year), 300-400 mg for children (2-9 years), and 500 mg for
individuals 10 years and older (NRC, 1989a). Sodium requirements increase during pregnancy and
21
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CCL Preliminary Regulatory Determination Support Document for Sodium
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lactation. The American Heart Association and the National Institutes of Health recommend feat healthy
adults restrict their sodium intake to no more than 2,400 mg/day in order to lower the risk of hypertension
(AHA, 2000; NIH, 1993). Typically, the average sodium intake ranges from 3,500 to 4,500 mg/day
(Karanjaetal., 1999).
About 3% of the U.S. population is on sodium restricted diets. In general, sodium exposure is limited
to levels of 250,500,1,000 or 2,000 mg/day in these diets. A no-added-salt diet restricts only foods that
are high in sodium. However, these so called no-added-salt diets still average about 4,000 mg of sodium
per day, indicating the abundance of sodium in the food supply (Cataldo and Whitney, 1986). Individuals
on sodium restricted diets may need to consider the level of sodium in drinking water supply when
planning their diet (Cataldo and Whitney, 1986).
Experimental studies performed on rats and human adults suggest a positive correlation between
excessive sodium intake and hypertension (NAS, 1977; WHO, 1979; NIH, 1993). One study, based upon
10,079 subjects in 32 countries, reports an increase in systolic pressure of 2.2 mm Hg for every 2,300 mg
increase in sodium intake (ICRG, 1988; Elliot et al., 1989). Extreme hypertension is associated with
coronary artery disease and stroke (Stamler, 1991). In addition, high sodium intake may result in
increased heart muscle thickness in response to increased blood pressure (Schmieder et al, 1988).
Despite consistent reports on adults, blood pressure and sodium intake reports on children are
inconsistent While some studies associate an increase in blood pressure with a high sodium diet
(Calabrese and Tuthill, 1977,1981; Tuthill and Calabrese, 1979), other studies fail to find a correlation
(Pomrehn et al., 1983; Faust, 1982; Armstrong.et al., 1982; Tuthill et al., 1980).
Earlier clinical trial studies have indicated that lower sodium intake does not yield convincing
evidence for risk reduction of cardiovascular disease in populations with normal blood pressures (Muntzel
andDrueke, 1992; Salt Institute^ 2000; NIH, 1993; Callaway, 1994; Kotohen and McCarron, 1998;
McCarron, 1998). However, results of the recent Dietary Approaches to Stop Hypertension (DASH)
trials at Brigham and Women's Hospital suggest that restricted dietary intake of sodium is, in fact,
beneficial for many people with hypertension (Marsha et al., 1999; Sacks et al., 2001). In addition to
sodium restriction, lifestyle and dietary changes such as weight reduction, exercise, stress reduction, and
adequate dietary potassium, calcium, and magnesium are effective non-medicinal treatments against
hypertension. Limiting cholesterol, dietary fat, and alcohol intake is also recommended (Whitney et al.,
1987).
While sodium salts are generally not considered acutely toxic to humans, acute effects and death have
been reported in cases of very high sodium intake (RTECS, 2000; WHO, 1979). The effects of high
sodium levels from ingestion appear to be more severe for infants than adults because infant kidneys are
not yet able to process the sodium (Sax, 1975).
Data on the reproductive toxicity of sodium are sparse. In a study done on rats, excessive sodium
chloride (1,570 mg sodium/kg body weight) caused fetal and maternal toxic effects. Maternal toxicity
effects included decreased pregnancy rates and decreased body weight gain, while fetotoxic effects
included high mortality rate (Karr-Dullien and Bloomquist, 1979). Developmental effects were observed
only in a strain of rat pups bred to be hypertensive that were fed high sodium diets for up to 4 months
after birth. No developmental effects in rat strains with normal blood pressure were noted hi this study.
22
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CCL Preliminary Regulatory Determination Support Document for Sodium
November, 2001
Although sodium is not considered carcinogenic, it may influence genotoxic events, thus increasing
the likelihood of tumor development High oral doses of sodium chloride in the presence of carcinogens
may cause damage to the gastrointestinal tract and lead to an increase in DNA synthesis and cell
regeneration. Gastric tumors could, therefore, be a potential adverse health effect (Tatematsu et al., 1975;
NRC, 1989b; Takahashi etal., 1983).
4.2 Dose-Response Characterization and Implications in Risk Assessment
Although numerous human studies have examined sodium intake and blood pressure effects, they
cannot serve to characterize dose-response relationships. First, the results are inconsistent; second, the
sodium intake measurements are indirect (as determined by the amount of sodium excreted in the urine);
and third, the results are influenced by other factors such as nutrients in the diet, lifestyle, and behavioral
patterns rather than sodium itself (Muntzel andDrueke, 1992; Salt Institute, 2000; Nffl, 1993; Callaway,
1994; Kotehen and McCsirron, 1998; McCarron, 1.998).
Dose-response data are controversial. As noted above, the American Heart Association
recommends that healthy adults restrict their sodium intake to 2,400 mg/day (2000). In the DASH study,
sodium sensitive individuals who reduced their sodium intake by 2,300 mg/day from average levels of
3,500-4,500 mg/day lowered their systolic blood pressure by 3.7 mm Hg (compared to 1 mm Hg in
normal individuals). Furthermore, hypertensive individuals that increase dietary calcium, potassium,
magnesium, and fiber (by following the high fruit and vegetable DASH diet)j but do not change sodium
levels, achieve similar reductions in systolic pressure (Harsha et al., 1999). A combination of the DASH
diet with sodium restriction yields additional reductions in blood pressure among hypertensive and
normotensive subjects (Sacks et al., 2001). Thus, dose-response effects are difficult to characterize
because they are population and lifestyle dependent.
43 Relative Source Contribution
Food is the principle source of exposure to sodium. Of the total amount of sodium present in food,
only a relatively low amount (10%) is naturally occurring (Sanchez-Castillo et al., 1987a,b). The
majority of dietary sodium comes from sodium chloride that is added during food processing and
preparation. Sanchez-Castillo et al. estimate that 15% of dietary sodium comes from salt added during
cooking and at the table, whereas 75% is from salt added during food processing and manufacture
(1987a,b). The first National Health and Nutrition Examination Survey reported that approximately 32%
of the sodium chloride consumed comes from baked goods and cereals, 21% from meats, and 14% from
dairy products (Abraham and Carroll, 1981). Using data from a two-year dietary survey, Subar et al.
found that 23.4% of the dietary salt intake comes from table salt and processed foods such as cold cuts
and other processed meats, condiments, and snack foods (i.e. chips, popcorn; 1998). Yeast breads
provide 10.9% of the sodium, cheese, 5.6%, and ham, 4.1%. Together, these foods contribute 44.1% of
total sodium intake. .
Reported dietary intakes of sodium from various studies range from 1,800 mg/day to 5,000 mg/day,
depending on the methods of assessment used (Abraham and Carroll, 1981; Dahl, 1960; Pennington et al.;
1984, Karanja et al., 1999; Kurtzweil, 1995). The amount of discretionary sodium intake is highly
variable and can be quite large. The Food and Drug Administration found that most American adults tend
to eat between 4,000 and 6,000 mg of sodium/day, while individuals on a sodium-restricted diet usually
ingest less than 1,000 to 3,000 mg/day (Kurtzweil, 1995). In the assessment of pretreatment diets for the
23
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CCL Preliminary Regulatory Determination Support Document for Sodium
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participants in the DASH trials, sodium levels range from about 3,500 to 4,500 mg/day (Karanja et al.,
1999).
If the relative source is calculated from the median value for sodium in drinking water (16 mg/L)
using 4,000 mg sodium/day as a baseline for dietary sodium and 2 L/day as a water intake, drinking water
contributes only 0.8% of the total dietary sodium. If the relative source is calculated from the 99th
percentile value (about 500 mg/L), drinking water contributes 25% of the daily sodium. If me 2.4 g/day
recommended intake is used as a baseline, systems at the median concentration contribute 1.3% of the
recommended intake, but systems at the 99th percentile contribute 41.6% of the total. Habitual intake of 2
L of water per day at this concentration is not advisable. However, thepalatability of the water could be
adversely affected by high sodium concentration, which would likely diminish total water intake and lead
to corrective measures.
4.4 Sensitive Populations
Populations expected to have an increased sensitivity to sodium include infants/children, individuals
with hypertension, the elderly (blood pressure increases with age), African Americans (the incidence of
hypertension is disproportionally high among African Americans) and individuals with renal diseases.
Several studies indicate that younger children are more sensitive to high sodium levels than are adults
(Elton et al. 1963; Gauthier, 1969; DeGenaro and Nyhan, 1971). This heightened sensitivity is associated
with the immature kidney? s decreased ability to control sodium levels. On a mg sodium per kg body
weight basis, however, the sodium requirement for infants and children is greater than for adults (NRC,
1989a).
The elderly are also more sensitive to high sodium exposure because they have a higher incidence of
cardiovascular disease (including hypertension) than younger subjects (Sowers and Lester, 2000). In
addition, since the elderly tend to have a higher taste threshold for salt, they may also have a higher
dietary salt intake (Hyde and Feller, 1981; Stevens, 1996). African-Americans, in particular, are more
susceptible to sodium-induced adverse health effects because of high incidence of hypertension (Sullivan,
1991; Svetkey et al., 1996).
Individuals with decreased renal function comprise another group that is sensitive to high sodium
intake. One study demonstrates that 4,600 mg/day of sodium chloride significantly elevates systolic
blood pressure in patients wilh chronic renal failure (Muntzel and Drueke, 1992). In addition, Muntzel
and Drueke postulated that abnormal kidney function is a factor in salt retention by salt-sensitive
individuals. Sodium retention has also been reported in rats given high doses of sodium chloride,
following-partial nephrectomy (Muntzel and Drueke, 1992). Dietary sodium restrictions are
recommended for individuals with acute or chronic renal problems and for those with nephrotic syndrome
(Whitney, et al. 1987). Renal problems are associated with about 10% of the population with
hypertension (Whitney, et al. 1987).
Among the sodium-sensitive population, dietary restrictions alone are insufficient for preventing
adverse heath effects that result from high sodium levels. Programs for hypertensives include weight
reduction, exercise, stress~reduction, and adequate dietary potassium, calcium, and magnesium, in
addition to sodium restriction. As mentioned earlier, limiting cholesterol, dietary fat, and alcohol intake
24
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CCL Preliminary Regulatory Determination Support Document for Sodium
November, 2001
is also recommended. At blood pressures over 95/160 mm Hg (diastolic/systolic), diet and behavior
modification are often combined with pharmaceutical measures.
4.5 Exposure and Risk Information
While nearly the entire public water system population is exposed to sodium through their drinking
water, only about 7 million, or 8%, are exposed to water at concentrations above the 126 mg/L
benchmark, a level that comprises about 10% of the dietary guideline for sodium. The dietary guideline
level, however, is habitually exceeded by most of the U.S. population by 1,100 to 2,100 mg/day
(Abraham and Carroll, 1981; Dahl, 1960; Pennington et at, 1984; Karanja et al., 1999; Kurtzweil, 1995).
4.6 Conclusion
Despite the evidence that sodium may have adverse health effects in humans by contributing to
hypertension, data from studies indicate mat the most effective hypertension reduction programs do not
involve supplementation or restriction of a single element. Instead, a well balanced, nutritionally sound
diet combined with other behavioral changes such as exercise and stress reduction are the most effective
measures. In addition, since sodium levels in drinking water are usually low, water from public water
systems is unlikely to significantly contribute to adverse health effects. For these reasons, regulation may
not present a meaningful opportunity for health risk reduction for persons served by public drinking water
systems. However, the EPA may issue a Drinking Water Advisory to provide guidance to communities
that may be exposed to drinking water contaminated with sodium chloride or other sodium salts.. All
preliminary CCL regulatory determinations and further analysis will be presented in the Federal Register
notice.
5.0 TECHNOLOGY ASSESSMENT
If a determination has been made to regulate a contaminant, SDWA requires development of
proposed regulations within 2 years of making the decision. It is critical to have suitable monitoring
methods and treatment technologies to support regulation development according to the schedules defined
in the SDWA.
, - - f . ' • . • ...
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
establishes a Maximum Contaminant Level (MCL), there must be an analytical method suitable for
routine monitoring. Therefore, EPA needs to have approved methods available for any CCL regulatory
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. Sodium can be measured by
well-documented analytical methods (see Table 5-1).
25
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CCL Preliminary Regulatory Determination Support Document for Sodium
November, 2001
Table 5-1: Analytical methods for sodium
Method
EPA 200.7
SM3111B
Type
Inductively Coupled
Plasma Optical Emission
Spectroscopy
(ICPyAtomic Emission
Spectrometry
Atomic Absorption (AA),
Direct Aspiration
Method Detection
Limit (ng/L)
30
IDL2
Optimum
concentration range
30-1000
5.2 Treatment Technology
Because sodium is being dealt with through guidance, treatment technologies have not been reviewed.
6.0 SUMMARY AND CONCLUSIONS - DETERMINATION OUTCOME
Three statutory criteria are used to guide the preliminary determination of whether regulation of a
CCL contaminant is warranted: 1) the contaminant may adversely affect the health of persons; 2) the
contaminant is known or is likely to occur in public water systems with a frequency, and at levels, of
public health concern; and 3) regulation of the contaminant presents a meaningful opportunity for health
risk reduction for persons served by public water systems. As required by SDWA, a decision to regulate
a contaminant cgtimritg foe Tfl>A to propose a Maximum Cnintatnrnant T.eve1 (roal (MHT.G) and
promulgate a National Primary Drinking Water Regulation for the contaminant. A 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 weight of evidence favors the conclusion that sodium concentrations greater than 120 mg/L can
have an effect on blood pressure, especially for sodium-hypertensives. Hypertension affects almost SO
million people in the United States. Control of body weight, adequate intake of nutrients such as
potassium, calcium and magnesium, sodium restriction, exercise, and stress all influence blood pressure.
In addition to hypertension, cholesterol, dietary fat and alcohol intake are risk factors for cardiovascular
problems. A
«
Sodium is known to occur in nearly all public water systems and, in a few cases, at levels of public
health concern for salt-sensitive hypertensives (greater than 120 mg/L). However, these concentrations
exceed the taste threshold of 30. mg/L and affected consumers would likely reduce their intake and
implement corrective measures.
26
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CCL Preliminary Regulatory Determination Support Document for Sodium
November, 2001
Based on available monitoring data, 7.1 million people are exposed to sodium at levels above the
benchmark level of 120 mg/L, a concentration that would provide about 10% of the dietary guideline for
sodium. The majority of sodium intake is from salt added to food during processing or preparation. An
estimate of daily sodium intake in american diets, and median sodium concentrations in water, show that
water contributes only 0.8% of the total dietary sodium. Sensitive populations include the elderly,
because blood pressure increases and taste sensitivity to salt decreases with age, infants and children, and
African Americans. Sodium may have a stronger effect on hypertensive individuals with renal disease.
Those with normal blood pressure may be influenced by sodium to a lesser extent. Blood pressure is
influenced more by nutrients in the diet, lifestyle, and behavioral patterns rather than by sodium intake.
In conclusion, sodium generally occurs at low levels in drinking water, and when it occurs at high
levels the taste may be expected to cause people to reduce their consumption. In addition, drinking water
is only a minor source of dietary sodium compared with food, and sodium is only one factor among many
that contributes to hypertension and heart disease. Therefore, regulation of sodium in drinking water is
unlikely to represent a meaningful opportunity for health risk reduction. The most effective means to
protect the health of PWS users is to identify groups who are more sensitive than the general population,
and provide dietary guidance through the public health community. The EPA may issue an advisory to
provide guidance to communities that may be exposed to elevated concentrations of sodium chloride or
other sodium salts in their drinking water. The advisory would provide appropriate cautions for
individuals on low-sodium or sodium-restricted diets. In addition, EPA presently requires periodic
monitoring of sodium at the entry point to the distribution system. This requirement provides the public
health community with information on sodium levels in drinking water to be used in counseling patients
and is the most direct route for gaining the attention of the affected population. All preliminary CCL
regulatory determinations will be presented in the Federal Register Notice.
27
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CCL Preliminary Regulatory Determination Support Document for Sodium
November, 2001
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