Salinity in drinking water refers to the presence of dissolved inorganic salts, primarily sodium and chloride. This measurement is often quantified as Total Dissolved Solids (TDS). While a salty taste is the most immediate indicator of high salinity, the primary concern is the potential long-term health consequences of consuming elevated levels of these dissolved ions. This article examines the sources, health risks, regulatory guidelines, and mitigation steps.
Sources of Increased Salinity in Tap Water
Salinity in water sources often originates from a combination of natural geological factors and human activities. Naturally, water acquires dissolved salts through the chemical weathering and dissolution of mineral deposits as it moves through the ground. Groundwater in contact with certain rocks for extended periods can accumulate significant salt concentrations.
In coastal regions, excessive pumping of freshwater aquifers reduces the pressure that naturally keeps the ocean at bay. This disruption allows denser saltwater to move inland, a process called seawater intrusion. Seawater intrusion contaminates the freshwater supply with high concentrations of sodium and chloride, and is exacerbated in areas experiencing drought or increased water demand.
Human-driven sources (anthropogenic inputs) are also major contributors to rising salinity levels. The widespread use of de-icing salts on roads, parking lots, and sidewalks during winter leads to concentrated runoff that enters water systems. Industrial wastewater discharges and brine waste from water softening systems introduce high salt loads into the environment. Water softeners exchange hardening minerals like calcium and magnesium for sodium ions, and this salty discharge often pollutes local water sources.
Safety Concerns and Health Effects of High Sodium Water
The safety of salty tap water depends significantly on the concentration of sodium ions, which affects individuals differently. For the general population, mildly salty water is primarily an aesthetic issue. However, consuming water with high sodium levels over time contributes to an individual’s overall sodium load. Sodium regulates blood pressure, and excessive intake can lead to fluid retention, increasing blood volume and straining the heart and blood vessels.
This physiological response is directly linked to the development of hypertension and subsequent cardiovascular issues. Studies suggest that communities with elevated sodium in drinking water may have a higher incidence of elevated diastolic blood pressure readings in adolescents, though long-term impacts require continued study. The kidneys excrete excess sodium, and chronic overconsumption can overwork this system, potentially leading to long-term kidney function concerns.
Vulnerable Populations
Certain groups face a greater danger from consuming high-sodium water compared to the general public. Individuals managing conditions like hypertension or heart failure are often prescribed strict sodium-restricted diets. For these patients, drinking water with elevated sodium can account for a disproportionately large percentage of their total daily sodium intake. This sometimes contributes up to 64% of their total sodium budget, making it difficult to maintain therapeutic dietary restrictions.
Infants constitute another highly susceptible population due to their immature kidney function. When powdered formula is mixed with high-sodium tap water, the resulting solution contains significantly elevated sodium concentrations. Studies demonstrate that neonates consuming formula diluted with high-sodium water experience an increase in systolic and mean arterial blood pressure. This excessive sodium load is difficult for the infant’s underdeveloped kidneys to process, posing a serious health risk.
Understanding Regulatory Standards for Salinity
Salinity in public water systems is measured by analyzing the concentration of dissolved substances, primarily Total Dissolved Solids (TDS) and chloride. In the United States, the Environmental Protection Agency (EPA) addresses these contaminants through the National Secondary Drinking Water Regulations. These standards are set as Secondary Maximum Contaminant Levels (SMCLs), which are non-mandatory guidelines.
The SMCL for chloride is 250 milligrams per liter (mg/L), and for Total Dissolved Solids (TDS) it is 500 mg/L. These levels are established primarily based on aesthetic considerations because water exceeding these concentrations tends to have an objectionable salty taste. Unlike Maximum Contaminant Levels (MCLs), which are legally enforceable standards for contaminants that pose a direct health risk, SMCLs serve as goals to ensure public acceptance of drinking water quality related to taste, odor, and appearance.
Practical Steps for Testing and Mitigation
If tap water tastes noticeably salty, the first step is to contact the local public water utility. They can provide the most recent water quality report, which includes measured levels for Total Dissolved Solids, sodium, and chloride. Homeowners relying on private wells should arrange for a specialized laboratory test to determine the exact levels of sodium and chloride in their water.
For long-term mitigation of high salinity, only specific treatment technologies are effective. Standard carbon filters, commonly found in pitcher and refrigerator filters, are unable to remove dissolved inorganic salts like sodium and chloride ions. The most effective home treatment method is reverse osmosis (RO), which uses a semi-permeable membrane to filter out nearly all dissolved solids.
Reverse osmosis systems can reject between 95% and 99% of dissolved salts, making them highly effective for reducing sodium levels for individuals on restricted diets or for preparing infant formula. Another option is distillation, which involves boiling water into steam and then condensing it back into a liquid, leaving all dissolved salts behind. Both RO and distillation are proven methods for ensuring the final drinking water product is safe and palatable by removing the salt-contributing ions.