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Risk Management

New Zealand risk management approach for toxic cyanobacteria in drinking water Abstract

Alexander Kouzminov New Zealand Ministry of Health

Cyanobacterial blooms are common seasonal phenomena occurring worldwide

John Ruck

in fresh, estuarine and coastal waters,

Massey University, New Zealand

including those used for drinking-water supplies, recreation and stock watering. In

Susanna A. Wood

New Zealand, the frequency of blooms and their geographic spread is likely to grow

Cawthron Institute, New Zealand

with increasing eutrophication and global climate change. The New Zealand Ministry

C

yanobacteria (blue-green algae) that form blooms and produce toxic compounds have been identified as an escalating threat around the world.1 Illnesses and cases of fatalities associated with cyanotoxins have been recorded in both wild and domestic animals and in humans.2,3 Cyanobacterial blooms occur across New Zealand4 and the cyanobacterial species responsible for them produce a range of cyanotoxins (see Table 1). These cyanotoxins have been found in numerous waterways throughout New Zealand. Microcystins are the most common cyanotoxin in New Zealand waters.5,6 The human health risk posed by toxic cyanobacteria in drinking water has resulted in the New Zealand Ministry of Health developing national criteria for their monitoring and management. During the summer months of 2002/03 the Waikato River, a major drinking-water supply for Hamilton City and many other smaller towns along the river, experienced blooms of the potentially toxin-producing cyanobacteria Anabaena, Microcystis, Cylindrospermopsis and Oscillatoria7 (Environment Waikato Regional Council [Environment Waikato], unpublished data). In January 2003, low levels of saxitoxins were detected in raw and treated water at the Hamilton City drinking-water intake. Anabaena spp. were dominant in the raw water when saxitoxins were detected. Submitted: March 2007

This paper documents the key events of the Waikato River bloom and its management and compares key aspects of the draft drinking-water standards in place in 2002/03 with the New Zealand risk assessment, management and regulatory approach for cyanobacteria and cyanotoxins in drinkingwater, which has been recently developed by the New Zealand Ministry of Health.8

criteria for assessing and managing the risk of toxic cyanobacteria in drinkingwater supplies. This paper investigates a cyanobacterial bloom incident in the summer 2002/03 in the Waikato River and hydro lakes, which are a major drinkingwater supply for Hamilton City and many other smaller towns along the river. The procedures invoked by the Hamilton City Council and other authorities to deal

Waikato River cyanobacterial incident 2002/03 – integrated risk management case study During the summer of 2002/03 blooms of cyanobacteria were reported in drinking water source waters and recreational water bodies throughout New Zealand, with some of the most heavily affected occurring in the Waikato and Bay of Plenty Regions (see Figure 1). This paper is focused on the impact of cyanobacteria on drinking-water supplies in the Waikato River and the hydro lakes along its length; however, problems were also experienced in nearby recreational lakes.7,9

with this bloom event are considered in terms of the best practice of the day and compared with the Drinking-Water Standards for New Zealand 2005. The presence of cyanobacteria has significant economic effects because of increases in water supply treatment costs or the need to use an alternative source, and there are also social effects from the disruption of recreational use of water bodies and loss of confidence in the quality of reticulated, treated water supplies. Notional evaluation of economic cost of monitoring regimes and control, based on the Waikato River cyanobacterial bloom incident, is also given. The multi-barrier and processcontrol risk management approach, reliant on good vertical communication systems

Waikato River and hydro lakes – chronology of events and actions The Waikato River has a history of seasonal cyanobacterial blooms.10 Warm, dry weather in December 2002 produced ideal

Accepted: April 2007

Correspondence to: Dr John Ruck, College of Sciences, Massey University at Wellington, Private Box 756, Wellington, New Zealand. Fax: +64 4 801 2694; e-mail: [email protected]

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of Health has recently developed national

between central and local government, is an advanced approach useful for any country that regularly experiences cyanobacterial problems. Key words: cyanobacteria, cyanotoxins, drinking water, integrated risk management. (Aust N Z J Public Health. 2007; 31:275-81) doi:10.1111/j.1753-6405.2007.00061.x

AUSTRALIAN AND NEW ZEALAND JOURNAL OF PUBLIC HEALTH © 2007 The Authors. Journal Compilation © 2007 Public Health Association of Australia

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Kouzminov, Ruck and Wood

conditions for rapid growth of cyanobacteria across the country. Routine, ongoing monitoring of drinking-water source waters for freshwater algae and cyanobacteria undertaken by Hamilton City Council revealed the first signs of increases in cyanobacterial cell concentrations in the Waikato River in the last week of 2002. The presence of cyanobacteria began to cause taste and odour problems in Waikato drinking-water supplies. Analysis of samples revealed that Anabaena spp. were the cyanobacterium dominant in the Waikato River. Other cyanobacteria found in the Waikato River were Oscillatoria sp. and Microcystis sp. (Environment Waikato, unpublished data). In the first week of January 2003, sample analysis showed a rapid increase in cyanobacterial concentrations from sites along the Waikato River. These contained Anabaena spp. and Microcystis spp. at levels exceeding 30,000 cells/mL (see Figure 2). At the time of the Waikato River bloom the following alert level response system was being used; 2,000 cells/mL (Vigilance Level), 20,000 cells/mL (Alert Level 1), and 50,000 cells/mL (Alert Level 2). On 9 January 2003, a meeting of officials from Waikato District Health Board, Environment Waikato, Hamilton City Council and Table 1: Cyanobacterial genera known to occur in New Zealand fresh waters and the toxins they are known to produce worldwide.5,9 Genera

Cyanotoxins known to be produced

Anabaena

anatoxin-a,a anatoxin-a(S), microcystins,a saxitoxins,a cylindrospermopsin

Anabaenopsis

microcystins

Aphanocapsa

microcystins

Aphanizomenon

anatoxin-a, cylindrospermopsin, saxitoxins, microcystins

Arthrospira

microcystins, anatoxin-a

Cylindrospermumb

cylindrospermopsin

Cylindrospermopsis

cylindrospermopsin, saxitoxins

Lyngbya

aplysiatoxins, lyngbyatoxin-a, saxitoxins

Microcystis

anatoxin-a, cylindrospermopsin, microcystins, saxitoxins

Nodularia

nodularin

Nostoc

microcystinsa

Oscillatoria

anatoxin-a, aplysiatoxins, microcystins,a anatoxin-a(S), homoanatoxin-a

Phormidium

microcystin,a anatoxin-a, homoanatoxin-a

Planktothrix

microcystins,a homoanatoxin-a, anatoxin-a, aplysiatoxins, saxitoxins

Pseudanabaena

microcystins

Raphidiopsis

cylindrospermopsin, anatoxin-a, homoanatoxin-a, microcystins

Snowella

microcystins

Synechocystis

microcystins

Woronichinia

microcystins

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cyanobacterial experts was held to co-ordinate responses, discuss the risks the cyanobacterial blooms posed to public health, and to assess how well the Hamilton City drinking-water treatment plant was coping with the problem. Several central government departments, regional councils and territorial authorities (TAs) were involved in risk management and problem mitigation during the 2002/03 Waikato River incident. As many as 10 separate organisations were involved and highquality communication among them was essential to deal with the problem effectively. Health authorities warned the public living in the Waikato River basin between Orakei Korako, north of Taupo, and Port Waikato to the west about the risk posed by cyanobacteria. The advice was to avoid contact with untreated water and not to drink it, and not to boil, as boiling may increase toxicity as a result of cell lysis and release of intracellular toxin(s). Numerous warning signs were erected along the Waikato River. The general public was provided with advice on the precautions to be taken and given information on the possible symptoms that could develop following exposure. Notification of water-related adverse health events was encouraged. Concerns over the untreated water extended to livestock and animals. Farmers were advised not to use Waikato River water for stock. Hamilton City Council and Environment Waikato, which were involved in the abstraction of drinking-water from source water of the Waikato River, were notified by local health officials that they needed to undertake risk assessment, regular monitoring for Figure 1: Waikato River catchment, Bay of Plenty. Sites where water samples were regularly taken along the Waikato River during the summer of 2002/03. Expanded sections of the river indicate hydro-lakes.

Notes: Cyanotoxins shown in bold type are known to be produced by species from the associated genera in New Zealand. (a) The results of cyanotoxin testing on environmental samples indicate this toxin is produced by species from the associated genera in New Zealand. (b) Rigorous identification of the causative species was not carried out. This taxon is likely to have been Cylindrospermopsis given the habitat sampled.

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Dealing with toxic cyanobacteria in drinking water

cyanobacteria, and to develop contingency plans for the worst case scenario. When total cyanobacterial concentrations exceeded 30,000 cells/mL at sites on the Waikato River (see Figure 2) and were expected to go above 50,000 cells/mL, Hamilton City Council considered further actions to safeguard its drinking-water supply. The draft drinking-water standards in use at the time stated that when cell concentrations exceeded 50,000 cells/mL, monitoring frequency should increase from weekly to daily. In addition, as advised by the Ministry of Health, the water body may be closed temporarily and contingency plans activated. For example, use of alternative water sources, supply by tankers or in bottles, use of advanced treatment processes (powdered-activated carbon, PAC) and management of raw water sources to reduce cell growth (reservoir aeration). Many of these activities were already in place, including the additional and specific testing for the presence of cyanotoxins and assessment of health risk. In addition, advanced (PAC) treatment was installed in the Hamilton City water treatment plant by the middle of January 2003. Alternative drinking-water sources were not utilised due to (a) the absence of notification of ill health, and (b) sporadic results for cyanobacterial and cyanotoxin concentrations along the Waikato River were insufficient to justify the local Medical Officer of Health closing the drinking-water intake, as required by the Health Act 1956. By mid January 2003 the bloom in some parts of the Waikato River started to diminish and cell concentrations fell to safe levels, possibly due to further heavy rains diluting the cyanobacterial

blooms (see Figure 2), but were still slightly above the 2,000 cells/mL recommended as the trigger level when drinking-water source waters should be continually monitored and drinking-water treated to ensure adequate drinking-water system performance to remove cyanotoxins.

Hamilton City water supply – chronology of events and actions The cyanobacterial bloom caused taste and odour problems with many Waikato drinking-water supplies (affecting about 960,000 consumers in total), including the Hamilton City Council’s supply, which provides water for around 117,000 consumers. There are 12 registered intakes from the Waikato River that serve 36 water distribution zones.11 Even though there were no notified cases of cyanotoxin poisoning and/or illness as a result of consumption of drinking water or contact with the river water, the high cell concentrations together with the presence of cyanobacteria capable of producing toxins led Waikato District Health Board to ask for management action by Hamilton City Council in the first week of 2003. Immediate actions included: (a) sampling raw and treated water for cyanobacteria and toxins; (b) undertaking a risk assessment; (c) preparation of a contingency plan; and (d) the establishment of communication pathways between the territorial authority’s contact person, responsible for these actions, and Waikato District Health Board Public Health Service to confirm progress in the above matters and to tackle the problem.

Figure 2: Cyanobacteria in the Waikato River during the summer of 2002/03.

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Hamilton City Council and other TAs were provided with advice from the Ministry of Health on cyanobacteria in waterways and how to prepare and develop a Public Health Risk Management Plan (PHRMP) for drinking-water supplies.12 The PHRMP typically forms a significant part of an overall contingency plan designed to manage cyanobacterial and cyanotoxin incidents. A template for the signage was provided and the signs were erected by TAs in the affected areas and along the Waikato River. Very low concentrations of saxitoxins (0.01 µg/L) were detected in Hamilton City’s drinking-water system on 16 January using an ELISA. Low levels of saxitoxins continued to be detected in the drinking water supply until early February. The highest concentration measured was 0.04µg/L on 27 January 2003. Hamilton City Council, in response to the contingency plans, started dosing the water with PAC (8-12 mg/L) from 15 January onwards. The aim was to adsorb any cyanotoxins present. After the first toxin results were received the Hamilton City Council managed the problem by changing its monitoring frequency from weekly to twice weekly. By 15 January the monitoring and toxin testing had been increased to daily. Hamilton drinking water was dosed for nearly a month with PAC to remove saxitoxins, despite the end of a health warning on drinking-water source waters from Waikato River water. The City Council spent $NZ1,000 a day dosing the city’s drinking water with PAC. This was purely a precautionary measure. By the end of January the cyanobacterial concentrations at the city water treatment plant’s uptake had fallen to about 2,000 cells/mL. Four treatment plants in the Waikato District Council area, which service a population of about 15,000 people, did not use PAC at the time of the incident. Although treated water samples from the Waikato District Council showed no cyanotoxins present, cyanobacterial cells were still present after treatment. For example, samples from the Te Kauwhata water treatment system (1,700 consumers) showed Anabaena spp. at the level of 364 cells/mL in the beds of the plant (Waikato District Health Board (WDHB), personal communication). Soon after the event the health and water supply agencies involved began discussions on how well their drinking-water systems could tolerate future toxic cyanobacterial blooms. They

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concluded that the summer 2002/03 incident was an invaluable experience for future management planning. In response to the incident, Hamilton City Council spent approximately $NZ195,000 over a three-month period (JanuaryMarch 2003), which included: • $NZ50,000 on monitoring. • $NZ100,000 on treatment chemicals. • $NZ45,000 on dosing equipment (Hamilton City Council, personal communication). In addition, in 2004 $NZ30,000 was spent on capital improvements involving new dosing plant/equipment (Hamilton City Council, 2004, personal communication). The PAC dosing plant that the Hamilton City Council put in place was only a temporary measure until the water supplier built Granulated Activated Carbon (GAC) filter beds as part of a significant plant upgrade. As a direct result of the 2002/03 Waikato River cyanobacterial incident, a $NZ5 million upgrade of Hamilton’s water treatment plant was fast-tracked to permanently remove taste and odour problems from the city’s water. The Hamilton City Council acknowledged that a planned upgrade to the water treatment plant would cost up to $NZ8.5 million extra to avoid future potential problem associated with cyanobacterial bloom events.13 The extra cost would come from providing the combination of GAC filtration (secondary filters) to address taste and odour and cyanotoxins risk, and UV disinfection, to provide advanced pathogen protection. There have been several bloom events since 2003. These continue to affect the Waikato drinking-water supplies.

New Zealand risk management and regulatory guidelines for cyanobacteria and cyanotoxins in drinking-water During the Waikato River and hydro lakes’ cyanobacterial bloom in 2002/03 the New Zealand risk management and regulatory guidelines for cyanobacteria and cyanotoxins in drinking water were in a developmental stage. The provisional World Health Organization guidelines14 and Ministry of Health policy and guidelines15,16 were the only published advice available. The Ministry of Health draft policy document (Ministry of

Table 2: Guideline values for a drinking-water source and recommended actions.17 Guideline value

Threshold level

Actions by local authorities

Vigilance Level

2,000 cells/mL, or 0.2 mm3/L biovolume, or 10 µg/L chlorophylla

Continue regular monitoring of raw and treated water to ensure adequate system performance, and consider analysis (bioassay test) of the treated water to confirm the absence of toxins.

Alert Level 1 20,000 cells/mL, or 2 mm3/L biovolume, or 10 µg/L chlorophylla

Prepare to implement water supply contingency plan, use an alternative source of water, or use water treatment processes capable of removing cells or toxins, or provide drinking water by tanker or bottles.

Alert Level 2

Monitoring frequency should be increased to at least twice weekly (preferably daily), the water body should be closed temporarily, contingency plan should be activated, including advanced treatment processes.

50,000 cells/mL, or 5 mm3/L biovolume, or 25 µg/L chlorophyll a, or toxin concentration exceeds PMAV (Table 3)a

Note: (a) PMAV – Provisional Maximum Acceptable Values. For details see Table 3.

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Health, unpublished) on the proposed revision of the guidelines for drinking-water quality management provided guidance values for potential toxin-producing cyanobacteria and associated compliance conditions, for a drinking-water source, and specified managerial actions in response to proposed thresholds (or Alert Level Framework) being exceeded (see Table 2). The revised New Zealand risk management and regulatory guidelines for safety of drinking water, including protection against cyanobacteria and cyanotoxins, are based on a precautionary approach.17 This includes a multi-barrier and process-control risk management mechanism. It is complemented by a monitoring program used as a final quality control, which provides a trigger for remedial action where necessary. This approach was developed by the Ministry of Health during 2000-05 and the key elements are incorporated in the following policy support documents: • Drinking Water Standards for New Zealand 2005 (DWSNZ:2005).8 • Draft Guidelines for Drinking Water Quality Management for New Zealand 2005 (draft Guidelines 2005).17 • How To Prepare and Develop Public Health Risk Management Plans for Drinking Water Supplies.12 • Public Health Grading of Community Drinking-Water Supplies 2003.18 The various components of this risk management system complement and mutually reinforce each other, maximising the effectiveness of procedures used to reduce contaminants. The aim is to develop water quality management processes that are effective and affordable. The protection of drinking-water supplies from contamination by cyanobacteria and cyanotoxins starts with identification of the cyanobacterial content in a drinking-water source and is continued through the treatment plant/distribution system, finishing at the consumer’s tap. The effectiveness of source water protection under the Resource Management Act 1991 is assessed by methods specified in the draft Guidelines 200517 and the PHRMPs,12 which include source water quality routine monitoring, preventive and control measures against cyanotoxins defined in an individual water safety plan developed by each drinking-water supplier. The responsibilities of preventing, monitoring and managing cyanobacteria and cyanotoxins rest with many different organisations, including drinking-water suppliers, territorial authorities and regional councils involved. Table 3: Provisional Maximum Acceptable Values (PMAVs) for cyanotoxins in drinking water.17 Name

PMAV, mg/L DWSNZ:2000 DWSNZ:2005

Anatoxin

0.003

0.006

Anatoxin-a(S)

0.001

0.001

Cylindrospermopsin

0.003

0.001

Homoanatoxin-a

0.001

0.002

Microcystin-LR toxicity equivalents

0.001

0.001

Nodularin

0.001

0.001

Saxitoxins (as STX eq)

0.001

0.003

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The main purpose of these risk management protocols for cyanobacteria/toxins is to provide the additional benefit of reducing the likelihood of cyanobacterial cells and cyanotoxins becoming abundant in supplies. The PHRMP should also specify risk-management principles during treatment and distribution that a particular water supply should comply with, as defined in the DWSNZ:2005. The DWSNZ:2005 has two key components: the numerical standards (maximum acceptable values, MAVs) and the compliance requirements.8 The compliance criteria for cyanotoxins include protocols for their management. The DWSNZ:2005 defines four priority classes of determinands.8 The priority classes are ranked according to the potential impact of the determinand on public health. Cyanotoxins are now defined in the DWSNZ:2005 as Priority 2 determinands, when present at concentrations more than 50% of their provisional maximum acceptable values (PMAVs) (see Table 3) in a distribution zone. When assigned as Priority 2 determinands, cyanotoxin concentrations in the drinking-water system, including the source waters, treated water and water in the distribution system, must be analysed twice weekly until the cyanotoxin is reclassified as a Priority 3 determinand. Monitoring of determinands in the lower potential risk categories, Priorities 3 and 4, is at the drinking-water supplier’s discretion, unless the Drinking Water Assessor (DWA), a health officer trained for the purpose, requires it for public health reasons. The Ministry of Health protocols for categorising drinking-water source water risks from cyanobacteria and their toxins depend on the size of the drinking-water supply. Ongoing monitoring of drinking-water source waters should be carried out every three months for supplies with more than 10,000 people, or where blooms have occurred in the past during the less critical period May-October (when there is no and/or rare cyanobacterial bloom formation in New Zealand surface waters), and for others (less than 10,000 people) once in six months. Monthly monitoring during the most critical period (November-April) is desirable for all supplies regardless of their size, as specified in the draft Guidelines 2005.17 Cyanobacterial cell concentrations and cyanotoxin analysis must be carried out by Ministry of Health-recognised laboratories accredited to NZS/ISO/IEC/EN 17025:2000 Standards by the International Accreditation New Zealand. Water suppliers must also develop protocols on what actions will be taken if PMAVs are exceeded.

Discussion Evaluation of the effectiveness of the risk management approach During the 2002/03 Waikato River incident, risk management guidelines relied heavily on cell concentrations as triggers for actions related to compliance requirements. The growing number of cyanobacterial bloom incidences in New Zealand has raised the Ministry of Health’s concern about the public health implications. Outcomes of the Waikato River incident reinforced the need for a new section ‘Cyanotoxin Compliance Criteria’ within the revised DWSNZ:2005.


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The proposed draft Guidelines 2005 provided more flexibility for the water supplier regarding the way they monitor their source water for cyanobacteria and cyanotoxins. The draft Guidelines 2005 provided information and advice to water supply authorities on (a) the assessment of risk from cyanotoxins, (b) monitoring and managing cyanobacteria and cyanotoxins in drinking-water supplies, including the source water, (c) preventing cyanobacterial blooms and thus protecting the source water, and (d) minimising the risk of public exposure to cyanotoxins. The 2002/03 Waikato River and hydro lakes cyanobacterial contamination has encouraged TAs to change their risk management practices, which are now incorporated into their contingency and emergency planning. TAs and local health officials have begun to assess the vulnerability of their water treatment plants. They have started to assess how well they would cope with potential contamination of water source(s) by cyanobacterial bloom events. They have also started to identify what local conditions should be considered in their PHRMPs for drinking-water supplies. At the time of the 2002/03 Waikato River incident New Zealand drinking-water analytical laboratories did not have the capacity to test for all of the known cyanotoxins at the concentrations specified in the DWSNZ:2005, or to process the volume of samples that a major cyanobacterial incident generates. Because of the lack of mandatory legal obligations, managers of waterways were not motivated to test potentially contaminated water supplies for cyanotoxins. When Hamilton City Council had to deal with a serious cyanobacterial incident, it had at its disposal the draft of the revised NZDWS:2005 and the draft Guidelines 2005 as a guide, and thus the incident and the response provided a test case for best practice in managing such incidents, both in New Zealand and internationally. Overall, the threat to Hamilton City’s drinking water supply was managed effectively using the most effective actions possible at the time, and by minimising the health risk to consumers. The costs to the Hamilton City Council of monitoring cyanobacteria to enable sound management of the risk during the 2002/03 Waikato River incident were very high. At times two or three samples a day were taken for both cyanobacterial enumeration and cyanotoxin analyses over the period, which in hindsight was probably unnecessary. At the time of the incident, analysis of toxins as recommended by the Ministry of Health could not be performed due to the lack of routine validated analytical methods available in New Zealand. In several cases these analyses were carried out by Australian laboratories, leading to delay in decisions. Although test results on January 20-23 showed that cell concentrations in the Hamilton supply’s intakes were close to the trigger level of 2,000 cells/mL (see Figure 2), and saxitoxins levels were well below the PMAV, the monitoring and toxin analyses were continued at the same frequency. These actions to some degree exceeded the intentions of the draft policy’s guidelines documents in place at the time of the incident. Because of the unpredictability of the bloom TAs took a

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precautionary stance, taking numerous tests from multiple monitoring sites. They also implemented increased barrier control measures during and after the time of the 2002/03 incident. Hamilton City Council has now modified risk management plans in place for its drinking-water supplies. It has adopted risk management principles, a process-control approach, and risk management planning techniques, significantly improving its readiness should future toxic cyanobacterial events occur. The Hamilton City Council and its water treatment plant have performed effectively during the cyanobacterial bloom incident. It is believed that the city’s upgraded treatment system will minimise health risk to consumers from potential contamination of drinking-water sources if new cyanobacterial bloom incidents occur. The cyanobacterial blooms in the Waikato River and hydro lakes (2002/03) have also highlighted the challenges TAs face in managing the problems when reliant on bloom formation information that is often inadequate. In New Zealand, 72% of drinking water (in terms of total population) comes from surface water supplies.11 It is therefore likely that an increase in cyanobacterial blooms will have significant economic effects because of an increase in water supply treatment costs or the need to use alternative drinking-water sources. In addition, there are social effects from possible loss of confidence in the quality of reticulated, treated water supplies.

Conclusions In 2000, the national policy and guidelines regarding the risk assessment and management of cyanotoxins for drinking-water supplies were fragmentary and in an embryonic stage. In the course of putting in place its current regime for drinking-water safety, the Ministry of Health developed an integrated risk assessment and management approach for cyanotoxins in drinking-water supplies. A comprehensive package was developed and finetuned by experience gained with the Waikato River and related incidents. Multi-barrier and process-control risk management represent an advanced, state-of-the-art approach useful for any country that regularly experiences cyanobacterial problems. The best practice demonstrated may be applied generally in the management of water quality, because of the significant social and economic benefits gained through greater assurance that rivers and lakes, used for water supply and recreation, are managed appropriately and safely. Good vertical communication systems between the central and local government are an essential part of this risk assessment and management approach.

Acknowledgements The authors would like to thank Dr Michael E.U. Taylor (New Zealand Ministry of Health) for his valuable comments during the preparation of the manuscript. The authors express their gratitude to Marie Porter (Hamilton City Council), Dr Bill Vant (Environment Waikato Regional Council), Tony Pipe, Dr Dell Hood, and Jenette Maree Blake (Waikato District Health Board Public Health Service, Hamilton) for provision of data used


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in this manuscript; and Barry Mattingley and Alan Ferguson (Environmental Science and Research Institute Ltd, Christchurch) for technical data regarding Waikato water supplies. Disclaimer. Any opinions expressed in this paper are those of the authors and do not, necessarily, reflect the official positions and policies of the New Zealand Ministry of Health.

References 1. Codd GA, Morrison LF, Metcalf JS. Cyanobacterial toxins: risk management for health protection. Toxicology and Applied Pharmacology. 2005;203:26472. 2. Ressom R, Soong FS, Fitzgerald DJ, Turczynowicz L, Saadi OE, Roder D, et al. Health Effects of Toxic Cyanobacteria (Blue-green Algae). Canberra (AUST): National Health and Medical Research Council; 1994. 3. Azevedo SM, Carmichael WW, Jochimsen EM, Rinehart KL, Lau S, Shaw GR, et al. Human intoxication by microcystins during renal dialysis treatment in Caruaru-Brazil. Toxicology. 2002;181-182:4-446. 4. Pridmore RD, Etheredge MK. Planktonic cyanobacteria in New Zealand inland waters: distribution and population dynamics. New Zealand Journal of Marine and Freshwater Research. 1987;21:491-502. 5. Wood SA, Stirling DJ, Briggs LR, Sprosen J, Holland PT, Ruck JG, et al. Survey of cyanotoxins in New Zealand waterbodies between 2001 and 2004. New Zealand Journal Marine and Freshwater Research. 2006;40:585-97.

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6. Wood SA, Briggs LR, Sprosen J, Ruck JG, Wear RG, Holland PT, et al. Changes in levels of microcystins in rainbow trout, freshwater mussels and cyanobacteria in Lakes Rotoiti and Rotoehu. Environmental Toxicology. 2006;21:205-22. 7. Ryan E, Hamilton DB, Barnes GE. Occurrence of Cylindrospermopsis raciborskii in Waikato lakes of New Zealand. New Zealand Journal of Marine and Freshwater Research. 2003;37:829-36. 8. Ministry of Health. Drinking-Water Standards for New Zealand 2005. Wellington (NZ): Government of New Zealand; 2005. 9. Wood SA, Stirling DJ. First identification of the cylindrospermopsin producing cyanobacteria Cylindrospermopsis raciborskii in New Zealand. New Zealand Journal of Marine and Freshwater Research. 2003;37:821-8. 10. Lam CWY. Blue-green Algae in the Waikato River [dissertation]. Auckland (NZ): University of Auckland; 1977. 11. Water Information System New Zealand (WINZ Database). Christchurch (NZ): Institute of Environmental Science and Research, Christchurch Science Centre; 2006 [cited 2006 November 21]. Available from http://www.drinkingwater. co.nz/general/waterdatabase.asp. 12. Ministry of Health. How To Prepare and Develop Public Health Risk Management Plans for Drinking Water Supplies. Wellington (NZ): Government of New Zealand; 2001. 13. New Zealand Water and Wastes Association. Upgrade Jump to $15M. Waikato Times. 2003 May 22. 14. Chorus I, Bartram J, editors. Toxic Cyanobacteria in Water. A Guide to their Public Health Consequences, Monitoring and Management. London (UK): E & FN Spon; 1999. 15. Ministry of Health. Guidelines for Drinking-water Quality Management for New Zealand. Wellington (NZ): Governement of New Zealand; 1995. 16. Ministry of Health. Drinking-water Standards for New Zealand. Wellington (NZ): Government of New Zealand; 2000. 17. Ministry of Health. Draft Guidelines for Drinking-water Quality Management


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