Learning Center
Plans & pricing Sign in
Sign Out

SB Contamination of Glasgow s Water with Cryptosporidium


									SPICe Briefing

02/100 03 September 2002


In August 2002, cryptosporidium was detected in the Mugdock Reservoir in Milngavie, Glasgow. As a result, approximately 140,000 Glasgow residents were advised to boil all tap water used for drinking, preparing food, brushing teeth and bathing babies. The management and handling of the contamination incident will be debated in the Scottish Parliament on 4th September 2002. This briefing aims to outline the main issues and provide some background information for the debate.

Cryptosporidium parvum is a parasite that can infect man and a wide range of domestic and wild animals. The organism can be acquired from contaminated food, milk, drinking water, poorly maintained swimming pools, farm animals and other infected people. It exists within the gut cells of a host and later in its life cycle is excreted in stools in the form of ‘oocysts’, the infectious form of the parasite. If the oocysts are swallowed they can cause ‘cryptosporidiosis’, a disease which is notifiable under the Public Health (Notification of Infectious Diseases)(Scotland) Regulations 1988. Cryptosporidiosis is characterised by loss of appetite, nausea and vomiting, abdominal pain and fever. The incubation period is between 2-7 days and symptoms can last from 1 to 3 weeks. There is no specific treatment and
providing research and information services to the Scottish Parliament

care is usually directed at treating the symptoms. The illness is generally considered unpleasant as opposed to serious, but is potentially life-threatening to the young, the elderly and those with compromised immune systems (e.g. those with AIDS). More severe cases may require hospital treatment for dehydration. It is not known how many oocysts need to be swallowed to cause infection although the number is thought to be small.

Proper hygiene and careful food preparation can eliminate most routes of transmission, while properly functioning water treatment works can handle low levels in drinking water. However, heavy rain or contamination from farms may result in higher levels within the water supply which cannot be filtered out completely. Cryptosporidium is highly resistant to chemical disinfectants and therefore physical barriers (i.e. water filtration) form the main line of defence. Higher levels detected may result in a ‘boil water’ notice being served to the public.

There is no standard protocol for dealing with contamination of the water supply by cryptosporidium. This is mainly due to the fact that it is not known what level of oocysts is considered a risk to health. Past incidents have shown that low levels may lead to illness, while high levels may not.1 In 1998, an expert working group on cryptosporidium set up by the Drinking Water Inspectorate published its third report, commonly known as the ‘Bouchier Report’. The purpose of the group was to assess lessons learned from previous outbreaks of Cryptosporidiosis, review recent research and consider whether advice given on the monitoring and treatment of water supplies and management of outbreaks needed to be altered. One of the group’s conclusions was: “It is not possible to recommend a health-related standard for cryptosporidium in drinking

Therefore, unlike other agents and chemicals, there is no threshold by which water authorities must abide. The report did however contain many other recommendations related to the monitoring and treatment of water.






The responsibility for managing contamination incidents and outbreaks resides with NHS Boards. In Scotland, there is no pre-determined investigation level of

Personal Communication with Professor Bill Reilly, Scottish Centre for Infection and Environmental Health 2 Expert Working Group on Cryptosporidium in Water (1998) “Cryptosporidium in Water Supplies: Third Report of the Group of Experts to: Department of the Environment, Transport and the Regions & Department of Health” Drinking Water Inspectorate, London

providing research and information services to the Scottish Parliament

oocysts, although the Water Quality Regulation Team at the Scottish Executive set a target of zero. Oocyst levels are kept under continuous surveillance in liaison with NHS Boards and the Local Authority Environmental Health Departments. If an unusually high level of the organism is detected a ‘Problem Assessment Group’ may be convened to decide if further action needs to be taken. This group will consider a number of factors such as the nature and history of the local water supply, past occurrences of outbreaks, how many positive samples have been collected and whether the level is rising or falling. If the group judges the contamination to be of concern an ‘Incident Control Team’ will be convened to implement the local ‘Water Hazard Plan’. Plans differ from one area to another depending on the characteristics of the water supply and surrounding locality.3

The main legislation and directions governing the quality of publicly supplied water and the control of cryptosporidium are the Water (Scotland) Act 1980 and The Cryptosporidium (New Water and Sewerage Authorities) Direction 2002. The main provisions are set out in the table below.
The Water (Scotland) Act 1980 • Water authorities must supply wholesome water for domestic purposes. It is a criminal offence to supply water unfit for human consumption; • Scottish Ministers must take enforcement action against a water authority that fails in its duty to supply wholesome water unless the failure is trivial or the water authority is complying with a legally binding undertaking to remedy the matter; • Local authorities must take appropriate steps to keep themselves informed about the wholesomeness of public and private water supplies in their area and notify the water authority if not satisfied; • Wholesomeness is defined for public supplies in the Water Supply (Water Quality) (Scotland) Regulations 1990 and for private supplies in the Private Water Supplies (Scotland) Regulations 1992. The Cryptosporidium (New Water and Sewerage Authorities) Direction 2002 • Water authorities must implement the recommendations contained in the ‘Bouchier Report’ • Sets out a framework for assessing the risk of cryptosporidium in public water supplies in Scotland and requires the water authorities to assign a score to each of their supplies depending on the assessed risk • Water Authorities must continuously monitor high-risk supplies for cryptosporidium. • Water Authorities must develop and maintain adequate liaison arrangements with Local Authorities and NHS Boards
Derived from: Environment & Rural Affairs Department (2000) “Drinking Water Quality in Scotland 2000” Scottish Executive, Edinburgh


Personal Communication with Professor Bill Reilly, Scottish Centre for Infection and Environmental Health:

providing research and information services to the Scottish Parliament

Cryptosporidium was detected in the Mugdock reservoir on Friday 2nd August following heavy rain and flooding in the area. The next day an Incident Control Team was set up, comprising representatives of Greater Glasgow NHS Board, the Scottish Centre for Infection and Environmental Health, Scottish Water, the Scottish Executive, Glasgow Council, East Dunbartonshire Council and West Dunbartonshire Council. That evening the contamination was made public when it was realised that levels had risen, and just after 8pm the incident team issued a ‘Boil Water’ notice to residents of Glasgow, Bearsden and Milngavie. Over the weekend, supplies were diverted from Craigmaddie reservoir to supply city residents. By Monday 5th August, the notice was extended to residents of Clydebank and on Wednesday 7th August, the boil water notice was lifted. No cases of Cryptosporidiosis were recorded in city residents4. Two days after the boil water notice was lifted in Glasgow, an alert was issued to Edinburgh residents when a temporary filtration failure resulted in higher levels of cryptosporidium in the water5. The notice was lifted shortly afterwards when further tests showed there was no cause for concern. After both incidents, criticism was levied at Scottish Water and the two NHS Boards for, on the one hand, waiting too long to inform Glasgow residents, and on the other, alerting the Edinburgh public when there was no risk. Subsequently, the Scottish Executive convened a Ministerial Group on Health and the Public Water Supply to examine the handling of both incidents and any lessons that could be learned. The Drinking Water Quality Regulator and the Water Industry Commissioner were asked to conduct a full investigation. Initial needs identified by the group include6: • Clearer guidance on the criteria that doctors and scientists use to make judgements on the health risks posed by cryptosporidium; • Assurances that the cryptosporidium direction is being fully implemented; • A review of Scottish Water's arrangements to ensure that it holds accurate information on the networks across Scotland in order to allow effective communications with members of the public; • Urgent work on how incidents are handled at a local level to ensure proper co-ordination and communication. In addition the Health Minister, Malcolm Chisholm, has requested the Bouchier Committee to update their advice from 1998 and consider whether a healthrelated standard can be identified for Scotland.7

4 5

Scottish Centre for Infection and Environmental Health (2002) ‘SCIEH Weekly Report’ Vol 36 No. 2002/32 Scottish Executive Press Release: “Cryptosporidium found in Edinburgh Water” 9th August 2002 6 Scottish Executive Media Briefing: 14th August 2002 7 Scottish Executive Press Release: “Glasgow water gets watchdog treatment” 8th August 2002

providing research and information services to the Scottish Parliament

The water supply for the majority of Glasgow residents (72.3%8) comes from Loch Katrine via a Victorian aqueduct to the Mugdock Reservoir in Milngavie. The aqueduct is considered to be at high risk of surface water ingress and consequent contamination. The treatment works at Milngavie have been described as rudimentary and unable to filter the water to a level that would remove parasitic oocysts.9 The reservoir was the source of a previous outbreak of Cryptosporidiosis in 2000 in which there were 90 confirmed cases, including 6 people who required hospitalisation and 1 death. In the report of the outbreak by Greater Glasgow Health Board10, concern was expressed that future outbreaks may occur unless the treatment works were upgraded. This concern was reiterated in a recent press release from Greater Glasgow NHS Board:
“As long as the mains water from Loch Katrine (which supplies both the Craigmaddie and Mugdock Reservoirs) is not filtered, there is always a chance the cryptosporidium will remain, at a relatively low level in the water supply. From time to time there may be increases in cryptosporidium to such a level that the threat to the public health warrants the issue of a boil water notice to protect the public from this threat.”11

On August 27th, East Dunbartonshire Council rejected a planning application from Scottish Water for a new £100 million treatment works at Milngavie. This followed opposition from local residents and Scottish Natural Heritage who believed the chosen site would have a negative effect on the amenity value of the reservoirs. The council voted 9-7 against the plans. Scottish Water has 6 months to appeal against the decision. If an appeal is initiated, an inquiry will be held which can take up to a year. A final decision can be taken by the Inquiry Reporter or by Scottish Ministers12.


Department of Public Health (2001) “Report of an Outbreak of Cryptosporidiosis in the area supplied by Milngavie Treatment Works – Loch Katrine Water” Greater Glasgow Health Board 9 Ibid. 10 Ibid. 11 st Greater Glasgow NHS Board Press Release: “Cryptosporidium Incident Control Team” 1 August 2002 12 Scottish Executive Press Release: “Procedure on the rejection of Mugdock Scheme” 28th August 2002

providing research and information services to the Scottish Parliament

S1W-26592 - Des McNulty (Clydebank and Milngavie) (Lab) : To ask the Scottish Executive whether the selected monitoring methodology at the proposed water treatment plant at Milngavie meets the world's best practice and reflects an accurate assessment of the prevalence of water-borne Cryptosporidium. Answered by Ross Finnie (24 June 2002): The recovery rate for Cryptosporidium oocysts using the monitoring methodology proposed for Milngavie is around 50%. However, the methodology proposed is the best currently available. S1W-26590 - Des McNulty (Clydebank and Milngavie) (Lab) : To ask the Scottish Executive which agency is responsible for ensuring that Cryptosporidium is eliminated from drinking water supplies and does not reach customers' taps. Answered by Ross Finnie (24 June 2002): The Drinking Water Quality Regulator for Scotland is responsible for ensuring that public drinking water supplies are wholesome and meet the requirements of The Water Supply (Water Quality) (Scotland) Regulations. S1W-26589 - Des McNulty (Clydebank and Milngavie) (Lab) : To ask the Scottish Executive what penalties may be charged by Scottish Water against its contractors if Cryptosporidium is found in the treated water after filtration by the proposed water treatment plant at Milngavie. Answered by Ross Finnie (24 June 2002): This is a contractual matter between Scottish Water and its contractors. S1W-26587 - Des McNulty (Clydebank and Milngavie) (Lab) : To ask the Scottish Executive what maximum level of Cryptosporidium is allowable in drinking water supplies under relevant Scottish guidelines. Answered by Ross Finnie (24 June 2002): There is no maximum level set for Cryptosporidium in The Water Supply (Water Quality) (Scotland) Regulations. The regulations require that water does not contain any micro-organism or parasite at a concentration which would constitute a potential danger to human health. S1W-26586 - Des McNulty (Clydebank and Milngavie) (Lab) : To ask the Scottish Executive what minimal level of Cryptosporidium removal is required under relevant legislation and European directives for water treatment plants. Answered by Ross Finnie (24 June 2002): Neither the European Drinking Water Directive nor The Water Supply (Water Quality) (Scotland) Regulations set performance criteria for Cryptosporidium removal at water treatment works. Where there is an identified risk of Cryptosporidium entering a water supply, The Cryptosporidium (Scottish Water) Directions 2002 require that a treatment process
providing research and information services to the Scottish Parliament

and operating protocols, appropriate for the identified risk, are put in place to minimise that risk. S1W-26588 - Des McNulty (Clydebank and Milngavie) (Lab) : To ask the Scottish Executive what penalties may be levied against Scottish Water if specified Cryptosporidium removal rates are not met at the proposed water treatment plant at Milngavie. Answered by Ross Finnie (24 June 2002): I refer the member to the answer given to question S1W-26586 today. However, if Scottish Water supply water unfit for human consumption, they shall be guilty of an offence unless they can demonstrate that they had exercised all due diligence for securing that the water was fit for human consumption. Any decision on whether or not an offence had been committed and any penalties levied against Scottish Water would be a matter for the procurator fiscal. S1W-26591 - Des McNulty (Clydebank and Milngavie) (Lab) : To ask the Scottish Executive what methodology has been selected by Scottish Water to monitor Cryptosporidium in water supplies before and after treatment at the proposed water treatment plant at Milngavie; whether the chosen methodology meets relevant British and international standards, and whether the chosen methodology is used elsewhere in the United Kingdom. Answered by Ross Finnie (24 June 2002): The Cryptosporidium (Scottish Water) Directions 2002 and the associated guidance issued by Scottish ministers in April 2002, specifies the necessary requirements for sampling and analysis for Cryptosporidium in public water supplies. The method specified is used throughout the UK.

Research Notes are compiled for the benefit of Members of Parliament and their personal staff. Authors are available to discuss the contents of these papers with Members and their staff but cannot advise members of the general public.

providing research and information services to the Scottish Parliament

To top