Senior Scientist, NIWA, Hamilton
Room I1.09, University of Waikato
In June 2003 the Minstries of Environment and Health promulgated new water quality microbiological guidelines for freshwater and marine recreational areas. The freshwater component marks a departure from the previous approach, that was based on a large USA epidemiological study on two lakes. The new approach is based on a quantitative (Monte Carlo) health risk assessment for campylobacteriosis in New Zealand waters. This disease is potentially waterborne and forms more than half the current notified disease burden (current reported rate is over 300 per 100,000 people per annum). This assessment found that 5% of the current rate of infection by Campylobacter could be attributable to freshwater contact recreation.
This approach, and associated work, has raised the profile of quantitative health risk asssessment procedures, with the result that they are now becoming an essential part of an AEE (Assessment of Environmental Effects) when RMA consents for treated wastewater discharges are being sought (e.g., Mangere, Christchurch, Dunedin, Tauranga, Waimakariri District). Large dollops of public money are at stake in identifying the appropriate degree of treatment and location of the discharge.
There is a danger that such an attractive quantitative procedure can induce a false sense of security, whereas it has many attendant uncertainties. I will try to identify these, and suggest some means of addressing them.