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Whatcom County Health Department
Drinking Water Program, Environmental Health Division
Phone: (360) 676-6724
E-mail: Environmental Health

 

 
Sodium in Drinking Water

Sodium and Chloride in Drinking Water

The compound known as "salt"  consists of the elements sodium (Na) and chloride (Cl). Many people use the word salt when  intending to refer only to sodium. Every water supply contains some sodium and chloride.

Sodium Levels:
Sodium levels in drinking water that are less than 20 mg/L are considered safe for most  people. In the seacoast area, however, elevated levels of sodium and chloride occur  naturally due to the proximity to seawater. Substantially higher levels of sodium and  chloride may also be due to contamination by activities of man including: use of road  de-icing salts, discharges from water softeners, human or animal waste disposal, leachate  from landfills and many other activities.

Health Implications:
At present there are no health standards for sodium and chloride in drinking water. A  review by EPA in the mid-1980s showed that elevated levels of sodium in drinking water did  not cause high blood pressure or heart disease, rather only that sodium should be avoided  by those people who already had such medical conditions.

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 of sodium per day, and that sodium intake be  limited to no more than 2400 mg/day. A Food and Drug Administration publication states  that most American adults tend to eat between 4,000 and 6,000 mg of sodium per day.

When considering the health importance of sodium and chloride, EPA  assumes that water users consume two liters of water per day and recognizes that, on  average, 20 percent of a person's daily sodium intake is from drinking water. The  rest of an average person's sodium intake is usually from food. There are no known  health concerns with chloride. Persons on a sodium-restricted diet should evaluate all  possible sources of sodium when attempting to reduce overall intake. It is often much  easier and less expensive to make a dietary change than to excessively purify drinking  water.

EPA has recommended that sodium levels in drinking water not exceed  20 mg/L for people on a physician-prescribed "no salt diet". This is a  very stringent level. For comparison purposes, regular milk has a sodium concentration of  approximately 500 mg/L.

High levels of sodium and chloride result in poor tasting water. EPA  has identified a concentration of over 250 mg/L above which both sodium and chloride can  be expected to impart a "salt" taste to drinking water. This level is based on  aesthetic concerns and is only advisory in the EPA Safe Drinking Water Act program.

The main source of sodium and chloride in Whatcom County:
The most common source of significantly elevated levels of sodium and chloride in well  water in Whatcom County is seawater from storm spray, underground intrusion or relic  salt-water pockets. Residents in these areas may choose to bathe with the water, but use  bottled or treated water for drinking, cooking and for watering plants. The level of  sodium in the water should be considered and compared to the total intake of sodium in a  person's diet. A person on a sodium-restricted diet should avoid drinking this water.

Control of other sources of sodium and chloride:
Normally the best method to control sodium and chloride in drinking water is to prevent or  better manage those activities that dispose of salt near the water supply source(s). In  addition to seawater, other common sources of salt in water supplies include:

  • Water softeners: Water softeners add sodium to drinking water in  two ways: during the hardness removal process, and indirectly by the discharge of water  brine into subsurface disposal systems. The amount of salt added by ion exchange can be  substantial if a water's hardness is high.

Other sources:
Many water treatment chemicals have sodium as a  basic ingredient. These chemicals often perform a valued treatment function. However, they  do raise the sodium level in waters proportional to the rate applied.

Treatment:
Sodium and chloride are costly to remove from  water. Treatment types include:

  • Reverse Osmosis: not practical for high volume needs due to cold  water "reject" rate.
  • Distillation: very costly to operate.
  • Ion Exchange-Deionization: technically practical but not often used  on a large scale.

Where treatment is going to be installed, the size options range  from an under-the-sink system to full house treatment. If only pure drinking water is your  goal, then an under-the-sink system will suffice.

The presence of elevated levels of sodium and chloride increases the  water's corrosiveness, possibly increasing damage to plumbing fixtures. To reduce  this damage, a treatment system would need to be installed that will service the entire  structure. Bottled water is also an option to address health concerns (posed by leached  lead and copper) in the interim period while a long-term solution is being investigated.

For more information:
E-mail us at water@co.whatcom.wa.us or call us at (360) 676-6724. Ask to speak to an Environmental  Health Specialist in the Water Program.

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