Table of Contents
See Sodium AquaWiki™
Background
Sodium (Na) is a highly abundant element distributed widely throughout various environmental compartments mainly including seawater, rocks and minerals, soil, lakes, and inland waters. In the aquatic environment, Na occurs mainly in the form of NaCl and seawater contributes its major source on Earth where its concentration is approximately 11,000 parts per million (ppm). Whereas, in soil, it occurs mostly in the form of rock salt, soda ash, and sodium feldspar and these minerals have major contributions to Na occurrence in soil and water through weathering and erosion processes. Fresh surface water reservoirs such as lakes and inland waters usually contain low Na levels however these sources also contribute to its levels in groundwater reservoirs through leaching and runoff processes as well as atmospheric deposition.
Other major sources of increased Na levels in drinking water include agricultural and industrial emissions and the water treatment process. In plants and animals, Na is required as an essential nutrient because of its key role in carrying out numerous biological processes and fluid balance. In drinking water, the detected Na levels are found relatively in low concentrations therefore, humans mainly take sodium through their diet to meet their body requirements. When consumed in appropriate amounts, Na has high significance to the body and no toxic effects have been documented. However, the excessive intake of Na can trigger several health conditions. These include the development of hypertension leading to an increased risk of developing cardiovascular diseases. Its elevated consumption can also result in fluid retention and edema in the body that can cause congestive heart failure and renal dysfunctioning.
Osteoporosis is the condition of bone disease having reduced bone density and can be associated with high Na intake, particularly among postmenopausal women. Some other diseases such as stomach cancer, and kidney stones have also been documented due to high Na intake by individuals. As mentioned, all the associated health implications associated with excessive Na intake are mainly due to its consumption either through diets or dietary supplements. There is weak epidemiological evidence demonstrating adverse health outcomes related to Na intake through drinking water as the detected levels of Na in drinking water have been reported at low levels with no health effects. Levels of Na in drinking water also depends regional variances for example, coastal regions contain higher concetration of Na compared to the other locations due to seawater intrusion.
Particulary in the US, no population-based study has been reported to address a correlation between elevated Na levels in drinking water and its associated health impacts in humans. This is mainly because Na levels in the US drinking water are regularly monitored and found within safe limits and is not considered a public health concern. Due to this reason, US Environmental Protection Agency (EPA) has established secondary maximum contaminant levels (SMCL) of 20 mg/L for Na in drinking water and this SMCL is non-enforceable and only serves as a guideline to monitor Na levels in drinking water. As per EPA guidelines, all public water utilities in the US are required to provide a consumer confidence report (CCR) to the consumers containing information related to water source, adopted treatment strategies, and presence of any contaminants including Na. Any concerns regarding Na levels in drinking should be properly communicated and if found, the elevated levels must be reduced before the water is supplied to the consumers.
Moreover, regular monitoring of Na levels should be carried out in states to ensure public health safety and population-based investigations exposed to Na containing drinking water can provide a better understanding of Na toxicity in the US. Furthermore, it is important to mention that Na-associated health impacts can vary among individuals based on various factors. These include overall dietary patterns, underlying health conditions, lifestyle, age, gender and genetic predispositions. Therefore, it is highly recommended to consult health professionals for suitable advice and guidance.
Although, Na has been reported to be beneficial for human health due to its role in many biological reactions in the body. However, if consumed in excess and for prolonged periods, Na has been associated with numerous health implications. Saveral cellular and molecular mechanisms have been proposed in studies through which, Na can induce adverse health effects in humans. These include disturbances in osmotic balance within ceslls causing osmotic stress that results in cellular dysfunction (Titze et al. 2002).
High Na levels in body can also cause ionic imbalance of other ions in cells such as potassium, calcium and magnesium that results in altered enzyme activities and signal transduction (Gurtovenko and Vattulainen 2007; Liu and Xie 2010). Moreover, induction of oxidative due to the generation of reactive oxygen species (ROS) leading to cellular and molecular damage has also been associated with high Na levels in the body (Yaribeygi et al. 2019). ATP production by mitochondria is an important process in cellular respiration. This production can be altered through impaired mitochondria due to excess Na levels in the cell (Guan et al. 2009). Furthermore, high Na levels can activate the immune cells leading to the development of chronic inflammation. Also, Na toxicity has been significantly correlated with endothelial cells walls which can contribute to vascular damage and cardiovascular diseases (Dmitrieva and Burg 2015).
Therefore, a balanced Na intake is essential in minimizing Na-associated health risks in humans. Various metabolic processes are involved in maintaining body’s Na balance and fluid regulation. The ingested Na is first absorbed in the digestive system (small intestine) and is transported to various tissues and organs through bloodstream. Kidneys play a crucial role in maintaining Na levels and excess amount is excreted form the body in the form of urine. Furthermore, in hot environments, the body regulate the Na by removing excess Na in the form of sweat. Several enzymes are also involved in regulating Na metabolism in the body. These enzymes include aldosterone, antidiuretic hormone (ADH), and atrial natriuretic peptides (ANP) (Schrier 2006).
Detection Methods and Removal Strategies
Na can be detected and quantified in drinking water using various available techniques. Ion-selective electrode (ISE) is a widely used technique for quantifying Na in drinking water. In this technique, an ion-selective electrode specific to Na ions is used to generate electrical potential which is propotional to Na ions in a water sample (Levy 1981). Flame photometery uses light emitted from excited Na ions at a specific wavelength that results in detection of Na in water sample (Banerjee and Prasad 2020). Among other includes colorimetric methods making use of specific chemical reagents. However the colorometri methods are preferred where the estimated results are desired with less sensitivity. For more sensitive detection and at very low levels, Inductively coupled plasma mass spectrometry (ICPMS) is widely used technique with high accuracy and precision. However the technique has limitation because of high analytical costs. A relatively cheaper method for Na detection in drinking water comprise of using atomic absorption spectrophotmoter (AAS) which is cheaper compared to ICPMS and can give results at lower levels with high accuracy after proper calibration of instrument (Ieggli et al. 2011). It is worth mentioning that the choice of preference of suitable analytical method is based on various factors including desired results, sensitivity, available technique, costs and qualified persons available for analysis.
Several methods have been proposed so far to reduce Na levels in drinking water. Some commonly used methods include reverse osmosis (RO) which involve forcing water to pass through a semipermeable membrane resulting in removal of Na from the water (Li et al. 2014). Ion exchange resins are also applied that uses exchange of Na ions with other ions mainly H or K ions (Da̧browski et al. 2004). Recently, the application of biochar produced from different materials has also proved effective removal of Na from water (Filipinas et al. 2021). Distillation is a cost-effective Na removal method that involves heating of water to vaporize and then condense the water to get purified water. Since Na ions do not vaporize, they remain in the original water and as a result, purified water is collected. Modern methods for Na removal use nano-filteration membrane which is proved a very effective approach to remove Na from drinking water (Loh et al. 2022).
Public Perspective
Following frequently asked questions (FAQs) try to address some general public concerns in the US, especially the NYC and NJ region.
While there is no drinking water standard for Na, state and federal agencies recommend Sodium levels in water not exceed 20 milligrams per liter (mg/L) for people on very low Na diets and 270 mg/L for people on moderately restricted sodium diets.
Acute effects may include nausea, vomiting, convulsions, muscular twitching and rigidity, and cerebral and pulmonary oedema. Excessive salt intake seriously aggravates chronic congestive heart failure, and ill effects due to high levels of Na in drinking-water have been documented.
For most people, the salt levels found in tap water are not harmful and the amount found in a serving of drinking water is very low with North American tap water having in the range of 18 to 41 mg per liter of Na. In comparison, filtered bottled water contains Na in the range of 4 to 8 mg per liter.
The most common and effective way to remove salt from water is through physical filtration. Specifically, reverse osmosis systems are capable of removing salt and a wide variety of other contaminants from softened water.
The immediate symptoms of eating too much salt include increased thirst, swollen feet or hands, headache (in some cases), and rise in blood pressure.
Boiling water does not remove sodium and will only increase concentrations because of evaporation of water leaving behind the elevated Na levels in water.
Naturally soft water typically contains between 10 to 50 parts per million (ppm) of Na. It has been suggested that water with a Na content of up to 200 ppm is safe to drink. Unless your water is very hard to start with, the softened water sodium content is unlikely to exceed this.
When you drink plenty of water, your body can flush the excess sodium in your body. It is important to drink plenty of water if you have too much sodium in your blood because your kidneys will flush out the excess sodium and help to lower your blood pressure over the long term.
Without treatment, extremely high levels of Na may lead to a coma and become life threatening. Symptoms of high sodium levels (hypernatremia) include thirst, urinating (peeing) very little, vomiting, diarrhea, confusion, muscle twitching and seizures.
Reverse Osmosis (RO) systems can remove between 94% and 98% Na content in your water. It is important to note that RO is one of the best options to eliminate various contaminants from the water. In fact, this filtration system can also remove harmful waterborne bacteria.
Conclusion
Na is a naturally occurring element that can be found in drinking water through various natural and anthropogenic origin. It is an essential nutrient for humans and have high significance in carrying out various biological reactions. Literature suggest that its levels in drinking water are safe for human consumption and is not a serious public health concern. However, its prolonged exposure must be avoied to minimize the associated health risks. In the US, levels of Na in drinking water are under safe limits. Because of its high biological significance, EPA has set a non enforceable SMCL for Na in drinking water. It is recommended that the Sodium levels should be tested and monitored regularly to ensure safe drinking water supply to the US residents. Moreover, any consumer concerns should be removed by sharing up to date information related to their drinking water and if elevalted levels are detected in drinking water, it must be subjected to suitable treatment to reduce Na levels.
References
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Da̧browski A, Hubicki Z, Podkościelny P, Robens E. 2004. Selective removal of the heavy metal ions from waters and industrial wastewaters by ion-exchange method. Chemosphere. 56(2):91-106.
Dmitrieva NI, Burg MB. 2015. Elevated sodium and dehydration stimulate inflammatory signaling in endothelial cells and promote atherosclerosis. PloS one. 10(6):e0128870.
Filipinas JQ, Rivera KKP, Ong DC, Pingul-Ong SMB, Abarca RRM, de Luna MDG. 2021. Removal of sodium diclofenac from aqueous solutions by rice hull biochar. Biochar. 3:189-200.
Guan L, Han B, Li Z, Hua F, Huang F, Wei W, Yang Y, Xu C. 2009. Sodium selenite induces apoptosis by ros-mediated endoplasmic reticulum stress and mitochondrial dysfunction in human acute promyelocytic leukemia nb4 cells. Apoptosis. 14:218-225.
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- Yasir A. Rehman, Ph.D.
Dr. Rehman was born in Rawalpindi, Pakistan. He completed his MSc from PMAS – Arid Agriculture University Rawalpindi in 2011 where his thesis comprised a health risk assessment of subjects living in the vicinity of wastewater channels in urban settings and its relationship with the incidence of Malaria.
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OTHER RESEARCH ON WATER CONTAMINANTS BY DR. YASIR
