The evidence for this analysis is based on a review of international experience relevant to the provision of safe drinking water in New Zealand. The evidence includes 38 outbreaks of serious drinking waterborne disease occurring in 13 affluent countries (9 in the USA, 7 in Canada, 6 in England, 3 in Finland, 2 each in Denmark, Norway, Sweden, Switzerland and 1 each in Australia, Ireland, Japan, New Zealand, and Scotland). These resulted in a total of 77 fatalities in 9 fatal outbreaks and they caused over 460,000 cases of gastrointestinal illness in the 38 outbreaks considered. All these outbreaks were preventable if the threat posed by microbial pathogens in drinking water had been recognised and suitable preventive measures had been implemented and consistently maintained.
The experience captured in this review goes intentionally beyond the specific details of the North Havelock outbreak in order to serve the purpose of Part 2 of the Inquiry. The 38 case studies were chosen on the basis of relevance to the provision of safe drinking water anywhere in New Zealand, a country with substantial agricultural activity, generally low population density and many small to medium size communities.
This review of international experience is organised according to 6 well-established principles for ensuring safe drinking water that were first developed in 2001 at an expert meeting in Adelaide, South Australia between the World Health Organization microbial pathogens expert group and the National Health and Medical Research Council of Australia working group on revising the Australian Drinking Water Guidelines. These principles are used for this document because they have stood the test of time and continuing experience. The first and by far the most important of these principles is: “The greatest risks to consumers of drinking water are pathogenic microorganisms. Protection of water sources and treatment are of paramount importance and must never be compromised.” Unfortunately, an initial review of evidence from Part 1 of this Inquiry clearly indicates that those responsible for the safety of the North Havelock drinking water supply and hence the health of the community’s consumers apparently had not embraced any of these guiding principles for ensuring safe drinking water. In particular, there was remarkable urgency demonstrated increasing chlorination after the minimum time allowed for attaining clear results after the 2015 E. coli contamination incident, yet there was no apparent urgency in obtaining results for an investigation to explain what had caused the microbiological contamination in the first place. This circumstance makes it difficult to avoid a conclusion that chlorination was seen as a greater concern than microbial contamination. If chlorination is regarded as untenable for consumers, for whatever reasons, then water purveyors and public health officials are obliged to require investment in alternative disinfection technologies with all of the attendant costs, treatment and reticulation system maintenance obligations that may be associated with those technologies.
The North Havelock outbreak was severe in its consequences, but the vulnerability that allowed it to occur could have resulted in an even more severe outcome. In particular, if livestock faecal contamination had included the pathogen E. coli O157:H7, the pathogenic strain of E. coli that was involved in the fatal Walkerton outbreak and in fatal outbreaks in Cabool, USA, Saitama, Japan and Washington County, USA, fatalities and severe illness among young children could have occurred in North Havelock. Drinking water contamination events causing human illness are inevitably complex, but the root causes are remarkably common and simple – risk assessment needs to be tiered with global common cause issues understood first before greater detail on contributory causal factors is pursued and elaborated.
While detail is ultimately important, the complexity arising from site specific details must not be allowed to interfere with achieving a thorough understanding of whether the overriding principles are being respected. International best practice for achieving risk management has been developed around the water safety plan approach. That approach, which is intended to be inherently preventive, can only be as effective as the care and commitment invested in preparing and continuously updating it allows. A water safety plan must be conscientiously developed and truly owned by those who must use it, not by an external third party. If a water safety plan is not owned by those running the water system it may become just another document taking up space on an office shelf.
Systemic problems that are evident in many of the international outbreaks reviewed and are certainly evident in North Havelock and likely elsewhere in New Zealand are the resource limitations and inadequate capabilities of small water purveyors. Although providing drinking water of adequate quality can often be comparatively routine, provision of high quality, safe drinking water 24 hour a day, 7 days a week, 365 days a year is a challenging interdisciplinary responsibility. Ensuring safe drinking water in the face of the pervasive challenge posed by microbial pathogens and the countless ways that pathogen contamination can occur is a daunting technical challenge. Allowing a fragmented system of drinking water supply by many small jurisdictions is a common problem worldwide that inevitably contributes to vulnerability for contamination. Some jurisdictions including England and the states of South Australia, Victoria and Western Australia have addressed this risk by creating larger, capable, regional or statewide water authorities to provide the critical mass of expertise for ensuring safe drinking water. Such measures are politically difficult to implement, but they can be remarkably effective.
Ultimately, a drinking water purveyor can only be relied upon to consistently provide safe drinking water if those responsible for delivering public drinking water take personal ownership of the considerable public health responsibility that providing drinking water entails. There should be no room for complacency among those who must accept this responsibility.
In closing, the common theme across all of the international outbreak evidence is one of complacency. Our affluent societies have known for many decades how to prevent outbreaks yet we continue to allow them to happen by failing to do what we know needs to be done. In this sense, an analogy may be drawn with recurring outbreaks of communicable diseases like measles and mumps that occur because of a failure to maintain adequate immunisation. These circumstance reveal the inevitable tension between individual rights and societal benefit. In the case of drinking water, individual biases about water disinfection and treatment should not be allowed to endanger innocent consumers, especially when such biases are based on urban myths and are not founded on authentic public health evidence.