SECTION A: Why Monitor Water?
A.1 Health risks
Water contaminated by human or animal excreta may contain a range of pathogenic (disease-causing) micro-organisms, such as viruses, bacteria and protozoa. These organisms may pose a health hazard when the water is used for recreational activities such as swimming and other high-contact water sports. In these activities there is a reasonable risk that water will be swallowed, inhaled (Harrington et al 1993), or come in contact with ears, nasal passages, mucous membranes or cuts in the skin, allowing pathogens to enter the body.
Research is continuing into the health risks associated with contamination of water by sewage and excreta. Until recently scientists believed that gastro-enteritis was the main health effect, but it is now becoming clear that respiratory health effects are also important, and may even be more prevalent than gastro-enteritis.
See Note G(i) for evidence on respiratory illness caused by water contamination.
In most cases the ill-health effects from exposure to contaminated water are minor and short-lived. However, there is the potential for more serious diseases, such as hepatitis A, giardiasis, cryptosporidiosis, campylobacteriosis and salmonellosis (Philip 1991).
Adhering to the guideline values and using the framework set out in this document should ensure that people using the water for recreation or collecting shellfish for eating are informed of health risks, and can make appropriate decisions to avoid exposing themselves to significant health risks.
Do these guidelines measure the level of pathogens in the water? In fact it is difficult and impractical to do this directly. Instead, we measure the levels of ‘indicator’ micro-organisms, which indirectly tell us about the levels of pathogens. The marine guidelines were developed from many studies relating bacteriological indicators to illness in the general public after bathing (see especially the WHO review by Prüss 1998). These studies include, but are not confined to, those carried out at seven New Zealand marine beaches in 1994–95 (McBride, Salmond, et al 1998). The freshwater guidelines were developed from the findings of the Freshwater Microbiology Research Programme Report: Pathogen Occurrence and Human Health Risk Assessment Analysis, November 2002 (McBride, et al 2002).
The guidelines work with a defined ‘tolerable risk’ rather than no risk at all. For most healthy people water conforming to the guideline value will pose a minimal level of risk. However, water conforming to the guideline values may still pose a potential health risk to high-risk user groups such as the very young, the elderly and those with impaired immune systems.
See Note G(ii) for more information on health risks.
A.2 State of the environment reporting
Regional councils and the Ministry for the Environment have responsibilities under the RMA to monitor the state of the environment. Reporting on state is achieved regionally through state of the environment reports and nationally through national state of the environment reporting.
The purpose of state of the environment monitoring and reporting is to use environmental performance indicators (EPIs) to measure and monitor human activities and their effects on the environment. The Government’s objectives for the state of the environment monitoring and reporting are to:
- systematically report on the state of New Zealand’s environmental assets
- systematically measure the performance of its environmental policies and legislation
- better prioritise policy and improve environmental decision making.
Over time, the information produced through monitoring environmental performance indicators will:
- contribute to raising the level of knowledge about the state of New Zealand’s environment
- increase our ability to report on environmental health and trends
- provide the tools for effective evaluation of policy
- provide the information base for more informed policy and management decisions.
This document serves as a monitoring protocol for two confirmed indicators for human health and values for marine and freshwater environments:
- the percentage of monitored beaches in each grade
- the percentage of the season beaches or coastal areas were suitable for contact recreation or shellfish gathering.
‘Beaches’ refers to both marine and freshwater recreation sites.
The national objectives of these indicators are to:
- quantify the human health risks at recreational water sites and shellfish-gathering areas
- measure the general state of recreational water areas
- report on the overall suitability of recreational water areas for bathing.
See Note G(iii) for more information on state of the environment reporting.
Integrating public health and state of the environment data
The purpose of the microbiological water quality guidelines for marine and freshwater recreational areas is to help control the public health risk from microbiological contamination in recreational waters and to provide a framework for monitoring and reporting on the general health of beaches. Integrating the needs of both state of the environment and public health monitoring may present some challenges, but it is achievable.
Microbiological information is generated more intensively to keep stock of short-term variation that can affect the public health risk of water quality. This monitoring takes place on a weekly basis, although at times follow-up monitoring is required to identify the permanence of an identified guideline exceedance.
The purpose of state of the environment monitoring is to collect sufficient data to produce information on the general health of the environment. This information can then be used to measure how well our management practices, policies and laws are working, and whether environmental outcomes are being achieved. The beach grades generated through the combination of the catchment assessment and the microbiological assessment provide the state of the environment information to the public on the general condition of the recreational area with respect to public health risk. The microbiological information collected to assess the public health risk at the beach on a weekly basis is aggregated over five years to generate the Microbiological Assessment Category that is used in the beach grading process.
