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Sodium in Drinking Water

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EPA decided to include sodium on the CCL primarily as a vehicle to reexamine and correct the current, outdated guidance.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 adultweighing 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.