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Blue-Green Algae (Cyanobacteria) in Inland Waters: Assessment and Control of Risks to Public Health
6 Assessments of the risks to human and animal health
Responsibilities for risk assessments
6.1 Assessments of the risks to human and animal health from blue-green algal blooms are likely to be made for different purposes - and with different degrees of formality - by different "stakeholders" including:
- owners and employers, including Scottish Water; for their duties in law to employees, customers and to other members of the public;
- regulatory bodies; local authorities, for the assessment of risk to public health, and SEPA, for determination of sources of pollutants, their impact and regulation;
- individuals; for their interests as employees or parents or in connection with their recreational interests.
6.2 The roles and responsibilities of these and other stakeholders are outlined in Section 9.
6.3 The responsibility for risk assessments by the owners of waters and by employers relates to their responsibilities to protect employees and others and, for Scottish Water, their customers.
6.4 Risk assessments by local authorities and SEPA are likely to be directed in part to determining inspection and monitoring priorities and schedules (Section 5). The interest of local authorities is primarily in determining the existence, or otherwise, in their areas of nuisances or hazards to health. That of SEPA is primarily in determining the state of the environment and in the regulation and control of sources of pollutants. A shared approach should be possible on specific waters where these interests require similar information.
Types of risk assessment
6.5 Risk assessments in respect of blue-green algal hazards in inland Scottish waters can be considered under three general headings, (i) generic assessments of the risk for the whole of each of the areas covered by the LAPs, (ii) pro-active assessments for individual waters and (iii) reactive assessments in response to identified occurrence or consequences of algal blooms.
6.6 Each LAP should include an overall assessment of blue-green algal problems for the whole of the NHS Board area. This should provide a general summary of blue-green algal problems for the area and identify the waters that represent the greatest risks because of their history of algal blooms and/or their use.
6.7 Proactive individual assessments for all inland waters would be neither practical nor cost effective. These should normally be confined to those waters identified in the LAP as presenting the greatest risks. However, the responsibilities identified in paragraph 6.1 and Section 9 (for example, those for employers) are not affected by any classification of waters in the LAP.
6.8 Stakeholders receiving reports on occurrences or consequences of algal blooms for waters relating to their interests should consider the need for a reactive risk assessment. This should aim to identify the magnitude and nature of the risks and define any interventions that might be required to lessen these risks.
Content of risk assessments for individual waters
6.9 Proactive risk assessments should include consideration of inspection and monitoring programmes and the need for appropriate action (such as erection of signs). They should take account, in structured ways, of information relating to any previous algal blooms (Table 5.1) and to the nature and intensity of use for the water in question.
6.10 Subsequent interventions would normally depend on the results of inspections and/or monitoring or the outcomes of any reactive risk assessments.
6.11 Reactive risk assessments (made in reaction to reports from the public of the appearance or consequence of algal blooms, suspected health incidents, or to inspections or monitoring) should consider how the water in question is used and the resultant risk to human and animal health (not the probability of occurrence of a bloom).
6.12 For either proactive or reactive risk assessments, therefore, assignment of waters to high, medium and low risk categories according to their use can help to prioritise the needs for inspection and/or monitoring and action. Table 6.1 gives outline descriptions of the features of waters falling into each of these categories.
6.13 A reactive risk assessment should define clearly the need for and nature of any interventions to mitigate the risks identified and for further inspection and/or monitoring.
Table 6.1:
Categories of risk related to the use of waters (and hence the probability and extent of exposure).
Risk category | Nature and intensity of use |
High | Waters that are either consumed by people or animals or used for activities involving immersion or appreciable skin contact. |
Medium | Waters for which the risk of ingestion of blue-green algal material or of toxins is small and appreciable skin contact with blooms is unlikely. Standing waters that are used for spray irrigation of crops. |
Low | Waters that are inaccessible or not used or are used only for angling, or other non-contact activities. |
Defining categories for frequency of occurrence or risks for algal blooms
6.14 It is essential that different views about criteria for assignment of waters to each of the categories defined in Tables 5.1 and 6.1 are discussed by bodies seeking co-operative action on monitoring.
Templates for risk assessments
6.15 Examples of templates for proactive and reactive risk assessments are provided in Annex F. Stakeholders might prefer to use their own formats but, if so, the information contained in the risk assessment should be at least that indicated in Annex F.
Specific considerations for public drinking water supplies
6.16 There are a few Scottish public water supply reservoirs where problems associated with algal growth recur. At these, the water treatment systems in place have been designed to cope or the water authority is able to use an alternative water source. Should circumstances arise where neither of these provisions applies, appropriate alternative measures would be put in place to ensure the safety of the water supply.
6.17 Scottish Water is required to comply with the Security and Emergency Measures Direction (SEMD). This requires it, amongst other things, to have emergency plans in place to cover such eventualities as loss of water supply (Paragraph 3.8) and to have routine liaison meetings about emergency issues with Local Authorities and Health Boards. These emergency plans are subject to an annual audit and certification by an independent person.
6.18 Consultation with Scottish Water in the production of LAPs for management of blue-green algae should ensure that these are compatible with any emergency plans drawn up under the SEMD.
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