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Sodium in Drinking Water
Sodium is included on the Environmental Protection
Agency (EPA) Drinking Water
Contaminant Candidate List (CCL). The CCL is a list of contaminants
which, at the time of publication, are not subject to any proposed or
promulgated national primary drinking regulation (NPDWR), are known or
anticipated to occur in public water systems, and may require regulations
under the Safe Drinking Water Act (SDWA). As required by the 1996
Amendments to SDWA, EPA published the list in February 1998 to aid in
priority-setting for the agency's drinking water program. Items on the CCL
are divided into three categories: those which are priorities for
additional research, those which need additional occurrence data, and
those which are priorities for consideration for rulemaking.
Why was sodium included on the
Contaminant Candidate List?
The issue of sodium posed a unique challenge for the
Agency priority setting and contaminant candidate listing process. On one
hand, high levels of salt intake may be associated with hypertension in
some individuals. On the other hand, sodium levels in drinking water are
usually low and unlikely to be a significant contribution to adverse
health effects.
This low level of concern is compounded by the
legitimate criticisms of EPA's 20 milligrams per liter (mg/l) Drinking
Water Equivalency Level (DWEL or guidance level) for sodium. EPA believes
this guidance level for sodium needs updating, and is probably low. If a
health benchmark for drinking water were established using current
information and current drinking water health assessment procedures, it
would likely be higher. This revision could establish a new level at which
sodium occurrence would not meet the criteria for inclusion on the CCL as
a drinking water contaminant of concern. There was insufficient time to
complete a reassessment of the sodium guidance in advance of the CCL
issuance.
Given the state of the data, EPA faced a dilemma on
whether or not to list sodium. A decision not to list would be justified
by the fact that much is known about sodium, and it does not appear to be
a drinking water risk comparable to other priority contaminants. In fact,
this was the logic supporting the decision not to include sodium on the
previous drinking water priority list in 1991. However, a decision to list
sodium would afford EPA the opportunity to address the confusion
surrounding the current guidance for sodium in drinking water.
Will EPA develop a drinking
water regulation for sodium?
EPA decided to include sodium on the CCL primarily as a
vehicle to reexamine and correct the current, outdated guidance.
Therefore, sodium is listed, not as a Regulatory Determinations Priority,
but as a Research Priority to allow time to evaluate and revise the Agency
guidance. When this is completed, EPA will reevaluate whether sodium
merits retention on the CCL for any further action.
Should I be concerned about
sodium in my drinking water?
No. Sodium levels in drinking water from most public
water systems are unlikely to be a significant contribution to adverse
health effects.
How much does water contribute to sodium in my diet?
A Food and Drug Administration publication, "Scouting
for Sodium and Other Nutrients Important to Blood Pressure" (FDA
95-2284) states that most American adults tend to eat between 4,000 and
6,000 mg of sodium per day, "and therapeutic sodium restricted diets can
range from below 1,000 mg to 3,000 mg per day." It lists the following
nutrient guidelines for food labeling:
-
Low-sodium: 140 mg or less per serving (or, if
the serving is 30 g or less or two tablespoons or less, 140 mg or less
per 50 g of the food)
-
Very low-sodium: 35 mg or less per serving
(or, if the serving is 30 g or less or two tablespoons or less, 35 mg or
less per 50 g of the food)
-
Sodium-free: Less than 5 mg per serving
In a National Inorganics and Radionuclides Survey,
conducted by EPA in the mid-1980s, about 3/4 of 989 water systems included
had concentrations of sodium of less that 50 mg/l. Assuming that an adult
weighing 70 kilograms (about 150 pounds) drinks two liters (about 8
glasses) per day, he or she would typically ingest less than 100 mg of
sodium per day from drinking water. Based on this data, a 1/4-liter
serving (about an 8-ounce glass) would contain less than 12.5 mg of
sodium, well within FDA's "very low sodium" category.
It is important to note that sodium is an essential
nutrient. The Food and Nutrition Board of the National Research Council
recommends that most healthy adults need to consume at least 500 mg/day,
and that sodium intake be limited to no more than 2400 mg/day.
To reduce my sodium intake, should I buy
bottled water instead of using tap water?
It is not necessary to switch to bottled water to
maintain a healthy, low-sodium diet. Levels of sodium in a serving of
drinking water are very low in most water systems. Also, FDA imposes
quality standards for bottled water that are equivalent to EPA's drinking
water standards. To reduce the risks of adverse health effects due to
sodium, consult a physician or registered dietitian to plan a healthy diet
that reduces the sodium content in your total food intake.
--------------------------------
Reference:
"Sodium in Drinking Water," Ground Water & Drinking Water.
U.S. Environmental Protection Agency. July 5, 2004.
<http://www.epa.gov/safewater/ccl/sodium.html>. |
