The Third Ministerial Conference on Environment and Health held in London on 16-18 June was attended by more than 70 health, environment and transport ministers from 51 countries, making this the largest event of its kind ever held in Europe. A major agenda item for the conference was a legally binding Protocol on Water and Health which aims to protect human health and well-being by improving the management of water resources, and reducing the incidence of water-related diseases.

Representatives from 35 countries signed the Protocol, and the document will become legally binding after 16 member governments formally ratify the agreement. Disputes over alleged breaches of the Protocol will then be subject to adjudication by the International Court of Justice.

The Protocol covers not only drinking water but also water used for recreation, aquaculture and shellfish harvesting, the transport of water, and the use of wastewater and sewage sludge for agricultural purposes. The agreement binds participating nations to take appropriate measures to provide all their citizens with:

• wholesome drinking water,
• adequate sanitation,
• effective protection of drinking water sources and ecosystems from agricultural and industrial pollution,
• safeguards against water-related diseases from recreational use, aquaculture, shellfish harvesting, and agricultural use of wastewater or sewage sludge,
• effective monitoring and response systems for water-related disease incidents and risks.

The Protocol provides guidance on the principles and approaches to be adopted by participating nations on the following basis:

• the precautionary principle (ie preventive action should not await absolute scientific proof),
• the polluter-pays principle,
• the sovereign right of nations to exploit their own resources, and their responsibility to ensure that their actions do not cause damage to the environment of other states or beyond the limits of national jurisdiction,
• the management of water resources to provide adequately for the needs of future generations,
• recognition that preventive action to reduce or avoid disease is more efficient and cost-effective than remedial action,
• the management of water resources at the lowest appropriate administrative level,
• acceptable and sustainable management of water resources recognising social, economic and environmental values,
• promotion of efficient water use through economic instruments and awareness-building,
• public access to information and participation in decision making concerning water and health,
• integrated management of whole catchments or aquifiers taking into account social and economic development as well as ecological and water resource factors,
• special consideration for the protection of people who may be particularly vulnerable to water-related disease,
• equitable access to water of adequate quantity and quality for all people,
• people and institutions with rights and entitlements to water should also contribute to the protection of the water environment and conservation of water resources,
• implementation of the required measures should take account of local problems, needs and knowledge.

The Protocol requires countries to establish targets and target dates within 2 years for the achievement of levels of performance to maintain or increase protection against waterborne disease, and to provide mechanisms for public participation in this process. Parties are obliged to collect and evaluate data on progress towards these targets, and to publish summary reports on progress in a standardised format.

The Protocol also requires the establishment of comprehensive national and/or local surveillance and early warning systems, and national and local contingency plans for dealing with waterborne outbreaks, incidents and risks. Parties must agree to promote public awareness, education, training, research and development, and public access to information. Provisions are also made for cooperation in relation to transboundary waters, international support for national action, reviews of compliance with the Protocol, and regular meetings of the parties to the agreement.

The Ministerial Conference was followed by a 2 day technical meeting, Watershed 99, which was charged with developing a consensus agenda of policy and research priorities to support the implementation of the Protocol. The 200 delegates who attended discussed global and local perspectives on sustainable use of water resources, and examined strategies for health risk assessment in relation to potable and recreational use of surface and ground water supplies.

Details of the Conference can be found at:
www.who.dk/london1999

Two months before the Third Ministerial Conference on Environment and Health, the WHO released a background report entitled Water and Health in Europe which details conditions currently prevailing in the member nations. The report highlights the contrast between some relatively affluent countries and their poorer counterparts with respect to the adequacy and quality of water supplies, and the incidence of waterborne disease. However even countries regarded as having generally good quality water supplies suffer intermittent or localised problems affecting some of their population.

It is estimated that as many as one person in seven in the WHO European region does not have access to safe drinking water. Access to reliable supplies is a problem in many areas, and even those connected to reticulated systems may suffer frequent interruptions in supply. In a press release accompanying the report, Günter Klein, Director of Environment and Health at WHO's European office said "If we persist with intensive agriculture, industrialisation and overexploitation of our water resources, it will become increasingly difficult to ensure a supply of safe water in many parts of Europe, including a number of big cities."

A survey of member nations revealed a total of 710 water-related outbreaks (drinking and recreational water) recorded by 19 countries over an 11 year period. In a number of eastern European countries, there has been a resurgence of waterborne diseases usually associated with third world conditions including cholera, typhoid fever and hepatitis A. Surveillance and reporting mechanisms vary greatly in different countries, and it is likely that waterborne disease (and gastrointestinal disease from all sources) is significantly under-recognised and under-reported.

The Introduction to the report presents a succinct and frank appraisal of how these problems have developed over several decades. The provision of safe and reliable water supplies and adequate sanitation were key factors in the economic and social development of Europe in the first half of this century. Despite wide variations in pricing structures, water supply and sanitation services remain low in cost with most citizens paying less than 1% of annual income for access. However this very success may have contributed to the declining perception of the importance of water supplies among individuals and governments alike. Reliable cheap water supplies were taken for granted, and little importance was placed on the technical or human resources required for their management.

Decreasing government involvement in western Europe, and political upheaval in eastern Europe have contributed to overexploitation and unsustainable management practices which have now reached a point where public health may be threatened. The report calls for recognition of the true social value of water, and highlights the cost-effectiveness of investment in water supply and sanitation as a public health measure.

A central issue in assessing the health risk posed by Cryptosporidium in water supplies, is the problem of determining whether the oocysts are infectious to humans. The accepted "gold standard" for infectivity testing, the infection of laboratory animals such as mice is both slow and expensive, and until very recently has not been applicable to the "human" genotype of C.parvum (which does not normally infect other mammals).

A variety of methods have been developed to assess the condition of oocysts in environmental samples including excystation assays, "vital dye" stains and more recently, the presence of messenger RNA or ribosomal RNA sequences. However while each of these techniques provides some measure of metabolic activity and/or structural integrity, adequate validation against animal studies is lacking, and it is not clear how well these tests correlate with infectivity. This has contributed to uncertainty in both the interpretation of water testing results, and the assessment of the effectiveness of disinfection techniques for water treatment.

Researchers from Tufts University recently published some observations on the potential of ribosomal RNA (rRNA) and messenger RNA (mRNA) as markers of infectivity for Cryptosporidium oocysts(1). Both types of RNA have been shown to decay rapidly after death in mammalian tissues, and it has been generally assumed that this is also the case for oocysts. However this study shows that decay rates differ markedly for different RNA transcripts.

The stability of two RNA markers was initially examined in C. parvum oocysts which had been heat inactivated(2) (65ºC x 15 min) then stored at room temperature for several weeks. It was found that beta-tubulin mRNA was not detectable even 1 hour after inactivation, whereas the small subunit (SS) rRNA persisted for at least 11 weeks. This gave an initial indication that beta-tubulin mRNA was relatively unstable and might be useful as a marker of infectivity.

Experiments were then done to test the persistence of beta-tubulin mRNA and SS rRNA in oocysts stored at room temperature or 4ºC. A fresh preparation of oocysts from calves was assayed for excystation (90% excystation rate) and for infectivity in baby mice (8/8 mice infected with an inoculum of 106 oocysts). The preparation was split into two portions with one being stored at room temperature and the other at 4ºC. At various time intervals, duplicate aliquots were removed for infectivity testing and for storage at -70ºC. RNA extractions from the stored aliquots were carried out in a single batch to minimise variations between samples, and RT-PCR was used to amplify the desired products.

At room temperature, oocysts retained some infective ability at Week 15 (20% of mice infected) but were not infectious at Week 20. The disappearance of beta-tubulin mRNA appeared to parallel the loss of infectivity with none detected at Week 15. The SS rRNA transcript persisted throughout the 20 week storage period. These observations were confirmed in a repeat experiment. Another mRNA transcript of unknown biological function was also tested, and was found to decrease on storage at room temperature but still remained detectable after infectivity was lost. At 4ºC oocysts remained infectious for at least 39 weeks (100% of mice infected), and both beta-tubulin mRNA and SS rRNA remained detectable throughout this time.

As the oocyst suspension used in the experiments was much more concentrated than any environmental sample likely to be encountered, the authors also tested serially diluted suspensions and found that the beta-tubulin PCR product was detectable at a level of 10 oocysts.

The authors believe the beta-tubulin mRNA transcript may be a useful marker for infectivity and are now assessing the suitability of the method for environmental samples. This particular marker has advantage due to the presence of an intron in the beta-tubulin gene which allows the PCR product from mRNA to be distinguished from the PCR product from DNA which may be co-purified during RNA extraction. DNA is more chemically stable than mRNA and generally persists longer in adverse environmental conditions, however the PCR product from beta-tubulin mRNA can be distinguished by its shorter length due to splicing out of the intron sequence.

Recent work on UV sterilisation of oocysts has shown that excystation and "vital dye stains" do not provide a sensitive measure of reductions in infectivity(3). Oocysts of the Iowa isolate (also known as the Harvey Moon isolate) of C. parvum were subjected to UV irradiation from a medium pressure UV source, then assessed by excystation assay, DAPI-PI staining and infection of neonatal mice. Control experiments on untreated oocysts were used to determine that the experimental manipulations did not significantly reduce infectivity, and that the oocyst preparations displayed the expected infectious dose (dose to infect 50% of exposed mice =approx. 75 oocysts).

Four different UV doses were used in bench scale studies - 41, 82, 123, and 246 mJ/sq cm (1mJ/sq cm = 1mW/csq cm). For each UV dose, three dilutions of each sample of treated oocysts were used to inoculate neonatal mice (1,000, or 10,000 or 100,000 oocysts with 23-28 mice for each inoculum level).

There was a large discrepancy between in vivo and in vitro assays. DAPI-PI staining and excystation assay of oocyst suspensions from the 3 lowest UV doses suggested that only a low degree of inactivation had occurred (66-89% of oocysts still viable by DAPI-PI, 84-85% viable by excystation). At the highest UV dose DAPI-PI staining suggested about 4% of oocysts were viable, while excystation indicated 1% viable.

However the mouse infection experiments showed a large decline in infectivity at all UV doses. At UV doses of 41, 82 and 246 mJ/sq cm, no mice were infected. At a dose of 123 mJ/sq cm, only 1 of 25 mice inoculated with 100,000 oocysts was infected. These observations suggest that at least 3.9 logs of inactivation was achieved at all UV doses tested here.

Similar results were obtained with a demonstration scale UV reactor with a flow rate of 814 L/min and UV doses between 19 and 159 mJ/sq cm. Again there was a large reduction in infectivity for all UV doses (around 4 logs) but DAPI/PI and excystation tests showed little effect at low doses and a maximum 2 logs inactivation at high doses. The UV doses delivered to oocysts in the reactor were calculated using a complex mathematical model to account for water turbidity.

The authors note that previous studies have suggested that very high UV doses are necessary to inactivate C. parvum oocysts, however such studies have employed low pressure UV with a narrow emission range while the UV source used here had a broad emission range and a higher irradiance. The earlier studies also used mainly in vitro methods to estimate inactivation, which as this study has clearly shown, do not accurately reflect the degree of change in infectivity.

(1) Widmer G, Orbacz EA and Tzipori S. (1999) Beta-tubulin mRNA as a marker of Cryptosporidium oocyst viability. Applied and Environmental Microbiology 65 (4) p1584-1588.

(2) It should be noted that the authors use the word "viable" to mean "infectious", and "inactivated" to mean "noninfectious" although others sometimes distinguish between these terms.

(3) Bukhari Z. Hargy TM, Bolton JR, Dussert B and Clancy JL (1999) Medium-pressure UV for oocyst inactivation. Journal of the American Water Works Association 91 (3) p86-94.

As part of the consultation phase for the new Interim Enhanced Surface Water Treatment Rule and the Stage 1 Disinfectants / Disinfection By-products Rule(1), the US EPA carried out an analysis of the expected benefits and costs for implementation of these changes in regulation(2,3). In both cases considerable uncertainty surrounds the degree of health risk, resulting in a wide range of possible benefit-cost ratios.

Disinfectants / Disinfection By-products Rule (D/DBP)
The D/DBP Rule is aimed at lowering levels of disinfection byproducts in drinking water in order to reduce the potential risk of cancers which may be associated with prolonged exposure to high levels of these chemicals.

Information on the degree of risk comes from two different sources; animal toxicological studies, and human epidemiological studies. From the animal studies, it was estimated that between 0 and 100 excess cancer cases (all types) might be expected each year in the US population given current levels of DBPs in drinking water. This estimate takes into account uncertainty factors for extrapolation from short term/high exposure studies in laboratory animals to long term/low level exposure in diverse human populations.

From the epidemiological studies it was estimated that between 1,100 and 9,300 excess cases of bladder cancer might be expected each year, but as interpretation of these studies remains controversial it was not possible to exclude the possibility that no excess cases might arise. Only bladder cancer was considered as most studies with stronger methodology have focussed on this type of cancer.

Given the widely divergent estimates derived from these two lines of evidence, it was not possible to adopt a middle range consensus value for cancer risks. Therefore in subsequent analysis a possible range from 0 to 9,300 cancer cases per year was assumed.

From current knowledge of DBP levels and the predicted effects of changes in water treatment, a 24% reduction in DBP exposure across the US population was estimated for implementation of the Stage 1 D/DBP Rule. It was then assumed that the percentage reduction in cancer risk would parallel the reduction in DBP exposure, corresponding to a reduction of between 0 and 2,232 cases of cancer each year. The distribution of fatal and non-fatal cases was assumed to be the same as for bladder cancer (23% fatal, 77% non-fatal cases).

The economic value of a reduction in the number of cancer cases was then calculated by assuming that each fatal case avoided had a value of $5.6 million, and each non-fatal case avoided had a value of $587,500. This yielded a range of possible benefits from $0 to $4 billion per year. These estimates assume immediate benefits, although it is recognised that any cancer-related health benefits would accrue gradually. The figures also do not take into account any other health benefits (ie reduction in non-cancer risks) that may also be achieved by reducing DBP levels in drinking water.

Calculation of the costs for implementation of the Stage 1 D/DBP Rule was somewhat more straightforward, with nationwide costs estimated at $700 million annually (annualised at a 7% discount rate). About 84% of this amount would be required for installation, operation and maintenance of equipment, while 13% would be needed for system monitoring, and 2% for state charges.

Five different approaches were then used to compare benefits with costs. Explanation of these methods is beyond the scope of this summary, however they included overlap technique, break even analysis, household cost of compliance, a probability approach, and an approach to minimise maximum regrets.

The latter approach, known as "min-max regrets" is seen as perhaps providing the best illustration of balancing competing issues in public health protection. This analysis considered the overall effects of three regulatory options; no action, Stage 1 D/DBP Rule, or a more stringent Stage 2 Rule. For each option, the cost of compliance was added to the cost of remaining cancer cases after compliance, for different assumed levels of cancer risk. This shows the "downside risk" or maximum social loss if the real health risks turn out to be very different from the assumed value.

Using this method of analysis, the Stage 1 Rule was deemed to provide the smallest maximum potential loss to society. Therefore the authors conclude that the benefit-cost analysis generally supports the incremental approach to DBP reduction that has been adopted in the US, where the initial step will be achieved without major changes in technology.

However they also note that definitive answers on health risks cannot be expected in the immediate future, and in fact recently raised concerns over short term health effects may broaden the estimates of risk even more. Further reductions in DBP levels beyond the Stage 1 D/DBP Rule will probably require substantial and expensive changes in technology, and it may become even more difficult to compare the potential benefits and costs.

Interim Enhanced Surface Water Treatment Rule (IESWTR)
The IESWTR is targeted at achieving better control of pathogen levels in drinking water, and ensuring that control of pathogens is not compromised by the implementation of the D/DBP Rule. Several of the requirements of the IESWTR are specifically aimed at reduction of Cryptosporidium levels, although compliance is judged by surrogate markers (in particular turbidity) rather than by measurement of oocysts in water.

In estimating the benefits which may be achieved by the Rule, the authors considered only a reduction in Cryptosporidium infection although it would be expected that illness due other pathogens might also be reduced. The possible impact of avoiding waterborne outbreaks was not estimated, as the probability of such events could not be estimated.

A quantitative risk modelling approach was used to estimate the proportion of endemic illness that may be currently attributable to Cryptosporidium oocysts in drinking water. The inputs to the model included dose-response information from the first published human volunteer study, daily water intake, oocyst numbers in raw water, removal by filtration, viability after water treatment, and percentage of exposed people who become ill. A Monte Carlo simulation was carried out to generate a probability distribution of the predicted number of infections and illnesses. The authors note that good quality data on many of these parameters is absent, and there is a large degree of uncertainty in the estimates. Therefore a number of different assumptions are presented in the paper to illustrate the range of benefits that may be achieved.

Using the assumption that filtration plants currently remove 2.5 logs of oocysts on average (with some plants better and some worse), it was predicted that 1.5 million Cryptosporidium infections might occur each year from drinking water systems affected by the IESWTR, with 643,000 of these resulting in illness. This figure is vastly in excess of the number of recognised case of cryptosporidiosis from all sources reported in the US each year, however it is known that laboratory diagnosed cases of gastro-intestinal pathogens represent only a small fraction of all cases in the community. The true number of cases of Cryptosporidium infection in the US and the proportion attributable to drinking water are presently unknown.

Based on figures from the Milwaukee outbreak it was estimated that a fatality rate of 0.0125% might be predicted, although this figure is very tentative. Life threatening Cryptosporidium infections are limited to people with severely compromised immune systems (predominantly people with AIDS), and since many in this group currently avoid consumption of tap water they may not be exposed to infection via this route.

If it is assumed that implementation of the IESWTR will result in an improvement in average log removal by water treatment plants to 3.0 logs, then a fall to 208,500 illnesses per year would be predicted (ie 434,500 illnesses avoided). To convert these potential health benefits to economic costs, the authors assumed the mean benefit for each illness avoided was $2,000 (direct medical costs only) and the statistical value of a life saved was $5.6 million. This yields a total annual benefit of about $1.5 billion. The authors briefly discuss the special circumstances surrounding fatality risks from cryptosporidiosis (ie restriction of the risk to a small subgroup of the population who already face a shorter than normal life expectancy) but conclude that there is no accepted method to adjust economic values for these factors.

The cost of implementing the IESWTR is estimated at $307 annually (using 7% cost of capital). Total capital costs are estimated at $759 million, and operation and maintenance at $106 million annually. Annual treatment costs will be $192 million and turbidity monitoring $96 million. The authors conclude that despite the large uncertainty in estimating the contribution of Cryptosporidium in drinking water to endemic illness, the value of the benefits of the IESWT Rule are likely to outweigh the costs.

(1) Refer to Health Stream Issue 13 for an outline of the changes under these Rules.

(2) Odom R, Regli S, Messner M, Cromwell J and Javdan M (1999) Benefit-cost analysis of the Stage 1 D/DBP Rule. Journal of the American Water Works Association 91 (4) p137-147.

(3) Regli S, Odom R, Cromwell J, Lustic M and Blank M (1999) Benefits and costs of the IESWTR. Journal of the American Water Works Association 91 (4) p148-158.

Dr Jennifer Clancy of Clancy Environmental Consultants (CEC) recently visited Sydney and Melbourne to present one day seminars on Method 1622 for the isolation of Cryptosporidium from water samples(1). Method 1622 was developed by CEC under contract to the US EPA to replace the current "ICR method"(2) which has long been acknowledged as being unsatisfactory. Under the terms of the contract, CEC was required to develop and validate a more reliable technique using commercially available technologies within a nine month timeframe.

The method has been subjected to blinded validation in 12 laboratories with satisfactory results. Dr Clancy reported that overall recovery rates for oocysts were in the range of 35% to 45%, based on the use of positive spikes of 100 oocysts in 10 litres of water. Common practice has been to use positive spikes several logs higher than this, but it is felt that recoveries calculated in this manner are not a valid indicator of the recovery levels in natural water samples which generally contain only low numbers of oocysts.

To date none of the participating labs have recorded any false positive or false negative results - indicating that the method is both reliable and specific. An immunomagnetic separation step allows oocysts to be separated from most contaminating materials and other microorganisms that might produce false positive results on microscopy. The relative absence of debris also allows the entire concentrate from 10 litres of water to examined on 1 or 2 slides, removing the uncertainty associated with counting only a portion of the sample.

However Dr Clancy noted that the identification of protozoa still depends on the skill and experience of the microscopist, and emphasised the need for adequate staff training and periodic crosschecking of results with other observers.

The new method is being used in several large research studies in the US and Canada, and is expected to replace the ICR method in all US laboratories over the next few months.

A similar method (Method 1623) for combined isolation of Cryptosporidium and Giardia has been validated and is also in use in field studies. This method is identical to Method 1622 except that two types of immunomagnetic beads are used (specific for Cryptosporidium and Giardia respectively). Neither method is species-specific (ie oocysts/cysts from all Cryptosporidium species and all Giardia species will be detected, not just C. parvum and G. lamblia which can infect humans).

Following the experience with the Information Collection Rule, where regulatory inflexibility forced the continued use of a method which was known to be incapable of producing meaningful results, the US EPA has moved to adopt a "performance based measurement system" for Cryptosporidium detection techniques.

New regulations will allow the development and use of alternative isolation and detection methods providing they are validated in a similar manner to the Method 1622, and demonstrated to achieve the same level of reliability and specificity. This move has been welcomed by the water industry and the broader environmental management field, and it is hoped that a similar flexible approach will be adopted in other areas of EPA regulation.

(1) The Method 1622 protocol can be obtained from the US EPA Microbiology Home Page at:
http://www.epa.gov/nerlcwww/

(2) ICR = Information Collection Rule, a US EPA regulation which required larger water utilities to carry out an 18 month Cryptosporidium monitoring program from July 1997 to December 1998. The isolation technique specified under this Rule had variable and often very low recovery rates for oocysts, and was prone to both false positive and false negative results. (See Health Stream Issue 2 and Issue 4 for more details)

Deficiencies in laboratory quality assurance have led to a number of notable false alarms over Cryptosporidium both in water supplies and in medical practice. Variability in testing methods and estimation of recoveries have also contributed to the uncertainty surrounding the public health significance of Cryptosporidium in water supplies.

Lower arsenic limit for US

The US EPA is likely to lower the current 50 microgram /litre standard for arsenic in drinking water following the release of a report by the National Academy of Sciences. The standard was set on the basis of evidence relating to arsenic-induced skin cancers, however according to the draft NAS report released on 24 March, prolonged exposure to arsenic contaminated water at this level may lead to elevated risks for lung or bladder cancers. Only about 1% of public water systems in the US have arsenic levels above 20 micrograms/ ml, however private water supplies may have higher levels of contamination. Proposals for the new standard will be announced in early 2000 following consultation with stakeholders.

New WHO publication on Cyanobacteria

The CRCWQT recently co-sponsored the Australian launch of a new World Health Organisation publication Toxic Cyanobacteria In Water: A Guide To Their Public Health Consequences, Monitoring And Management. Several CRCWQT researchers have made contributions to the book which is published by E&F Spon (http://www.efnspon.com/)
ISBN/ISSN: 0-419-23930-8.

Cryptosporidium outbreak hits UK

A Cryptosporidium outbreak suspected to be waterborne has affected the Cumbria region of north west England. Health authorities were notified of an unusually high Cryptosporidium reading (3.4 oocysts / litre) in a 10 litre grab sample taken by a local water company on 20 April. It was decided not to issue a boil water notice as the delay between sampling and obtaining a result meant that the affected water had already been consumed, and results from subsequent water samples were in the normal range for the supply (0.2 oocysts /litre or less).

Surveillance for cryptosporidiosis in the region was intensified, and it became evident that reported case numbers had risen sharply shortly after the contamination was detected. By 12 May a total of 217 cases had been identified in a region of 1.5 million people, corresponding to about 20 times the normal occurrence rate. Analysis of isolates from affected people has shown the presence of C. parvum genotype 2 which is transmitted readily between humans and other mammals. Initial investigations on the source of the contamination have focussed on sheep grazing in the catchment area.

Canada issues algal warning

Health Canada has issued a warning to consumers of products containing blue-green algae (cyanobacteria), following the detection of microcystin toxins in some products. Tablets and powders made from blue-green algae grown in natural lakes or cultivated ponds have been promoted as dietary supplements and more recently (although without scientific foundation) for the treatment of Attention Deficit Disorder in children.

A preliminary survey undertaken by a researcher at the University of Alberta found that some naturally grown products exceeded the WHO and Health Canada microcystin guidelines for daily consumption. Consumers have been warned not to give the products to children as they may be more likely than adults to suffer liver damage from the toxin. Adult have also been advised not to consume the products on a long term basis. Health Canada is now undertaking a larger survey of blue-green algal products.

Moon probe to make a splash

The 18 month mission of the Lunar Prospector probe will come to a spectacular end on 31 July when NASA fight controllers deliberately crash the spacecraft onto the Moon's surface. The probe will be aimed at the 60 kilometre Mawson crater near the south pole, which is suspected to contain a high concentration of water ice. Under the original mission plan, the probe would have been allowed to crash at random when its fuel supply was exhausted, however NASA decided to accept the new plan proposed by researchers at the University of Texas after it was endorsed by independent experts. Scientists are hopeful that the impact will cause the release of water vapour or its byproduct OH which could be detected by observatories on earth. This would provide definitive proof of water in the permanently shadowed craters at the Moon's poles.

Pure Drink or Pure Hype?

The US environmental lobby group, the Natural Resources Defense Council, has called for tightening of bottled water standards following a study of more than 1,000 samples of bottled water. The NRDC report, Bottled Water: Pure drink or Pure Hype?, forms part of a citizen's petition to the Food and Drug Administration. The NRDC tested 103 brands of bottled water and concluded that it was not necessarily cleaner or safer than most tap water.

The report highlights many anomalies in US federal and state regulations on bottled water, and notes that misleading marketing claims still abound despite some recent tightening of the rules governing advertising. The NRDC have recommended that regulation and testing requirements for bottled water should be made at least as strict as those for tap water, and that manufacturers should be required to disclose the water source and method of treatment.

London acts on ground water threat

The British government has approved a plan to extract millions of litres of water from the water table underneath London. Ground water levels beneath the city have risen about 50 metres since the 1960s as industrial use of ground water has declined. The extraction plan is designed to control water levels before they become a threat to infrastructure such as underground railways.

Fluoride in top 10 achievements

Fluoridation of drinking water has been included in the list of Ten Great Public Health Achievements, 1900-1999 by the Centers for Disease Control and Prevention in the US. The achievements were selected on the basis of opportunity for prevention and the impact on death, illness and disability in the population. About 144 million of the US population receive fluoridated water, which is credited with a 40-70% reduction in tooth decay in children and a 40-60% reduction in tooth loss among adults.

The other topics making the list were vaccination, motor-vehicle safety, safer workplaces, control of infectious diseases, decline in deaths from heart disease and stroke, safer and healthier foods, healthier mothers and babies, family planning, and recognition of tobacco use as a health hazard.

Report urges abolition of irrigation subsidies

A report by the Australian Academy of Technological Sciences and Engineering and the Institution of Engineers has called for radical reforms in the irrigated farming industry. According to the report the industry accounts for over 70% of water use in Australia, but most farms use wasteful irrigation methods and seldom employ objective techniques for improving water efficiency. Significant changes in the urban water industry have occurred in recent years, the rate of reform in rural areas has been much slower, partly because of political sensitivities.

The report urges full cost recovery for irrigation schemes and cites Victoria's Goulburn Valley as an example of a region which is under paying for water use. The authors estimate that revenue from farmers in the Goulburn would need to double to provide adequate returns for the system. They advocate the inclusion of full costs for dealing with the environmental impacts of irrigation such as salinity, excess nutrients, toxins and drainage problems. The report also estimated that requirements for irrigation water could rise by 66% over the next 20 years, a rate of growth which would be unsustainable in some areas of Australia.

Sydney water health claims dropped

An Australian High Court class action suit against Sydney Water Corporation for illnesses allegedly suffered as a result of the water contamination incidents last year was withdrawn on June 18. It is believed that the legal firm representing the 400 claimants decided to drop the case after local and overseas experts advised that no causal link could be established between illnesses suffered by the claimants and consumption of tap water during the incidents.

Feeling thirsty?

A team of scientists from Australia's Howard Florey Institute and the University of Texas have found that the sensation of thirst is controlled by a complex interaction of neural signals. Volunteers were injected with a salt solution to stimulate thirst, then brain activity was monitored with a scanner which showed a pattern of stimulation and depression in several regions of the brain.

Changes in brain activity when subjects rinsed their mouth with water, or drank their fill showed that a combination of signals from the mouth, throat and stomach were required for the sensation of thirst to disappear.

It appears that the brain is able to gauge the volume of water consumed from these signals, and modulates intake even before water has been absorbed into the blood stream

The thirst reflex tends to decline with age, and may be exaggerated or reduced in patients with neurological or psychiatric disorders. In some cases, the resultant disturbances in blood chemistry can have serious health effects. The researchers hope that a better understanding of the mechanism of thirst will assist in the management of such illnesses.

Global warming security fears

Delegates at a Canadian Arctic security conference held in May have discussed the security implications for Canada if global warming should result in melting of the Northwest passage. Under United Nations conventions, countries are granted special rights over ice-covered waters adjoining their land mass. This has effectively given Canada control of the straits and islands of the region, however if the ice melts the sea lanes would become international waters, providing a new route for shipping between Europe and Asia.

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