Table of Contents
Background
Potassium (K) is a commonly occurring element in the Earth’s crust found in the form of various minerals such as feldspar, muscovite, and hornblende. Moreover, K is also found in seawater with a mean concentration of about 400 mg/L. K is widely applied in agriculture as a fertilizer and also an essential nutrient for animals and plants and plays a significant role in many biological processes in the cell as well as helps regulate fluid balance, provide muscle support, and nerve functioning to maintain a healthy heartbeat. K can be found in drinking water but its level may vary depending on the water source. In general, drinking water contains relatively low K levels ranging from a few milligrams to several hundred mg/L. Drinking water containing K greatly contributes to the daily K intake of an individual.
Drinking water contamination from K can be due to various sources. These sources may be natural in the form of dissolved mineral form mainly and can occur in both ground and surface water reservoirs or can be through human activities. The anthropogenic sources of K contamination involve agricultural runoff containing residues of K fertilizers, and water treatment processes that involve the addition of K during water treatment as a mineral supplement to help maintain the mineral content in the water, leaching from supply pipes since the old pipes made of materials such as iron or copper can leach metal ions into the water causing a potential increase in K levels. Further, human activities involving industrial processes and wastewater discharge, and improper treatment also significantly contribute to the increased K levels in drinking water.
In the US, K levels in drinking water can vary depending on the water sources and the adopted treatment process. The USEPA does not regulate K levels in drinking water, but it does have secondary drinking water standards for various contaminants, including MCLG of not more than 60 mg/L for K. These standards are non-enforceable and set to provide guidelines for good drinking water quality. As per SDWA requirements, the EPA periodically reviews and updates its drinking water standards. It is worth mentioning that while EPA does not regulate drinking water K levels, other countries and regions may have different regulations for K levels based on the detected concentrations and major contributing sources. Being an essential nutrient for the human body, K is involved in many biological functions.
However, its high levels in drinking water can result in potential health impacts through various pathways and mechanisms. For example, consumption of K-contaminated drinking water for an extended time may lead to a medical condition called hyperkalemia. A condition characterized by high K levels in the blood leading to symptoms of muscle weakness, fatigue, and abnormal heart rhythms. It should be noted that K levels in drinking water have been found in low concentrations and pose a very low risk of developing hyperkalemia from drinking water K contamination. However, individuals with an already existing medical condition such as kidney problems or those taking certain medications can be at a higher risk of hyperkalemia development and should consult their healthcare providers if they face concerns related to K levels in their drinking water.
Additional symptoms associated with increased K intake through drinking water may include nervous system effects (tingling, numbness, and muscle twitching), and kidney problems that may even result in kidney damage over time. Therefore, it is necessary to regularly monitor for K levels in drinking water and the water suppliers should regularly share the detected levels with the consumers for satisfaction. Any detected concentrations above the prescribed limits should be taken into account by lowering the K levels by adopting suitable treatment strategies.
K is required by the human body in smaller amounts and plays a key role in various metabolic functions. K metabolism in the human body involves various processes. After initial absorption in the small intestine, it is distributed throughout the body and mainly found in intracellular fluids (Pohl et al. 2013). A proper balance of K levels is essential and is dependent on a balance between K intake and excretion from the body. This balance is governed by various hormones and enzymes that control K intake and release in cells. Kidneys play a critical role in the regulation of K levels by filtering K from the bloodstream and excreting the excess from the urine (Besouw and Bockenhauer 2019). However, if the exposure to K is high, it can trigger toxic impacts such as hyperkalemia which is characterized by elevated blood K levels.
Various cellular and molecular mechanisms have been proposed associated with K toxicity in the human body. This mainly includes cell membrane depolarization and altered ion channel functioning which is responsible for controlling the ionic flow in and outside of the cell (Brayden 1996; Rienecker et al. 2020). Furthermore, high K exposure can also interfere with enzyme activities resulting in altered cellular metabolism. Several molecular mechanisms have also been proposed that involve the changes in gene expression levels that results in abnormal cell functioning. Studies have shown that exposure to high levels of K can alter the expression of genes involved in oxidative stress, inflammation, and other biological processes.
For example, high potassiumexposure has been shown to trigger the gene function involved in oxidative stress, which can contribute to oxidative damage to cellular components (Coetzee et al. 2019; Kasai 1997). An imbalance in the K cations present in the intracellular fluid has been demonstrated to trigger oxidative stress responses that may result in serious health implications (Udensi and Tchounwou 2017). Moreover, the development of hypertension and other cardiovascular diseases has also been associated with K-level disturbances in the cell (Castro and Raij 2013). So far, the data is scarce related to elevated K exposure through drinking water and its resultant toxicity mechanisms. No epidemiological evidence is available to demonstrate this phenomenon, particularly in the US population possibly because of safe detected levels of K in drinking water. However, it is important to consider low to moderate exposure for longer periods and explore the cellular and molecular impacts in epidemiological studies to develop a better understanding of K toxicity in human-exposed populations.
Detection Methods and Removal Strategies
Detection and quantification of K in drinking water can be carried out through various analytical platforms. Among the most widely used methods for K detection in drinking water include atomic absorption spectrophotometer (AAS) attached to a suitable detection system such as a flame or graphite furnace (FAAS/GFAAS). The method is cost-effective, sensitive, and capable of detecting K at ppm (mg/L) and ppb levels (µg/L) (Dkhar et al. 2014; Ling et al. 2019). However, to achieve the low detection limits, the instrument requires careful operating conditions and samples pre-treatment to maintain precision and accuracy during the analysis. The method is based on the light absorption by K atoms to measure the K levels in a water sample.
For more sensitive analysis and detection at very low levels, the ICP-based method is usually preferred with optical emission or mass spectrometric detectors (OES/MS). ICP uses a combination of high-temperature plasma and mass spectrometry to quantify K in a water sample (Albratty et al. 2017). However, the limitation of the method includes expensive per sample costs. Ion chromatography (IC) is also a high-resolution method for the separation and detection of K ions present in drinking water. A column filled with ion-exchange resin is used and water is passed through the column to exchange ions with K in the sample and detect the measured K ions concentrations up to ppm levels (Jackson 2001). Colorimetric methods can also be used for K detection in drinking water where quick, and less sensitive results are required as these methods are capable of quantifying estimated K levels.
It is important to remove excessive K levels from the drinking water. For this, various methods have been developed with the potential of efficient K removal from drinking water. Some of these notably include the ion exchange method which involves the use of a resin bed to exchange K ions in water with other ions such as Na or H (Hu and Boyer 2018). Reverse osmosis (RO) systems have been widely used to remove a range of contaminants in drinking water. A semi-permeable membrane is used and water is allowed to pass through with pressure resulting in the removal of K (Jeppesen et al. 2009).
The method is expensive since it requires regular replacement of membrane but due to its high potential of removing various contaminants, the method is widely used for water purification. Electrodialysis is another method for K removal from drinking water which uses an application of an electric potential across a membrane to filter K ions present in the water sample (Xu and Huang 2008). Moreover, distillation can also be used as a K-removal strategy on a small scale. The method is based on the evaporation of water followed by condensation of purified vapor that results in the removal of various contaminants from drinking water including K.
Public Perspective
Following frequently asked questions (FAQs) try to address some general public concerns in the US, especially the NYC and NJ region.
According to the WHO, the adequate K intake of K for adults (19–>70 years of age) is 4.7 g/day. This is equivalent to 78 mg/kg body weight per day for a 60 kg adult.
K is an essential mineral and electrolyte involved in heart function, muscle contraction, and water balance. Its sustained intake may help reduce high blood pressure, salt sensitivity, and the risk of stroke. Additionally, it plays a protective role against osteoporosis and kidney stones.
K in drinking water generally does not pose a health risk in healthy individuals. K levels in drinking water from water softeners using potassium chloride can be very high, and may significantly increase an individual’s intake of potassium which could cause hyperkalemia in susceptible individuals.
People with kidney problems should be cautious about consuming too much K, as this can lead to hyperkalemia.
There are various methods available to remove K from drinking water including RO, ion exchange, distillation, etc.
When you have kidney disease, your kidneys cannot remove extra potassium in the right way, and too much potassium can stay in your blood.
Some known symptoms associated with high K include hyperkalemia, fatigue, muscle weakness, abnormal heart rhythms, and nausea.
Your heart and muscles can be most affected by high K levels.
Potassium levels can be tested with a blood test or a urine test prescribed by your doctor. Urine K can be checked in a single urine sample. But it is more often measured in a 24-hour urine sample.
Although K may cause some health effects in susceptible individuals, K intake from drinking water is well below the level at which adverse health effects may occur.
Conclusion
K is a naturally occurring element that can be found in various forms and can contaminate drinking water through both natural and anthropogenic sources. Although, the detected K levels in the US drinking water are generally low, however, their long-term exposure may result in certain health implications. USEPA has not regulated K in drinking water due to its low detection and biological significance of being an essential nutrient for human health. But, K levels have been classified into secondary drinking water standards. Regular monitoring of Potassium in drinking water must be taken so that the levels may not exceed the limits and ensure a safe drinking water supply to the US residents.
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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
