Table of Contents
Background
Calcium (Ca) is among the most abundant element in the Earth’s crust with wide environmental occurrence in the form of various rock minerals mainly in the form of carbonates, sulfates, fluoride, silicates, and phosphates. Limestones, marble, chalk, and coral reefs contain a significant amount of Ca with a major composition of carbonates. Because of its high abundance, Ca has broad applications in the manufacturing of materials such as cement, lime, and building material. The element has high significance for plant growth and plays a vital role in the chemistry of soil and its content is directly associated with soil fertility. In water, Ca ions occur in the natural surface water sources such as rivers, lakes, and streams in the dissolved form. Whereas, groundwater contamination occurs when Ca minerals leach down into the underground aquifers from the surrounding rocks. In the biological systems, Ca is essential for many living organisms as it plays a crucial role in various biological processes in humans including bone and teeth formation, muscular contraction, nerve function, and cellular signaling. Ca is either taken by humans from their diet or through environmental absorption. In drinking water, Ca is commonly found and is considered a beneficial mineral for human health.
Ca gets dissolved in drinking water through natural and anthropogenic sources including geological and industrial processes respectively. It is one of the main factors that play a crucial role in water hardness. Although, water hardness is not generally considered harmful to human health, but can affect household appliances, plumbing, and stop detergent effectiveness. Water hardness is typically measured in mg/L. As per US Geological Survey (USGS), water containing Ca content between 120-180 mg/L is considered hard. When taken through drinking water, Ca contribute to the dietary intake of this essential mineral hence contributing to the overall Ca intake for humans. It should be noted that the Ca intake from drinking water to total dietary intake mainly depends on specific sources of water and individual consumption patterns.
However, Ca can have unfair taste and aesthetic qualities due to its slight mineral taste. In the US, Ca content in drinking water is dependent on geological variations and sources and commonly occurs as minerals in the US water reservoirs. Areas or regions with limestone and chalk abundances including Midwest, Southeast, and Rocky Mountain regions contain higher Ca levels in water compared to the others due to naturally occurring Ca-rich minerals. Public water systems in the US are regulated by USEPA under Safe Drinking Water Act (SDWA) which establishes MCL for contaminants in drinking water. For, Ca, no MCL has been established by EPA considering its beneficial role to humans and lacking evidence of health implications associated with drinking water Ca exposure to humans. However, Ca levels are generally assessed by measuring total dissolved solids (TDS) levels for which, EPA has set MCL of 500 mg/L. If consumers face any concerns related to high Ca levels in their drinking water, they are advised to contact a local drinking water facility in the state to get their water tested and if found high, suitable treatment strategies must be adopted to ensure clean drinking water supply to the US residents.
Furthermore, the regulations and guidelines for contaminants in drinking water including Ca may vary among individual states in the US. Despite its beneficial role in human health, high intake of Ca may results in various health problems notably hypercalcemia in which blood gets saturated with Ca above the normal range of 8.5-10.5 mg/dL causing symptoms such as vomiting, constipation, excessive thirst, frequent urination, and muscles weakness, etc. Among other Ca-associated health problems include kidney stones, mineral imbalance in the body, bone health, cardiovascular issues, etc. Furthermore, high Ca levels in the blood can also interact with other medications and minerals therefore it is advisable to take any Ca supplements after consultation with the healthcare professionals. It is worth noting that epidemiological evidence has been reported in the US demonstrating the health impacts associated with Ca intake among individuals consuming Ca-rich drinking water. Systematic monitoring in this context can provide a clear picture of adverse health outcomes linked to Ca exposure.
Various cellular and molecular mechanisms have been proposed to address Ca toxicity. Among these include Ca signaling dysregulation due to excessive Ca influx that may result in disruption of normal cellular signaling pathways ultimately altering the gene expression, cell proliferation, and cellular death (Song et al. 2019), mitochondrial dysfunction resulting in impaired energy production and oxidative stress (Kawamata and Manfredi 2010; Pivovarova and Andrews 2010), inhibition in enzymatic activities effecting in cellular metabolism, protein synthesis and DNA repair processes (Bentle et al. 2006), cell membrane damage, neuronal damage and cell death (Farber 1981; 1990). Furthermore, prolonged Ca intake can also lead to altered pathways associated with inflammation and tissue damage (Dominguez-Gutierrez et al. 2018).
However, these mechanisms associated with Ca toxicity are complex and the outcome is dependent on the cell type, exposure duration, concentration, and individual susceptibility. In-vitro evidence suggests excessive Ca levels are associated with the generation of reactive oxygen species (ROS) resulting in oxidative stress (McElnea et al. 2011; Quintanar-Escorza et al. 2010). Moreover, Ca has also been associated with altered gene expression (Mizuno and Banzai 2008; Nakade et al. 2001). However, it is worth mentioning that most of the molecular and cellular evidence associated with Ca exposure are based on water testing laboratory findings and there is data scarcity in the context of epidemiological evidence demonstrating drinking water exposure to Ca and its associated human health implications. This suggests the need for further research in this context to address a detailed overview of Ca toxicity among exposed humans consuming elevated Ca-containing drinking water.
Metabolism of Ca in the body involves various biological processes including its intestinal absorption which is dependent on vitamin D and passive cellular diffusion causing an increase in Ca-binding proteins (Bronner 2003; Hallberg et al. 1992). This is followed by the distribution of absorbed Ca throughout the body and regulated by various hormones (Guerreiro et al. 2007). In this context, parathyroid hormone (PTH) plays a key role in maintaining Ca balance throughout the body (Abrams et al. 2005). The excretion of Ca through the body is regulated by kidneys by removing excess Ca in body mainly aided by PTH and calcitrol (Winer et al. 2010), hence maintaining the overall Ca-associated homeostasis.
Detection Methods and Removal Strategies
Several methods for determining Ca levels in drinking water have been suggested which can be adopted based on their availability, affordability, sensitivity, and desired detection limits. Among the most commonly applied Ca quantification methods include highly sensitive and precise Inductively Coupled plasma (ICP) linked to various detectors mainly optical emission spectroscopy (ICP-OES) and mass spectrometry (ICP-MS) (Mitko and Bebek 2000; Quarles Jr et al. 2020). The method is capable of detecting Ca levels in drinking water at very low levels i.e. µg-ng/L. However, the method has a high operating cost and is recommended where the desired results are at very low levels.
Among other methods of Ca quantification involve atomic absorption spectrometry (AAS) in which Ca measurement is done by absorbing light by Ca atoms in a water sample after being atomized and exposed to a specific light wavelength resulting in quantitative assessment of Ca by calculating the amount of absorbed light proportional to Ca levels in drinking water (Araújo et al. 1998; Uždavinienė and Tautkus 2007). Titration can also be used to detect Ca levels in drinking water however, this method provides an estimate of Ca ions present in a water sample. Moreover, ion-selective electrodes (ISE) (Maj-Zurawska et al. 1989), and colorimetry are also used for Ca estimation in water (Lopez-Molinero et al. 2013). Specific strips/kits have been developed that are capable of providing a rapid, qualitative, or quantitative estimation of Ca in drinking water. However, these strips also provide an estimated overview of Ca levels.
For accurate detection, the recommended methods included ICP or AAS-based analysis for Ca quantification. Hard water with high Ca levels may be subjected to different treatment methods based on their availability and cost-effectiveness. Among widely used methods to remove Ca from drinking water include the ion exchange method which involves the use of resin beads that facilitate the exchange of Ca ions with Na or K ions (Hailu et al. 2019). Reverse osmosis (RO) is the most widely used removal strategy capable of removing various environmental chemicals from drinking water including Ca. The method involves the use of a semi-permeable membrane through which water is forced to pass resulting in capturing of impurities in the water (Ketharani et al. 2022; Zhao et al. 2014). Lime softening is also a cheap and widely used method that utilizes calcium hydroxide (CaOH) to precipitate Ca and Mg ions(Ghernaout et al. 2018). Other Ca removal methods from drinking water include electrochemical precipitation, distillation, and the use of specific sequestering agents such as polyphosphates or citric acid.
Public Perspective
Following frequently asked questions (FAQs) try to address some general public concerns in the US, especially the NYC and NJ region.
Hard water is not a health hazard and generally contributes a small amount toward the total Ca and Mg needed in the human diet
Hard water can appear cloudy if the solubility of mineral salts is exceeded. Furthermore, if the Ca concentration surpasses 100 ppm, the water will taste unfair. Neither of these presents a risk, but consumers prefer a “clean” appearance and taste.
Ca and Mg contribute to the total hardness of your water. Normally, Ca ranges from 1-400 mg/L and Mg ranges from 1-600 mg/L in private well water.
Ca is an important determinant of water hardness, and it also functions as a pH stabilizer, because of its buffering qualities. Ca also gives water a better taste to drinking under normal levels.
Boiling water is certainly one of the most effective ways to soften it. The boiling will have the effect of draining the hard water minerals to the bottom, like Ca and Mg.
Long-term consumption of hard water can cause kidney dysfunction, which may lead to other diseases such as cerebrovascular disease, diabetes, and others.
The chemical treatment uses Sodium Carbonate for water Ca and limestone removal from water. The principle of the chemical treatment is that the carbonate and Ca ions will bond to form insoluble precipitates, which will be forced out of the water and slowly soften it.
Vinegar is very effective in dissolving the Ca, Mg, and other mineral deposits of hard water. The added advantage is that it kills bacteria, mold, and other germs. Using vinegar as a softener for hard water is a simple hack to treat hard water at home.
The most common way to treat hard water is with a water softener. This consists of a water filtration system that filters out the hard water minerals in your water. As the water travels into the filter, it passes through a bed of resin that traps the Ca and Mg, which are then replaced with Na ions.
RO Systems can remove various commonly occurring chemical contaminants (metal ions, aqueous salts), including sodium, chloride, copper, chromium, and lead. It may also reduce arsenic, fluoride, radium, sulfate, calcium, magnesium, potassium, nitrate, and phosphorous.
Common signs of hard water are Dry and itchy skin, Dull and filmy hair after showering, Soap that won’t lather, dull laundry, and Mineral deposits on faucets and fixtures.
Conclusion
Ca is a widely occurring natural mineral in the environment and has broad industrial and manufacturing applications. The mineral gets enriched in drinking water through various natural and anthropogenic sources. It has high significance to human health as it plays a vital role in many biological processes. The reported levels of Ca in drinking water are usually safe and are not reported as a public health concern however, high Ca levels can result in water hardness which is linked with an unpleasant taste and aesthetic problems.
However, its excessive intake should be avoided as various health issues have been associated with high Ca intake. Due to its beneficial role to humans, the intake of Ca through drinking water is low and mostly taken as a supplement by humans. Furthermore, no MCL has been set for Ca and its levels are usually based on TDS levels detected in the drinking water. In the US, epidemiological studies focusing on monitoring Ca levels in drinking water should be conducted to give a better understanding of Ca toxicity associated with drinking water exposure.
References
Abrams SA, Griffin IJ, Hawthorne KM, Gunn SK, Gundberg CM, Carpenter TO. 2005. Relationships among vitamin d levels, parathyroid hormone, and calcium absorption in young adolescents. The Journal of Clinical Endocrinology and Metabolism. 90(10):5576-5581.
Araújo AN, Costa RC, Lima JL, Reis BF. 1998. Sequential injection system in flame atomic absorption spectrometry for the determination of calcium and magnesium in mineral waters. Analytica chimica acta. 358(2):111-119.
Bentle MS, Reinicke KE, Bey EA, Spitz DR, Boothman DA. 2006. Calcium-dependent modulation of poly (adp-ribose) polymerase-1 alters cellular metabolism and DNA repair. Journal of Biological Chemistry. 281(44):33684-33696.
Bronner F. 2003. Mechanisms of intestinal calcium absorption. Journal of cellular biochemistry. 88(2):387-393.
Dominguez-Gutierrez PR, Kusmartsev S, Canales BK, Khan SR. 2018. Calcium oxalate differentiates human monocytes into inflammatory m1 macrophages. Frontiers in Immunology. 9:1863.
Farber JL. 1981. The role of calcium in cell death. Life sciences. 29(13):1289-1295.
Farber JL. 1990. The role of calcium ions in toxic cell injury. Environmental health perspectives. 84:107-111.
Ghernaout D, Simoussa A, Alghamdi A, Ghernaout B, Elboughdiri N, Mahjoubi A, Aichouni M, El-Wakil AE-A. 2018. Combining lime softening with alum coagulation for hard ghrib dam water conventional treatment. International Journal of Advanced and Applied Sciences. 5(5):61-70.
Guerreiro PM, Renfro JL, Power DM, Canario AV. 2007. The parathyroid hormone family of peptides: Structure, tissue distribution, regulation, and potential functional roles in calcium and phosphate balance in fish. American Journal of Physiology-Regulatory, Integrative and Comparative Physiology. 292(2):R679-R696.
Hailu Y, Tilahun E, Brhane A, Resky H, Sahu O. 2019. Ion exchanges process for calcium, magnesium and total hardness from ground water with natural zeolite. Groundwater for Sustainable Development. 8:457-467.
Hallberg L, Rossander-Hulten L, Brune M, Gleerup A. 1992. Calcium and iron absorption: Mechanism of action and nutritional importance. European Journal of Clinical Nutrition. 46(5):317-327.
Kawamata H, Manfredi G. 2010. Mitochondrial dysfunction and intracellular calcium dysregulation in als. Mechanisms of ageing and development. 131(7-8):517-526.
Ketharani J, Hansima M, Indika S, Samarajeewa D, Makehelwala M, Jinadasa K, Weragoda S, Rathnayake R, Nanayakkara K, Wei Y. 2022. A comparative study of community reverse osmosis and nanofiltration systems for total hardness removal in groundwater. Groundwater for Sustainable Development. 18:100800.
Lopez-Molinero A, Cubero VT, Irigoyen RD, Piazuelo DS. 2013. Feasibility of digital image colorimetry—application for water calcium hardness determination. Talanta. 103:236-244.
Maj-Zurawska M, Rouilly M, Morf WE, Simon W. 1989. Determination of magnesium and calcium in water with ion-selective electrodes. Analytica chimica acta. 218:47-59.
McElnea E, Quill B, Docherty N, Irnaten M, Siah W, Clark A, O’Brien C, Wallace D. 2011. Oxidative stress, mitochondrial dysfunction and calcium overload in human lamina cribrosa cells from glaucoma donors. Molecular vision. 17:1182.
Mitko K, Bebek M. 2000. Determination of major elements in saline water samples using a dual-view icp-oes. ATOMIC SPECTROSCOPY-NORWALK CONNECTICUT-. 21(3):77-85.
Mizuno M, Banzai Y. 2008. Calcium ion release from calcium hydroxide stimulated fibronectin gene expression in dental pulp cells and the differentiation of dental pulp cells to mineralized tissue forming cells by fibronectin. International Endodontic Journal. 41(11):933-938.
Nakade O, Takahashi K, Takuma T, Aoki T, Kaku TJ. 2001. Effect of extracellular calcium on the gene expression of bone morphogenetic protein-2 and-4 of normal human bone cells. Journal of bone mineral metabolism. 19:13-19.
Pivovarova NB, Andrews SB. 2010. Calcium‐dependent mitochondrial function and dysfunction in neurons. The FEBS journal. 277(18):3622-3636.
Quarles Jr CD, Toms AD, Smith Jr R, Sullivan P, Bass D, Leone J. 2020. Automated icp-ms method to measure bromine, chlorine, and iodine species and total metals content in drinking water. Talanta Open. 1:100002.
Quintanar-Escorza M, González-Martínez M, del Pilar I-OM, Calderón-Salinas J. 2010. Oxidative damage increases intracellular free calcium [ca2+] i concentration in human erythrocytes incubated with lead. Toxicology in Vitro. 24(5):1338-1346.
Song Z, Wang Y, Zhang F, Yao F, Sun C. 2019. Calcium signaling pathways: Key pathways in the regulation of obesity. International Journal of Molecular Sciences. 20(11):2768.
Uždavinienė D, Tautkus S. 2007. Determination of calcium in mineral waters by flame atomic absorption spectrometry. Chemija. 18(4).
Winer KK, Sinaii N, Reynolds J, Peterson D, Dowdy K, Cutler Jr GB. 2010. Long-term treatment of 12 children with chronic hypoparathyroidism: A randomized trial comparing synthetic human parathyroid hormone 1-34 versus calcitriol and calcium. The Journal of Clinical Endocrinology and Metabolism. 95(6):2680-2688.
Zhao S, Huang G, Cheng G, Wang Y, Fu H. 2014. Hardness, cod and turbidity removals from produced water by electrocoagulation pretreatment prior to reverse osmosis membranes. Desalination. 344:454-462.
- 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.
Share this research on social media
OTHER RESEARCH ON WATER CONTAMINANTS BY DR. YASIR
