Clean Drinking Water

Clean drinking water: is our precious resource contaminated?

See ANH's latest review on Europe's highest authority on food safety, the European Food Safety Authority, which issued a decision in late November 2008 to allow food supplements containing fluoride as an active ingredient. On top of intakes from tap water in countries like the USA and Ireland where around two-thirds or three-quarters of the water supply is fluoridated, or the UK, where around 15% is mass-medicated in this way, this could tip some people well over the safe limits. More than this, we try to understand how it's possible for EFSA to be so leniant on fluoride, when legally speaking, it shouldn't go near the stuff! Fluoride is a medicine, not a food. Find out more in our December 2008 review. 

About water

Water is a truly remarkable chemical substance that is arguably our single most important natural resource. If we do not consume water for a few days, we die, whilst we can survive for weeks without food.

Water appears to be unique when compared with the 15 million or so chemicals we know something about. It is its unique and anomalous properties that are, probably more than anything else, responsible for life on our planet. One aspect of its uniqueness that we so often take for granted without giving it thought is that the solid form (ice) is less dense than the liquid form (water). Another unique feature is that, given its very low molecular weight, water would be expected to boil at around –90oC, but it doesn’t! We all know that water is comprised, as its formula H2O suggests, of two atoms of hydrogen and one of oxygen, but there is so much more to it than that…

In the water molecule, the single electron of each hydrogen atom is shared with one of the six outer-shell electrons of the oxygen atom (creating two covalent bonds), leaving four electrons that form two non-bonding pairs. So many of the unique properties of water originate from the way in which the size and nuclear charge of the water molecule’s single oxygen atom distorts the electronic charge clouds of the atoms of other elements when these are chemically bonded to it.

Importance of water molecule clusters

Liquid water is much more than millions of discrete H2O molecules. It is actually a highly mobile, vibrating and forever changing cluster of water molecules in which the hydrogen bonds between individual water molecules are continuously breaking and reforming.

We know that water structure, or the arrangement of the molecules in a given volume of water, varies according to many factors including temperature and pressure. We also know that the structure and properties of water within cells, particularly adjacent to membranes in cells or organelles (sometimes referred to as vicinal water), is very different to the structure of bulk water. The key point here is that the unique structure of water within cells is purely a result of the geometry of the surrounding hydrogen bonding sites.

We also know that to get water into cells (cellular hydration), the main purpose of water consumption, there can be advantages in having smaller rather than larger clusters of water. Some scientists argue that a hydrogen-bonded cluster in which four H2Os are located at the corners of an imaginary tetrahedron is an especially favourable (low-potential energy) configuration, but the lifetime of such clusters will be incredibly brief (theoretically measurable in a picosecond [10-12 second] time scale).

The bottom line is that, although there are hundreds of products available that purport to provide us,,often without supporting scientific evidence,,with the correct form of structured water, we should not deviate from the primary object of water in health: water should be delivered to the body to optimize its flow into the body’s cells.

In addition, the body is almost certainly more capable of dealing with water in its pure state, rather than water that is loaded with contaminants, some of which have only become commonplace in our diets or water sources within the last 20 to 50 years.

Is our drinking water contaminated?

On a global scale there is no doubt that pathogenic microbes in water present easily the greatest proven risk to human health.

The World Health Organization and many national or regional authorities have stipulated safe levels for a diverse range of toxins, these levels being based largely on limited data on individual contaminants and on the degree of water purity that is technically and economically feasible from a water treatment viewpoint. These levels have never been developed according to risk assessments on the combined impact of numerous contaminants because the scientific data required to evaluate toxic mixtures in drinking water, as well as in other aspects of our environment, is more or less impossible to obtain.

It is not hard to argue that the existing systems of risk analysis based on detection of individual elements and compounds by mass spectrometry (MS) and high pressure gas liquid chromatography (HPLC) and comparison with ‘accepted standards’ is technically flawed as it ignores the effects of mixtures. Grabbing this problem by the horns is a US company (Environmental Toxicology Laboratory Inc.) that is developing a means of assessing the toxicity of mixtures in drinking water by evaluating the swimming pattern of a chemically ultra-sensitive, flagellate micro-organism when subjected to different quality waters.

The key categories of contaminant in drinking water are summarised in the below:

• Pathogenic organisms
  Chlorination of water exists to control or eliminate pathogens from our water supply, but periodic outbreaks of Escherichia coli, Cryptosporidium, coliforms and gastro-intestinal viruses are testament to the fact that treatment does not always exclude these disease organisms. The double-edged sword is that if we wish to increase the concentration of chemicals in our water to guard against infectious agents, we must also accept the increased risk posed by the chemicals used to treat the water.
   
• Disinfection products
  Sodium hypochlorite, chlorine gas and chlorine dioxide are extremely widely used for water disinfection purposes and there is increasing evidence that these chlorinated compounds can contribute to some very serious health problems. Known harmful effects include eye/skin irritations, stomach discomfort and anaemia. Absorption of chlorine can be greater through the skin from the taking of showers and baths than via drinking water. Most of the long-term health problems associated with chlorine are caused by chlorine by-products. Ozone is also sometimes used for drinking water disinfection, but its use is also not without risk from by-products.
   
• Disinfection by-products
  Hundreds of different compounds can be formed from the reaction of sodium hypochlorite (chlorine) with other compounds present in drinking water and many of these are known to be more hazardous than chlorine itself. They include 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone, or ‘mutagen-X’, also commonly referred to as MX and the trihalomethane (THM) group (e.g. bromodichloromethane, chloroform, bromoform). Additionally, where chlorine dioxide or ozone are used in disinfection to reduce formation of hazardous trihalomethanes, toxic by-products may be formed, such as chlorite (from chlorine dioxide) and bromate (from a reaction between ozone and bromide which may be naturally occurring in source waters). Many members of this group are carcinogenic and they may contribute to liver, kidney and central nervous system disorders. Children and babies (especially the unborn) are particularly vulnerable to such compounds.
   
• Inorganic chemicals
  These comprise a very long list, including various metals such as aluminium (used to clarify water in treatment plants), lead (in old water pipes and solder), cadmium (naturally occurring or from water pipe solder and electroplating); arsenic (naturally occurring in some waters); and also fluoride (naturally occurring and/or added to some water supplies in a misguided attempt to reduce dental caries). While there are many potential adverse effects caused by excessive intakes of any of these inorganic chemicals individually, no one is in a position to elucidate what the combined effects of the multitude of chemicals in a given water supply might be.
   
• Organic chemicals
  These include a large range of industrial chemicals like dichlorobenzene and dichloroethane, pesticides (herbicides, insecticides and fungicides and their breakdown products), dioxins (probably the most inherently toxic group of compounds known), endocrine-disrupting xeno-oestrogens (from contraceptive pills and plasticizers in food and drinking containers and plastic tableware) and a wide range of other persistent compounds discharged by industrial chemical plants, dry cleaners, timber preservation plants, run-off from landfill sites, agriculture, etc. Some of the most persistent compounds still causing problems in the environment are those which are no longer used industrially, such as polychlorinated biphenyls (PCBs). Persistent organochlorine compounds are fat soluble and accumulate over time in the body. Endocrine-disrupting chemicals are now known to cause biological effects at any detectable level, with limits of detection being down to around 0.1 nanograms per litre for bisphenol A (a plasticizer) and estradiol (from contraceptive pills). In addition, we don’t know categorically the significance of long-term or lifetime exposures to low levels of mixtures of these compounds but much of the existing scientific evidence suggests that persistent organic pollutants (POPs) and endocrine disrupters may present very substantial, long-term health risks.
   
• Radionuclides
  Alpha and beta particles, as well as radium and uranium are among several radioactive contaminants that have been found in water sources as a result of decay or erosion of both naturally occurring minerals or rocks in the Earth’s surface and of man-made materials or wastes.

Risk assessment of water contaminants

With the rapid development of highly sensitive analytical equipment such as combined High Pressure Liquid Chromatography/Mass Spectrometry and Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES), detection of extremely small quantities of contaminants in drinking water is now feasible. However, it is not just the presence of these contaminants that is an issue, it is how biologically significant their presence is.

Risk assessment approaches are increasingly being used to evaluate the relative importance of contaminants in drinking water, as in other areas of human health. By and large, these assessments are based on dose-response data derived from laboratory tests on surrogate species such as rats and mice for assessing risks in humans and on fish and other wildlife for assessing risks in the environment. More comprehensive risk assessments employ a tiered approach, so that substances that represent zero or minimal risk are eliminated from detailed, time-consuming and expensive risk assessment early in the process. Uncertainty and probability are also incorporated into the more complete risk assessments for contaminants that are thought to present a more serious risk to health.

One of the greatest problems with these classical, risk assessment paradigms used to assess contaminant risks to date is that they have not taken adequately into account the cumulative risks associated with long-term (lifetime) exposures, nor have they taken into account the effects of mixtures of contaminants. The reason for this is almost certainly that governments appreciate the consequences of such comprehensive risk assessment: most drinking water would likely be assessed as unsafe for human consumption.

Taking control of the situation – in your home

So we are left with justifications from myopic, pseudo-science-justified risk assessment regimes, almost as defective as the ones that have been recently used to assess the safety of nutrients, which have been carefully adjusted to inform us that our tap water is safe most of the time. On weighing up a large part of the available evidence, I simply do not believe it.

Using some sort of point-of-use filtration system to reduce the diverse range of contaminants in tap water has to be one of the best investments for any household. If these systems rely on replaceable filters, it is essential that the filter is replaced according to the manufacturer’s specification, otherwise they can themselves release contaminants into the drinking water or become hotbeds of microbial contamination.

References

Anonymous, Current Drinking Water Standards, US Environmental Protection Agency, 2002 (http://www.epa.gov/safewater/mcl.html).

Falconer IR. Are endocrine disrupting compounds a health risk in drinking water? Int J Environ Res Public Health, 2006;3(2):180-4.

Fujimoto T, Kubo K, Aou S. Prenatal exposure to bisphenol A impairs sexual differentiation of exploratory behaviour and increases depression-like behaviour in rats. Brain Res, 2006; 1068(1): 49-55. Epub Dec 27, 2005.  Hirose A, Nishikawa A, Kinae N, Hasegawa R. 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX): toxicological properties and risk assessment in drinking water. Rev Environ Health, 1999;14(3):103-20.

Liu K, Cruzan JD, Saykally RJ. Water clusters. Science, 1996; 27: 929-93.

Lower, S. A gentle introduction to the structure of water (website) http://www.chem1.com/acad/sci/aboutwater.html and associated links

Ritter L at al. Sources, pathways, and relative risks of contaminants in surface water and groundwater: a perspective prepared for the Walkerton inquiry. J Toxicol Environ Health A, 2002; 65(1): 1-142. Review.

Rodriguez-Mozaz S, de Alda MJ, Barcelo D. Monitoring of estrogens, pesticides and bisphenol A in natural waters and drinking water treatment plants by solid-phase extraction-liquid chromatography-mass spectrometry. J Chromatogr A, 2004; 1045(1-2): 85-92.

Chlorine – The boon or bane of our drinking water?

As I write this article ensconced in a hotel room in Kolcata (formerly Calcutta), amidst a visit to Ayurvedic interests in India, the importance of methods of controlling water-borne pathogens couldn’t be more at the forefront of my mind. The World Health Organization (WHO) estimates that as much as 80% of all diseases and over one-third of deaths in developing countries are caused by the consumption of contaminated water and, on average, as much as one-tenth of each person’s productive time is sacrificed to water-related diseases.[1] Diarrhoeal diseases linked with unsafe water are a primary cause of morbidity and mortality in infants and young children in developing countries. Across the globe, the WHO estimates that 1.8 billion episodes of childhood diarrhoea occur annually, mostly in developing countries. This contributes to the death of more than 3 million children and one million adults a year.[2]

In contrast, water-borne diseases are infrequent in the developed world, primarily thanks to widespread chlorination of our water supply. This technological development, which has been applied to virtually every municipal water source in the industrialised world since the 1920s, is often hailed as yielding one of the greatest public health victories of the last 100 or so years.[3 ]

Although there is no doubt that chlorination of drinking water has reduced water-borne diseases to a minor threat for many of us in the west – there is mounting evidence that this benefit it not without considerable cost. In this second article on drinking water, I have chosen to look more closely at health issues relating to the chlorination of drinking water, given that chlorine is far and away the most widely used disinfection agent. I will focus in particular on the health implications associated with chlorination by-products which are formed when chlorine reacts with organic compounds in water, rather than on chlorine itself. These by-products which include compounds belonging to the trihalomethane (THM) group, have increasingly been associated with cancer and adverse reproductive outcomes.[3]

History of chlorination

Early efforts aimed at making drinking water safe in Europe, during the late 1800s, centred on physically filtering out bacteria and other pathogens through sand. Sand filtration became the main method of water treatment in the early twentieth century after German microbiologist Robert Koch, who isolated Vibrio cholerae, the bacterium which causes cholera which had plagued European city-dwellers for centuries, showed that the bacterium could be filtered out through sand. Across the Atlantic, however, it was typhoid (caused by another bacterium, Salmonella typhi) that was the most important threat in drinking water, but partial mitigation was also achieved via sand filtration.

Although this rather crude method, which is still used in water treatment facilities today, provided some relief for Europeans and Americans, it wasn’t until chlorination was introduced as an adjunct to sand filtration in the early 1900s that these diseases were more or less eliminated from the western world.

However, its long history of use has brought with it new problems, including the development of chlorine tolerance or even resistance by certain pathogens, which require higher and higher levels of chlorination to achieve control. Furthermore, the spotlight is increasingly on chlorine and other halogens (such as fluoride) because of the growing body of evidence suggesting direct or indirect health risks. However, risk/benefit assessments, despite being fraught with confounding problems and other difficulties, continue to be used to justify use of chlorine given its low cost, and indications that the health risks caused by waterborne diseases (which include increased risk of cancer) considerably outweigh those of chlorine and its by-products.

Of the four key disinfection agents used, chlorine, chlorine dioxide, ozone and chloramine (chlorine reacted with ammonia), chlorine’s effectiveness (in the higher dose ranges) compares well with the best of the bunch, ozone, except in the case of treating protozoa like Cryptosporidia and Giardia, when it is comparatively ineffective.[4] The use of free chlorine as a disinfection agent, added as chlorine gas, or as sodium hypochlorite (bleach) or calcium hypochlorite, far outstrips the use of any other disinfection agent.

Chlorine – what happens when it’s added to water

Chlorine is generally added to the water supply to control pathogens with the aim of providing a level of free chlorine of at least 0.5 mg per litre (mg/L). Interestingly, levels of 0.6 mg/L or more may provide problems of acceptability by consumers on the basis of taste, while the WHO Drinking Water Guidelines (which many countries have adopted) specify that dosages 10 times greater than the target dose (5 mg/L) should not be exceeded and are deemed safe.[5]  However, mounting evidence (see below) suggests that where organic components (e.g. bromates, fulvates or organic matter) are present in water, such levels would be far from safe given the potential for lifetime exposure to significant levels of disinfection by-products (DFBs). These include trihalomethanes (THMs), haloacetic acids (HAAs) and haloacetonitriles (HANs), which have been associated with mutations, cancers and reproductive effects in both animal and human studies.

When chlorine is added to water it hydolyses (reacts with water) more or less completely to form hypochlorous acid (HOCl) as long as the pH is greater than 4 and the chlorine dose does not exceed 100 mg/L (20 times over the WHO guideline threshold). Hypochlorous acid under more alkaline conditions dissociates to the hypochlorite ion (OCl-), which is a considerably less efficient disinfection agent than hypochlorous acid itself. Under alkaline conditions (pH of 9), hypochlorite ions become the dominant species, while at a more acidic pH of 6.5, only about 10% will dissociate to the hypochlorite ion. Accordingly, chlorine will be considerably less efficient (but safer) as a disinfection agent in alkaline waters.[3]

Research has also shown that exposure to THMs increases dramatically (by at least 50%) in hot compared with cold water, with the by-products being absorbed both through the skin and by inhalation.[6] This suggests that exposure to THMs from showers and baths may be at least, if not more, important than exposure from water consumed orally (in drinks and foods). Chloroform, exposure and estimated internal dose due to inhalation and dermal absorption of a 10 minute shower or a half hour bath are equivalent to the dose from ingesting 2 litres of tap water.[7] Uptake is temperature dependent, so that absorption through the skin while bathing is 30 times greater in water at 40°C compared with 30°C.[8] Swimming provides a source of uptake; a one hour swim can result in a chloroform dose of 65 μg/kg, 141 times greater than that received from a 10 minute shower.[9]

Disinfection by-products associated with water chlorination

The first suggestions that chlorination of water might increase cancer risk were proposed during the 1970s, and this has led to further research on risk potential and the discovery that other adverse effects, particularly reproductive ones, might be important.

Cancer

Feeding studies first showed that THMs could cause tumours of the liver, kidney and intestines in rodents during the 1970s.[10] A 1992 meta-analysis by Morris and colleagues from the Division of Biostatistics at the Medical College of Wisconsin, pooled data from 10 relevant case-control and cohort studies, took into account confounding factors and concluded that exposure to chlorination by-products in drinking water causes a 10-40% increase in bladder and colorectal cancers.[11]

However, since only three of these studies included exposure data, the Iowa Womens’ Health Study was established, using a cohort of 28, 237 post-menopausal women, to better assess this association. The results were published by Timothy Doyle and colleagues from the Division of Epidemiology, School of Public Health, University of Minnesota in 1997 and provided conclusive evidence that women who lived in communities with higher levels of chloroform (one of the most important THMs) in drinking water, were at “significantly increased risk of cancer, particularly colon cancer”.[12] This cancer happens to be the most common cancer present in both men and women in the UK.

Reproductive effects

In 2000 a group of statisticians at Imperial College London, led by Mark Nieuwenhuijsen, reviewed relevant toxicological and epidemiological evidence on the potential role of chlorination by-products in the induction of adverse reproductive effects. Effects that have been associated with chlorination by-products include spontaneous abortion, stillbirth, reduced birth weight and survival, developmental disabilities and congenital malformations of the cardiovascular and neurological systems (e.g. neural tube defects such as spina bifida).[13] The scientists showed that exposures from showers, baths, drinking water, drinks and foods caused significant absorption of chlorination by-products and these may contribute to increased risk of a diverse range of adverse reproductive effects. However they also demonstrated that the available research is inconclusive and sometimes contradictory, given that it is difficult to compare studies as most use chloroform as the key marker for chlorination by-products and different mixtures of by-products under different conditions may cause significant variations in risk.

What the UK authorities say about chlorination by products

In a letter  from the Drinking Water Inspectorate (DWI) to sewerage companies in 1999, the DWI and Department of Health appears to have done everything it can to cover themselves by noting possible risks as well as the need to minimise exposure, while at the same time avoiding the difficult decision of banning chlorination. Michael Rouse, Chief Inspector from the DWI, quoting the Committee on Carcinogenicity of Chemicals in Food, Consumer Products and the Environment (COC)  said:

“Overall, the further epidemiological studies fail to provide persuasive evidence of a consistent relationship between chlorinated drinking-water and cancer. It remains possible that there may be an association between chlorinated drinking water and cancer which is obscured by problems such as the difficulty of obtaining an adequate estimate of exposure to chlorination by-products, misclassification of source of drinking water (including the use of bottled water), failure to take adequate account of confounding factors (such as smoking status), and errors arising from non-participation of subjects…. "We therefore consider that efforts to minimise exposure to chlorination by-products remain appropriate, providing that they do not compromise the efficiency of disinfection of drinking-water."

In my view, the COC’s assessment seems to have ignored the crucial Iowa Womens’ Health Study, but, cleverly, in their terms, this one major study does not provide evidence of a “consistent relationship” given that there are no other directly relevant of this nature. Consumers can make up their own minds about what this COC statement means.

How to reduce your risk

While risk assessments continue to favour chlorine as the agent of choice in disinfection because of its low cost and the concomitant high risk of disease from waterborne pathogens, it is unlikely that we will see elimination of chlorine and its by-products from our water supply in the near future. Although on the basis of present scientific knowledge ozonation appears more favourable, some argue that this is only because ozonation by-products have been less well studied than chlorination ones. Ultra-violet also holds promise, but cost effective treatment methods using ultra-violet disinfection have yet to be developed for large scale water treatment.

The WHO provides an interesting perspective on chlorination. It indicates that chlorination of water at point of use in developing countries could lead to a 35-39% reduction in diarrhoeal episodes, while the promotion of hygiene practices such as hand-washing would contribute to a reduction of 45%!  Since risk is directly proportionate to dosage, it is important to consider the variety of ways in which exposure to chlorination by-products can be reduced. I have listed some of the most important ways individuals can reduce their exposure below:

• Avoid having very hot, long showers and baths, unless you have installed a full-house filtration system (such as reverse osmosis [RO]) which will eliminate the majority of DBPs
• Use an activated carbon filter attached to your shower head to reduce levels of chlorine when showering
• Swim in salt-water or ozone-disinfected swimming pools wherever possible
• Filter your tap water before drinking it, using a system known to reduce concentrations of chlorination by-products, such as RO. Jug filters (containing activated carbon filters) reduce chlorine concentrations in water, but may have little effect on some of the by-products.
• Drink bottled water from a good, natural source, but ensure it's from a source close to you and not from the other side of the world. See UNISON protest reported 21 August 2008 on this subject
• Use DFB-free water for all drinking and cooking purposes, and where possible, for washing and swimming as well
• When dishwashing in unfiltered tap water, use rubber gloves

References

United Nations Conference on Environment and Development (UNCED). Agenda 21: Programme of Action for Sustainable Development. Chapter 18. Protection of the Quality and Supply of Freshwater Resources, 1992.

World Health Organization. The World Health Report 2006. Bridging the Gap. WHO, Geneva, 2005.

Galal-Gorchev, H. Chlorine in water disinfection. Pure & Appl. Chem., 1996; 68: 1731-1735.

Regli S et al. In: Safety of Water Disinfection: Balancing Chemical & Microbial Risks (Ed. Craun GF), pp. 39-80. ILSI Press, Washington, DC, 1993.

Clark RM et al. In: Safety of Water Disinfection: Balancing Chemical & Microbial Risks (Ed. Craun GF), pp. 181-198. ILSI Press, Washington, DC, 1993.

World Health Organization. Rolling Revision of the WHO Drinking-Water Guidelines. WHO, Geneva, 2004.

Gordon SM, Wallace L, Callaghan P, et al. Effect of water temperature on dermal exposure to chloroform. Environ Health Perspect, 1998; 106: 337–45.

Gordon SM, Wallace L, Callaghan P, et al. Effect of water temperature on dermal exposure to chloroform. Environ Health Perspect, 1998; 106: 337–45.

Levesque B, Ayotte P, LeBlanc A, et al. Evaluation of dermal and respiratory chloroform exposure in humans. Environ Health Perspect, 1994; 102: 1082–7.

Doyle TJ, Zheng W, Hong CP, Sellers TA,  Kushi LH, Folson AR. The association of drinking water source and chlorination by-products with cancer incidence among postmenopausal women in Iowa: a prospective cohort study. Am J Public Health, 1997; 87: 1168-1176.

Nieuwenhuijsen MJ, Toledano MB, Eaton NE, Fawell J, Elliott P. Chlorination disinfection byproducts in water and their association with adverse reproductive outcomes: a review. Occup Environ Med, 2000; 57; 73-85.

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