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MTBE Debate For Australia

The fuel additive MTBE (methyl tertiary butyl ether) recently emerged as an issue of concern for the Australian water industry, a few months after the approval of the Fuel Standards Act in December 2000. The Act specifies new requirements for petrol and diesel fuels to be phased in over a four year period beginning in January 2002. These changes are designed to reduce air pollution levels in urban areas, and will bring Australian standards for fuel quality into line with changes in international standards. This is expected to result in a reduction in rates of respiratory illnesses and lower cancer risks, with an estimated saving of up to $3 billion in health costs in Australia over the next 20 years.

Attainment of the new standards will require changes in petrol formulation to reduce emission levels. Internationally, this has generally been achieved by adding oxygenate compounds to petrol. MTBE is one of several compounds that can be used for this purpose, and has achieved market domination because of its low cost. However MTBE from petrol has been associated with significant water pollution problems in the United States since use of this agent escalated in the 1990s, resulting in calls from some water authorities for a complete ban (1).

During the period leading to formulation of specific standards for fuel components, some independent petrol retailers in Australia submitted that continued importation of MTBE-containing fuel from Asia was necessary to maintain viability in the competitive market with locally refined petrol (2). This was strongly opposed by representatives of the Australian water industry and a number of environmental groups on the grounds that MTBE posed an unacceptable threat to water supplies.

After several months of debate, the Australian Federal Environment Minister announced on 15 July that MTBE levels in petrol sold in Australia would be limited to 1% v/v from January 2004. The states of Queensland, South Australia and Western Australia have already put in place bans on MTBE in petrol in response to perceived environmental risks.

MTBE emerged as a significant issue for water utilities in the US in 1996 when it was detected in groundwater supplies for the city of Santa Monica only two years after it was introduced into fuel supplies in California. Testing revealed MTBE to be present in 7 of 11 wells, with concentrations reaching as high as 600 micrograms/L (ppb), resulting in closure of the affected wells. The contamination was traced to leaking underground fuel storage tanks.

MTBE possesses several properties that enable it to rapidly spread to groundwater supplies. It does not bind well to soil particles, is highly water soluble and poorly biodegradable. As a result it moves more rapidly through soil than other petrol components, with travel distances of up to 4.8 km (3 miles) being documented. There have been a number of recorded incidents where small fuel spills have caused detectable water contamination problems, including one spill of 30-38 litres (8 to 10 gallons) from an automobile accident which affected 24 private wells. Conventional water treatment methods are not very effective for removal of MTBE, and techniques such as air stripping, advanced oxidation processes, and granular activated carbon must be used.

Taste and odour thresholds for MTBE in drinking water are low, with one study of four people trained in water tasting reporting a taste threshold as low as 2-5 micrograms /L, although the taste was not considered objectionable until levels of 50 micrograms/L had been reached. Studies in less highly selected groups of people have suggested average odour thresholds ranging from 15 to 180 micrograms/L in water.

The taste and odour have been described in various studies as being bitter, solvent-like or plastic-like. The US EPA has set an advisory level of 20-40 micrograms/L in drinking water based on taste and odour, but some states such as California have set an aesthetic level of 5 micrograms/L in recognition of the fact that some individuals may be more sensitive to the compound than others.

The human health effects of MTBE exposure have prompted much debate. There have been many anecdotal reports of adverse effects such as headache, dizziness, eye and nose irritation and nausea attributed to inhalation exposure to fuel containing MTBE or other oxygenates, however studies under controlled conditions have failed to demonstrate consistent associations. Some studies have suggested that adverse publicity about the introduction of fuel additives may have influenced people's perception of health effects, and that common symptoms of respiratory infections or other illnesses may have been attributed to fuel exposure in some instances. However the possibility that some individuals in the population are more sensitive to MTBE than others can not be ruled out.

Animal toxicity data from chronic inhalation exposure suggests that even under worst case scenarios, people with occupational exposure are unlikely to suffer non-cancer health effects, and risks for the general public are much lower. However, as aptly expressed by one reviewer, "rats don't retch" and animal studies can not provide evidence on the aesthetic aspects of exposure in humans.

Assessments of the potential cancer risks posed by MTBE are also a source of controversy. In its 9th Report on Carcinogens published in 1999, the US National Toxicology Program reviewed the evidence on MTBE and concluded that the available rodent cancer data "were not sufficient for listing in the Report as reasonably anticipated to be a human carcinogen". The same conclusion was reached by the International Agency for Research on Cancer, however some critics have charged that both bodies have acted unreasonably, and in contravention of their own criteria, in discounting some of the data from animal studies when making their decisions (3). A number of other bodies including the US EPA have concluded that MTBE is an animal carcinogen and may potentially be carcinogenic to humans.

In response to mounting concerns over water and environmental contamination, the US EPA began moves in March 2000 to reduce or eliminate MTBE in petrol under the Toxic Substances Control Act, a process that may take several years to complete (4). Many in the US water industry have urged more urgent action, citing accumulating evidence of widespread contamination of water supplies across the nation.

While initial concerns focused in groundwater supplies because of their vulnerability to contamination from spills and leaking underground tanks, surface water supplies may perhaps be more frequently affected by MTBE. The preliminary results of a random survey of 954 US water systems indicated that detectable levels of MTBE were present in 8.7% of all supplies, comprising 14% of surface waters and 5% of groundwaters sampled. Contamination was five times more common in areas where gasoline containing MTBE was used.

The contribution of different MTBE sources to surface water contamination has not been well established, however studies have shown that two-stroke motors in small water craft burn fuel very inefficiently, and that up to 30% of fuel is released unburnt into the environment. Thus recreational boating may be a significant source of MTBE in some surface waters. While airborne MTBE may potentially enter surface waters, evidence suggests that this is not a significant source, and that most airborne MTBE from release of tank vapours and evaporation remains in the air and is decomposed by photochemical reactions with a half-life of about three to seven days.

The pervasive nature of the additive was underlined by a recent study of petrol supplies in the states of Indiana, Illinois and Michigan, which found that MTBE could be detected in more than 70% of samples despite the fact that ethanol is the predominant fuel oxygenate used in these three states. Researchers attribute the contamination to residual amounts in storage tanks and fuel transport vehicles from other areas.

While advocating urgent action to eliminate MTBE use in fuel, US water authorities have also called for a more thorough evaluation of the potential environmental effects of alternative fuel additives to ensure that similar problems will be avoided in future. They have also called for a re-examination of mandatory requirements to add oxygenates to fuel in the US, given the outcomes of research undertaken at the University of California suggesting that modern automobile engines are capable of meeting US clean air standards without the use of such additives. However, the feasibility of completely banning MTBE has been questioned by many in the petroleum industry, and the need to retain the substantial health benefits achieved through improved air quality has been emphasised by the public health community.

The controversy over MTBE in the US is in contrast with the situation in Europe where MTBE is also used as a fuel additive, but is not presently perceived as a significant threat to water supplies. Several important differences exist, however, in the use of the additive in Europe. Firstly, in most European countries MTBE is added to petrol only as an octane booster at a level of about 1.6% v/v, in contrast to the 11-15% v/v used in the US for air pollution control. Secondly, European regulations governing underground fuel storage tanks have been more stringent and more strictly enforced than in the US. Thirdly, in Europe petrol is mainly dispensed under suction rather than under pressure, considerably lessening the likelihood of spills.

The relatively high cost of petrol in Europe also means that diesel fuel (which does not contain MTBE) is a competitive alternative to petrol for passenger vehicles, reducing the volume of petrol used. Higher costs and a different taxation structure have also been cited as providing more incentive for European petrol producers to avoid spills and wastage than in the US market. To date there have been few reports of MTBE groundwater contamination in Europe, although some researchers have warned that anticipated increases in MTBE levels in fuel to meet new European emission standards may bring with them similar problems to those that have occurred in the US.

(1) In the 1970s, MTBE was used in the US as an octane booster at 1-3% v/v. Use increased in the 1990s when the Clean Air Act required minimum oxygen levels for petrol sold in some metropolitan areas. MTBE is now used at 11% to reduce ozone production or 15% to control carbon monoxide emissions. MTBE-containing petrol constitutes about 27% of all petrol sales in the US.

(2) At present about 70% of liquid fuel used in Australia is locally refined, and MTBE is not added to locally produced petrol. Some petrol imports contain MTBE at levels of 3 to 7% v/v.

(3) Methly-tertiary-butyl-ether (MTBE) misclassified. Mehlman MA (2001) American Journal of Industrial Medicine 39:505-508.

(4) Advance Notice of Intent to Initiate Rulemaking under the Toxic Substances Control Act to Eliminate or Limit the use of MTBE as a Fuel Additive in Gasoline, Federal Register Vol 65 No 58 p16093-16109, 24 March 2000.

New Approaches For Water Quality Testing

The American Academy of Microbiology recently released a report advocating a radical overhaul of current approaches for measuring microbial water quality. The report Reevaluation of Microbial Water Quality: Powerful New Tools for Detection and Risk Assessment, was the outcome of a meeting of twenty-two international experts which took place in Florida during March 2000.

The report calls for the adoption of new technologies, particularly those based on molecular biology techniques, to provide more reliable methods of assessing human health risks, better early warning systems for hazardous events threatening water supplies, and improved ways of identifying and tracing contamination sources.

It makes a number of recommendations in the areas of microbial risk assessment, development of reliable molecular fingerprinting tools and databases to characterise pathogen characteristics and occurrence, improved education and communication to overcome barriers to acceptance of new methodologies, and consensus mechanisms for the assessment and development of standard techniques.

While acknowledging the contribution of traditional water quality measurements based on coliform bacteria to the protection of public health over the last century, the report underlines the inadequacy of this approach to assessing risks from pathogens other than faecal bacterial species. The traditional indicators are unreliable for assessing contamination risks for faecal viruses and protozoa, or for non-faecal pathogens such as Legionella. The chlorine sensitive nature of the coliform group also means that such measurements may provide a misleading assurance of safety for chlorinated supplies that are prone to contamination by more resistant organisms.

Citing recent instances of severe public health and economic impacts from contamination of drinking water, recreational water and shellfish supplies, the report notes several factors likely to lead to increases in risks of foodborne and waterborne diseases. International travel allows the rapid spread of pathogens from one continent to another via human carriers, and likewise the global nature of the food trade makes all countries vulnerable to imported pathogens. Ever increasing reliance on aquaculture to replace declining natural shellfish and fish catches means that coastal sewage pollution will pose a health risk to greater numbers of people.

Over the last few decades, advances in microbiology and molecular biology have had a huge impact in medicine, agriculture, bioremediation and many other areas, however these technologies have been very slow to penetrate the field of water quality measurement. Since water supplies are often prone to contamination from multiple point and non-point sources, identification and tracing of pollution sources is needed to implement effective management measures. Molecular techniques are seen to hold great promise in this area, and it is anticipated that direct detection of a range of microorganisms in environmental samples will soon be possible.

The report notes that there are both practical and behavioural barriers to the adoption of new methods. Concerns exist over the reliability of different technologies, and the potential for misinterpretation and misuse of results. In order to foster the development of new methods and their adaptation to routine use, it is essential that mechanisms are developed to enable reporting of results in a manner that does not expose innovative water utilities to bad publicity or recrimination.

Better education of policy makers is also needed, and scientists should ensure that their findings are presented in the context of the issue and with adequate explanation of the uncertainties involved in risk assessment.

The report urges more concerted attempts to document waterborne outbreaks and collect relevant information on their causes, and international collaborative approaches to developing, refining and standardising new methods for microbial water quality testing. While acknowledging that the practicality of advanced detection techniques such as gene chip technology have not yet been fully proven, it concludes that adoption of the new methodologies is essential to advance microbial risk assessment and provide more effective risk management for water supplies in the future.

The report is available from the web site of the Academy of Microbiology: www.asmusa.org/acasrc/aca1.htm

Value of Cyanobacterial Control

In the field of environmental regulation, as in other regulatory activities, there is an increasing need to provide evidence that the costs of compliance are justified by the benefits delivered to the community. In many areas the estimation of benefits in economic terms is not straightforward, as the benefits are "non-market goods" such as enjoyment of amenity which are not directly paid for by users. However, a number of techniques have been developed to estimate the equivalent monetary value of such benefits.

British researchers have carried out an assessment of the value of recreational and amenity values of a large water reservoir in Leicestershire which has been affected by cyanobacterial blooms in the past. The study estimated the annual value of the reservoir to users, and compared this to the costs incurred by the National Rivers Authority (NRA) in combating cyanobacterial blooms.

The Rutland Water reservoir is situated in a park some 1,260 hectares in area, and provides a range of recreational activities including sailing, fishing, windsurfing as well as walking and picnicking facilities. The reservoir experienced a large bloom of Microcystis aeruginosa in the summer of 1989, which forced its closure for a period of 6 weeks. Several animal deaths were attributed to the bloom and the closure of the reservoir attracted national media attention. Many other water bodies in the UK also experienced cyanobacterial blooms in 1989, and the NRA initiated a large program of data collection, analysis, modelling and remediation measures.

Three years after the reservoir closure, the researchers carried out a survey of visitors to determine patterns of usage, the activities undertaken and the value placed on the recreational and amenity benefits. The method used to estimate the economic value was the Contingent Valuation technique, whereby users were asked to state what amount of money they would be willing to pay each year to ensure continued access to the facilities. Visitors were shown a photoboard illustrating the current state of the reservoir (bloom-free), some basic information on cyanobacteria, and the condition of the reservoir during the 1989 bloom.

A total of 641 visitor parties were interviewed over a period of 18 days, representing 82.6% of those who were approached to take part. Participants were asked if they were willing to pay additional taxes to fund remedial water quality work to keep the reservoir free of cyanobacterial blooms. A total of 66.8% said they were willing to pay, 28.5% said they were unwilling and the remainder stated they did not know. Among those who did not wish to pay, the most common reasons given were that it was someone else's responsibility to pay, and that they paid too much tax already.

When asked how much they would be willing to pay each year, individual answers ranged from 0 to 1,000 pounds, with a mean of 16.74 pounds and a median of 2.00 pounds. In order to assess the influence of extreme values on these estimates, the authors analysed a number of data subsets which excluded either high or low values or both. Two measures were then chosen to calculate the mean willingness to pay (WTP), the whole sample mean of 16.74 pounds (without trimming extreme data), and the lower bound confidence interval on the mean of 11.71 pounds from a dataset that excluded the highest bid.

The total number of visitors to the Rutland Water reservoir was not recorded in the year of the survey, however the estimate from the following year was 800,00 to 1,000,000 visitors. A figure of 900,000 visitors was therefore used in calculations, together with data on the number of visitors per party, number of visits per year and type of visitor from the survey.

This process yielded an estimate of the overall willingness to pay ranging from 364,608 to 521,225 pounds per year. Specific data on the costs of measures undertaken at Rutland Water reservoir after the 1989 blooms was not available, however the average annual cost of cyanobacterial works undertaken in England and Wales by the NRA during the period 1998 to 1993 was 295,000 pounds. Thus the amenity and recreational value to the community of preserving access to the reservoir is clearly greater than the cost of water quality management measures.

Measuring the Recreational and Amenity Values Affected by Toxic Cyanobacteria: A contingent valuation study of Rutland Water, Leicestershire (Chapter 3); Pearson MJ, Bateman IJ and Codd GA. In Economics of Coastal and Water Resources: Valuing Environmental Functions, Kluwer, Dordrecht, The Netherlands (2001).

ISBN: 0792365046

Update On US Arsenic Rule

The US EPA has received three expert reports on arsenic commissioned early this year as part of the review of the Arsenic Rule. The incoming Bush administration ordered the EPA to review the newly promulgated Arsenic Rule which was legislated in the last days of the Clinton government (1).

The revised Rule would have lowered the arsenic standard for drinking water from 50 ppb (parts per billion or micrograms per litre) to 10 ppb. The development of the proposed Rule had been criticised from many quarters, with some environmental lobbyists saying it was not strict enough to protect public health, while representatives of the water industry voiced concerns over the interpretation of the scientific evidence on health risks, the validity of EPA assumptions, and lack of transparency of calculations on the economic impact.

After withdrawing the Rule, the EPA commissioned three expert reviews:

• An examination of water treatment cost issues by a working group of the National Drinking Water Advisory Council (NDWAC).
• A review of issues surrounding the estimates of benefits and the cost-benefit analysis by a panel under the Science Advisory Board of the EPA (SAB).
• An analysis of issues relating to health risks by a sub-committee of the National Academy of Sciences (NAS).

The Arsenic Cost Working Group delivered its report on 24 August, the SAB review of benefits was submitted on 30 August, while the NAS report on health risks was released on 11 September.

Cost Analysis

The report examined the methodology used by the EPA to estimate national compliance costs for the Arsenic Rule, and made a number of recommendations for revision of the cost estimates. In addition, the Working Group recommended the adoption of improved methodology for costing of future drinking water rules, noting that the resources allocated to such estimates should be commensurate with the expected economic impact of the change.

On the whole, the reviewers concluded that the EPA had produced a credible estimate of the cost of arsenic compliance given the constraints of present rulemaking, data gathering, and cost models. However they also felt that the cost estimates could be further improved using more recent information on treatment technologies, and reassessing a number of assumptions including those on administrative and training costs.

In the area of waste disposal, the reviewers recommended that the EPA reassess the effectiveness of the Toxic Characteristics Leaching Procedure (TCLP) test which is used to determine whether a substance is to be classified as hazardous. Recent research on arsenic waste suggests that the TCLP test may underestimate toxicity. The water industry had expressed concerns over the EPA assumption that arsenic waste would be regarded as non-hazardous, and that specialised disposal would not be required.

The report also recommended that the revised cost estimates should present more detailed breakdowns of capital and recurrent costs, and the number of water supply systems affected and the populations served. It also recommended that more detailed consideration should be given to point-of-use treatment systems for small supplies, including requirements for inspections of individual household systems. In considering the disproportionate compliance costs for small systems, the reviewers recommended that the NDWAC convene a working group to review EPA’s methodology and assumptions for determining national affordability for drinking water regulations.

Benefits Analysis

This report addressed five questions relating to assessment of benefits of the Arsenic Rule, and made general comments on the benefits-cost analysis produced by the EPA.

Treatment of latency of benefits - the review found the EPA analysis was flawed in its treatment of the latency of benefits associated with reduction of arsenic exposure. It noted that the expression "cessation-lag" was more appropriate to describe the predicted gradual decrease in cancer risks if people currently exposed to arsenic at 50 ppb had their exposure reduced to a lower level (2). The primary EPA analysis assumed an immediate single step drop in cancer risks rather than a slow decline, while the alternative analyses assumed a single step drop at the end of the time period. Both approaches are erroneous.

Treatment of health endpoints other than bladder and lung cancer - the reviewers noted there was considerable evidence of non-cancer health effects of arsenic including ischaemic heart disease, hypertension, diabetes and skin cancers. They suggested that while present data may be insufficient to establish dose-response relationships, careful analysis of such studies might indicate whether these effects occurred at arsenic levels being considered for regulatory decision.

Whether reduction/elimination of exposure should be evaluated as a separate benefits category - the EPA estimate of benefits relates to the value of fatal or non-fatal cancers avoided, not to the societal benefits of lower exposure levels (ie the non-health value that people might attach to the risk reduction). The reviewers concluded this was the appropriate approach.

Treatment of total benefits and costs and incremental benefits and costs for alternatives - the reviewers applauded the EPA for presenting costs and benefits of a range of regulatory options (ie consideration of different arsenic levels), but recommended that these should be broken down into categories to illustrate the differing impacts on large and small water supplies. This would allow a better understanding of how rapidly costs escalate as systems decrease in size. They also recommended that the benefits should be presented in terms of morbidity and mortality avoided as well as in monetary equivalent terms.

Treatment of uncertainties in the analysis - the benefit-cost analysis contains uncertainties in measurement of exposure, measurement of dose-response, variation in health outcomes, and measurement of costs. The reviewers considered the applicability of sensitivity analysis and the Monte Carlo technique. They concluded that sensitivity analysis of a range of alternatives, with explicit statement of the assumptions for each was appropriate for most aspects of the analysis. For some aspects where a distribution can be specified a Monte Carlo simulation would be desirable.

General comments - the reviewers commended a number of aspects of the EPA analysis but noted a concerns about the calculation of costs and benefits, and presentation of the results, especially in the Executive Summary of the EPA report.

Health Risks Analysis

This review included evaluation of additional evidence from publications on epidemiology, toxicology and risk assessment published since the 1999 National Research Council report Arsenic in Drinking Water. The reviewers noted that the additional evidence supported the role of chronic arsenic exposure in hypertension and diabetes. There were also reports of associations with adverse reproductive effects and respiratory illness, however these required verification by further studies. Four additional epidemiological studies of arsenic exposure in drinking water and internal cancers had been published; two from Taiwan, one from Chile and one from the US. Of these, all but the US study had shown increased cancer risks associated with arsenic exposure. The specialised population in the US study was felt to limit its applicability to the general population, and exposure measurement in this study was considered unorthodox (3). The other three studies had some improvements in methodology over the older Taiwan studies, and supported the findings from the earlier studies.

Some advances have been made in understanding the metabolism of arsenic, but the mechanisms by which adverse health effects are produced remain unclear. Given the diverse impacts on different organ systems, it is believed that the effects of arsenic are probably exerted through several biological modes of action. These may operate independently and they may exhibit different dose-response relationships. In the absence of data to the contrary, the reviewers concluded that arsenic should be treated as a genotoxic carcinogen (ie assumed to act directly on DNA to cause cancer). Therefore, in keeping with EPA policy, the low dose extrapolation of the dose-response curve should pass through zero (ie assuming no threshold exists). Thus any exposure is considered to entail some risk of producing cancer. This assumption produces a higher estimate of risk than if a threshold model were assumed.

It appears that arsenic metabolism may be influenced by genetic factors, age, arsenic dose and micronutrient levels, resulting in considerable variability in the host response to exposure. It has not been established whether cancer risks relate to cumulative exposure, average lifetime exposure or peak exposure levels. The internal cancers most strongly associated with arsenic (bladder and lung cancer) are also strongly associated with smoking, and some studies suggest a synergistic interaction between the two exposures. If this relationship exists, it would affect the accuracy of extrapolating risk levels from one population to another if smoking patterns differ between the populations.

The reviewers concluded that the dose-response data from the early Taiwanese studies still remained the most appropriate basis for risk estimates. By extrapolating from this data through the zero point, they calculated estimated lifetime excess risks of lung cancer and bladder cancer in the US population for exposure to different concentrations of arsenic.

Theoretical Maximum-Likelihood Estimates of Excess Lifetime Risk (Incidence per 10,000 people)

These risk estimates are somewhat higher than those estimated in the original EPA report prior to proposal of the 10ppb limit for arsenic. These differences are attributable to use of a different comparison population by the reviewers, different statistical methods and use of US background rates for cancer rather than Taiwanese rates. The reviewers note that even their highest estimated cancer risk (45 cases per 10,000 males exposed to 20ppb arsenic over a lifetime) would be extremely difficult to detect by epidemiological studies.

The EPA has extended the effective date for finalisation of the Arsenic Rule until 22 February 2002 in order to provide time for further public comment and discussion. Following the release of the National Academy of Sciences review of health risks, many environmental lobby groups have called for an even lower standard than the 10ppb previously proposed by the EPA.

(1) See Health Stream 21 for a report on withdrawal of the Arsenic Rule.
(2) The term "latency" is normally used to describe the time delay between exposure to a cancer causing agent and development of a detectable cancer.
(3) See Health Stream Issue 15 From the Literature for a review of this study (Lewis DR et al. 1999).

Climate Change and Waterborne Disease

A study of waterborne disease outbreaks in the US has shown that more than half were associated with severe storm events. Researchers at the Johns Hopkins University in Baltimore compiled data from the US EPA database of waterborne outbreaks and meteorological records from the 2105 watershed regions covering the United States. Outbreaks attributed to cross connections or back siphonage of sewage were excluded from analysis as were chemically related drinking water outbreaks and recreational water outbreaks.

Outbreak locations were assigned to the relevant watershed area, and monthly precipitation readings from weather stations within each watershed were analysed. A total of 548 waterborne outbreaks between 1948 and 1994 were included in the analysis. Of these, 51% were associated with extreme rainfall events ( highest 10% of rainfall figures) prior to the outbreak. Consideration of the top 20% of storm events produced an association with 68% of outbreaks. These associations were statistically significant.

For surface water outbreaks the association was strongest for rainfall events during the same month as the outbreak, while for groundwater supplies the strongest association was seen with a two month delay period. These observations are consistent with the immediate effects of contaminated runoff on surface water supplies, as opposed to the slower and more complex routes by which surface water contaminants may reach underground water tables.

This study confirms the findings of smaller regional studies and anecdotal observations from many waterborne disease outbreaks. Given the increasing frequency of heavy rainfall events, attributed by some to global warming trends, it has been speculated that waterborne disease outbreaks attributable to weather events are likely to rise in the future. Effects on illness rates through increasing foodborne infections and insect-borne diseases have also been predicted.

The association between extreme precipitation and waterborne outbreaks in the United States, 1948-1994.
Currerio FC et al. Am J Public Health (2001) 91(8) p1194-1199.

News Items

A Consumer's Guide to Drinking Water
The CRC for Water Quality and Treatment has produced a consumer's guide to drinking water that outlines all aspects of drinking water - from the catchment to the tap. The guide provides an overview of water in Australia and around the world and discusses how water is collected, treated, distributed, used and regulated. It has been developed for the general public, community and environment groups, students and others seeking information on our water supply systems.

The guide is available here

• Several revisions to the ADWG were released in September by the NHMRC. These comprised a revised Chapter 4 (Radiological Quality of Drinking Water), and revised or new Fact Sheets on Thermotolerant Coliforms and E. Coli, Coliforms, Burkholderia pseudomallei, Microcystins, Nodularin, Cylindrospermopsin, Radium-226 and Radium-228, Other beta and gamma emitting Radioisotopes, Aluminium, Boron, Copper, Monochloramine, and Atrazine.

These items can be downloaded from the NHMRC website:
http://www.nhmrc.gov.au/publications/synopses/eh19syn.htm

• The Public Consultation period for the Framework for Drinking Water Quality Management closed on July 6. Modifications to the Framework, in response to comments received during the consultation process and integration into the ADWG are now in progress.
• A Discussion Paper on Microbial Indicators of Water Quality is scheduled for release shortly.

Walkerton Inquiry
Public hearings into the E. coli outbreak that killed 7 people and affected about 2,500 in the town of Walkerton, Ontario were scheduled for completion on 25 September. The Inquiry has examined a wide range of issues relating to drinking water quality management and regulation, in addition to the specific circumstances surrounding the outbreak.

Among the material submitted was a 400 page report from the Office of Ontario's Chief Coroner which focused on the systemic deficiencies which allowed the outbreak to occur. The report made 57 recommendations based on assessment of the outbreak including:

• clear delineation of the responsibilities of oversight agencies, and adequate resourcing of these activities
• annual inspections and spot checks on water treatment facilities, and follow up to ensure deficiencies are addressed
• an orientation program on drinking water risk, management and regulation for municipal politicians and elected public utility commissioners
• improved training of water supply operators including knowledge of health risks
• accreditation of private testing laboratories and mandatory requirements for reporting adverse monitoring results

The Inquiry is expected to complete its work later this year.

Update On Cryptosporidium Outbreaks
As reported in our last issue, waterborne Cryptosporidium outbreaks recently occurred in Belfast, Northen Ireland, and North Battleford, Saskatchewan, Canada.

Initial investigations attributed the Belfast outbreak to overflow of untreated water from a blocked drain into the filtered water stream. According to information from the local public health unit, the water supply in question was not considered to be at risk of Cryptosporidium contamination and thus water leaving the plant was not subject to continuous monitoring under Drinking Water Inspectorate regulations. However continuous monitoring was being carried out on an aging aqueduct through which the water was delivered to part of the city. Monitoring at the plant was commenced only after the outbreak was recognised.

The boil water order on North Battleford was lifted on 25 July, three months after the outbreak was detected. The outbreak is believed to have affected at least 1300 people across several Canadian provinces. A number of changes have been made to the operation of the surface water treatment plant including provision to allow water to run to waste, and more stringent operating and monitoring guidelines. A UV treatment stage will be added to the plant before the end of the year. A Commission of Inquiry into the outbreak is currently underway.

Contact Information

The printed version of Health Stream is available free of charge - to be added to our mailing list please contact Pam Lightbody (email or fax + 61 3 9903 0576). Past issues can be found under Publications, and there is a searchable archive of articles, news items and literature summaries.