4* -CCfcfV Fact Sheet: Announcement of Preliminary Regulatory
^8S^Cr*\ Determinations for Priority Contaminants on the Drinking
Water Contaminant Candidate List
Agency
1. What is the Contaminant Candidate List?
The Safe Drinking Water Act (SDWA), as amended in 1996, requires EPA to publish a
list of contaminants (referred to as the Contaminant Candidate List, or CCL) to assist in priority-
setting efforts. SDWA also requires the Agency to select five or more contaminants from the
current CCL and determine, by August 2001, whether or not to regulate these contaminants with
a National Primary Drinking Water Regulation (NPDWR).
The CCL was developed with considerable input from the scientific community and
stakeholders. A draft CCL requesting public comment was published in October of 1997 and a
final in March of 1998. The CCL contains 60 contaminants (50 chemicals and 10 microbes) that
are not subject to any current or proposed NPDWRs.
2. What contaminants are EPA considering for regulation?
In 1998,20 of the 6Q contaminants were classified as priorities for regulatory
determination because it was believed at that'time that there were sufficient data to evaluate both
exposure and risk to public health, and to support a determination of whether or not to proceed to
promulgation of an NPDWR.
Since then, 12 of the 20 priority contaminants were found to have insufficient
information to support a regulatory determination. In addition, sodium was added to the list of
regulatory determination priorities.
Below are the 9 contaminants that have sufficient data and information to consider for a
determination of whether or not to regulate. Please see the appendix for summary information on
each contaminant.
• Acanthamoeba - microscopic amoeba commonly found in the environment
Aldrin - banned insecticides, used primarily on corn and cotton
• Dieldrin — banned insecticides, used primarily on corn and cotton
Hexachlorobutadiene — used primarily to make rubber compounds
Manganese - essential nutrient, occurs naturally, and has a variety of uses
• Metribuzin — herbicide used primarily on soybeans, potatoes, and alfalfa
Naphthalene - intermediary manufacturing product and moth repellent
Sodium - essential nutrient, naturally occurring element
Sulfate - present hi the diet, naturally occurring element
1
-------
3. What did EPA decide and what happens next?
Our preliminary determination is that regulatory action is not appropriate for any of the
nine contaminants. After a 60. day comment period and .stakeholders meeting, EPA will publish
the final deterrninations in late 2002. Should the Agency determine that regulations are
necessary, they must be proposed in late 2004, and promulgated by the summer of 2005.
4. What analyses did EPA undertake to make this decision?
When making a determination to regulate, SDWA requires consideration of three areas:
projected adverse health effects, extent of contaminant occurrence, and whether regulation would
present a meaningful opportunity for health risk reduction (see SDWA § 1412(b)(l)(A)).
EPA developed the evaluation approach based on recommendations from National
Research Council (NRC) and the National Drinking Water Advisory Council (NDWAC, one of
the formal means that we work with stakeholders on drinking water issues). For each of the nine
contaminants, EPA evaluated the sufficiency of current analytical and treatment methods; the
best available peer reviewed data on health effects; and up to approximately seven million
analytical records on contaminant occurrence. For those contaminants with adequate methods, as
well as health effects and occurrence data, EPA employed an approach to assist in making
preliminary regulatory determinations that follows the themes recommended by the NRC and
NDWAC to satisfy the three SDWA requirements under section 1412(b)(l)(A)(i)-(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, EPA estimated a health-
related bench-mark level for each contaminant. Then, for a given contaminant EPA estimated
the number of public water systems and population served by those systems above these bench-
mark values, and the geographic distribution using a large number of state occurrence data that
broadly reflect national coverage. Use and environmental release information, and ambient water
quality data,-were used to augment the State data and evaluate the likelihood of contaminant
occurrence.
The findings from these evaluations were used to make a preliminary determination on
whether to regulate a contaminant based on the three SDWA statutory requirements noted above.
As mentioned earlier, the findings of these evaluations are summarized in the appendix.
In addition, EPA has asked the Science Advisory Board to review the supporting data and
analysis, the approach used for making regulatory determinations, and the preliminary regulatory
-------
determinations.
5. Additional Considerations
As previously stated, EPA is only making regulatory determinations on CCL
contaminants that have sufficient information to support a regulatory determination at this time.
The Agency continues to conduct research and/or to collect occurrence information on the
remaining CCL contaminants. EPA has been aggressively conducting research to fill identified
data gaps and recognizes that stakeholders may have a particular interest in-the timing of future
regulatory determinations for other contaminants on the CCL. Stakeholders may be concerned
.that regulatory determinations for such contaminants should not necessarily wait until the end of
the next regulatory determination cycle.
In this regard, it is important to recognize that the Agency is not precluded from
monitoring, conducting research, developing guidance, or regulating contaminants not included
on the CCL to address an urgent threat to public health (see SDWA section 1412(b)(l)(D)); or
taking action on CCL contaminants when information becomes available. As previously
mentioned, the Agency continues to conduct research and/or to collect occurrence information
for contaminants on the CCL (except the nine for which preliminary determinations are being
made) and may proceed with regulatory determination prior to the end of the next regulatory
determination cycle.
We are soliciting comment on which of the remaining CCL contaminants stakeholders
believe should have the highest priority for future regulatory determinations and their reasons in
support of such comments, comment on which of the remaining CCL contaminants stakeholders
believe should be the subject of regulatory determinations at the earliest opportunity and their
reasons in support of such comments.
6. Where can I find more information about this notice and the CCL?
For general information on the CCL, please visit the EPA Safewater Web site at
http://www.epa.gov/safewater or contact the Safe Drinking Water Hotline at 1-800-426-4791.
The Safe Drinking Water Hotline is open Monday through Friday, excluding Federal holidays,
from 9:00 a.m. to 5:30 p.m. Eastern Time. In addition to this fact sheet, the following documents
are electronically available to the public at EPA's web site on the CCL:
(A) The Federal Register announcing the preliminary regulatory determinations for priority
contaminants on the CCL; and
(B) The technical support documents for the CCL Regulatory Determinations Federal
Register:
-------
>• Analysis of National Occurrence of the 1998 Contaminant Candidate List (CCL)
Regulatory Determination Priority Contaminants in Public Water Systems.
»> Health Effects Support Document for Acanthamoeba
>• Health Effect Support Document for Aldrin and Dieldrin
>• Regulatory Determination Support Document for Aldrin and Dieldrin
>• Health Effects Support Document for Hexachlorobutadiene
»• Regulatory Determination Support Document for Hexachlorobutadiene
> Health Effects Support Document for Manganese
*• Regulatory Determination Support Document for Manganese
»> Health Effect Support Document for Metribuzin
»• Regulatory Determination Support Document for Metribuzin
i- Health Effect Support Document for Naphthalene
»• Regulatory Determination Support Document for Naphthalene
»• Draft Drinking Water Advisory: Consumer Acceptability Advice and Health
Effects Analysis on Sodium
>• Regulatory Determination Support Document for Sodium
*• Draft Drinking Water Advisory: Consumer Acceptability Advice and Health
Effects Analysis on Sulfate
> Regulatory Determination Support Document for Sulfate
For a hard copy of this fact sheet (EPA 815-F-02-003), the Federal Register notice,
and/or any of the supporting documents for the CCL Regulatory Determinations notice, please
contact EPA's Water Resource Center at 1-800-832-7828.
-------
Appendix
CCL Regulatory Determination Information Sheet
Acanthamoeba
Background
> Acanthamoeba are microscopic amoeba commonly found in the environment.
Adverse health effects
> Several species have been found to infect humans. The two major disease conditions are
keratitis and granulomatous amoebic encephalitis (GAE).
Acanthamoeba keratitis. Keratitis, or corrieal infection, occurs when amoebas enter the
eye via contact lenses or through a cut in the cornea. Infection occurs predominantly in
individuals who wear soft contact lenses and is thought to be a consequence of improper
storage, handling, and disinfection of the lenses or lense case; wearing lenses in hot tubs
and during swimming; and the formation of bacterial biofilms on contact lenses and lens
storage cases. Acanthamoeba keratitis is not known to be produced by ingestion of
drinking -water, inhalation during showering, or other standard uses of drinking -water.
GAE. Occurs mostly in chronically ill individuals with compromised immune systems.
Routes of entry are the respiratory tract and skin lesions.
Occurrence and exposure
> Acanthamoeba are found worldwide in a wide range of environmental media, it is assumed that
finished drinking water may be source of exposure, however, PWSs do not monitor for
Acanthamoeba.
> Between 1973 and 1996 an estimated 700 Acanthamoeba keratitis cases occurred hi the U.S.
There appears to be an increased incidence in keratitis over the past decade that may be
attributed to the increase in the number of contact lens wearers.
*• GAE is not a reportable disease in the U.S.; however, about 110 cases of GAE have been
reported world-wide; 64 cases have been reported in the U.S., of which 30 cases were diagnosed
in AIDS patients. Reports indicate that the possible routes of entry of Acanthamoeba in
individuals are through the respiratory tract and from skin lesions. Thus, it is unlikely that
any of the cases were associated with ingestion of Acanthamoeba in drinking water.
Preliminary regulatory determination
»• The Agency has made the preliminary determination not to regulate Acanthamoeba with a
NPDWR since regulation would not present a meaningful opportunity for health risk for the
people served by public drinking water systems. Several species of Acanthamoeba infect
humans and can be found worldwide hi a range of environmental media (e.g., soil, dust, and
fresh water). Because of this, it is assumed that finished drinking water may be source of
1
-------
Appendix
exposure. However, Acanihamoeba keratitis is not known to be produced by ingestion of
drinking water, inhalation during showering, or other standard uses of drinking water. Rather,
keratitis is associated with poor hygiene practices among contact lens wearers. GAE has been
reported in a very small number of individuals known to be at risk for developing this disease;
there have been a total of 64 U.S. cases which is a low incidence even considering the possible
vulnerability of an estimated number of immunocompromised and diabetic individuals of 10
million. It is unlikely that any of the cases were associated with ingestion of Acanihamoeba in
drinking water.
An effective means to protect public health is to identify those groups of individuals who may be
at risk or more sensitive than the general population to the harmful effects ofAcanthamoeba in
drinking water and target them with protective measures (e.g., encourage contact lens wearers to
follow manufacturers' or health care practitioners' instructions for cleaning and rinsing their
contact lens). EPA intends to release a guidance document addressing the risks of
Acanthamoeba infection.
-------
Appendix
CCL Regulatory Determination Information Sheet
Aldrin and Dieldrin
Background
* Aldrin and dieldrin are the common names of two structurally similar insecticides. They are
discussed together because aldrin readily changes to dieldrin in the body and in the environment,
and they cause similar adverse health effects.
> Popular pesticides for corn and cotton from 1950-1970.
> Banned in 1974 except to control termites, banned for all uses in 1987.
*• EPA issued health advisories in 1992 (aldrin) and 1988 (dieldrin).
Adverse health effects
*• Both are classified as, "likely to be carcinogenic to humans."
> EPA used only the best available peer reviewed data and analyses to characterize health effects.
Based on this characterization, the Agency estimated a health-related benchmark, or Health
Reference Level1 (HRL = 0.002 ng/L for both aldrin and dieldrin), against which to evaluate the
occurrence data.
Occurrence and exposure
*• For the most part, exposure occurs when people eat contaminated foods.
*• Aldrin and dieldrin were monitored under the Agency's Unregulated Contaminant Monitoring
program2 from 1993-1999.
> EPA estimated the number of PWSs with detections >1/^HRL and >HRL; the population served at
. these bench-mark values; and the geographic distribution using a large number of State
occurrence data that broadly reflect national coverage.
Aldrin detections >'/aHRL and >HRL. 0.02% of the reporting PWSs (2 out of 12,165)
experienced detections of aldrin at >VfflORL, and >HRL affecting 0.02% of the
population served (8,600 out of 47.8 million people).
Dieldrin detections >'/2HRL and >HRL. 0.09% of the reporting PWSs (11 out of 11,788)
have detections of dieldrin at >I/^HRL, and >HRL 0.07% of the population served
(32,000 out of 45.8 million).
Preliminary regulatory determination
• The Agency has made the preliminary determination not to regulate aldrin or dieldrin with
a NPDWR since regulation would not present a meaningful opportunity for health risk for the
people served by public drinking water systems. EPA recognizes that aldrin and dieldrin are
probable human carcinogens, but the chemicals have been banned for most uses since 1974, and
-------
Appendix
have relatively low levels of occurrence in drinking water supplies. It is likely that there will be
so few people exposed to aldrin and dieldrin in their drinking water that a national regulation to
control these two pesticides may not be significant in reducing cancer risk.
-------
Appendix
CCL Regulatory Determination Information Sheet
.Hexachlorobutadiene
Background
•• Used to make rubber compounds, also used as a solvent.
Adverse health effects
• Classified as, "likely to be a carcinogen to humans."
EPA used only the best available peer reviewed data and analyses to characterize health effects.
Based on this characterization, the Agency estimated a health-related benchmark, or Health
Reference Level1 (HRL = 1 ug/L), against which to evaluate the occurrence data.
Occurrence and exposure
Most exposure to hexachlorobutadiene comes from breathing it hi workplace air. People living
near hazardous waste sites containing hexachlorobutadiene may be exposed to it by breathing air
or by drinking contaminated water.
Hexachlorobutadiene was monitored under the Agency's Unregulated Contaminant Monitoring
program2 from 1988-1992 ("Round 1") and 1993-1999 ("Round 2"). '
EPA estimated the number of PWSs with detections >H-HRL and >HRL; the population served'at
these bench-mark values; and the geographic distribution using a large number of State
occurrence data that broadly reflect national coverage.
Round 1 detections >V£HRL and >HRL. 0.16% of the reporting PWSs (20 out of 12,284)
had detections >1/2HRL, affecting 0.57% of the population served (407,000 out of 71.6
million). The percentage of'reporting PWSs with detections >HRL is 0.11% (14 out of
12,284), affecting 0.37% of the population served (263,000 out of 71.6 million).
Round 2 detections >!/2HRL and >HRL. 0.08% of the reporting PWSs ^/fflRL (18 out
of 22,736), affecting 2.3% of the population served (1,6 out of 67 million). The
percentage of the reporting PWSs with detections >HRL is 0.02% (4 out of 22,736),
affecting 0.005% of the population served (3,350 out of 67 million).
• Qualifying statement ,
Round 1 monitoring results are influenced by the State of Florida, which may have
incomplete and problematic data that may inflate the occurrence estimate.
Although the two rounds differ somewhat (for population-exposed to concentrations
greater than the HRL), the differences are relatively small (approximately a quarter
million), and the maximum estimate still shows a very low occurrence. The lower of the
two rounds represents the more recent data.
Preliminary regulatory determination
-------
Appendix
The Agency has made the preliminary determination not to regulate hexachlorobutadiene
with an NPDWR because the contaminant does not occur with a frequency, or at levels, of public
health concern. Monitoring data indicate that hexachlorobutadiene is infrequently detected in'
public water supplies. In addition to the fact that these detections are low, it is important to note
that when hexachlorobutadiene is detected, it very rarely exceeds the HRL or a value of one-half
theHRL.
-------
Appendix
CCL Regulatory Determination Information Sheet
Manganese
Background
• • Essential nutrient, occurs naturally at low levels in soil, water, and food
• Variety of uses: production of steel, batteries, matches, animal feed, ceramics and nutritional
supplements.
Adverse health effects
• Manganese is needed for normal growth and function; however, several diseases are associated
with both deficiencies and excess intake of manganese.
Major source of manganese intake in humans (with the exception of possible occupational
exposure) is dietary ingestion; however, manganese is not considered to be very toxic when
ingested with food, and reports of adverse effects are rare.
• Several reports of toxicity to humans exposed to manganese by inhalation which can lead to
neurological symptoms (e.g., tremor, gait disorders, etc.). Much less is known about oral intake
of manganese. •
• EPA used only the best available peer reviewed data and analyses to characterize health effects.
Based on this characterization, the Agency estimated a health-related benchmark^ or Health
Reference Level1 (HRL = 300 jig/L), against which to evaluate the occurrence data.
Occurrence and exposure
• . Monitored under the NIRS study3.
EPA estimated the number of PWSs with detections >!/fflRL and >HRL; the population served at
these bench-mark values; and the geographic distribution using a large number of State
occurrence data that broadly reflect national coverage.
Detections >1AHRL. 6.1% of the reporting ground water PWSs had detections >1£HRL
(60 out of 989), affecting about 4.6% of the population served (68,200 out of 1.5
million).
Detections >HRL. 3.2% of the reporting ground water PWSs with detections >HRL (32
out of 989) affecting 2.6% of the population served (39,000 out of 1.5 million).
Preliminary regulatory determination
The Agency has made the preliminary determination not to regulate manganese with a
NPDWR because it is generally not considered to be very toxic when ingested with the diet and
since drinking water accounts for a relatively small proportion of manganese intake. Thus,
regulation would not present a meaningful opportunity for health risk reduction for persons
-------
Appendix
served by PWSs.
-------
Appendix
CCL Regulatory Determination Information Sheet
Metribuzin
Background
• Herbicide, applications primarily targeted to soybeans, potatoes, alfalfa, and sugar cane.
• Geographic distribution of use reflects the distribution of these crops across the U.S.
Adverse health effects
• Evidence is inadequate to classify as a human carcinogen.
For non-carcinogenic effects, the thyroid and liver are the most sensitive organs (impacting organ
weight, serum levels, and enzyme activity).
• EPA used only the best available peer reviewed data and analyses to characterize health effects.
Based on this characterization, the Agency estimated a health-related benchmark, or Health
Reference Level1 (HRL = 91 ug/L), against which to evaluate the occurrence data.
Occurrence and Exposure
• Monitored under the Agency's Unregulated Contaminant Monitoring program2 from 1993-1999.
• EPA estimated the number of PWSs with detections >^HRL and >HRL; the population served at
these bench-mark values; and the geographic distribution using a large number of State
occurrence data that broadly reflect national coverage.
Detections >'/2HRL or >HRL. No PWSs had a detections >'/£HRL or >HRL.
Preliminary regulatory determination
The Agency has made the preliminary determination not to regulate metribuzin with a
NPDWR because it does not occur with a frequency, or at levels, of public health concern.
-------
-------
Appendix
CCL Regulatory Determination Information Sheet
Naphthalene
Background
• Naturally present in fossil fuels and is formed when wood or tobacco are burned.
Used in the manufacture of plastics, dyes, solvents, and other chemicals.
• Crystalline naphthalene is used as a moth repellent and as a solid block deodorizer for diaper
pails and toilets.
Adverse health effects
• Classified as a possible human carcinogen, via inhalation.
• Effects on the liver and eye (cataracts) after chronic exposure.
• High doses cause break down of the red blood cells.
EPA used only the best available peer reviewed data and analyses to characterize health effects.
Based on this characterization, the Agency estimated a health-related benchmark, or Health
Reference Level1 (HRL = 140 ug/L), against which to evaluate the occurrence data.
Occurrence and exposure
• The major source of human exposure to naphthalene is through moth-balls through either
breathing the vapors or handling.
• People also may be exposed by breathing tobacco smoke and air near industries that produce
naphthalene. .
• Usually naphthalene is not found in water because it evaporates or biodegrades quickly.
• Monitored under the Agency's Unregulated Contaminant Monitoring program2 from 1988-1992
("Round 1") and 1993-1999 ("Round 2").
• EPA estimated the number of PWSs with detections >'/2HRL and >HRL; the population served at
these bench-mark values; and the geographic distribution using a large number of State
occurrence data that broadly reflect national coverage.
Round 1 detections >'/fflRL and >HRL. 0.01% of the reporting PWSs (1 out of 13,452)
had detections at both >YzHKL and >HRL, affecting 0.007% of the population served
(5,400 out of 77.2 million).
Round 2 detections >1/2HRL and >HRL. 0.01% of the reporting PWSs had detections
>MHRL (2 out of 22,923), affecting 0.002% of the population served (1,300 out of 67.5
million). No PWSs had detections >HRL.
Preliminary regulatory determination
The Agency has made the preliminary determination not to regulate naphthalene with an
10
-------
Appendix
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 HRL or a value of one-half of
theHRL.
11
-------
Appendix
CCL Regulatory Determination Information Sheet
Sodium
Background
• Essential nutrient, naturally occurring element
• Used in de-icing roads, water treatment chemicals, domestic water softeners
Adverse health effects
• A large body of evidence suggests that excessive sodium intake may contribute to .age-related
increases in blood pressure (hypertension). High blood pressure is a multi-factorial disorder with
dietary sodium as one of a number of factors influencing its incidence.
• EPA used only the best available'peer reviewed data and analyses to characterize health effects.
Based on this characterization, the Agency estimated a health-related benchmark value based on
dietary intake because of the lack of suitable dose-response data. A benchmark value of 120,000
ug/L was used to evaluate the occurrence data.
Occurrence and exposure
• Food is the mam source of exposure, primarily in the form of sodium chloride (table salt).
• Discretionary sodium intake is variable and can be quite large. The FDA has found that most
American adults tend to eat between 4,000 and 6,000 mg/day.
Sodium-restricted diets range from below 1,000 to 3,000 mg/day.
Monitored under the NIRS study3.
EPA estimated the number of PWSs with detections >1A benchamrk value and >benchmark; the
population served at these bench-mark values; and the geographic distribution using a large
number of State occurrence data that broadly reflect national coverage.
Detections >1A benchmark. 22.6% of the reporting ground water PWSs have detections
>'/2 benchmark value (224 out of 989) affecting approximately 18.5% of the population
served (274,000 out of 1.5 million people).
Detections >benchmark. 13.2% of the reporting ground water PWSs with detections
>benchmark vaule (131 out of 989) affecting approximately 8.3% of the population
served (123,000 out of 1.5 million people).
Preliminary regulatory determination
The Agency has made the preliminary determination not to regulate sodium with an
NPDWR since the amount of sodium in drinking water is not projected to cause adverse health
effects and since drinking water accounts for a relatively small proportion of sodium intake.
Thus, regulation would not present a meaningful opportunity for health risk reduction for persons
12
-------
Appendix
served by PWSs.
This preliminary decision is based on the minor impact of the sodium in drinking water when
compared to the sodium hi foods.
There are inconsistencies and uncertainties m the data on the relationship between sodium intake
and cardiovascular disease for populations with normal or subnormal blood pressures. Blood
pressure is greatly influenced by nutrients in the diet, lifestyle, and behavioral patterns rather
than sodium itself.
EPA intends to 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 will provide appropriate cautions for individuals on low-sodium or sodium-restricted
diets.
13
-------
Appendix
CCL Regulatory Determination Information Sheet
Sulfate
Background
• Present in the diet, naturally occurring element
• Used for a variety of commercial purposes
• SDWA requires the following:
That EPA make a determination whether to regulate sulfate; and
EPA and the CDC to conduct a study to establish a dose-response relationship for
adverse effects of sulfate, including the health effects that may be experienced by
sensitive" subpopulations (i.e., infants and travelers).
Adverse health effects
• Laxative effect follpwing high acute exposures (>500 mg/L)
Sulfate Study •
In January of 1999, EPA and the CDC completed the study required by SDWA. .
Investigators were unable to study infants because they could not identify enough
exposed individuals from which to draw a study population.
In experimental trials with adult volunteers representing a transient population, the
.investigators did not find an association between acute exposure to sodium sulfate in tap
water and reports of diarrhea.
• Sulfate Workshop
As a supplement to the Sulfate Study, the CDC, in coordination with EPA;, convened an
expert workshop, open to the public, in September of 1998.
Expert scientists reviewed the literature and the Sulfate Study results and favored a
health advisory for sulfate-containing drinking water levels greater than 500 mg/L.
The most sensitive endpoint was considered to be diarrhea.
• EPA adopted the recommendation by experts at the Sulfate Workshop of 500 mg/L as a health-
related benchmark, or Health Reference Level1 (HRL), against which to evaluate the occurrence
data.
Occurrence and exposure
• Monitored under the Agency's Unregulated Contaminant Monitoring program2 from 1993-1999.
• EPA estimated the number of PWSs with detections >l/zHRL and >HRL; the population served at
these bench-mark values; and the geographic distribution using a large number of State
occurrence data that broadly reflect national coverage.
14
-------
Appendix
Detections >1AHKL. 5% of the reporting PWSs had detections >1/2HRL (820 out of
16,495 PWSs), affecting about 10.2% of the population served (5.1 million out of 50.4
million people).
Detections >HRL. 1.8% of the reporting PWSs had detections >HRL (300 out of 16,495
PWSs), affecting about 0.9% of the population served (448,300 out of 50.4 million
people).
Preliminary Regulatory Determination
The Agency has made the preliminary determination not to regulate sulfate with an
NPDWR since regulation would not present'a meaningful opportunity for health risk reduction
for persons served by public drinking water systems.
This preliminary decision is based on the weight of evidence suggesting that the risk of adverse
health effects to the general population is limited and acute (a short duration laxative-related
response) and occurs at high drinking water concentrations (>500 mg/L, and in many cases
>1,000 mg/L).
In addition, either people develop a tolerance for high concentrations of sulfate in drinking water,
or they decrease the amount of the water they drink at one time, most likely because of the taste
of the water (the taste threshold is 250 mg/L).
EPA intends to issue an advisory to provide guidance to communities that may be exposed to
drinking water contaminated with high sulfate concentrations.
15
-------
Appendix
Footnotes
JFor hexachlorobutadiene, manganese, metribuzin and naphthalene EPA derived a health-related
benchmark, or "HRL", against which to evaluate the occurrence data using the RfD approach as
follows: HRL = (RfDxBWyDWxRSC.
Where:
RfD = Reference Dose
BW = Body weight for and adult, assumed to be 70 kg
DW = Drinking water consumption, assumed to be 2 L/day
RSC = The relative source contribution, or the level of exposure believed to result
from drinking water when compared to other sources (e.g., air), and is assumed to
be 20% for the HRL unless noted otherwise.
The HRL's for sulfate and sodium are unique to each contaminant. The available data do
not support the derivation of an RfD for sulfate. However, 500 mg/L is a concentration at which
adverse effects did not occur in any of the reported studies. This value was used as the HRL.
The value used to evaluate the occurrence data is not designated as an HRL because of
the lack of suitable dose-response data and the considerable controversy regarding the role of
sodium in the etiology of hypertension. Instead a benchmark value is used. The benchmark for
sodium was derived from the recommended daily dietary intake (2.4 g/day) as dissolved in 2
liters of water (1.2 g/L). It is important to note that the recommended intake is not related
directly to dose-response information and is lower than most estimates of the present average
daily intake of the U.S. population. A RSC of 10% was applied in recognition that foods and
discretional use of table salt are the major source of sodium exposure. This results in a
benchmark value of 120 mg/L, assuming 2 liters of water per day (i.e., 2,400 mg/day/2L x 10% ==
120 mg/L).
Occurrence data for most of the regulatory determination priority contaminants (aldrin, dieldrin,
hexachlorobutadiene, metribuzin, naphthalene, and sulfate) are from the monitoring results (State
finished drinking water occurrence data) under the Agency's Unregulated Contaminant
Monitoring (UCM) program. These data form part of the Agency's basis for its estimates of
national occurrence. The UCM program was initiated in 1987 to fulfill a SDWA requirement of
the 1986 amendments that PWSs [all non-purchased community water systems (CWSs) and non-
purchased non-transient non-community water systems (NTNCWS)]mpnitor for specified
"unregulated" contaminants to gather scientific information on their occurrence for future
regulatory decision making purposes.
The UCM program was implemented in two phases, or "rounds." The first round of
UCM monitoring began in 1987, and the second in 1993. EPA reviewed, edited and filtered the
data to meet various data quality objectives for the purposes of this analysis. Only data meeting
16
-------
Appendix
the quality objectives described below were used. -
Round 1 consists of data from 24 States with approximately 3.3 million analytical records
from approximately 22,000 PWSs. Round 2 of data from 20 States with approximately 3.7
million records from slightly more than 27,000 PWSs. The actual number of systems and
records varies for each contaminant according to the number of reported records for a particular
contaminant.
An additional EPA study conducted in the mid-1980s, the National Inorganic and
Radionuclide Survey (MRS), provides a statistically representative sample of the national
occurrence of many regulated and unregulated inorganic contaminants in ground water CWSs.
3An additional EPA study conducted in the mid-1980s, the National Inorganic and Radionuclide
Survey (MRS), provides a statistically representative sample of the national occurrence of many
regulated.and unregulated inorganic contaminants in ground water CWSs.
The MRS database includes manganese and sodium and provides contaminant
occurrence data from 989 community water systems served by ground water. The MRS does not
include surface water systems. The selection of CWSs included in MRS was designed so that
the contaminant occurrence results are statistically representative of national occurrence at CWSs
using ground water sources (the survey was focused on ground water systems, in part, because
ground water has a higher occurrence and concentrations of naturally occurring lOCs). Most of
the MRS data are from smaller systems (based on population served) and each of the 989
statistically randomly selected CWSs was sampled at a single time between 1984 and 1986.
The MRS data were collected from ground water CWSs in 49 States. Data were not
available for the State of Hawaii. MRS data were designed to be stratified based on system size
(population served by the system), and uniform analytical detection limits were employed.
United States Environmental Protection Agency April 2002
Office of Water (4607M) EPA 815-F-02-003
www.epa.gov/water 17
------- |