Study survey’s health risk in NZ rivers

18 December 2020

Media Release

A pilot study gathering data on the human health risks posed by New Zealand rivers and streams is getting underway this summer.

Scientists from ESR are leading the pilot study analysing a range of pathogens in freshwater, to begin updating the data that quantifies the risks for people using them for recreation.

The Ministry for the Environment funded Quantitative Microbial Risk Assessment (QMRA) pilot project will analyse samples from 16 freshwater sites from Northland to Southland.

The purpose of the pilot is to test methods for a comprehensive nationwide QMRA study, which if funded, is expected to begin in late 2020.

The last study of this type was a survey carried out over 20 years ago. That study informed New Zealand’s recreational water quality guidelines which were established in 2003. These are the principal guidelines used by regional and unitary councils to manage health risks posed by faecal pollution.

Scientists say that since the last national survey there have been significant changes in land use and waste management practises, which may have led to changes in the presence or abundance of pathogens in New Zealand’s freshwaters, or their relationship with the microbial indicators that are used for monitoring.

ESR microbiologist Dr Sarah Coxon says the most commonly recognised risk to human health posed by contact with freshwater is faecal contamination, which can contain a range of pathogenic organisms, including bacteria, viruses and protozoa.

Dr Coxon says since the last full QMRA survey there have also been significant advances in laboratory analyses that allow more sensitive detection of pathogens, and characterisation of the risk they pose to people’s health.

“We need to ensure that the public health advice in the guidelines accounts for any change, and is correctly estimating the human health risk.”

The pilot will be analysing water samples for a range of pathogens including Campylobacter, Salmonella, pathogenic E. coli, Giardia, Cryptosporidium, adenoviruses, enteroviruses, and noroviruses. The samples will be compared with indicator organisms E.coli and enterococci, as well as markers for sources of faecal identification.

The pilot gets underway in late January 2020 and results are expected in June 2020. The results will inform a full QMRA study which is expected to take around three years.

ENDS

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