H. The Cryptosporidium Regulations
Two major outbreaks of drinking water related cryptosporidiosis, one in 1995 and the other in 1997, which identified the need for further measures to protect public health.
In August 1995, in the Torbay area of Devon, there was an outbreak of cryptosporidiosis with 575 reported cases in which mains drinking water was strongly implicated. However, the Inspectorate’s case of supplying water unfit for human consumption against the water company was rejected by the Court on the grounds that epidemiological evidence was not admissible. In the light of this case, the Inspectorate was not able to take any action against another water company following an outbreak in parts of north London and Hertfordshire in spring 1997 when there were 345 reported cases in an outbreak that was probably linked to the mains water supply.
The Regulations
The Government introduced new Regulations based on a treatment standard. The Water Supply (Water Quality) (Amendment) Regulations 1999 came into force on 30 June 1999. In England these have been incorporated into the new Water Supply (Water Quality) Regulations 2000. These Regulations set a treatment standard of an average of less than one oocyst in 10 litres of water supplied from a treatment works. The Regulations specified continuous sampling of an average of not less than 40 litres per hour with samples being taken each day for analysis. As it is a treatment standard it does not take into account different species of Cryptosporidium, nor whether any oocysts detected are viable or non-viable.
Implementing the Regulations
Water companies were required to carry out a risk assessment for each of their water treatment works by 30 September 1999. The assessment considered the source water, the catchment and the treatment provided. The assessments, which were checked by the Inspectorate, established whether there was a significant risk of contravening the standard. Guidance on risk assessment was issued with the Regulations and has been posted on the Inspectorate’s website. The guidance identifies factors that contribute towards the assessment of significant risk i.e. direct abstraction, abstraction with storage of seven days or less from a river or stream, evidence of rapid surface water connection to an aquifer used for groundwater abstraction, or past history of an unexplained outbreak of drinking water related cryptosporidiosis where no specific action has been taken to prevent recurrence.
The significant risk classification does not imply a contravention of the standard but rather that there is potential for a significant number of Cryptosporidium oocysts to be present at times in the treated water. For works identified as at significant risk, water companies must treat the water to ensure that the standard is met. They must also demonstrate compliance by continuously monitoring the water leaving the works and reporting the results of the daily analysis to the Inspectorate.
332 out of the 1481 treatment works in England and Wales were identified as being at significant risk. Of the 332 at significant risk, 158 were works treating surface water and 174 were groundwater abstractions. Monitoring at the highest risk sites began on 1 April 2000 and monitoring has commenced at other works, in accordance with a programme agreed with the Inspectorate. As an alternative to continuous monitoring, a water company may install treatment plant capable of continuously removing or retaining particles greater than one-micron diameter. As currently drafted, the Regulations require physical removal of oocysts and do not take into account any form of disinfection.
Improvement Programmes
Regulatory monitoring is required to demonstrate that the standard is being met. Some ground waters and a small number of surface waters do not currently have physical treatment barriers capable of removing Cryptosporidium oocysts. Where such water treatment works have been identified as at significant risk under the Regulations, the Inspectorate has agreed an improvement programme with the water company for appropriate treatment to be installed or in some cases for the source to be abandoned or changed. Until treatment is installed or other action taken water companies are encouraged to monitor the treated water continuously and report these operational results to the Inspectorate. However, these data are not included in the regulatory results reported below.
Analysis of Samples
The protocol issued with the Regulations lays down the requirements for the laboratory facilities and analytical method that must be used for compliance testing. Analysis can only be carried out at laboratories approved by the Inspectorate and these are subject to unannounced inspections. Samples must be analysed within three days of being taken, unless there has been a significant increase in turbidity of the water being sampled or some other indication that the number of Cryptosporidium oocysts in the water may have increased. In this case, analysis must be completed within a day of the sample being taken.
Strict rules are laid down for all aspects of sampling and analysis to permit the use of the analytical results as evidence in a Court of Law. Initially sole suppliers were specified for the key materials used in the sampling and analysis procedures but guidance on demonstrating the equivalence of alternative technologies was provided. A number of alternative methodologies have now been approved and full details of all approved procedures and guidance on demonstration of equivalence has been posted on the Inspectorate’s web site.
Sample Results
Regulatory monitoring results are available for the first nine months operation of the Regulations, from 1 April 2000 to 31 December 2000. During this period 36,916 samples have been taken from 188 sites. Oocysts have been detected in 2,755 (7.46%) samples taken from 108 (57.4%) sites. The great majority of detections, 91%, have been in the range 0.01 – 0.10 oocysts per 10 litres. Seven results from two sites have contravened the standard, the highest count was 4.91 oocysts per 10 litres. Outbreaks of cryptosporidiosis have not been associated with these contraventions and the Inspectorate is unaware of any outbreaks associated with water treatment works identified as at significant risk.
It is too early to draw firm conclusions from the results because not all sites have yet come on stream for continuous monitoring and often have yet to have completed a full year’s seasonal conditions. Some sites are only being monitored operationally at present; and weather conditions, particularly autumn rainfall, in some areas, were exceptional. However, a lot of very useful data have been collected already and early indications are that the regulations are providing the required public health protection with treated drinking water not being a major source of exposure of the population to Cryptosporidium oocysts.
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Published 11 July 2001
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