Sydney's 1998 water quality crisis

Clancy, Jennifer L.

doi:10.1002/j.1551-8833.2000.tb08909.x

Cited by 35 publications

(19 citation statements)

References 11 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Water Works Assoc.). The additional requirements for confirmatory DAPI staining and Nomarskidifferential interference contrast microscopic examination have also improved the specificity of the method (10,11). The inclusion of low-level spike doses (ϳ100 [oo]cysts) has also improved the robustness of the methods in determining the effectiveness of laboratory QC measures.…”

Section: Discussionmentioning

confidence: 99%

Modifications to United States Environmental Protection Agency Methods 1622 and 1623 for Detection of Cryptosporidium Oocysts and Giardia Cysts in Water

McCuin¹,

Clancy²

2003

Appl Environ Microbiol

Self Cite

View full text Add to dashboard Cite

Collaborative and in-house laboratory trials were conducted to evaluate Cryptosporidium oocyst and Giardia cyst recoveries from source and finished-water samples by utilizing the Filta-Max system and U.S. Environmental Protection Agency (EPA) methods 1622 and 1623. Collaborative trials with the Filta-Max system were conducted in accordance with manufacturer protocols for sample collection and processing. The mean oocyst recovery from seeded, filtered tap water was 48.4% ؎ 11.8%, while the mean cyst recovery was 57.1% ؎ 10.9%. Recovery percentages from raw source water samples ranged from 19.5 to 54.5% for oocysts and from 46.7 to 70.0% for cysts. When modifications were made in the elution and concentration steps to streamline the Filta-Max procedure, the mean percentages of recovery from filtered tap water were 40.2% ؎ 16.3% for oocysts and 49.4% ؎ 12.3% for cysts by the modified procedures, while matrix spike oocyst recovery percentages ranged from 2.1 to 36.5% and cyst recovery percentages ranged from 22.7 to 68.3%. Blinded matrix spike samples were analyzed quarterly as part of voluntary participation in the U.S. EPA protozoan performance evaluation program. A total of 15 blind samples were analyzed by using the Filta-Max system. The mean oocyst recovery percentages was 50.2% ؎ 13.8%, while the mean cyst recovery percentages was 41.2% ؎ 9.9%. As part of the quality assurance objectives of methods 1622 and 1623, reagent water samples were seeded with a predetermined number of Cryptosporidium oocysts and Giardia cysts. Mean recovery percentages of 45.4% ؎ 11.1% and 61.3% ؎ 3.8% were obtained for Cryptosporidium oocysts and Giardia cysts, respectively. These studies demonstrated that the Filta-Max system meets the acceptance criteria described in U.S. EPA methods 1622 and 1623.

show abstract

Section: Discussionmentioning

confidence: 99%

Modifications to United States Environmental Protection Agency Methods 1622 and 1623 for Detection of Cryptosporidium Oocysts and Giardia Cysts in Water

McCuin¹,

Clancy²

2003

Appl Environ Microbiol

Self Cite

View full text Add to dashboard Cite

show abstract

“…The Sydney incident highlighted the difficulties in responding to Cryptosporidium and Giardia test results and emphasised the importance of a preventive riskmanagement approach, rather than relying on end-point testing (Davison et al 1999;Clancy 2000;Hrudey & Hrudey 2004). The Sydney experience drove the development of the …”

Section: Nsw Health Response Protocolmentioning

confidence: 99%

Water safety plans: planning for adverse events and communicating with consumers

Byleveld

Deere²,

Davison³

2008

Journal of Water and Health

View full text Add to dashboard Cite

A wide range of microbial and chemical characteristics in drinking water have the potential to affect human health. However, it is not possible or practical to test drinking water for all potentially harmful characteristics. If drinking water is contaminated, people may already be exposed by the time test results are available. The 'boil water alert' issued in Sydney, Australia in 1998 following the detection of Cryptosporidium and Giardia in the finished water supply, highlighted the uncertainties associated with the public health response to test results.The Sydney experience supports the international consensus that a preventive risk-management approach to the supply of drinking water (manifesting as water safety plans (WSPs)) is the most reliable way to protect public health. A key component of a comprehensive WSP is that water suppliers and health authorities must have plans to respond in the case of water contamination and/or outbreaks. These plans must include clear guidance on when to issue warnings to consumers, and how these warnings are to be communicated. The pressure on health authorities to develop clear and systematic boil-water guidance will increase as utilities all over the world develop their WSPs.

show abstract

“…Recently, almost 5 years after the episode, a rebuttal has been published arguing that water contamination did occur (Cox et al 2003). However, all parties agree that excess illness was absent in the community, and because there are some serious inconsistencies in the case for these latest claims, we accept Clancy's account (Clancy 2000).…”

Section: % Of P[h])mentioning

confidence: 93%

“…The Sydney, Australia, water crisis in 1998 has been described as a case of issuing an advisory for Sydney residents to boil water on the basis of erroneous monitoring results (Clancy 2000), what amounts to a false-positive (type I) error. Increased surveillance and targeted telephone surveys revealed no consistent evidence of any increase in diarrheal disease, nor any increase in laboratory-diagnosed cases of cryptosporidiosis, despite the apparent detection of massive numbers of Cryptosporidium oocysts in the treated water supplied to 3 million consumers (McClellan 1998).…”

Section: % Of P[h])mentioning

confidence: 99%

Risk management and precaution: insights on the cautious use of evidence.

Hrudey

Leiss

2003

Environ Health Perspect

View full text Add to dashboard Cite

Risk management has been widely advocated as a rational means for environmental decision making, assisting us in dealing with the wide array of dangers that we face in our uncertain world, ranging from pathogens in drinking water to terrorist attacks. Done well, risk management is inherently precautionary in the sense that it should make use of effective risk assessment to predict, anticipate, and prevent harm, rather than merely reacting when harm arises.Some of the insights that have supported the movement toward making better use of available evidence for medical decision making, particularly in the field of diagnostic screening, have important but usually overlooked insights for environmental decision making. In particular, the use of four key concepts used for judging the quality of evidence in medical diagnosis-sensitivity, specificity, positive predictive value, and negative predictive value-are relevant to the assessment of environmental hazards, especially those that have low probabilities of occurrence. Applying these concepts rigorously allows us to see more clearly both the value and the limitations of the precautionary approach, as well as to reveal more quantitatively the logical flaw in the notion of "zero risk." The key question, we suggest, is not whether to be precautionary, but how precautionary we ought to be in specific cases, in relation to the quality of our screening evidence. Interpreting Evidence about HazardsOur premise can be illustrated by considering an analogy with airport security. Suppose that we have acquired impressive new scanning technology with the following detection capabilities: a) when someone is carrying a dangerous weapon, 99.5% of the time it will respond positively, and b) when someone is not carrying such a weapon, 98% of the time it will respond negatively. If our best intelligence indicates that about 1 in 10,000 passengers screened will be carrying a detectable, dangerous weapon, we can ask how well the screening evidence will allow us to manage this risk. In particular, we can ask, if we get a positive result how likely is that detection to be correct? Given the properties described, common intuition will lead us to expect that this detection should be reliable.The answer to our question depends on considering that, on average, we will need to screen 9,999 unarmed passengers to find the 1 who is carrying a weapon. The characteristics described provide for a false-positive rate of 2% (98% of the time unarmed passengers will show up as negative). This means that, on average, we will get 199.98 or, effectively, 200 false positives detected for every true positive. Consequently, the answer about how likely it is that a positive detection will be correct turns out to be only 0.5% (1 in 201).Of course, these numbers are hypothetical, but they likely overestimate both the realistic capability of such technology and the frequency of passengers truly carrying weapons. The frequency of the hazard we are seeking to detect is a critical determinant of the ability of any scr...

show abstract

Sydney's 1998 water quality crisis

Cited by 35 publications

References 11 publications

Modifications to United States Environmental Protection Agency Methods 1622 and 1623 for Detection of Cryptosporidium Oocysts and Giardia Cysts in Water

Modifications to United States Environmental Protection Agency Methods 1622 and 1623 for Detection of Cryptosporidium Oocysts and Giardia Cysts in Water

Water safety plans: planning for adverse events and communicating with consumers

Risk management and precaution: insights on the cautious use of evidence.

Contact Info

Product

Resources

About