Guideline for Sampling and Testing of Water associated with Monitoring of Aerial 1080 Baiting Operations (2nd edition)

Date: July 2008

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1. Introduction

The risk of potential contamination of New Zealand water supplies by 1080, particularly following aerial application of baits for pest control, has been addressed by research on the environmental effects and degradation of 1080 in water (e.g. Eason et al. 1992, 1993; Ogilvie et al. 1996; Booth et al. 1999; Eason & Wright 2001; Fisher et al. 2003; Suren 2006). Landcare Research maintains a database of the results of over 2000 water samples tested by the toxicology laboratory for 1080 contamination since 1990. As summarised by Booth et al. (2007), 3.6% (76) of the water samples contained detectable 1080 residues and in most of them (70) the 1080 concentration measured was less than 1ng/mL (parts per billion). There is no evidence that drinking water has been contaminated and the extensive research and monitoring in catchments treated with 1080 indicates that this is highly improbable if current safety procedures are followed.

If 1080 were somehow to get into drinking water supplies the Ministry of Health recommends that water should not be used for drinking until tests show that the concentration of 1080 is below 2 ng/mL (http://www.moh.govt.nz). The Drinking Water Standards for New Zealand (MoH 2005) require that, should residues be detected at more than 50% of the maximum acceptable value (MAV), additional water sampling should be undertaken and continue until it has been established that residue concentration does not exceed the MAV. The figure of 2 ng/mL is an approximation of 50% of the provisional MAV of 3.5 ng/mL.

This document provides general technical advice for agencies undertaking water monitoring after aerial 1080 baiting operations, such as the Department of Conservation, regional or unitary council pest control managers, or Medical Officers of Health (MOH) who are involved in assessing the need for sampling.

2. Sampling strategies

2.1 Why test for 1080?

Each aerial 1080 poisoning operation requires approval by the MOH, and in some cases the regional council (under the Resource Management Act 1991). Water monitoring may be requested by any of these agencies, although it is usually the MOH who makes the request where water from the area is used for human consumption, i.e. potable water. Different testing regimens are required to meet different needs. Crown Research Institute (CRI) researchers have in the past undertaken water monitoring to determine if they can find any 1080 residues in small streams in the heart of catchments after aerial application or after deliberately ‘spiking’ streams with baits to address questions relating to the breakdown of bait, duration of contamination, and distance that residues travel (Suren 2006). Research questions often require intensive sampling regimens different from the sampling requirements associated with the need to define whether or not 1080 residues are present in drinking water.

2.2 Where to take samples

The number of sampling sites for water monitoring will be dependent on the questions being addressed, the nature of the terrain, the surrounding land use, and the presence of domestic water supplies in the area. Because each area is different, the selection of sampling sites will be specific to each operation.

If sampling is focused on determining the presence or absence of residues in drinking water, samples may be taken from:

2.3 When to take samples

In all instances, appropriate sampling intervals and frequency should be confirmed with the regional council hydrologist, whose advice should be sought when designing the water monitoring programme.

It is important to ensure that sampling is undertaken during the most likely time period for occurrence of 1080 in waterways. Previous monitoring data suggest that most water samples with detectable concentrations of 1080, and certainly the ones that have been above 1 ng/mL (part per billion), were collected within 48 hours of aerial bait application. Recent research by Suren (2006) showed that 1080 was rapidly leached from pellet baits placed in small streams (>90% of 1080 leached within 24 hours), and 1080 was detectable in the water for a short period of time.

Water samples taken within 8 hours of bait application are expected to provide the greatest likelihood of detecting any residual 1080. Ideally, sampling from the same relevant point on a waterway at 8 hours and again at 24 hours after bait application will be useful to confirm whether or not 1080 is present in detectable concentrations.

2.4 Sampling mechanisms

Samples should be taken, whenever possible, 30 cm below the water surface. Sample bottles should be rinsed two or three times in the water source before collecting the sample. However, this practice should not be used when the sample comes from rivers or streams with high contents of suspended solids.

3. Requirements for sampling

3.1 Sample handling

Because 1080 is known to degrade in biologically active stream water more rapidly at higher temperatures (Parfitt et al. 1994; Ogilvie et al. 1996), water samples should be analysed as soon as practicable and until analysis, kept frozen to ensure that any 1080 in the sample does not degrade. Since 1080 is an ionic compound, polypropylene plastic sample bottles should be used and these need to be able to withstand freezing to −20°C. Sample bottles can be obtained from plastic wholesalers or from pharmacies. Each sample should be at least 200 mL in order to provide sufficient water for repeat testing; sample bottles should be no more than 80% full to allow for expansion when freezing.

3.2 Sample integrity

It is vital that water samples are taken from each site in a way that ensures that samples are not contaminated by the sampler, sample containers, or subsequent handling.

The limit of detection in water samples for the testing method is some 15 million times lower than the typical concentration in possum baits (the method limit of detection is 0.1 ng/mL (ppb)). Hence the method for testing the sample is extremely sensitive and even minute amounts of 1080 will be detected. Sample containers must not therefore become contaminated in any way, even externally.