HEALTH
RISKS FROM DRINKING
DEMINERALISED WATER
https://www.purepro.info/pdf/nutrientschap12.pdf
PurePro ECO RO Membrane Solution !
The New Generation RO Membrane with a Mineral Guard Technology
PurePro Eco RO Membrane features next-generation membrane technology offering the highest quality permeate at 30% lower energy consumption. Enabled with a Mineral Guard technology, this membrane can retain essential minerals in your drinking water, making it safe, pure and healthy.
English version:
(please download)
https://www.who.int/water_sanitation_health/dwq/nutritionschap12.pdf
Chinese version: (please download)
https://www.purepro.us/zh_tw/water_sanitation_health_nutrientschap12.pdf.pdf
HEALTH RISKS FROM DRINKING
DEMINERALISED WATER
National Institute of Public Health
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.
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
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
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
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 low-mineral 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
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
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.
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 tg/dL, 37 tg/dL, and 42 tg/dL. The level of
concern is 10 tg/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 tg/L for the
two infants with the highest blood lead; 66 tg/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
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);
·
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
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. In
addition to an increased risk of sudden death, it has
been suggested that intake of water low in magnesium may
be associated with a higher risk of motor neuronal
disease, pregnancy disorders (so-called preeclampsia),
sudden death in infants, and some types of cancer.
Recent studies suggest that the intake of soft water,
i.e. water low in calcium, is associated with a higher
risk of fracture in children, certain neurodegenerative
diseases,
pre-term birth and low weight at birth and some types of
cancer. Furthermore, the possible role of water calcium
in the development of CVD cannot be excluded.
International
and national authorities responsible for drinking water
quality should consider guidelines for desalination
water treatment, specifying the minimum content of the
relevant elements such as calcium and magnesium and TDS.
If additional research is required to establish
guidelines, authorities should promote targeted research
in this field to elaborate the health benefits. If
guidelines are established for substances that should be
in deminerialised water, authorities should ensure that
the guidelines also apply to uses of certain home
treatment devices and bottled waters.
References
1.
Sadgir P,
Vamanrao A. Water in Vedic Literature. In: Abstract
Proceedings of the 3rd international Water History
Association Conference (http://www.iwha.net/a_abstract.htm),
Alexandria: 2003.
2.
Working group
report (Brussels, 20-23 March 1978). Health effects of
the removal of
substances
occurring naturally in drinking water, with special
reference to demineralized and desalinated water. EURO
Reports and Studies 16. Copenhagen: World Health
Organization, 1979.
3.
Guidelines on
health aspects of water desalination. ETS/80.4. Geneva:
World Health Organization, 1980.
4.
Williams AW.
Electron microscopic changes associated with water
absorption in the jejunum.Gut 1963; 4: 1-7.
5.
Schumann K,
Elsenhans B, Reichl FX, et al. Does intake of highly
demineralized water damage the rat gastrointestinal
tract? Vet Hum Toxicol 1993; 35: 28-31.
6.
Rakhmanin YuA,
Mikhailova RI, Filippova AV, et al. On some aspects of
biological effects of distilled water. (In Russian.) Gig
Sanit 1989; 3: 92-93.
7.
Deutsche
Gesellschaft für Ernährung. Drink distilled water? (In
German.) Med Mo Pharm1993; 16: 146.
8.
Bragg PC,
Bragg P. The Shocking Truth about Water. 27th
ed. Santa Barbara, CA, Health Science, 1993.
9.
Robbins DJ,
Sly MR. Serum zinc and demineralized water. Am J Clin
Nutr 1981; 34: 962963.
10.
Basnyat B,
Sleggs J, Spinger M. Seizures and delirium in a trekker:
the consequences of excessive water drinking? Wilderness
Environ Med 2000; 11: 69-70.
11.
Anonymous.
Hyponatremic seizures among infants fed with commercial
bottled drinking water – Wisconsin, 1993. MMWR 1994; 43:
641-643.
12.
Sauvant M-P,
Pepin D. Drinking water and cardiovascular disease. Food
Chem Toxicol 2002; 40: 1311-1325.
13.
Donato F,
Monarca S, Premi S, Gelatti U. Drinking water hardness
and chronic degenerative diseases. Part III. Tumors,
urolithiasis, fetal malformations, deterioration of the
cognitive function in the aged and atopic eczema. (In
Italian.) Ann Ig 2003; 15: 57-70.
14.
Monarca S,
Zerbini I, Simonati C, Gelatti U. Drinking water
hardness and chronic degenerative diseases. Part II.
Cardiovascular diseases. (In Italian.) Ann Ig 2003; 15:
41-56.
15.
Nardi G,
Donato F, Monarca S, Gelatti U. Drinking water hardness
and chronic degenerative diseases. Part I. Analysis of
epidemiological research. (In Italian.) Annali di igiene
- medicina preventiva e di comunita 2003; 15: 35-40.
16.
Verd
Vallespir S, Domingues Sanches J, Gonzales Quintial M,
et al. Association between calcium content of drinking
water and fractures in children. (In Spanish.) An Esp
Pediatr 1992; 37: 461-465.
17.
Jacqmin H,
Commenges D, Letenneur L, et al. Components of drinking
water and risk of cognitive impairment in the elderly.
Am J Epidemiol 1994; 139: 48-57.
19.
Yang CY, Chiu
HF, Chiu JF, et al. Calcium and magnesium in drinking
water and risk of death from colon cancer. Jpn J Cancer
Res 1997; 88: 928-933.
20.
Yang CY,
Cheng MF, Tsai SS, et al. Calcium, magnesium, and
nitrate in drinking water and gastric cancer mortality.
Jpn J Cancer Res 1998; 89: 124-130.
21.
Eisenberg MJ.
Magnesium deficiency and sudden death. Am Heart J 1992;
124: 544-549.
22.
Bernardi D,
Dini FL, Azzarelli A, et al. Sudden cardiac death rate
in an area characterized by high incidence of coronary
artery disease and low hardness of drinking water.
Angiology 1995; 46: 145-149.
23.
Garzon P,
Eisenberg MJ. Variation in the mineral content of
commercially available bottled waters: implication for
health and disease. Am J Med 1998; 105: 125-130.
24.
Iwami O,
Watanabe T, Moon CS, et al. Motor neuron disease on the
Kii Peninsula of Japan: excess manganese intake from
food coupled with low magnesium in drinking water as a
risk factor. Sci Total Environ 1994; 149: 121-135.
25.
Melles Z,
Kiss SA. Influence of the magnesium content of drinking
water and of magnesium therapy on the occurrence of
esalinized a. Magnes Res 1992; 5: 277-279.
26.
Yang CY, Chiu
HF, Cheng MF, et al. Esophageal cancer mortality and
total hardness levels in Taiwan’s drinking water.
Environ Research 1999; 81: 302-308.
27.
Yang CY, Chiu
HF, Cheng MF, et al. Pancreatic cancer mortality and
total hardness levels in Taiwan’s drinking water. J
Toxicol Environ Health 1999; 56: 361-369.
28.
Yang CY, Tsai
SS, Lai TC, et al. Rectal cancer mortality and total
hardness levels in Taiwan’s drinking water. Environ
Research 1999; 80: 311-316.
29.
Yang CY, Chiu
HF, Cheng MF, et al. Calcium and magnesium in drinking
water and the risk of death from breast cancer. J
Toxicol Environ Health 2000; 60: 231-241.
30.
Pribytkov YuN.
Status of phosphate-calcium metabolism (turnover) at
inhabitants of town Shevchenko using desalinated
drinking water. (In Russian.) Gig Sanit 1972; 1:
103-105.
31.
Rakhmanin YA,
Lycnikova TD, Michailova RI. Water Hygiene and the
Public Health Protection of Water Bodies. (In Russian.).
Moscow: Acad. Med. Sci. USSR, 1973: 44-51.
32.
Rakhmanin YA,
Bonasevskaya TI, Lestrovoy AP, et al. Public Health
Aspects of
Environmental
Protection. (In Russian.). Moscow: Acad. Med. Sci. USSR,
1976: (fasc 3) 68-71.
33.
Rubenowitz E,
Molin I, Axelsson G, Rylander R. Magnesium in drinking
water in relation to morbidity and mortality from acute
myocardial infarction. Epidemiology 2000; 11: 416-421.
34.
National
Institute of Public Health. Internal data. Prague: 2003.
35.
Kondratyuk
VA. On the health significance of microelements in
low-mineral water. (In Russian.) Gig Sanit 1989; 2:
81-82.
36.
Mudryi IV.
Effects of the mineral composition of drinking water on
the population´s health (review). (In Russian.) Gig
Sanit 1999; 1: 15-18.
37.
Lutai GF.
Chemical composition of drinking water and the health of
population. (In Russian.) Gig Sanit 1992; 1: 13-15.
38.
Anonymous.
How trace elements in water contribute to health. WHO
Chronicle 1978; 32: 382-385.
39.
Haring BSA,
Van Delft W. Changes in the mineral composition of food
as a result of cooking in “hard“ and “soft“ waters. Arch
Environ Health 1981; 36: 33-35.
40.
Oh CK, Lücker
PW, Wetzelsberger N, et al. The determination of
magnesium, calcium, sodium and potassium in assorted
foods with special attention to the loss of electrolytes
after various forms of food preparations. Mag Bull 1986;
8: 297-302.
41.
Durlach J.
(1988) The importance of magnesium in water. In
Magnesium in Clinical Practice Durlach J, ed. London:
John Libbey & Co Ltd, 1988:221-222.
42.
Kramer MH,
Herwaldt BL, Craun GF, et al.. Surveillance for
Waterborne-Disease Outbreaks–United States, 1993-1994.
MMWR 1996; 45 (No. SS-1): 1-33.
43.
Anonymous.
Epidemiologic notes and reports lead-contaminated
drinking water in bulk-storage tanks – Arizona and
California, 1993. MMWR 1994; 43(41): 751; 757-758.
44.
Thompson DJ.
Trace element in animal nutrition. 3rd ed.
Illinois: Int. Minerals and Chem. Corp., 1970.
45.
Levander OA.
Nutritional factors in relation to heavy metal
toxicants. Fed Proc 1977; 36: 1683-1687.
46.
Oehme FW, ed.
Toxicity of heavy metals in the environment. Part 1. New
York: M.Dekker, 1979.
47.
Hopps HC,
Feder GL. Chemical qualities of water that contribute to
human health in a positive way. Sci Total Environ 1986;
54: 207-216.
48.
Nadeenko VG,
Lenchenko VG, Krasovskii GN. Combined effect of metals
during their intake with drinking water. (In Russian.)
Gig Sanit 1987; 12: 9-12.
49.
Durlach J,
Bara M, Guiet-Bara A. Magnesium level in drinking water:
its importance in cardiovascular risk. In: Itokawa Y,
Durlach J. eds. Magnesium in Health and Disease. London:
J.Libbey & Co Ltd, 1989: 173-182.
50.
Plitman SI,
Novikov YV, Tulakina NV, et al. On the issue of
correction of esalini standards with account of drinking
water hardness. (In Russian.) Gig Sanit 1989; 7: 7-10.
51.
al-Qarawi SN,
el Bushra HE, Fontaine RE. Et al. Typhoid fever from
water esalinized using reverse osmosis. Epidemiol Infect
1995; 114: 41-50.
52.
Geldreich EE,
Taylor RH, Blannon JC, et al. Bacterial colonization of
point-of-use water treatment devices. J Amer Water Works
Assoc 1985; 77: 72-80.
53.
Payment P.
Bacterial colonization of reverse-osmosis water
filtration units. Can J Microbiol 1989; 35: 1065-1067.
54.
Payment P,
Franco E, Richardson L, et al. Gastrointestinal health
effects associated with the consumption of drinking
water produced by point-of-use domestic reverse-osmosis
filtration units. Appl Environ Microbiol 1991; 57:
945-948.
55.
Levin AI,
Novikov JV, Plitman SI, et al. Effect of water of
varying degrees of hardness on the cardiovascular
system. (In Russian.) Gig Sanit 1981; 10: 16-19.
56.
Novikov JV,
Plitman SI, Levin AI, et al. Hygienic regulation for the
minimum magnesium level in drinking water. (In Russian.)
Gig Sanit 1983; 9: 7-11.
58.
Rachmanin YA, Filippova AV,
Michailova RI. Hygienic assessment of mineralizing lime materials used
for the correction of mineral composition of low-mineralized water. (In
Russian.) Gig Sanit 1990; 8: 4-8.
59.
Muzalevskaya LS, Lobkovskii
AG, Kukarina NI. Incidence of chole- and nephrolithiasis, osteoarthrosis,
and salt arthropathies and drinking water hardness. (In Russian.) Gig
Sanit 1993; 12: 17-20.
60.
Golubev IM, Zimin VP. On the
standard of total hardness in drinking water. (In Russian.) Gig Sanit
1994; 3: 22-23.
61.
Guidelines for Drinking-water
Quality. 2nd edn, vol. 2, Health Criteria and Other
Supporting Information. Geneva: World Health Organization, 1996:
237-240.
62.
European Union Council
Directive 80/778/EEC of 15 July 1980 relating to the quality of water
intended for human consumption. Off J Eur Commun 1980; L229: 11-29.
63.
European Union Council
Directive 98/83/EC of 3 November 1998 on the quality of water intended
for human consumption. Off J Eur Commun 1998; L330: 32-54.
64.
Anonymous. GOST R 50804-95
Astronaut environment in piloted spaceships – general medical and
technical requirements. (In Russian.) Moscow: Gosstandard Rossii, 1995.
65.
Sklyar EF, Amiragov MS,
Berezkin SV, Kurochkin MG, Skuratov VM. Recovered water mineralization
technique. (In Russian.) Aviakosm Ekolog Med 2001; 35(5): 55-59.
The New Generation RO Membrane with a Mineral Guard Technology
PurePro Eco RO Membrane features next-generation membrane technology offering the highest quality permeate at 30% lower energy consumption. Enabled with a Mineral Guard technology, this membrane can retain essential minerals in your drinking water, making it safe, pure and healthy. https://www.pure-pro.com/purepro-Eco-RO-membrane.htm
[ The difference between water ionizer and alkaline RO ? ]