River and groundwater surveys find only tiniest trace of pesticides

The results of two recent sampling surveys offer reassurance to those concerned about the potential for pesticide contamination in the region’s fresh water, the Taranaki Regional Council says.

“Both surveys – one of rivers and streams, the other of groundwater, turned up minute traces of pesticides residues in only three samples across both surveys, and, importantly, no traces of glyphosate, which is best-known as Roundup and is very widely used,” says the Council’s Director-Environment Quality, Gary Bedford.

“Some in the community are concerned about the possibility of pesticide contamination in a region that is heavily farmed. These results offer reassurance.”

In the surface-water survey, Council officers took samples from nine waterways to test for about 200 different compounds, obtaining around 1800 analytical results.

Two samples yielded traces of organochlorine compounds but they were at levels barely above detection limit and well within relevant standards. They were of substances that have long been banned from sale and withdrawn from use.

Samples were taken from lower reaches of nine waterways in catchments where pesticide use is likely to be relatively high. They included the Waitara River, Waiongana River, Waiwhakaiho River, Te Henui Stream, Huatoki Stream, Oakura River, Waimoku Stream, Timaru River, and Waingongoro River. Sampling took place in November 2019, timed to avoid wet weather and tidal effects that may have diluted any contaminants present.

Full surface-water survey results can be seen here: www.trc.govt.nz/PS2020 [PDF, 603 KB]

Meanwhile, the latest ESR-led groundwater programme, under which councils nationwide provide samples for analysis and comparison, found a pesticide trace in a sample from one of the eight Taranaki wells included. It was at only 1% of the level deemed to make water unfit for drinking.
The eight Taranaki wells selected for the survey were in locations considered to have above-average risk of pesticide contamination, given the present and/or historical land uses. “So it’s a reasonable conclusion that the incidence of contamination across the whole region is even lower than these results indicate,” says Mr Bedford.

The latest ESR survey, conducted in 2018, was expanded this time to include tests for ‘emerging organic contaminants’ (EOCs) including those associated with caffeine, artificial sweeteners, some medications, skin-care products and packaging. Traces of such compounds were found in samples from five of Taranaki’s eight wells, similar to the national detection rate.

“This testing is a useful addition to the survey and the results set a baseline for future reference,” says Mr Bedford. “We’ll be keeping a close eye on the findings of current research into EOCs but we’ve been advised the traces found in this survey are most unlikely to be toxic to humans.”

The full report on ESR’s groundwater survey can be seen here: www.trc.govt.nz/PG2020 [PDF, 1.2 MB]