Australasian bittern - matuku/hūrepo - in wetland

Te Henga Wetland

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Technical Review of Herbicide Use and Risks

Charles Hyland, Chair, Soil & Health Association of New Zealand
26 Sept 2025

Executive summary

Two herbicide products have been reportedly used at Te Henga wetland: Polaris 450 (a 450 g/L glyphosate isopropylamine salt formulation) and Aquakynde (an anionic surfactant adjuvant). (Matuku Link)

[UPDATE March 2026: herbicide spraying again being undertaken – Waatea News]

The Environmental Protection Authority (EPA) approval for Polaris 450 (HSR000227) classifies the product as harmful if inhaled (H332), causes serious eye irritation (H319), and toxic to aquatic life with long-lasting effects (H411). The Polaris 450 Safety Data Sheet (SDS) also instructs users not to allow the product to enter waterways.

Aquakynde carries serious eye damage (H318) and aquatic harm (H402/H412) classifications; its active surfactant chemistry (e.g., sodium alkylbenzene sulfonate types) is known to be harmful to aquatic organisms at low mg/L levels.

Under New Zealand’s Hazardous Substances regime, most agrichemicals with aquatic hazards must not be applied into or onto water. For Polaris 450 specifically, the EPA has replaced the usual “no application into or onto water” rule with special “water application” controls: if application into or onto water is contemplated and the water could leave the application site, then the strictest aquatic controls apply (treated “as if” Aquatic Acute Category 1).

The Auckland Unitary Plan (AUP) E34 Agrichemicals adds local requirements on spray-drift management, setbacks, operator competence, and record keeping, with wetlands clearly treated as sensitive receiving environments.

Wetlands are intrinsically high-exposure settings: spray drift, wash-off, and hydrologic connectivity funnel herbicide–surfactant mixtures into standing water and saturated sediments with long residence times. Glyphosate binds to sediments and is microbially transformed into aminomethylphosphonic acid (AMPA), which can persist. A large literature shows that aquatic toxicity of glyphosate-based products is often driven by the surfactant system, not glyphosate alone, with amphibian eggs and larvae particularly sensitive at low mg/L concentrations.

Bottom line: Spraying in, over, or immediately adjacent to standing water in a wetland creates a high-risk exposure pathway that is difficult to keep compliant and is readily avoidable.

A precautionary pause, an independent compliance audit, switching to non-spray or contact-limited methods, and basic monitoring are warranted.

Te Henga wetland, Auckland Council

Photo: Te Henga wetland, Auckland Council

Products and hazards

Polaris 450 (glyphosate IPA, 450 g/L). EPA approval HSR000227 classifies Polaris 450 as H332, H319 and H411; its SDS further cautions “Do not allow product to enter waterways.” (Horticentre Group)

Aquakynde (anionic surfactant adjuvant). The attachment provided identifies serious eye damage (H318) and aquatic harm (H402/H412) with an anionic surfactant (e.g., benzenesulfonic acid, C10–13-alkyl derivatives, sodium salts; CAS series including 68515-73-1 / 68411-30-3). Representative SDS documents for these surfactants report fish LC50 ≈ 1.7 mg/L and Daphnia EC50 ≈ 2.9 mg/L, consistent with Aquatic Chronic hazard classifications. (Alconox)

Mixture concern. When glyphosate formulations are tank-mixed with additional surfactant, the overall aquatic hazard typically increases compared with glyphosate alone because surfactants can drive toxicity and membrane permeability in aquatic organisms. (PubMed)

Legal and planning framework (national and regional)

  • EPA “water application” controls for Polaris 450. For approval HSR000227, Clause 52 of the Hazardous Property Controls Notice (“no application into or onto water”) is expressly dis-applied. Instead, if application into or onto water is contemplated and the substance could leave the application site (via water movement), then Clauses 62–64 (the strictest aquatic controls) apply as if the substance were Aquatic Acute Category 1. In practical terms, that tightens controls substantially whenever treated water could flow beyond the site.
  • Auckland Unitary Plan (AUP) E34 — Agrichemicals. Sets local standards on buffers, drift management, operator competence, and records, and recognises wetlands/water bodies as sensitive receiving environments.
  • NZS 8409:2021 Management of Agrichemicals (NZS 8409). Widely referenced best-practice standard for agrichemical use; regional plans and guidance routinely point users to NZS 8409 for drift reduction, setbacks, and water protection. (GrowSafe)

Implication for Te Henga: Even where “water application” may be contemplated under HSR000227, meeting the strict controls and AUP E34 expectations in a complex wetland is demanding, and label instructions (e.g., do not allow to enter waterways) still apply. (Horticentre Group)

Wetland exposure pathways

In Te Henga’s mosaic of pools, drains, and saturated peat, likely exposure routes include:

  1. Direct application/overspray into standing water;
  2. Spray drift from bank-side treatments depositing droplets on water or saturated substrates;
  3. Wash-off/runoff after rainfall carrying dissolved glyphosate and surfactants into pools and drains; and
  4. Sediment interaction, where glyphosate sorbs and is transformed to AMPA. In wetlands with slow turnover and organic sediments, both glyphosate and AMPA can persist, extending exposure windows for aquatic plants, invertebrates, fish, amphibians, and microbial communities.

What good compliance should already cover

  • No routine spraying into/over standing water when practicable alternatives exist; where “water application” is proposed, apply HSR000227’s strict controls (treat as if Aquatic Acute Cat. 1) and document how off-site movement is prevented.
  • AUP E34 plan compliance: mapped buffers, defined wind and weather limits, drift-reduction setup (nozzle, pressure, boom height), operator competence, and full records.
  • Label and SDS adherence, including no-spray instructions, rates, frequency, re-entry intervals, and “do not allow to enter waterways.” (Horticentre Group)
  • Work to NZS 8409 practices for agrichemical use near water. (GrowSafe)

Health and ecological science relevant to decisions

  • Environmental fate. Glyphosate typically shows moderate persistence in aquatic and soil systems (typical reported half-lives from ~10–77 days in water depending on conditions and ~47–75 days in soil), with AMPA formation and persistence in sediments; bioaccumulation is low. (Horticentre Group)
  • Formulation-driven aquatic toxicity. Multiple studies show surfactants used with glyphosate (historically POEA and other systems) can drive toxicity of the end-use product at low mg/L levels relevant to shallow wetlands. Amphibian eggs and larvae are highly sensitive. (PubMed)
  • Mechanisms. Surfactants increase membrane permeability and facilitate uptake, producing greater effects than glyphosate alone; co-formulants and adjuvants can increase product toxicity or show independent toxicity. (PMC)

Findings specific to Te Henga

  • Both reported products carry explicit aquatic hazards; Polaris 450 further cautions against entry to waterways. Adding Aquakynde increases the likelihood of aquatic effects relative to glyphosate alone. (Horticentre Group)
  • Edge/bank applications without robust drift control, adequate buffers, and strict low-wind windows create realistic acute exposure for amphibians and macroinvertebrates, especially in shallow, low-flow pools common in wetlands. (PubMed)
  • The HSR000227 “water application” controls raise the compliance bar if any application into or onto water is contemplated and water could leave the site. In a hydrologically connected wetland like Te Henga, that condition is difficult to rule out.

ABOVE: Pāteke (brown teal) at Tiritiri Mātangi. In 2015 pāteke were reintroduced to Te Henga wetland. Photo: Sabines Sunbird

Recommendations

  1. Pause all spraying within and immediately adjacent to standing water pending an independent compliance review against EPA controls and AUP E34.
  2. Commission a qualified, independent agrichemical auditor (not the contractor) to verify wetland and water-body mapping, buffers, drift-reduction measures, operator competence, label/SDS compliance, and record keeping. (Horticentre Group)
  3. Implement short-term monitoring: baseline and post-event water and sediment sampling for glyphosate and AMPA at representative sites, plus simple biota checks (e.g., amphibian larval presence/absence transects) before and after the spray season.
  4. If vegetation control is still needed, avoid broadcast/foliar spraying over open water. Prefer cut-stump, drill-and-fill, or wiper/wick methods executed from stable ground with physical shielding and absorbent capture to prevent drips and runoff.
  5. Omit added surfactants where the herbicide label does not require them, and avoid high-hazard surfactants (e.g., POEA-type systems) near wetlands. (PMC)
  6. Pair manual/mechanical removal with rapid native revegetation to reduce repeat chemical interventions.
  7. Establish governance practices: pre-operation plans (buffers; nozzle/pressure; weather triggers; product batch IDs) and post-operation reports (treated area, volumes, weather, incidents). Notify iwi and local communities in advance and publish summary monitoring results.

Requests to the Parliamentary Commissioner for the Environment (PCE)

  1. Commission an independent review of Te Henga operations for consistency with EPA water-application controls (HSR000227) and AUP E34.
  2. Issue guidance to councils on minimum protections in wetlands: buffers, drift technology, method hierarchy (prefer non-spray/contact-limited methods), and monitoring.
  3. Encourage agencies to avoid surfactant-assisted foliar spraying in wetlands, allowing exceptions only with a formal, transparent decision record.
  4. Recommend baseline monitoring support so decisions are evidence-based (and the absence of measurements is not used as a defence).

Notes on the Safety Data Sheets

  • Aquakynde bullet points. Lists H318 and H402/H412 and identifies an anionic surfactant (e.g., alkylbenzene sulfonate, CAS series including 68515-73-1 / 68411-30-3). Representative SDSs for these chemistries document mg/L-level aquatic toxicity, aligning with heightened concern for wetland organisms. (Alconox)
  • Polaris 450 bullet points. Cite HSR000227 and H332/H319/H411 and reiterate waterway protection. The full SDS echoes these warnings. (Horticentre Group)

Scope and limitations

This review integrates product hazard information, New Zealand regulatory requirements, and peer-reviewed evidence on wetland exposure and toxicity, interpreted for Te Henga. It does not reconstruct field practices or verify on-site conditions. For a complete compliance assessment, obtain work plans, spray diaries, weather/wind records, equipment and operator certificates, GPS traces, and pair these with site inspections and basic sampling.

References

  1. Matuku Link. Pest Plant Control. https://matukulink.org.nz/pest-plant-control/
  2. Waatea News. Drone Glyphosate Spraying at Te Henga Proceeds Despite Court Appeal. https://waateanews.com/2026/03/06/economy-drone-glyphosate-spraying-at-te-henga-proceeds-despite-court-appeal/
  3. Environmental Protection Authority (EPA). Reissued approvals with water application controls — Glyphosate approvals including HSR000227. (see “HSR000227 – Glyphosate (as its isopropylamine salt) – soluble concentrates”; Clause 52 dis-applied; Clauses 62–64 apply “as if” Aquatic Acute Cat. 1 when water could leave the site). https://epa.govt.nz/industry-areas/hazardous-substances/rules-for-hazardous-substances/reissued-approvals-with-water-application-controls/
  4. ADAMA New Zealand. Polaris 450 Herbicide — Safety Data Sheet (17 Mar 2023). States H332/H319/H411 and “Do not allow product to enter waterways.” https://horticentre.co.nz/wp-content/uploads/SafetyDatasheets/Polaris-450-SDS.pdf
  5. Auckland Council. Auckland Unitary Plan — E34 Agrichemicals (operative in part). https://unitaryplan.aucklandcouncil.govt.nz/Images/Auckland%20Unitary%20Plan%20Operative/Chapter%20E%20Auckland-wide/5.%20Environmental%20Risk/E34%20Agrichemicals%20and%20vertebrate%20toxic%20agents.pdf
  6. Australian and New Zealand Governments (ANZG). Guideline values for freshwater: Glyphosate (technical brief; environmental fate, persistence, sorption). https://www.waterquality.gov.au/sites/default/files/documents/glyphosate_fresh_dgv_technical-brief.pdf
  7. Growsafe / Standards NZ. NZS 8409:2021 Management of Agrichemicals — overview and access. https://www.growsafe.co.nz/Growsafe/GrowSafe/AboutUs/NZS8409.aspx
  8. Howe, C. M., et al. (2004). Toxicity of glyphosate-based pesticides to four North American frog species. Environmental Toxicology and Chemistry, 23(8): 1928–1938. PubMed record: https://pubmed.ncbi.nlm.nih.gov/15352482/
  9. Relyea, R. A. (2005). The lethal impact of Roundup® on aquatic and terrestrial amphibians. Ecological Applications, 15(4): 1118–1124. Wiley abstract: https://esajournals.onlinelibrary.wiley.com/doi/abs/10.1890/04-1291 (open copy archived by NRC: https://www.nrc.gov/docs/ML1434/ML14345A564.pdf)
  10. Trumbo, J., et al. (2003). An assessment of the hazard of the herbicide Rodeo® and the non-ionic surfactant R-11® to non-target aquatic invertebrates and larval amphibians. California IPC (PDF): https://www.cal-ipc.org/wp-content/uploads/2017/12/Trumbo-aquatic.pdf
  11. Mesnage, R., & Antoniou, M. N. (2018). Ignoring adjuvant toxicity falsifies the safety profile of commercial pesticides. Frontiers in Public Health, 5: 361. https://pmc.ncbi.nlm.nih.gov/articles/PMC5786549/
  12. Mikó, Z., et al. (2023). Toxicity of POEA-containing glyphosate-based herbicides and their components to amphibian larvae under predation risk. Ecotoxicology and Environmental Safety, 253: 114654. https://pmc.ncbi.nlm.nih.gov/articles/PMC10008773/
  13. Representative anionic surfactant SDS (alkylbenzene sulfonates, showing mg/L aquatic toxicity):
    a) Alconox SDS (Sodium alkylbenzene sulfonate; fish LC50 1.67 mg/L; Daphnia EC50 2.9 mg/L). https://alconox.com/wp-content/uploads/2020/07/Alconox-SDS-english.pdf
    b) Forders SDS (Sodium C10–13 alkylbenzene sulfonate; aquatic toxicity section). https://www.forders.fi/storage/product_files/0/157140-157104_KTTeng.pdf

Heavy rain, soil and waterways – what’s the effect and what we can do about it?

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About the video

We all know that heavy rains cause soil loss and runoff. And we understand these are harmful to fresh water and the wider environment.

But many farmers, gardeners and land owners are unsure about where to start fixing these problems.

Join Philippa Jamieson, former editor of Organic NZ magazine, in conversation with soil scientist Charles Hyland and freshwater ecologist Dr Mike Joy as they discuss some of the mechanics of these problems and the relative virtues of various solutions.

This webinar aims to empower the organic community to intentionally manage their soils in order to achieve their sustainability and environmental goals.

About the panelists

Charles Hyland is a soil scientist and biogeochemist who moved to NZ in 2013 after working at Cornell University in the USA as a scientist for over ten years.  His career has focused on identifying complex environmental problems associated with agricultural systems and implementing effective innovative solutions. Organic agriculture has always been central to his work and worldview.

Mike Joy began lecturing at Massey University in ecology and environmental science in 2003. After seeing first-hand the decline in freshwater health in New Zealand, he became an outspoken advocate for environmental protection. He has been working for two decades at the interface of science and policy in New Zealand with a goal of strengthening connections between science, policy and real outcomes to address the multiple environmental issues facing New Zealand.

Aotearoa New Zealand | Policy Proposals on healthy waterways: Are they fit for purpose?

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Excellent water quality is of paramount importance for our Treaty obligations, agriculture, tourism industry, health and sense of national identity. In September 2019 the Ministry for the Environment released its proposals for dealing with the crisis in our freshwater: Action for healthy waterways. While the document outlines possible ways of ‘reducing soil loss, reducing nutrient run-off, and/or investing in upgrading wastewater and stormwater infrastructure’, there is one glaring omission – it does not address the need to monitor synthetic chemicals in our waterways.

New Zealand has chemicals in our waterways that are banned in Europe. Policy-makers tend to assume toxic chemicals assimilate into the environment. However, it is clear from global and local data that the pressures from ongoing diffuse sources (agricultural, industrial and household and pharmaceutical) exceed the capacity for the environment to disperse and degrade them. The only way to understand the pollution profile is, as the OECD recommends, to (1) commence transparent, centrally driven monitoring that seeks to comprehensively capture chemical pressures that will differ by region. (2) Then make the data public, so that citizens and scientists can access the data, and then (3) Civil society can debate the degree to which regulation (or not) is required in order to safeguard the life-supporting capacity of our freshwater (See Sn 5 of the RMA).

The Soil and Health Association and Physicians and Scientists for Global Responsibility (NZ) jointly produced a detailed submission to respond to the September discussion document. Twenty-one NGOs supported our submission document, and eight private organisations also requested to join, including major players in the regenerative agriculture movement. Surprisingly, this was not picked up by mainstream media. Chapter 10 of our publication outlines suggestions for reform. We also produced a summary paper.

Chemical production is predicted to increase exponentially, constituting a present and growing threat to human and environmental health, and risking the wellbeing of future generations. Chemical contaminants include pesticides, household products, resins, plastics, petroleum products, pharmaceuticals and personal care products. Currently, routine national monitoring for chemical contaminants in New Zealand freshwater that is publicly accessible, is confined to groundwater. While laudable, this is not sufficiently protective of public or environmental health.

Polluting synthetic chemical contaminants create intersecting social, cultural and economic harms. Without a mandate to monitor chemical contaminants in waterways as well as aquifers, territorial and national authorities will not have the capacity to safeguard:

  • The quality of our drinking water;
  • Māori customary fishing and traditional riverside food gathering;
  • Favourite Kiwi swimming areas;
  • Key tourist destinations as safe and ecologically healthy;
  • Food production and processing, and organic systems from contamination.

Excluding diffuse chemical contaminants from monitoring and regulation additionally leaves Māori without appropriate scientific resourcing to assert rangatiratanga and kaitiakitanga. We will be unable to protect biodiversity and our food chains, reverse declining fish populations and ensure that our agricultural exports are not inadvertently contaminated. And the possibility of endocrine disruption puts at risk our most vulnerable citizens – our babies.

Diffuse synthetic chemical emissions must be urgently addressed at a central government level. Chemicals accumulate, they can interact together additively and/or synergistically and be much more harmful to environmental organisms, and humans – than exposure to a single chemical. It’s an interesting fact that all vertebrates – from frogs to fish to humans, are similarly vulnerable to endocrine disrupting chemicals. For endocrine disrupting, carcinogenic and/or mutagenic substances, it is increasingly clear that there can be no ‘end-point’ – no degree of exposure that can be claimed to be safe. Our paper discusses this in depth, drawing on extensive references to support our discussion.

The solution is not to stick our heads in the sand, because it is not politically comfortable, nor convenient. Nor is it acceptable to wait for certainty – until scientific endpoints are established. It is evident, for many endocrine disruptors, that it may not be possible to establish endpoints because of the miniscule levels at which these chemicals cause harm, and because of the varying vulnerability at different life stages.

In such an environment, there remain many opportunities to ensure policy and regulation concerning freshwater are fit for purpose and can reasonably meet the foreseeable needs of future generations.

Reform Recommendations

  1. Where degraded areas are identified, scientists can utilise a suite of nationally regulated testing screens for diffuse chemical contaminants and publish this information for public debate.
  2. New Zealand can resource scientist experts in chemical toxicology, endocrinology and environmental chemistry and build on international research to innovatively evaluate the risk to both aquatic food chains and human health – at arms-length from industry.
  3. Our chemical risk assessment can adopt best practice alongside Europe, sending a firm message to trading partners and tourist operators that freshwater and food in Aotearoa is clean and safe.
  4. We can update regulations to recognise additional risk from chemical mixtures; and the risk from exposures at low levels that impacts the hormone system and can set the stage for disease and dysfunction.
  5. New Zealand can appropriately engage the precautionary principle as the key policy instrument that over-arches risk evaluation, rather than retaining it where it currently sits in legislation and policy, alongside social, cultural and economic considerations where it is
    rarely called upon, and frequently ignored.

We recommend that the monitoring of diffuse chemical pollutants in our fresh water is required as a national environment standard and that the recommendations for reform in this paper are included in any policy on protecting the quality of our fresh water.

Freshwater 2020 – Scope continues to exclude diffuse chemicals

Proposed National Environmental Standards for Freshwater continue to exclude the cumulative risk of environmental synthetic chemicals from national documentation and discussion. Environmental indicators ignore diffuse pollution from urban, agricultural and industrial sources. 

The Soil and Health Association, PSGR and our co-signatories joined many individuals and organisations in submitting to the September 2019 the Action for healthy waterways.

A record number of individuals and organisations submitted to the Ministry for the Environment– 17,500. The Summary of Submissions reveals that urban, agricultural and industrial synthetic chemical pollution was not an item of concern to the general public.

Inconsistent approach to chemical pollutants

In February 2020 the Report of the Freshwater Independent Advisory Panel was released.

– It did not mention synthetic chemicals, pesticides, or trace (heavy) metals.

In April 2020 the Our Freshwater 2020 was released by the Ministry for the Environment and StatsNZ.

– It did mention synthetic chemicals, pesticides, or trace (heavy) metals were a substantial problem.

In May 2020 National Environmental Standards for Freshwater and the National Policy Statement for Freshwater Management were released. They were accompanied by a Cabinet paper which was the key document for seeking agreement to an action for the healthy water ways package. They files also included regulatory impact analyses and appendices.

– None of these documents nor appendices mentioned synthetic chemicals, pesticides, or trace (heavy) metals.

Of the files released in May 2020, Appendix 7 contained the Summary of Submissions from 17,500 individuals who joined others in submitting to the national direction for our freshwater. This, it appears, was one of the primary documents informing the Cabinet paper.

However, it appears that not many, if any submitters were interested in the potential for synthetic chemicals, pesticides and trace metals to pollute New Zealand waterways.

As a result in the 190 page Summary of Submissions there was only one mention of synthetic chemicals: ‘Submitters also mention contamination of drinking water from other chemicals (including emerging contaminants), microbes and waste’ (page 173). Trace metals and pesticides were not mentioned.

This 2019-2020 process was largely a result of the failure of an earlier process which produced the National Policy Statement for Freshwater Management 2014 (amended 2017). This earlier process was criticised for its weak approach to nutrient (nitrogen) management.

Following the release of the 2020 suite of papers, the nitrogen level recommended in the Cabinet paper was also criticised for not following the bottom line recommendation of 1mg/L dissolved inorganic nitrogen level recommended by the Science and Technical Advisory Group who were invited to advise the Ministry for the Environment.

Therefore the Freshwater process managed by the Ministry for the Environment continues to fail to produce fit for purpose national standards that can assure that our freshwater will be safe for not only river life, but for human health for future generations.

View full paper

The October 2019 submission to the Ministry for the Environment Aotearoa New Zealand Action for healthy waterways has been kindly supported by the following NGOs:

  • Safe Food Campaign
  • Pesticide Action Network Aotearoa New Zealand
  • For the Love of Bees
  • Federation of Freshwater Anglers
  • Whitewater NZ
  • Biodynamics New Zealand
  • Waitaha Executive Grandmothers Council
  • Organic Dairy and Pastoral Group Inc
  • Te Waka Kai Ora – Maori Organics Aotearoa
  • Organic Farm New Zealand
  • Katikati Taiao
  • Manu Waiata Restoration and Protection Society

  • Orari River Protection Group
  • COBY – Coromandel Our Backyard
  • Te Waka Kai Ora – Maori Organics Aotearoa
  • ERP – Environment River Patrol Aotearoa
  • KEA – Kuaotunu Environmental Action
  • Weed Management Advisory Auckland
  • GE Free Aotearoa New Zealand
  • Econation 2020 Aotearoa New Zealand
  • Otago Organics

And these Private Sector Organisations:

  • Āta
  • Soil Connection
  • True Health
  • BioAg
  • Integrity Soils
  • Plenty Permaculture
  • Rings Road Herb Gardens
  • The Whistler

Fluoride in local body water supplies

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In New Zealand around 60% of public water supplies have fluoride added to prevent dental decay. The main chemicals used to fluoridate drinking water are known as silicofluorides. These fluorides are not pharmaceutical-grade fluoride products but unprocessed toxic industrial by-products of the phosphate fertiliser industry. There is conflicting evidence on the benefits of water fluoridation to dental health. There is also a growing medical concern about the cumulative negative wider health impacts of ingestion of fluoride. Many people in New Zealand already manifest dental symptoms of fluorosis – fluoride overdose. New Zealanders are already ingesting elevated levels of fluoride from plants and animals raised on land treated with phosphate which contains naturally occurring fluorides.

The Soil & Health Association is opposed to artificial fluoridation of public water supplies in New Zealand. We believe that adding fluoride to local body water supplies is a form of forced medication. We believe that individuals should have a right to choose whether they want to ingest fluoride or not. We believe that dental health is best achieved through a healthy diet and eating fresh, wholesome organic foods.

                                            Photo credit: Nick Holmes