Preliminary Studies On The Capacity Of Some Microorganisms: Fill & Download for Free

Yes it can be and this is true for most microbes and pathogens. If a given microorganism can be dispersed into air in an aerosol form, it can be distributed through the HVAC system. Some preliminary study says this particular virus can stay in aerosol form in air for nearly 3 hours. So, there is a definite possibility of transmission through the vent system. Most typical installations of HVAC do not carry filtration capability to deal with fine aerosols. Also, most of them do not have UV light based anti virus measures. So, there is not much a typical HVAC system can do against the virus. Except for ventilation of course. If your system has the capacity, you can reduce or eliminate recirculation and run the system entirely on single pass - air comes from outdoors, cools or warms indoors and is then exhausted - there by reducing viral concentrations indoors and reducing chances of infection

The biggest river in Africa and the longest is the NILE.This Nile river is critical for Egypt and slightly less critical for Sudan.Ethiopia - has a population of 109 million, compared to Egypt 101 million and Sudan 46 million. In Egypt it rains infrequently, unlike Ethiopia where rain is fairly common.So, the NILE river is now been dammed -in Ethiopia {to produce electricity} and over about 20–30 years the quantity and level of the NILE will be reduced by about 18–25%.Thus, Egypt has a good reason to worry.This issue is a very acute and also a political sore-spot between Egypt and Ethiopia.Water, Egyptian national pride and the economy of Egypt are all on the agenda.1… The NILE:- The Nile is a major north-flowing river in northeastern Africa, and is the longest river in Africa; about 6,650 km long. It is an "international" river as its drainage basin covers 11 countries: Tanzania, Uganda, Rwanda, Burundi, the Democratic Republic of the Congo, Kenya, Ethiopia, Eritrea, South Sudan, Republic of the Sudan, and Egypt.2… In particular, the Nile is the primary water source of Egypt and Sudan.3… The Nile has 2 major tributaries – the White Nile and the Blue Nile.The White Nile is considered to be the headwaters and primary stream of the Nile itself.The Blue Nile, however, is the source of most of the water & silt.The White Nile is longer and rises in the Great Lakes region of central Africa, with the most distant source located in both Rwanda or Burundi. It flows north through Tanzania, Lake Victoria, Uganda and South Sudan.4… The Blue Nile begins at Lake Tana in Ethiopia, and flows into Sudan from the southeast. The 2 rivers meet just north of the Sudanese capital of Khartoum.5… Problems:- Water sharing disputes. {Two very strong countries (E&E), are in conflict over water and pride.}The Nile's water has affected the politics of East Africa and the Horn of Africa for many decades.Countries including Uganda, Sudan, Ethiopia and Kenya have complained about Egyptian domination of its water resources. The new and political/co-operative *Nile Basin Initiative* promotes a peaceful cooperation among those states.6… Several attempts have been made to establish agreements between the countries sharing the Nile waters. On 14 May 2010 at Entebbe, Ethiopia, Rwanda, Tanzania and Uganda signed a new agreement on sharing the Nile water even though this agreement raised strong opposition from Egypt and Sudan.Ideally, such international agreements should promote equitable and efficient usage of the Nile basin's water resources. Without a better understanding about the availability of the future water resources of the Nile, it is likely that conflicts will arise between these countries relying on the Nile for their water supply, economic and social developments.{The problem is two fold- there is not enough water in the Nile to make every regional country happy, and increased populations, several growing economies and a higher standard of living of all the regional countries means that sharing what is “less” can never be ‘peaceful”.Africa has a long history of regional wars.7… Pollution and acidification of the Nile:- Data on concentrations of toxic substances and their impact on aquatic organisms and water quality is now readily available. But most information deals with Egypt; few studies have been done in Sudan, Ethiopia and Tanzania.Egypt is the most populous, agricultural and industrial country in the geographic Nile basin. Therefore, most of the sewage released to the river takes place in Lower Egypt. Lakes in northern Egypt are affected by drainage of phosphate-polluted water and this affects the diversity of their fish, phytoplank-ton and other microorganisms.Most Nile pollutants are derived from sources such as industrial wastewater, oil pollution, municipal wastewater, agricultural drainage, and this included artificial and natural cyano-toxins.In order to monitor pollutants, tests are conducted by the Egyptian ministries very frequently.The Nile river is more acid today, than it was 30 years ago. {In theory the Nile should be slightly alkaline- but it is been acidified slowly over the last few years, -this changes the ability of Nile fish and micro-organisms to survive in these waters.}**** The science! … The Nile River is the valued natural and exclusive source of fresh water in Egypt, where the drinking water supply is limited to the river - rain is not a relevant factor! The water quality of 24 sites between Aswan and Cairo along the Nile have been constantly investigated. This is critical to evaluate the suitability of water for aquatic life and drinking purposes. The water quality variations were mainly related to inorganic nutrients, phosphates and heavy metals, and those sites affected by the intensive load of urban, agricultural and industrial waste-water. All the indexes have and do show a serious deterioration of water quality compared with other sites. These results impact human, animal and fish life and are associated with higher health risks, where, most of the studied metals often exceeded the drinking water and aquatic life limits. The various scientific aquatic indices indicate that the Nile water quality has deteriorated and extended from poor to marginal-dangerous quality.The drinking water quality varies from marginal to unacceptable.Accordingly, the river has become unfit for aquatic life and the situation is getting worse by decreases in the water quantity from the Nile to Egypt by the building of the Ethiopian Renaissance Dam, where the dilution strength of the Nile system will reduced.8… The Grand Ethiopian Renaissance Dam.… is a major gravity dam on the Blue Nile in Ethiopia that has been under construction since 2011. It is in the Benishangul-Gumuz Region about 15 km east of the border with Sudan.It will be the largest hydroelectric power plant in Africa when completed, as well as the 7th largest in the world. It is 60% complete.Once completed, the reservoir could take up-to 15 years to fill with water, depending on hydrologic and weather conditions {rain} during the filling period and agreements reached between Ethiopia, Sudan and Egypt.9… Impact on EgyptThe precise impact of this dam on the downstream countries is still relatively unknown. After years of scientific investigation by international experts, Egypt fears a temporary [over several years- even a full generation ] reduction of water availability due to the filling of the dam and a permanent reduction because of evaporation from the reservoir. Some studies indicate that the primary factors which will govern the impacts during the reservoir filling phase include the initial reservoir elevation of the Aswan High Dam, the rainfall that occurs during the filling period and the negotiated arrangement between the 3 countries - Ethiopia, Sudan & Egypt.These studies also show that only through close and continuous co-ordination, the risks can possibly be minimized. {It is obvious that the risks and dangers to the Egyptian population are there, but with some co-ordination on political, scientific and logical conclusions, some of these risks can be reduced.}9.2… The reservoir volume (74 billion cubic meters) is about 1.5 times the average annual flow of the Blue Nile at the Sudanese-Egyptian border. This loss to downstream countries could be spread over several years if these countries reach an agreement. Depending on the initial storage in the Aswan High Dam and the filling schedule of this massive dam, flows into Egypt could be temporarily reduced, which may affect the income of 2 million farmers during the period of filling the reservoir. It may also "affect Egypt's electricity supply by 30- 40%, while the dam is being built".9.3… This Grand Ethiopian Renaissance Dam could also lead to a permanent lowering of the water level in Lake Nasser if floods are stored instead in Ethiopia. This would reduce the current evaporation of more than 10 billion cubic meters/yr, but it would also reduce the ability of the Aswan High Dam to produce hydro-power to the tune of a 100 MW loss of generating capacity for a 3 meter reduction of the water level. However, the increased storage in Ethiopia can provide a greater buffer to shortages in Sudan and Egypt during years of future drought, if these countries can reach a compromise.9.4… The dam will retain silt. It will thus increase the useful lifetime of the 3 dams in Sudan, and of the Aswan High Dam in Egypt. The beneficial and harmful effects of flood control would/could affect the Ethiopian part of the Blue Nile valley downstream of the dam and into Egypt. This issue has not been studied.10… Reactions: cooperation and condemnation.Egypt -after several studies by experts- has serious concerns about the project so that it requested to be granted inspection allowance on the design and the studies of the dam, in order to allay its fears, but Ethiopia has denied the request unless Egypt relinquishes its veto on water allocation.10.2… An international Nile treaty signed by the upper Nile states in 2010, - the Cooperative Framework Agreement, - has not been signed by either Egypt or Sudan, as they claim it violates the 1959 treaty which gives Sudan and Egypt exclusive rights to the Nile's waters.10.3… Egypt, Ethiopia and Sudan have established an International Panel of Experts to review and assess the study reports of the dam. The panel consists of 10 members; 6 from the 3 countries, and 4 international in the fields of water resources and hydrologic modelling, dam engineering, socioeconomic, and environmental.10.4… The panel submitted its preliminary report to the respective governments at the end of May 2013. Although the full report has not been made public, and will not be until it is reviewed by the governments of Egypt & Ethiopia.According - as publically acknowledged by the Egyptian government, - however, this report "recommended changing and amending the dimensions and the size of the dam". {Thus Egypt thinks, -less dam, more water for Egypt!}10.5… On 3 June 2013 while discussing the International Panel of Experts report with President Mohammad Morsi, Egyptian political leaders suggested methods to destroy the dam, including support for anti-government rebels.The next day- the Egyptian government denied that this was true.10.6… However, on 10 June 2013, he said that "all options are open" because "Egypt's water security cannot be violated at all," clarifying that he was "not calling for war," but that he would not allow Egypt's water supply to be endangered.10.7… In January 2014, Egypt left negotiations over the dam, citing Ethiopian intransigence.11… Ethiopia countered that Egypt had set an immediate halt on construction and an increase of its share to 90% as the preconditions, which were deemed wholly unreasonable. Egypt has since launched a diplomatic offensive to undermine support for the dam, sending its Foreign Minister, Nabil Fahmi to Tanzania and the Democratic Republic of the Congo to garner support.Egyptian media outlets declared the visits productive and that the leaders of those nations had expressed "understanding" and "support" of Egypt's position.Foreign Minister Fahmi and Water Resources Minister Muhammad Abdul Muttalib planned visits to Italy and Norway to express their concerns and try to compel them to pull their support for this dam.12… In April 2014 Ethiopia's PM invited Egypt and Sudan to another round of talks over the dam and Nabil Fahmi stated in May 2014 that Egypt was still open to negotiations.13… Following an August 2014 Tripartite Ministerial-level meeting, the 3 nations agreed to set up a Tripartite National Committee (TNC) meeting over the dam. The first TNC meeting occurred from 20 to 22 September 2014 in Ethiopia.14… The path to war…This acute dispute over the waters of the Nile River, specifically, Ethiopia’s plans to build her Dam on the river’s Blue Nile tributary - is waving a red-flag at Egypt. Egypt considers the dam to be a serious threat to its very survival.Ethiopia, on the other hand, sees the undertaking as essential for its development and has vowed to continue the project no matter what the ramifications.Ethiopia and Egypt are 2 of Africa’s most populous and powerful countries; any ongoing showdown between them is a major threat to peace, which is why the international community is slowly getting involved.15… Now >2019:- Both countries have expressed their preference for a negotiated long-term settlement for the dispute, but the road there has not been smooth. A round of negotiations in early October—following many others over the last few years—failed to reach a compromise.Egypt accuses Ethiopia of dismissing concerns its officials have raised about the threat to its water security. Ethiopia insists that pending issues can be resolved before the completion of the dam.15.2… 2019: Meanwhile, 2 other countries—Russia and the United States—have been looking for ways to mediate the dispute. Abiy and Egyptian President Abdel Fattah al-Sisi held a meeting on the sidelines of the Russia-Africa Summit in Sochi, Russia, in late October. And during which they merely agreed to allow a technical committee to continue its work. Their host, Russian President Vladimir Putin, pledged to help them reach an accommodation. The US has invited Egypt, Ethiopia, and Sudan, which is also affected by the dispute, for discussions in Washington. The 3 settled on a trilateral meeting on Nov. 6, which was also attended by U.S. Treasury Secretary Steven Mnuchin and World Bank President David Malpass. The 3 countries’ FMs agreed on holding 4 technical meetings on the dam. They’ve noted that they hope to reach agreement by Jan. 15, 2020 - but, failing that, the countries’ water ministers will refer the issue to their heads of state to seek further outside mediation.It is hard to know if Washington’s intervention will help reach an agreement before the new deadline, making genuine U.S. assistance pivotal in the endeavor.16… Two agreements, from 1929 and 1959, have guided the use of the Nile River north of Ethiopia thus far. The 1929 Anglo-Egyptian Treaty was signed by the UK, the colonial power in much of East Africa at the time, and monarchical Egypt—which was under British occupation—to allocate water rights along the basin. According to this treaty, Egypt and Sudan were guaranteed an annual supply of 48 billion and 4 billion cubic meters, respectively, out of an estimated yearly yield of 84 billion cubic meters of Nile water.Another agreement in 1959 between the United Kingdom and independent Egypt increased Egypt’s share to 55.5 billion cubic meters and Sudan’s to 18.5 billion cubic meters, with the rest shared by the other countries along the river. The new treaty also reaffirmed an essential provision from the 1929 agreement: Egypt had the right to veto any construction projects that could impede the flow of water into the Nile.Thus that these 2 agreements planted the seeds of today’s dispute is a foregone conclusion. Those negotiating them should have realized that Ethiopia—indeed, all states along the river other than Egypt and Sudan—would have trouble abiding by the terms and also sustaining their populations. Indeed recent Nile Basin Initiative population projects for 2050 put Egypt’s and Sudan’s populations well below those in some of the 8 other countries in the initiative, making the old water agreements appear less fair every day.17… And so, it should have come as no surprise when, in 2011, Ethiopia announced plans to build a large, $5 billion hydroelectric dam on the Blue Nile near the Ethiopia-Sudan border. This new dam will take at least 10 years to fill, which will decrease the river’s flow for at least that period by 25 %. For Ethiopia, the dam is an utmost necessity for its water needs and economic development, as it is set to supply the country with more than 6,000 megawatts of electricity, essential for the country’s agricultural and industrial development. But it would be devastating for Egypt, which relies on the river for irrigation, fishing, and transport.18… 2019:- Egypt has proposed in the latest negotiations that it be guaranteed at least 40 billion cubic meters of water annually and that Ethiopia take a longer time to fill its reservoir. But Cairo’s leverage is limited, and so Ethiopia has offered just 31 billion cubic meters, which is only slightly more than half the quantity the 1959 agreement had guaranteed. Such an offer does not even begin to address Egypt’s needs, let alone satisfy its national pride as one of the African continent’s most historically consequential states.19… 2020:- The immediate future:- Talks are stalled over how to deal with the impact of this $5 billion dam that could threaten Egypt- although over the next 3 -6 months, if the local African leaders & 2 or 3 major international countries can sit & talk - a breakthrough may happen... and thus avoid an ugly war……over water.27th January 2020:- Foreign ministers from Egypt, Ethiopia and Sudan gathered in Washington on Tuesday for last-ditch talks on the Renaissance Dam, which have led to bitter recriminations between Cairo and Addis Ababa.(Ethiopia wants the dam to boost its electricity supplies in mostly rural areas and revive the economy. Egypt sees the dam however as an existential threat, because it relies on the Nile for 90 % of its water supply.)The last meeting in mid-January, also mediated by the US, ended with a draft deal on the filling and operation of what would be Africa's largest hydroelectric project.What is at stake now is how to nail down the technical details."This year, after the mediation of the US, we’ve heard the relevant countries talk about applying a new vision of equitable sharing: we have never heard that before," - it was announced at a press conference.In this draft deal, Ethiopia agreed that it would fill the dam in stages during the rainy season. The move was seen as a compromise on its earlier intention to start generating electricity as soon as possible.While, the talks in Washington have made notable progress, they have not yet solved the trickiest question over the Renaissance dam's impact on countries downstream like Egypt and Sudan.Bottom line:- it made work out, or -if not- the Egyptian army may step in and create facts on the ground! …soon.

Pl read this article published by WHO that can answer your question though highly technical but useful referenceHEALTH RISKS FROM DRINKING DEMINERALISED WATER:Frantisek Kozisek National Institute of Public Health Czech Republic ______________________________________________________________________________ I. INTRODUCTION The composition of water varies widely with local geological conditions. Neither groundwater nor surface water has ever been chemically pure H2O, since water contains small amounts of gases, minerals and organic matter of natural origin. The total concentrations of substances dissolved in fresh water considered to be of good quality can be hundreds of mg/L. Thanks to epidemiology and advances in microbiology and chemistry since the 19th century, numerous waterborne disease causative agents have been identified. The knowledge that water may contain some constituents that are undesirable is the point of departure for establishing guidelines and regulations for drinking water quality. Maximum acceptable concentrations of inorganic and organic substances and microorganisms have been established internationally and in many countries to assure the safety of drinking water. The potential effects of totally unmineralised water had not generally been considered, since this water is not found in nature except possibly for rainwater and naturally formed ice. Although rainwater and ice are not used as community drinking water sources in industrialized countries where drinking water regulations were developed, they are used by individuals in some locations. In addition, many natural waters are low in many minerals or soft (low in divalent ions), and hard waters are often artificially softened. Awareness of the importance of minerals and other beneficial constituents in drinking water has existed for thousands years, being mentioned in the Vedas of ancient India. In the book Rig Veda, the properties of good drinking water were described as follows: “Sheetham (cold to touch), Sushihi (clean), Sivam (should have nutritive value, requisite minerals and trace elements), Istham (transparent), Vimalam lahu Shadgunam (its acid base balance should be within normal limits)” (1). That water may contain desirable substances has received less attention in guidelines and regulations, but an increased awareness of the biological value of water has occurred in the past several decades. Artificially-produced demineralised waters, first distilled water and later also deionized or reverse osmosis-treated water, had been used mainly for industrial, technical and laboratory purposes. These technologies became more extensively applied in drinking water treatment in the 1960’s as limited drinking water sources in some coastal and inland arid areas could not meet the increasing water demands resulting from increasing populations, higher living standards, development of industry, and mass tourism. Demineralisation of water was needed where the primary or the only abundant water source available was highly mineralized brackish water or sea water. Drinking water supply was also of concern to ocean-going ships, and spaceships as well. Initially, these water treatment methods were not used elsewhere since they were technically exacting and costly. 149 In this chapter, demineralised water is defined as water almost or completely free of dissolved minerals as a result of distillation, deionization, membrane filtration (reverse osmosis or nanofiltration), electrodialysis or other technology. The total dissolved solids (TDS) in such water can vary but TDS could be as low as 1 mg/L. The electrical conductivity is generally less than 2 mS/m and may even be lower (<0.1 mS/m). Although the technology had its beginnings in the 1960’s, demineralization was not widely used at that time. However, some countries focused on public health research in this field, mainly the former USSR where desalination was introduced to produce drinking water in some Central Asian cities. It was clear from the very beginning that desalinated or demineralised water without further enrichment with some minerals might not be fully appropriate for consumption. There were three reasons for this: • Demineralised water is highly aggressive and if untreated, its distribution through pipes and storage tanks would not be possible. The aggressive water attacks the water distribution piping and leaches metals and other materials from the pipes and associated plumbing materials. • Distilled water has poor taste characteristics. • Preliminary evidence was available that some substances present in water could have beneficial effects on human health as well as adverse effects. For example, experience with artificially fluoridated water showed a decrease in the incidence of tooth caries, and some epidemiological studies in the 1960’s reported lower morbidity and mortality from some cardiovascular diseases in areas with hard water. Therefore, researchers focused on two issues: 1.) what are the possible adverse health effects of demineralised water, and 2.) what are the minimum and the desirable or optimum contents of the relevant substances (e.g., minerals) in drinking water needed to meet both technical and health considerations. The traditional regulatory approach, which was previously based on limiting the health risks from excessive concentrations of toxic substances in water, now took into account possible adverse effects due to the deficiency of certain constituents. At one of the working meetings for preparation of guidelines for drinking water quality, the World Health Organization (WHO) considered the issue of the desired or optimum mineral composition of desalinated drinking water by focusing on the possible adverse health effects of removing some substances that are naturally present in drinking water (2). In the late 1970’s, the WHO also commissioned a study to provide background information for issuing guidelines for desalinated water. That study was conducted by a team of researchers of the A.N. Sysin Institute of General and Public Hygiene and USSR Academy of Medical Sciences under the direction of Professor Sidorenko and Dr. Rakhmanin. The final report, published in 1980 as an internal working document (3), concluded that “not only does completely demineralised water (distillate) have unsatisfactory organoleptic properities, but it also has a definite adverse influence on the animal and human organism”. After evaluating the available health, organoleptic, and other information, the team recommended that demineralised water contain 1.) a minimum level for dissolved salts (100 mg/L), bicarbonate ion (30 mg/L), and calcium (30 mg/L); 2.) an optimum level for total dissolved salts (250-500 mg/L for chloride-sulfate water and 250-500 mg/L for bicarbonate water); 3.) a maximum level for alkalinity (6.5 meq/l), sodium (200 mg/L), boron (0.5 mg/L), and bromine (0.01 mg/L). Some of these recommendations are discussed in greater detail in this chapter. During the last three decades, desalination has become a widely practiced technique in providing new fresh water supplies. There are more than 11 thousand desalination plants all over the world with an overall production of more than 6 billion gallons of desalinated water per day (Cotruvo, in this book). In some regions such as the Middle East and Western Asia more than half 150 of the drinking water is produced in this way. Desalinated waters are commonly further treated by adding chemical constituents such as calcium carbonate or limestone, or blended with small volumes of more mineral-rich waters to improve their taste and reduce their aggressiveness to the distribution network as well as plumbing materials. However, desalinated waters may vary widely in composition, especially in terms of the minimum TDS content. Numerous facilities were developed without compliance with any uniform guidelines regarding minimum mineral content for final product quality. The potential for adverse health effects from long term consumption of demineralised water is of interest not only in countries lacking adequate fresh water, but also in countries where some types of home water treatment systems are widely used or where some types of bottled water are consumed. Some natural mineral waters, in particular glacial mineral waters, are low in TDS (less than 50 mg/l) and in some countries, even distilled bottled water has been supplied for drinking purposes. Otherbrands of bottled water are produced by demineralising fresh water and then adding minerals for desirable taste. Persons consuming certain types of water may not be receiving the additional minerals that would be present in more highly mineralized waters. Consequently, the exposures and risks should be considered not only at the community level, but also at the individual or family level. II. HEALTH RISKS FROM CONSUMPTION OF DEMINERALISED OR LOW-MINERAL WATER Knowledge of some effects of consumption of demineralised water is based on experimental and observational data. Experiments have been conducted in laboratory animals and human volunteers, and observational data have been obtained from populations supplied with desalinated water, individuals drinking reverse osmosis-treated demineralised water, and infants given beverages prepared with distilled water. Because limited information is available from these studies, we should also consider the results of epidemiological studies where health effects were compared for populations using low-mineral (soft) water and more mineral-rich waters. Demineralised water that has not been remineralised is considered an extreme case of low-mineral or soft water because it contains only small amounts of dissolved minerals such as calcium and magnesium that are the major contributors to hardness. The possible adverse consequences of low mineral content water consumption are discussed in the following categories: • Direct effects on the intestinal mucous membrane, metabolism and mineral homeostasis or other body functions. • Little or no intake of calcium and magnesium from low-mineral water. • Low intake of other essential elements and microelements. • Loss of calcium, magnesium and other essential elements in prepared food. • Possible increased dietary intake of toxic metals. 1. Direct effects of low mineral content water on the intestinal mucous membrane, metabolism and mineral homeostasis or other body functions Distilled and low mineral content water (TDS < 50 mg/L) can have negative taste characteristics to which the consumer may adapt with time. This water is also reported to be less thirst quenching (3). Although these are not considered to be health effects, they should be taken into account when considering the suitability of low mineral content water for human 151 consumption. Poor organoleptic and thirst-quenching characteristics may affect the amount of water consumed or cause persons to seek other, possibly less satisfactory water sources. Williams (4) reported that distilled water introduced into the intestine caused abnormal changes in epithelial cells of rats, possibly due to osmotic shock. However, the same conclusions were not reached by Schumann et al. (5) in a more recent study based on 14-day experiments in rats. Histology did not reveal any signs of erosion, ulceration or inflammation in the oesophagus, stomach and jejunum. Altered secretory function in animals (i.e., increased secretion and acidity of gastric juice) and altered stomach muscle tone were reported in studies for WHO (3), but currently available data have not unambiguously demonstrated a direct negative effect of low mineral content water on the gastrointestinal mucous membrane. It has been adequately demonstrated that consuming water of low mineral content has a negative effect on homeostasis mechanisms, compromising the mineral and water metabolism in the body. An increase in urine output (i.e., increased diuresis) is associated with an increase in excretion of major intra- and extracellular ions from the body fluids, their negative balance, and changes in body water levels and functional activity of some body water management-dependent hormones.Experiments in animals, primarily rats, for up to one-year periods have repeatedly shown that the intake of distilled water or water with TDS ≤ 75 mg/L leads to: 1.) increased water intake, diuresis, extracellular fluid volume, and serum concentrations of sodium (Na) and chloride (Cl) ions and their increased elimination from the body, resulting in an overall negative balance.., and 2.) lower volumes of red cells and some other hematocrit changes (3). Although Rakhmanin et al. (6) did not find mutagenic or gonadotoxic effects of distilled water, they did report decreased secretion of tri-iodothyronine and aldosterone, increased secretion of cortisol, morphological changes in the kidneys including a more pronounced atrophy of glomeruli, and swollen vascular endothelium limiting the blood flow. Reduced skeletal ossification was also found in rat foetuses whose dams were given distilled water in a one-year study. Apparently the reduced mineral intake from water was not compensated by their diets, even if the animals were kept on standardized diet that was physiologically adequate in caloric value, nutrients and salt composition. Results of experiments in human volunteers evaluated by researchers for the WHO report (3) are in agreement with those in animal experiments and suggest the basic mechanism of the effects of water low in TDS (e.g. < 100 mg/L) on water and mineral homeostasis. Low-mineral water markedly: 1.) increased diuresis (almost by 20%, on average), body water volume, and serum sodium concentrations, 2.) decreased serum potassium concentration, and 3.) increased the elimination of sodium, potassium, chloride, calcium and magnesium ions from the body. It was thought that low-mineral water acts on osmoreceptors of the gastrointestinal tract, causing an increased flow of sodium ions into the intestinal lumen and slight reduction in osmotic pressure in the portal venous system with subsequent enhanced release of sodium into the blood as an adaptation response. This osmotic change in the blood plasma results in the redistribution of body water; that is, there is an increase in the total extracellular fluid volume and the transfer of water from erythrocytes and interstitial fluid into the plasma and between intracellular and interstitial fluids. In response to the changed plasma volume, baroreceptors and volume receptors in the bloodstream are activated, inducing a decrease in aldosterone release and thus an increase in sodium elimination. Reactivity of the volume receptors in the vessels may result in a decrease in ADH release and an enhanced diuresis. The German Society for Nutrition reached similar conclusions about the effects of distilled water and warned the public against drinking it (7). The warning was published in response to the German edition of The Shocking Truth About Water (8), whose authors recommended drinking distilled water instead of "ordinary" drinking water. The Society in its position paper (7) explains that water in the human body always contains 152 electrolytes (e.g. potassium and sodium) at certain concentrations controlled by the body. Water resorption by the intestinal epithelium is also enabled by sodium transport. If distilled water is ingested, the intestine has to add electrolytes to this water first, taking them from the body reserves. Since the body never eliminates fluid in form of "pure" water but always together with salts, adequate intake of electrolytes must be ensured. Ingestion of distilled water leads to the dilution of the electrolytes dissolved in the body water. Inadequate body water redistribution between compartments may compromise the function of vital organs. Symptoms at the very beginning of this condition include tiredness, weakness and headache; more severe symptoms are muscular cramps and impaired heart rate. Additional evidence comes from animal experiments and clinical observations in several countries. Animals given zinc or magnesium dosed in their drinking water had a significantly higher concentration of these elements in the serum than animals given the same elements in much higher amounts with food and provided with low-mineral water to drink. Based on the results of experiments and clinical observations of mineral deficiency in patients whose intestinal absorption did not need to be taken into account and who received balanced intravenous nutrition diluted with distilled water, Robbins and Sly (9) presumed that intake of low-mineral water was responsible for an increased elimination of minerals from the body. Regular intake of low-mineral content water could be associated with the progressive evolution of the changes discussed above, possibly without manifestation of symptoms or causal symptoms over the years. Nevertheless, severe acute damage, such as hyponatremic shock or delirium, may occur following intense physical efforts and ingestion of several litres of lowmineral water (10). The so-called "water intoxication" (hyponatremic shock) may also occur with rapid ingestion of excessive amounts not only of low-mineral water but also tap water. The "intoxication" risk increases with decreasing levels of TDS. In the past, acute health problems were reported in mountain climbers who had prepared their beverages with melted snow that was not supplemented with necessary ions. A more severe course of such a condition coupled with brain oedema, convulsions and metabolic acidosis was reported in infants whose drinks had been prepared with distilled or low-mineral bottled water (11). 2. Little or no intake of calcium and magnesium from low-mineral water Calcium and magnesium are both essential elements. Calcium is a substantial component of bones and teeth. In addition, it plays a role in neuromuscular excitability (i.e., decreases it), the proper function of the conducting myocardial system, heart and muscle contractility, intracellular information transmission and the coagulability of blood. Magnesium plays an important role as a cofactor and activator of more than 300 enzymatic reactions including glycolysis, ATP metabolism, transport of elements such as sodium, potassium, and calcium through membranes, synthesis of proteins and nucleic acids, neuromuscular excitability and muscle contraction. Although drinking water is not the major source of our calcium and magnesium intake, the health significance of supplemental intake of these elements from drinking water may outweigh its nutritional contribution expressed as the proportion of the total daily intake of these elements. Even in industrialized countries, diets deficient in terms of the quantity of calcium and magnesium, may not be able to fully compensate for the absence of calcium and, in particular, magnesium, in drinking water. For about 50 years, epidemiological studies in many countries all over the world have reported that soft water (i.e., water low in calcium and magnesium) and water low in magnesium is associated with increased morbidity and mortality from cardiovascular disease (CVD) compared to hard water and water high in magnesium. An overview of epidemiological evidence 153 is provided by recent review articles (12-15) and summarized in other chapters of this monograph (Calderon and Craun, Monarca et al.). Recent studies also suggest that the intake of soft water, i.e. water low in calcium, may be associated with higher risk of fracture in children (16), certain neurodegenerative diseases (17), pre-term birth and low weight at birth (18) and some types of cancer (19, 20). In addition to an increased risk of sudden death (21-23), the intake of water low in magnesium seems to be associated with a higher risk of motor neuronal disease (24), pregnancy disorders (so-called preeclampsia) (25), and some cancers (26-29). Specific knowledge about changes in calcium metabolism in a population supplied with desalinated water (i.e., distilled water filtered through limestone) low in TDS and calcium, was obtained from studies carried out in the Soviet city of Shevchenko (3, 30, 31). The local population showed decreased activity of alkaline phosphatase, reduced plasma concentrations of calcium and phosporus and enhanced decalcification of bone tissue. The changes were most marked in women, especially pregnant women and were dependent on the duration of residence in Shevchenko. The importance of water calcium was also confirmed in a one-year study of rats on a fully adequate diet in terms of nutrients and salts and given desalinated water with added dissolved solids of 400 mg/L and either 5 mg/L, 25 mg/L, or 50 mg/L of calcium (3, 32). The animals given water dosed with 5 mg/L of calcium exhibited a reduction in thyroidal and other associated functions compared to the animals given the two higher doses of calcium. While the effects of most chemicals commonly found in drinking water manifest themselves after long exposure, the effects of calcium and, in particular, those of magnesium on the cardiovascular system are believed to reflect recent exposures. Only a few months exposure may be sufficient consumption time effects from water that is low in magnesium and/or calcium (33). Illustrative of such short-term exposures are cases in the Czech and Slovak populations who began using reverse osmosis-based systems for final treatment of drinking water at their home taps in 2000-2002. Within several weeks or months various complaints suggestive of acute magnesium (and possibly calcium) deficiency were reported (34). The complaints included cardiovascular disorders, tiredness, weakness or muscular cramps and were essentially the same symptoms listed in the warning of the German Society for Nutrition (7). 3. Low intake of some essential elements and microelements from low-mineral water Although drinking water, with some rare exceptions, is not the major source of essential elements for humans, its contribution may be important for several reasons. The modern diet of many people may not be an adequate source of minerals and microelements. In the case of borderline deficiency of a given element, even the relatively low intake of the element with drinking water may play a relevant protective role. This is because the elements are usually present in water as free ions and therefore, are more readily absorbed from water compared to food where they are mostly bound to other substances. Animal studies are also illustrative of the significance of microquantities of some elements present in water. For instance, Kondratyuk (35) reported that a variation in the intake of microelements was associated with up to six-fold differences in their content in muscular tissue. These results were found in a 6-month experiment in which rats were randomized into 4 groups and given: a.) tap water, b.) low-mineral water, c.) low-mineral water supplemented with iodide, cobalt, copper, manganese, molybdenum, zinc and fluoride in tap water, d.) low-mineral water supplemented with the same elements but at ten times higher concentrations. Furthermore, a negative effect on the blood formation process was found to be associated with non-supplemented demineralised water. The mean hemoglobin content of red blood cells was as much as 19% lower in the animals that received non-supplemented demineralised water compared to that in animals 154 given tap water. The haemoglobin differences were even greater when compared with the animals given the mineral supplemented waters. Recent epidemiological studies of an ecologic design among Russian populations supplied with water varying in TDS suggest that low-mineral drinking water may be a risk factor for hypertension and coronary heart disease, gastric and duodenal ulcers, chronic gastritis, goitre, pregnancy complications and several complications in newborns and infants, including jaundice, anemia, fractures and growth disorders (36). However, it is not clear whether the effects observed in these studies are due to the low content of calcium and magnesium or other essential elements, or due to other factors. Lutai (37) conducted a large cohort epidemiological study in the Ust-Ilim region of Russia. The study focused on morbidity and physical development in 7658 adults, 562 children and 1582 pregnant women and their newborns in two areas supplied with water different in TDS. One of these areas was supplied with water lower in minerals (mean values: TDS 134 mg/L, calcium 18.7 mg/L, magnesium 4.9 mg/L, bicarbonates 86.4 mg/L) and the other was supplied with water higher in minerals (mean values: TDS 385 mg/L, calcium 29.5 mg/L, magnesium 8.3 mg/L, bicarbonates 243.7 mg/L). Water levels of sulfate, chloride, sodium, potassium, copper, zinc, manganese and molybdenum were also determined. The populations of the two areas did not differ from each other in eating habits, air quality, social conditions and time of residence in the respective areas. The population of the area supplied with water lower in minerals showed higher incidence rates of goiter, hypertension, ischemic heart disease, gastric and duodenal ulcers, chronic gastritis, cholecystitis and nephritis. Children living in this area exhibited slower physical development and more growth abnormalities, pregnant women suffered more frequently from edema and anemia. Newborns of this area showed higher morbidity. The lowest morbidity was associated with water having calcium levels of 30-90 mg/L, magnesium levels of 17-35 mg/L, and TDS of about 400 mg/L (for bicarbonate containing waters). The author concluded that such water could be considered as physiologically optimum. 4. High loss of calcium, magnesium and other essential elements in food prepared in low-mineral water When used for cooking, soft water was found to cause substantial losses of all essential elements from food (vegetables, meat, cereals). Such losses may reach up to 60 % for magnesium and calcium or even more for some other microelements (e.g., copper 66 %, manganese 70 %, cobalt 86 %). In contrast, when hard water is used for cooking, the loss of these elements is much lower, and in some cases, an even higher calcium content was reported in food as a result of cooking (38-41). Since most nutrients are ingested with food, the use of low-mineral water for cooking and processing food may cause a marked deficiency in total intake of some essential elements that was much higher than expected with the use of such water for drinking only. The current diet of many persons usually does not provide all necessary elements in sufficient quantities, and therefore, any factor that results in the loss of essential elements and nutrients during the processing and preparation of food could be detrimental for them. 5. Possible increased dietary intake of toxic metals Increased risk from toxic metals may be posed by low-mineral water in two ways: 1.) higher leaching of metals from materials in contact with water resulting in an increased metal content in drinking water, and 2.) lower protective (antitoxic) capacity of water low in calcium and magnesium. 155 Low-mineralized water is unstable and therefore, highly aggressive to materials with which it comes into contact. Such water more readily dissolves metals and some organic substances from pipes, coatings, storage tanks and containers, hose lines and fittings, being incapable of forming low-absorbable complexes with some toxic substances and thus reducing their negative effects. Among eight outbreaks of chemical poisoning from drinking water reported in the USA in 1993-1994, there were three cases of lead poisoning in infants who had blood-lead levels of 15 µg/dL, 37 µg/dL, and 42 µg/dL. The level of concern is 10 µg/dL. For all three cases, lead had leached from brass fittings and lead-soldered seams in drinking water storage tanks. The three water systems used low mineral drinking water that had intensified the leaching process (42). First-draw water samples at the kitchen tap had lead levels of 495 to 1050 µg/L for the two infants with the highest blood lead; 66 µg/L was found in water samples collected at the kitchen tap of the third infant (43). Calcium and, to a lesser extent, magnesium in water and food are known to have antitoxic activity. They can help prevent the absorption of some toxic elements such as lead and cadmium from the intestine into the blood, either via direct reaction leading to formation of an unabsorbable compound or via competition for binding sites (44-50). Although this protective effect is limited, it should not be dismissed. Populations supplied with low-mineral water may be at a higher risk in terms of adverse effects from exposure to toxic substances compared to populations supplied with water of average mineralization and hardness. 6. Possible bacterial contamination of low-mineral water All water is prone to bacterial contamination in the absence of a disinfectant residual either at source or as a result of microbial re-growth in the pipe system after treatment. Re-growth may also occur in desalinated water. Bacterial re-growth within the pipe system is encouraged by higher initial temperatures, higher temperatures of water in the distribution system due to hot climates, lack of a residual disinfectant, and possibly greater availability of some nutrients due to the aggressive nature of the water to materials in contact with it. Although an intact desalination membrane should remove all bacteria, it may not be 100 % effective (perhaps due to leaks) as can be documented by an outbreak of typhoid fever caused by reverse osmosis-treated water in Saudi Arabia in 1992 (51). Thus, virtually all waters including desalinated waters are disinfected after treatment. Non pathogenic bacterial re-growth in water treated with different types of home water treatment devices was reported by Geldreich et al. (52) and Payment et al. (53, 54) and many others. The Czech National Institute of Public Health (34) in Prague has tested products intended for contact with drinking water and found, for example, that the pressure tanks of reverse osmosis units are prone to bacterial regrowth, primarily do to removal of residual disinfectant by the treatment. They also contain a rubber bag whose surface appears to be favourable for bacterial growth. III. DESIRABLE MINERAL CONTENT OF DEMINERALISED DRINKING WATER The corrosive nature of demineralised water and potential health risks related to the distribution and consumption of low TDS water has led to recommendations of the minimum and optimum mineral content in drinking water and then, in some countries, to the establishment of obligatory values in the respective legislative or technical regulations for drinking water quality. Organoleptic characteristics and thirst-quenching capacity were also considered in the recommendations. For example, human volunteer studies (3) showed that the water temperatures of 15-350 C best satisfied physiological needs. Water temperatures above 350 or below 150 C 156 resulted in a reduction in water consumption. Water with a TDS of 25-50 mg/L was described tasteless (3). 1. The 1980 WHO report Salts are leached from the body under the influence of drinking water with a low TDS. Because adverse effects such as altered water-salt balance were observed not only in completely desalinated water but also in water with TDS between 50 and 75 mg/L, the team that prepared the 1980 WHO report (3) recommended that the minimum TDS in drinking water should be 100 mg/L. The team also recommended that the optimum TDS should be about 200-400 mg/L for chloride-sulphate waters and 250-500 mg/L for bicarbonate waters (WHO 1980). The recommendations were based on extensive experimental studies conducted in rats, dogs and human volunteers. Water exposures included Moscow tap water, desalinated water of approximately 10 mg/L TDS, and laboratory-prepared water of 50, 100, 250, 300, 500, 750, 1000, and 1500 mg/L TDS using the following constituents and proportions: Cl- (40%), HCO3 (32%), SO4 (28%) / Na (50%), Ca (38%), Mg (12%). A number of health outcomes were investigated including: dynamics of body weight, basal and nitrogen metabolism, enzyme activity, water-salt homeostasis and its regulatory system, mineral content of body tissues and fluids, hematocrit, and ADH activity. The optimal TDS was associated with the lowest incidence of adverse effect, negative changes to the human, dog, or rat, good organoleptic characteristics and thirst-quenching properties, and reduced corrosivity of water. In addition to the TDS levels, the report (3) recommended that the minimum calcium content of desalinated drinking water should be 30 mg/L. These levels were based on health concerns with the most critical effects being hormonal changes in calcium and phosphorus metabolism and reduced mineral saturation of bone tissue. Also, when calcium is increased to 30 mg/L, the corrosive activity of desalinated water would be appreciably reduced and the water would be more stable (3). The report (3) also recommended a bicarbonate ion content of 30 mg/L as a minimum essential level needed to achieve acceptable organoleptic characteristics, reduced corrosivity, and an equilibrium concentration for the recommended minimum level of calcium. 2. Recent recommendations More recent studies have provided additional information about minimum and optimum levels of minerals that should be in demineralised water. For example, the effect of drinking water of different hardness on the health status of women aged from 20 to 49 years was the subject of two cohort epidemiological studies (460 and 511 women) in four South Siberian cities (55, 56). The water in city A water had the lowest levels of calcium and magnesium (3.0 mg/L calcium and 2.4 mg/L magnesium). The water in city B had slightly higher levels (18.0 mg/L calcium and 5.0 mg/L magnesium). The highest levels were in city C (22.0 mg/L calcium and 11.3 mg/L magnesium) and city D (45.0 mg/L calcium and 26.2 mg/L magnesium). Women living in cities A and B more frequently showed cardiovascular changes (as measured by ECG), higher blood pressure, somatoform autonomic dysfunctions, headache, dizziness, and osteoporosis (as measured by X-ray absorptiometry) compared to those of cities C and D. These results suggest that the minimum magnesium content of drinking water should be 10 mg/L and the minimum calcium content should be 20 mg/L rather than 30 mg/L as recommended in the 1980 WHO report (3). Based on the currently available data, various researchers have recommended that the following levels of calcium, magnesium, and water hardness should be in drinking water: • For magnesium, a minimum of 10 mg/L (33, 56) and an optimum of about 20-30 mg/L (49, 57); 157 • For calcium, a minimum of 20 mg/L (56) and an optimum of about 50 (40-80) mg/L (57, 58); • For total water hardness, the sum of calcium and magnesium should be 2 to 4 mmol/L (37, 50, 59, 60). At these concentrations, minimum or no adverse health effects were observed. The maximum protective or beneficial health effects of drinking water appeared to occur at the estimated desirable or optimum concentrations. The recommended magnesium levels were based on cardiovascular system effects, while changes in calcium metabolism and ossification were used as a basis for the recommended calcium levels. The upper limit of the hardness optimal range was derived from data that showed a higher risk of gall stones, kidney stones, urinary stones, arthrosis and arthropathies in populations supplied with water of hardness higher than 5 mmol/L. Long-term intake of drinking water was taken into account in estimating these concentrations. For short-term therapeutic indications of some waters, higher concentrations of these elements may be considered. IV. GUIDELINES AND DIRECTIVES FOR CALCIUM, MAGNESIUM, AND HARDNESS LEVELS IN DRINKING WATER The WHO in the 2nd edition of Guidelines for Drinking-water Quality (61) evaluated calcium and magnesium in terms of water hardness but did not recommend either minimum levels or maximum limits for calcium, magnesium, or hardness.The first European Directive (62) established a requirement for minimum hardness for softened or desalinated water (≥ 60 mg/L as calcium or equivalent cations). This requirement appeared obligatorily in the national legislations of all EEC members, but this Directive expired in December 2003 when a new Directive (63) became effective. The new Directive does not contain a requirement for calcium, magnesium, or water hardness levels. On the other hand, it does not prevent member states from implementing such a requirement into their national legislation. Only a few EU Member States (e.g. the Netherlands) have included calcium, magnesium, or water hardness into their national regulations as a binding requirement. Some EU Member States (e.g. Austria, Germany) included these parameters at lower levels as unbinding regulations, such as technical standards (e.g., different measures for reduction of water corrosivity). All four Central European countries that became part of the EU in May 2004 have included the following requirements in their respective regulations but varying in binding power; • Czech Republic (2004): for softened water ≥ 30 mg/L calcium and ≥ 10 mg/L magnesium; guideline levels of 40-80 mg/L calcium and 20–30 mg/L magnesium (hardness as Σ Ca + Mg = 2.0 – 3.5 mmol/L). • Hungary (2001): hardness 50 – 350 mg/L (as CaO); minimum required concentration of 50 mg/L must be met in bottled drinking water, new water sources, and softened and desalinated water. • Poland (2000): hardness 60–500 mg/L (as CaCO3). • Slovakia (2002): guideline levels > 30 mg/L calcium and 10 – 30 mg/L magnesium. The Russian technical standard Astronaut environment in piloted spaceships – general medical and technical requirements (64) defines qualitative requirements for recycled water intended for drinking in spaceships. Among other requirements, the TDS should range between 100 and 1000 mg/L with minimum levels of fluoride, calcium and magnesium being specified by 158 a special commission separately for each cosmic flight. The focus is on how to supplement recycled water with a mineral concentrate to make it “physiologically valuable” (65). V. CONCLUSIONS Drinking water should contain minimum levels of certain essential minerals (and other components such as carbonates). Unfortunately, over the two past decades, little research attention has been given to the beneficial or protective effects of drinking water substances. The main focus has been on the toxicological properties of contaminants. Nevertheless, some studies have attempted to define the minimum content of essential elements or TDS in drinking water, and some countries have included requirements or guidelines for selected substances in their drinking water regulations. The issue is relevant not only where drinking water is obtained by desalination (if not adequately re-mineralised) but also where home treatment or central water treatment reduces the content of important minerals and low-mineral bottled water is consumed. Drinking water manufactured by desalination is stabilized with some minerals, but this is usually not the case for water demineralised as a result of household treatment. Even when stabilized, the final composition of some waters may not be adequate in terms of providing health benefits. Although desalinated waters are supplemented mainly with calcium (lime) or other carbonates, they may be deficient in magnesium and other microelements such as fluorides and potassium. Furthermore, the quantity of calcium that is supplemented is based on technical considerations (i.e., reducing the aggressiveness) rather than on health concerns. Possibly none of the commonly used ways of re-mineralization could be considered optimum, since the water does not contain all of its beneficial components. Current methods of stabilization are primarily intended to decrease the corrosive effects of demineralised water. Demineralised water that has not been remineralized, or low-mineral content water – in the light of the absence or substantial lack of essential minerals in it – is not considered ideal drinking water, and therefore, its regular consumption may not be providing adequate levels of some beneficial nutrients. This chapter provides a rationale for this conclusion. The evidence in terms of experimental effects and findings in human volunteers related to highly demineralised water is mostly found in older studies, some of which may not meet current methodological criteria. However, these findings and conclusions should not be dismissed. Some of these studies were unique, and the intervention studies, although undirected, would hardly be scientifically, financially, or ethically feasible to the same extent today. The methods, however, are not so questionable as to necessarily invalidate their results. The older animal and clinical studies on health risks from drinking demineralised or low-mineral water yielded consistent results both with each other, and recent research has tended to be supportive. Sufficient evidence is now available to confirm the health consequences from drinking water deficient in calcium or magnesium. Many studies show that higher water magnesium is related to decreased risks for CVD and especially for sudden death from CVD. This relationship has been independently described in epidemiological studies with different study designs, performed in different areas, different populations, and at different times. The consistent epidemiological observations are supported by the data from autopsy, clinical, and animal studies. Biological plausibility for a protective effect of magnesium is substantial, but the specificity is less evident due to the multifactorial aetiology of CVD.