This project will investigate and document a variety of existing surveillance systems relating to the detection of gastrointestinal disease in the community, and assess the feasibility of linking these with water quality data. Information will be collated from Australian and overseas sources, and methods of linking and extending current Australian systems to improve the sensitivity and speed of detection will be examined. Supplementary data sources such as records of pharmaceutical sales, sentinel medical practices and pathology lab records will be evaluated for their utility in helping to detect changes in disease incidence.
The project will also investigate whether such surveillance data might be linked with water quality data to flag any events which might signal a link between changes in water quality and outbreaks of gastroenteritis. The development of such a system would maximise the opportunity of rapidly recognising outbreaks of gastroenteritis that were possibly attributable to water, and could provide a trigger for appropriate investigations and interventions by health and water authorities. An early detection system would have the potential to prevent many cases of gastroenteritis and their associated morbidity and cost to the community by terminating epidemics earlier than would otherwise be the case.
This project has been jointly funded by the Melbourne Water Corporation and the CRCWQT and will be completed in late 1997.
WSAA also has the objective of identifying the need for public education in the field of drinking water and public health and mobilising support for such education.
The workshop was held at the CSIRO Division of Chemicals and Polymers conference facilities at Clayton, and was attended by about 38 participants and 37 observers. Both participants and observers represented a broad range of expertise in water quality, water treatment and distribution systems, public and population health, epidemiology, microbiology and risk assessment. Two international guest speakers, Professor Wolfgang Kühn (Technologie Zentrum Wasser, Germany) and Dr James Manwaring (American Water Works Association Research Foundation, USA), presented overviews of experience in Europe and the United States.
The overall aim of the workshop was to define the relative importance of
a range of drinking water quality issues in terms of population health in
Australia. The specific objectives addressed by the workshop were:
The Workshop was structured to provide time for formal presentations, discussion and question sessions among the participants, with limited time set aside for questions from the observers. The format permitted some key water quality issues to be discussed in detail, and the diversity of expertise allowed for a range of views to be represented.
Levels of participation were high, and it was evident that the interchange of views and knowledge between health and water industry representatives was a productive experience for all involved. The contributions of the overseas guests gave a clear perspective and overview of water quality regulation in Europe and the USA, and the contrasts in the approaches adopted in their respective countries.
The proceedings and outcomes of the Workshop will be written up for publication by WSAA in the near future.
The aim of the meeting was to assess the current state of knowledge about microbial risks from drinking water, to consider how these risks should be characterised and quantified, and to identify areas where action was needed in terms of public policy and research.
The report reviews the relationship between water use and population growth and development. Industrial growth and urbanisation in developing countries is accompanied by increasing demands for water, while water quality may be compromised by increasing pollution and pressure on inadequate water sources. Low water quality and/or inadequate water supply impact severely on the health and quality of life of much of the world’s population. The world Health Organisation estimates that in developing countries, infectious and parasitic diseases account for 71% of deaths in children and 44% of all deaths. Attempts to derive the fraction of such deaths attributable to water-related diseases are hampered by lack of data, but estimates of up to 80% have been made.
In developed nations, the threat of waterborne epidemics in urban populations seemed to have vanished as the establishment of water disinfection and sanitation systems in the early part of the century virtually eliminated bacterial pathogens which previously caused widespread and devastating infections. However, the recent emergence of the protozoan parasite Cryptosporidium parvum as an important waterborne human pathogen has shattered this belief, and it is clear that even developed countries may not be able to guarantee the safety of their drinking water.
The report comments that the accomplishments of the early parts of this century in dramatically reducing the incidence of infectious diseases have ironically resulted in a decline in research, education and funding for this area of public health.
In recent years, concerns over water quality in the developed world have focussed on chemical contaminants, and improvements in detection methods have seen detection thresholds for such contaminants progressively lowered. The possible association of some chemical contaminants with cancer risks has intensified public concerns on this issue, while the major socioeconomic impact of waterborne infectious disease has been little recognised, and the long term health consequences poorly appreciated. The meeting reiterated the paramount importance of adequate drinking water disinfection as the primary method of reducing waterborne illness.
However, this emphasis is now shifting as the emergence or resurgence of microbial pathogens, coupled with an increase in multiple antibiotic resistance and an increasing population of immunocompromised individuals, leads to professional, governmental and public recognition that infectious disease is still a major public health problem.
Historical attempts to control the spread of waterborne pathogens through quarantine, trade barriers, vaccination and antibiotic prophylaxis have been unsuccessful - the only proven measures are the provision of safe drinking water and adequate sanitation for the populations at risk. The inability of communities to pay for such services has often been raised as a barrier to implementation in the developing world, however this may be a false assumption. In many countries the poorest groups in the community already pay more for bottled water sold by local vendors than more affluent groups pay for piped water supplies.
In considering water quality monitoring, the meeting noted that while the traditional indicator organisms such as E. coli have proven to be adequate measures of the general sanitary quality of water, they clearly are inadequate for assessing the risks from protozoan and viral pathogens. There is also some doubt as to the applicability of these indicators in tropical regions where regrowth of faecal organisms can occur at ambient water temperatures. There is an urgent need to identify more appropriate indicators and/or to develop specific, sensitive and reliable tests for pathogens.
Surveillance and reporting of infectious diseases needed to be improved and standardised to some extent so that better quality data is made available for epidemiological analysis. The economic cost of surveillance can be recouped by the benefits generated from an effective surveillance system, and accompanying public health interventions.
Lack of appreciation of the true economic value and costs of good quality water was seen as a major obstacle in motivating governments and other bodies to protect and improve supplies. The impact of poor water quality on industry and tourism, as well as public health needs to be better understood and publicised.
The conclusions of the meeting emphasised the need for a combined effort from health organisations, water utilities, government and industry to develop coordinated approaches to combat the growing problem of the worldwide decline in microbiological water quality. Education about the significance of waterborne disease is needed at all levels, and the economic value of clean water must be promoted to motivate governments and international organisations to take action. The consequences of inaction will be a dramatic increase in outbreaks, epidemics and pandemics of waterborne disease, with massive human and economic consequences.
The entire report can be downloaded in Portable Document Format (pdf)
from the World Wide Web Site of the American Society for Microbiology at:
A workshop was hosted by NCEPH in December 1995 to discuss the current evidence for the role of aluminium in the aetiology of Alzheimer’s Disease, and explore the feasibility and desirability of carrying out a large scale prospective cohort study in Australia. The meeting concluded that such a study would be premature at this time, and identified a number of research areas relating to aluminium bioavailability and pharmacodynamics which would yield much needed information before further epidemiological studies should be contemplated. It was felt that these studies could be accomplished in a relatively short time frame, and would be productive not only with respect to the concerns of the water industry, but also for the general understanding of the role of aluminium in human physiology.
Following this workshop the Water Services Association of Australia commissioned a literature review “Biological Aspects of Aluminium in the Food and Water Supply” by Dr Fiona Cumming, Principal Nutrition Adviser of the Australia New Zealand Food Authority, Canberra. The review has been completed and will be published soon.
WSAA has also commissioned Deakin University and ANZFA to collect local data on total aluminium intake from food and drinking water. Studies of aluminium intake in the UK and USA have shown some differences between these populations, so this information is essential to provide an accurate picture of the Australian situation. The project “Aluminium in Food and Water Systems: an Australian Perspective” will be completed in late 1997
WSAA is also developing a research proposal for volunteer studies to investigate aluminium absorption and excretion from food and drinking water. Such investigations will help to resolve the question of whether aluminium from alum treatment of water supplies is preferentially absorbed in the gastrointestinal tract, compared to aluminium from food. This project is also scheduled for completion by late 1997.
Case-control studies are used primarily to identify risk factors for disease and to attempt to find the causes of disease. The advantage of these studies is that they can be undertaken quickly and are relatively inexpensive. Unlike cohort studies it is not necessary to follow a large number of people for a long period waiting for disease to develop in a few. Case-control studies also allow the identification of risk factors (and/or causes) of rare diseases which are difficult to study with a cohort design (because so few cases occur). They allow the relationship between many potential risk factors and a single disease to be examined, whereas cohort studies can examine the relationship between a single risk factor and many diseases.
However, case-control studies have several major disadvantages which severely restrict their applicability and reliability. The most important of these is their potential to generate spurious associations because of various biases that can be almost impossible to eliminate. Spurious associations are often produced by the action of so-called “confounding variables” but the effect of these can usually be eliminated if they are identified beforehand. Finally because so many possible risk factors can be studied the problem of positive findings arising by chance is a common problem and requires great care to be taken in interpreting studies where an unexpected finding (ie one not hypothesised in advance) has arisen.
The steps in carrying out a case-control study are outlined below:
Recruitment of cases and controls
The statistical power of case-control studies can be increased by choosing more than one control for each case - in practice a maximum of 4 controls per case is generally used as increases beyond this number provide little gain in power.
Exposure Ascertainment
The past exposures of cases and controls to factors of interest are generally
estimated by administration of a questionnaire to both groups. Other information
such as employer’s records may be used to estimate workplace exposures. It
is important that the same type of information source is used for cases and
controls so that the level of detail and accuracy is likely to be the same
- for example the use of hospital records for cases and GP records for controls
would not be considered valid.
In some studies questionnaires are not used - exposure may be inferred from information such as place of residence at time of diagnosis or death from the disease under study. Such estimates clearly are prone to considerable inaccuracies.
Studies on cancer and other diseases with long latent periods must focus on the relevant time period for exposures. For solid tumours this means that exposures in the range of 20-30 years before diagnosis are relevant, while for haematological cancers (leukemia, lymphoma) the relevant period is most likely to be 2-6 years prior to the onset of disease.
For fatal or incapacitating diseases, the affected person may have died or become too ill to be interviewed. In these cases, a “proxy” interview with the next of kin may be carried out, although this clearly is likely to produce less accurate results in terms of past exposure assessment. Some studies attempt to allow for this by conducting proxy interviews for the control subjects matched to such cases.
As well as including questions about exposure and potential confounding factors, it is common to include negative control questions - for example, if a link is being sought between a rare tumour and a specific herbicide, it is wise to include questions about exposure to a variety of herbicides. Thus a positive result for the herbicide under suspicion will be more plausible if other herbicides have negative results.
Bias
Each of the major processes involved in establishing a case-control study
can lead to bias which in turn might produce a spurious finding of an association
between an exposure and a disease when none exists, or might conceal a real
association.
Case selection bias occurs when the cases studied are only a subset of all cases and this subset is unrepresentative with respect to the risk factors being studied.
Information bias refers to the potential to create or conceal a relationship between an exposure and a disease as a result of an error in measuring exposure. Because of the reliance on the provision of accurate information from the memory of cases and controls, this is a potentially important form of bias that can easily produce suggestive evidence of a weak association. Even if care is taken to ensure comparability of information sources, it is difficult in case-control studies to ensure the absence of bias resulting from differential recall of information.
Most people who develop a serious illness probably contemplate the possible causes and thus may report past exposures and presumed exposures more fully and in more detail than controls. This is particularly so if the potential cause has received publicity or if detailed questioning has occurred during medical diagnosis of the disease. This type of bias is both difficult to avoid and difficult to quantify.
Confounding
A major problem of case-control studies is the difficulty of isolating the
effect of the risk factor/cause of interest from other possible causes of
the disease which it may be linked to. Confounding is defined as the occurrence
of a spurious linkage relationship between an exposure and a disease that
results because the exposure of interest is linked with a third extraneous
(confounding) variable that is the true cause of the disease. Confounding
is a particular problem in occupational studies linking various chemical exposures
to a disease, as individuals occupationally exposed to one chemical are also
likely to have been exposed to others.
When potential confounders have been identified and considered in advance, their influence can generally be removed by matching cases and controls for the confounding factor, or by the use of appropriate statistical techniques during analysis. However it is not possible to allow for unknown confounders that have not yet been identified as the cause of the disease in question.
Causation
Observational case-control studies, by themselves, can provide only evidence
of association not causation. Before deducing that the observed association
might represent a causal association, other factors must be examined:
Because of the methodological problems, many investigators regard case-control studies as one of the least trustworthy forms of epidemiological investigation. In particular, findings of weak associations are often discounted unless there is supporting evidence from other types of studies. This is because weak associations can easily be produced by the various forms of bias and confounding mentioned above.
However, case-control studies may be the only feasible option for studying the causes of rare diseases, and they can provide useful information provided that their limitations and weaknesses are recognised.
Mr Shane HaydonPrior to joining Melbourne Water, Shane was employed by the Dept. of Water Resources and the Rural Water Commission where he was involved in a wide range of water resource projects. Shane recently joined the Water Filter Study team at Melbourne Water, and will be responsible for coordinating water quality data and water transfer system operation during the Study.
Dr Malcolm Sim
Malcolm Sim is an Occupational and Public Health Physician with postgraduate
qualifications from the University of London, Monash University and Deakin
University. He is a Senior Lecturer in the Department of Epidemiology and
Preventive Medicine, Monash University and Head of the Unit of Occupational
and Environmental Health. He is also the Coordinator of post-graduate education
programs offered by DEPM.
During 1993 Malcolm spent 12 months as a visiting postdoctorate fellow in field epidemiology at the Centers for Disease Control and Prevention in the USA. His current research projects include a cohort study of mortality, cancer incidence and respiratory morbidity in the aluminium industry, health effects from phosphine use amongst Victorian grain farmers, human arsenic absorption from contaminated soil and groundwater in Victorian rural communities and lead exposure in human foetuses and neonates.
Dr Erich Kliewer
Erich Kliewer is a Fellow at the National Centre for Epidemiology and Population
Health. Prior to coming to Australia he held positions at the medical schools
of the University of Utah and the University of British Columbia. He has a
Bachelor and Masters degree in Science (Ecology) and an interdisciplinary
PhD in Epidemiology and Demography.
Erich's research interests are in chronic disease epidemiology, perinatal
epidemiology and migrant health.
In the CRC for Water Quality and Treatment he is involved in the study of
the health effects of exposure to cyanobacterial toxins.
Mr Stuart McConnell
Stuart McConnell holds a degree in Chemical Engineering from the University
of Melbourne, and is a senior chemical engineer with CMPS&F Environmental
in Melbourne. He is currently Section Manager - Risk Assessment, leading a
team of six professionals working in the field of health and environmental
risk assessment.
Stuart has been responsible for the development of CMPS&F’s technical capability in risk assessment and has worked on projects associated with contaminated land, air pollution, water pollution and drinking water quality. He is project manager for the DPIE / Melbourne Water funded research project “Treatment Requirements for Australian Waters” which examined the nature and sources of risk within the water supply system and the requirements for system management. Stuart is currently studying for a Master of Public Health at Monash University.
Mr Andrew Humpage
Andrew Humpage completed his undergraduate degree at Massey University, New
Zealand and holds a Master of Applied Science degree from the University of
South Australia. He is currently a Research Officer in the Department of Clinical
and Experimental Pharmacology at the University of Adelaide, working with
Prof. Ian Falconer on the toxic and tumourigenic effects of cyanobacterial
toxins on mammalian cells. He is also working on his PhD in connection with
this research.
Andrew previously worked at the Australian Centre for Water Quality and Treatment on a project funded by the Murray-Darling Basin Commission, examining the genetic and geographic distributions of toxicity in cyanobacterial populations. This project included the first identification of the type of neurotoxins produced by the common Australian species of cyanobacteria.
Dr Sri Ananthakumar
Sri Ananthakumar holds a Bachelor of the Science of Engineering degree in
Civil Engineering from University of Peradeniya, Sri Lanka, a Mechanical Engineering
degree in Water and Wastewater Engineering from the Asian Institute of Technology,
and PhD in Water /Environmental Engineering from Monash University. He has
been a water quality and planning engineer with Melbourne Water for the last
3 years, and previously worked for Commonwealth Industrial Gases Ltd.
During his time with Melbourne Water Corporation Sri has been involved with water quality improvement planning, water quality modelling and water quality research and development. He is part of the Melbourne Water team working on the Water Filter Study and will be responsible for database programming, linking health and water quality databases and preliminary data analysis for the Study.
Dr Martha Sinclair
Martha Sinclair holds a PhD in Genetics and Developmental Biology from Monash
University. Her research experience includes the genetic and molecular analysis
of clinical, environmental and biotechnology isolates of the bacterial genus
Pseudomonas. She joined DEPM in 1991, as a Research Fellow providing support
to Professor John McNeil for contract and consulting work in public health.
In this capacity she carried out a number of projects ranging from cost-effectiveness
evaluation to the organisation of clinical trials.
In 1996 Dr Sinclair was appointed to the position of Senior Research Fellow funded by the CRC for Water Quality and Treatment. In this position she is working with other DEPM staff on Program 1 - “Water Quality and Health Risk Assessment” of the CRCWQT. Her current responsibilities include the planning and establishment of Program 1 research projects, coordination of Program 1 administration, and responsibility for production of the Program 1 newsletter Health Stream.
Dr Geetha Ranmuthugala
Geetha Ranmuthugala is a PhD student at the National Centre for Epidemiology
and Population Health (NCEPH) at the Australian National University. She received
a scholarship from the CRC for Water Quality and Treatment and her research
interests are in water treatment processes and waterborne diseases.
After completing her medical training at the University of Papua New Guinea, Geetha worked as a clinician in Papua New Guinea, Sri Lanka and Tasmania. Thereafter, she successfully completed a Masters of Applied Epidemiology at NCEPH, undertaking several field projects evaluating the operations of General Practice Divisions and GP Sentinel Surveillance Networks.
Board of Management
The next meeting of the Board of Management of the CRCWQT will take place
on Monday 9th December in Canberra, hosted by ACTEW. A tour of ACTEW water
treatment facilities is also planned.
There will be an ACTEW-sponsored forum the following day on Drinking Water
Guidelines and Customer consultation processes.
Program 1 Advisory Group
The third meeting of this group will take place at the Department of Epidemiology
and Preventive Medicine, Monash University, Melbourne on Monday 11th November
1996.
Return to CRC Publications and Activities
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