In July 2023 FoE published a blog on pesticides in Queensland water supplies based on over 70,000 pesticide detections listed on the Queensland Government’s Pesticide Reporting Portal between late 2011 (in some locations) to March 2023. That blog attracted some media interest, including newspaper and radio, as well as hundreds of visits to the Friends of the Earth Australia website.

This blog is a follow up and looks at the potential ecological impact of pesticides flowing down rivers and creeks into the Great Barrier Reef (GBR). The blog will not discuss impacts of pesticides on the GBR but rather hopes to facilitate a better understanding of what is flowing into the GBR.

FoE argues that rather than tolerating Moderately Disturbed 95% ecological default guidelines (DGV’s) “previously known as trigger levels”, the Queensland Government, should be pushing for Slightly Disturbed/High Ecological 99% DGV’s in all waterways flowing into the GBR World Heritage Area. Unfortunately though, for many waterways flowing into the GBR they have historically been treated as little more than agricultural drains. It appears that in many locations this sad reality will continue into the indefinite future.

Whilst ecological guidelines can be useful indicators to the health of waterways, it could be argued that the guidelines themselves allow a “green light” for polluters to keep polluting waterways at supposedly “safe” levels. It also means that obvious failures in regards to pesticide labels, which supposedly don’t allow for water pollution, but actually do, are pushed aside and are rarely addressed.

The other glaringly obvious problem is that DGV’s exist for only a small fraction of pesticides used in Australia and that reviews for existing DGV’s occur rarely or not at all. For example in relation to  Atrazine, which represents the highest by quantity pesticide detected in GBR catchments, it has not had its DGV reviewed for almost a quarter of a century!!!

A major hindrance is that what may seem like the “greenest” course of action, is an entirely different proposition in the “real world”. This is especially the case if historical aspects of farm locations are taking into account and if one ignores the major economic contribution that agriculture makes to the Queensland and national economy. Eg Sugar is Australia’s second largest commodity crop after wheat, worth about $2bn/year. How many sugar users are aware of the ecological problems associated with the sugar cane industry? How is an equitable balance achieved?

FoE has determined that 22,492 breaches to Slightly Disturbed/High Ecological 99% DGV’s and 7,288 breaches to Moderately Disturbed 95% DGV’s occurred between late 2011* to March 2023 in testing across 39 locations. (*the actual amount is probably much higher as testing did not occur in many locations under several years after 2011).

Key ecological issues in relation to the health and Queensland rivers and waterways relate most significantly to the ongoing mismanagement of: Metolachlor, Diuron, Imidacloprid, Diazinon, Chlorpyrifos, Metsulfuron Methyl, Tebuthiuron, Imazapic and Atrazine.

87.2% of the 39 waterways sampled, breached 99% DGV’s for at least one pesticide, across the time period when all testing (including negative results) occurred. In some locations these breaches would have occurred relatively continously over a 11-12 year period and may have included up to eight pesticides.

33.3% of waterways sampled, regularly breached 95% DGV’s over the same period of time.

The most pesticide detections occurred at Barratta Creek at Northcote north of Ayr.

The highest volume of pesticides detected occurred at Sandy Creek at Homebush (south of Mackay), followed by Barratta Creek.

The highest average pesticide detection was at Coochin Creek, south of Beerwah.

Coochin Creek also recorded three* pesticides breaching the 95% DGV averaged out over the decade of pesticide testing at that location. (*including ‘sporadic and very high’ detections of Diazinon and Chlorpyrifos).

The Proserpine River at Glen Isla, Sandy Creek at Homebush and Coochin Creek all had 8 pesticides regularly breaching 99% DGV’s.

Arguably the waterway suffering the worst peaks in pesticide pollution was the Welcome Creek at Gooburrum, mainly because of excessively high detections of the insecticide diazinon.

This ongoing pollution represents a continuing failure of existing pesticide labels and farm management practices to stop toxic pollutants entering waterways and the GBR and an embarrassing failure of pesticide regulation in highly sensitive catchments that flow into a World Heritage Area.

Quick Overview

*Note that pesticides refer in this blog to herbicides, insecticides and fungicides

The graph represents a summary of all of the 72,000 pesticide detections, sourced from the Pesticide Portal based on type of chemical. (Please note that most locations did not have testing results going back to 2011). The ten pesticides most frequently detected were: Diuron, Atrazine, Hexazinone, Imidacloprid, 2,4-D, Metolachlor, Imazapic, Fluroxypur, MCPA and Tebuthiuron. The ecological guideline levels of these pesticides however varies considerably. For instance the 95% DGV for 2,4-D is set at just over 1200 times higher than Diuron. The 99% DGV for 2,4-D is 4.6 million times higher than the guideline level for Diazinon, meaning that although 2,4-D was detected many times more frequently than Diazinon, the potential impacts of Diazinon can be far more serious.

This graph highlights detection averages across all 39 locations. This is the cumulation of all detections as a whole, not catchment by catchment. Catchment totals vary significantly.  The highest average detection levels across the 39 locations were for Atrazine, Bromacil, Diuron, 2,4-D, Fluroxypur, Metribuzin, Metolachlor and Tebuthiuron.

In terms of pesticide loads entering waterways that flow into the GBR, Atrazine dominates, followed by Diuron and 2,4-D. However, Atrazine detections at locations such as Barratta Creek (north of Ayr) and Sandy Creek (south of Mackay) contributed over 50% of Atrazine and Diuron loads.

With regards to the Queensland data that FoE has accessed, 24 pesticides were tested for over 39 locations. The detections of the pesticides varied on where the samples were taken and were determined by what crops were grown in the various catchments. For instance, sugarcane will use different pesticides than bananas and vegetable crops may use a variety of different pesticides. In fact horticulture appears to pose the most risks (eg Coochin Creek, Welcome Creek, Don River etc) through use of insecticides such as Diazinon and Chlorpyrifos. Detections also varied on how far away samples were taken from the agricultural practice. Samples taken closer to agricultural areas will generally have higher levels of pesticides detected than sites kilometres downstream where significant dilution of pesticide load will occur.

Image above: The Don River at Bowen has seen very high levels of the insecticides Chlorpyrifos and Diazinon. The area is the largest producer of winter vegetable crops in Queensland. The industry is worth about $650million/yr. Tomatoes, capsicum, mangoes, cucurbits, beans and corn are the main commodities. Since testing began in 2017, 400 pesticide incidents have been recorded in the Don River with an average detection level almost 166 times higher than the 99% ecological trigger level. This high level is largely due to numerous detections of the insecticides Chlorpyrifos and Diazinon. DGV’s for both insecticides are exceedingly small, 0.00003µg/L and 0.00004µg/L (parts per billion). What restrictions or label changes have been implemented to stop this pollution occurring? Both Chlorpyrifos and Diazinon can also be used as insecticides in commercial and industrial areas as well as commercial turf, however in the Don River situation, it is apparent that the main residential and industrial areas are well east of the sampling location.

Ecological guideline levels for pesticides

Guideline levels for some pesticides and other contaminants are listed in the ANZECC Guidelines. The Draft Guideline Values (DGV’s) are an attempt to set levels for contaminants in a way that protects the majority of species in freshwater and marine waters. In very simplistic terms if a waterway is already degraded (eg an urban waterway) it is assumed that some species loss has already occurred.  The guidelines therefore allow for higher levels of contaminants in more degraded waterways than those that are pristine and where species loss has not been impacted. The highest DGV/trigger level afforded by the ANZECC guidelines are 99%, followed by 95%, 90% and 80% for the most impacted waterways. The guidelines also reflect the fact that some contaminants are more toxic than others to a range of aquatic organisms. The more toxic the substance to aquatic life, the lower the guideline level. Generally, these guidelines are not legally enforceable and they are regarded as being a generic starting point for assessing water quality.

The ANZECC default guidelines for Metsulfuron Methyl (below) for example were not established until 2021, with Queensland proposing guideline levels as early as 2017. Prior to this, few would have “batted an eyelid” if Metsulfuron Methyl was detected in waterways at any level. (Note that µg/L refers to parts per billion). The Queensland proposed guideline is also higher than the ANZECC DGV.

The problem becomes even more concerning when one realises that:

Approximately 12% of pesticides detected in Australian waterways have DGV’s with 43 pesticides having DGV’s. 88% of these pesticides had guidelines in 2000 with only 5 pesticides receiving default guideline levels since 2000 and all of these occurred after 2020. Meaning no updates or new chemicals listed between 2000-2020!!!

State Governments can also set their own guideline levels and in terms of Queensland this is the case, as 11 of the 24 pesticides tested in the GBR catchments for are not listed under the ANZECC guidelines. These are covered in: “Proposed aquatic ecosystem protection guideline values for pesticides commonly used in the Great Barrier Reef catchment area: Part 1 (amended)”.

Queensland also has guideline levels for four pesticides also listed under ANZECC guidelines, namely Metolachlor, Metsulfuron Methyl, Simazine and Tebuthiuron. It was difficult to determine which guidelines the Queensland Government uses in relation to these four herbicides. The Pesticide Reporting Portal uses ANZECC Guidelines with the provision that “Low Reliability Default Guideline Value. Subject to Revision. King et al (2017a) provides higher values the will form the basis of revised draft guidelines to be submitted to the National Water Reform Committee (NWRC) for endorsement as Australian and New Zealand water quality guidelines).” In terms of this blog, guidelines used for these four herbicides have been the ANZECC guidelines.

Graph represents differing 99% trigger/DGV levels for Slightly Disturbed/High Ecological Value waterways. The scale is in parts per billion and is on a scale from Diazinon 0.00003µg/L (lowest) to 590µg/L for Haloxyfop (highest). Glyphosate is not included in the Pesticide Portal testing regimes in Queensland, but has been added here to show its relatively high ecological trigger level (180µg/L) which incidently is 6 million times higher than the 99% trigger level for the insecticide Diazinon. Glyphosate has also been included in the graph due to it being the most frequently used herbicide in Australia and the pesticide that is receiving the most media attention. It figures then that the lower the guideline level the more risk that if that chemical enters a waterway, the more potential problems occurring.

You definately don’t want Diazinon entering any waterway. But it regularly does, with 479 detections across numerous GBR catchments! Note that Diazinon has the lowest DGV and is closely followed by Chlorpyrifos with a guideline level of 0.00004µg/L. Both of these organophospate insecticides are lethal to many aquatic species. The lowest guideline level for a herbicide is 0.0037µg/L for Metsulfuron Methyl. As mentioned previously, Metsulfuron Methyl did not obtain an DGV until 2021. Were Metsulfuron Methyl labels updated, by the Australian Pesticides and Veterinary Medicines Authority (APVMA) to incorporate the new guideline levels, by either reducing the amount of herbicide allowed to be used or restricting the use of Metsulfuron Methyl in high risk areas?

Graph shows differing 95% DGV’s for Moderately disturbed/agricultural ecosystems which is how the Queensland Government defines a large expanse of Queensland (including waterways that flow into the World Heritage Listed, Great Barrier Reef). As explained previously, these levels are set higher than 99% DGV/trigger levels. eg for Diazinon the 95% DGV level is at 0.01µg/L or 333 times higher than the 99% DGV level. Glyphosate’s 95% DGV is set at 320µg/L (77.8% higher) than its 99% DGV. 95% DGV’s then allow for higher levels of pollution than what would be expected for 99% DGV’s.

It telling that pesticides with higher DGV levels, (eg Haloxyfop, Glyphosate, 2,4-D) will rarely be exceed the guideline level. This controversially includes Atrazine which has a 95% DGV of 13µg/L. It seems odd that Atrazine has such a high DGV, but not surprising when one realises that many pesticides were granted these guideline levels almost a quarter of a century ago and have not been changed since then, despite a huge body of research implying alot of ecological problems associated with Atrazine, including this 20 year report published a year after the ANZECC guideline was granted.

From assessing pesticide data up to March 2023 from the Pesticide Reporting Portal, it is possible to calculate however many breaches there have been the ANZECC DGV’s, both by location and type of chemical.

It’s clear that the largest number of breaches are associated with the following pesticides. In the 39 catchments, Metolachlor breached the 99% ANZECC DGV 5610 times, Diuron 4907 times, Imidacloprid 4147 times, Imazapic 2173 times, Atrazine 1603 times, Isoxaflutole 1109 times, Metsulfuron Methyl 941 times, Hexazinone 862 times and Ametryn 430 times.

In terms of the 95% DGV, the most exceedances were for Diuron 2750 times, Imidacloprid 2161 times, Metsulfuron Methyl 596 times and Metolachlor 559 times. It should be understood that a breach of the DGV may only last for a short period of time, particularly after periods of heavy rain. These rainfall events will produce a flush of contaminants which will become more diluted the further away from the source of the pollution. However, the data also suggests chronic ongoing issues of pesticides in waterways.

If label rates are working, why are these pesticides ending up in waterways and frequently exceeding ecological guideline levels? Could it be that if further restrictions were placed on the rates that these chemicals could be applied, many would not be viable?

The labels themselves can present contradictory information, Eg the label for Metolachor states: “DO NOT apply to waterlogged soils DO NOT apply if heavy rains or storms that are likely to cause run-off are forecast within 2 days of application DO NOT irrigate to the point of run-off for at least 2 days after application… In Northern Queensland, application must be made to moist soil and rainfall or irrigation should occur within 24 hours of application.” How is rain and heavy rain defined? At what rate of rainfall does Metolachlor not enter waterways?

In terms of what percentage of pesticide detections breached 95% ecological guidelines, it is clear that Metsulfuron Methyl is a major problem (see graph above). Also note that although Metsulfuron Methyl did not have as many detections (<1000), it is the highest in terms of percentage of detections that breached the ecological guidelines due to its very low DGV.  Other key problem chemicals, in terms of 95% DGV’s include: Fipronil, Diazinon, Chlorpyrifos, Imidacloprid and Diuron. As a regulator how do you address stopping widespread water pollution without reducing label rates or cancelling pesticide registration entirely?

Clearly the most problematic pesticides in terms of 99% DGV’s are Diazinon and Chlorpyrifos. The above graph reveals that the average Diazinon detection was a whopping 762 times higher than the 99% trigger level, with Chlorpyrifos at 727 times the 99% trigger level. 11 pesticides had average detection levels equal to or above the 99% DGV. Metsulfuron Methyl 27.2 times,  Metolachlor 22.8 times, Tebuthiuron 10.9 times, Diuron 4.9 times, Imidacloprid 3.2 times, Imazapic 2.8 times, Isoxaflutole 2.3 times, Fipronil 1.5 times and Atrazine 1 time. (Ametryn came in at 12th at 96% of the 99% DGV). Is this the major reason why the Queensland Government will not tolerate 99% DGV Slightly Disturbed/High Ecological Values across swathes of farmland draining into the GBR? Current pesticide mis-management across most GBR catchments makes attaining the 99% DGV an ‘impossible dream’.

Pesticide use is essentially a licence to pollute areas off-site of application, sometimes at levels that are exceedingly high. Tracking the source of the pollution is not easy, particularly if a number of users have applied the same chemical near the same time as each other. Yet what efforts are really underway to resolve the problem?

Could it be that for the pesticide to remain effective they need to be applied at levels which will knowingly pollute waterways. Waterways therefore become ecological ‘sacrifice zones’ which ‘magically’ will be diluted downstream. Any reduction in usage rates, could render the viability of the pesticide ineffective. If this is the case, then unique waterways providing habitat for a myriad of species are still being regarded as being little more than agricultural drains, that pesticide users are allowed to pollute with impunity. Flooding and poor location of farms, where farms were originally located in high risk and inappropriate locations only increases the problems and makes the issue more difficult to solve.

With the lower (and less ‘rigid’) 95% ecological DGV/trigger level used for moderately disturbed ecosystems, Metsulfuron Methyl (5.6 times) higher than 95% DGV) is the pesticide with the highest average detection level above the ANZECC guidelines. Chlorpyrifos 2.9 times, Diazinon 2.3 times, Diuron 1.7 times,  Imidacloprid 1.4 times and Fipronil 1.1 times also had average detection levels above the 95% DGV. These pesticides appear to be of key concern in moderately disturbed ecosystems, with four being insecticides. It is obvious then that users of these agricultural chemicals in a third of GBR catchments struggle to even meet the 95% guideline level.

Welcome Creek at Gooburrum (above) located north of Bundaberg recorded levels of Diazinon 36,000 times over the ANZECC 99% DGV in March 2021. At the same time, Chlorpyrifos was detected at 500 times the 99% DGV, Imidacloprid at 67 times the DGV and Fipronil at 10 times. 8 different pesticides were detected at the same time.  Average levels of Diazinon over March to April 2021 were almost 16,000 times over the 99% DGV. Welcome Creek probably comes in at the worst performing of all the waterways draining into the GBR. How can this ever be regarded as sustainable and ‘responsible agricultural’ management? No investigation into the source of the pollution was apparently followed up. Why?

Coochin Creek (above) just south east of Beerwah. Cocktails of chemicals including synergistic effects are ignored by regulators. Eg taking a random date such as 2.15pm the 8^th of May 2022, Diazinon was recorded at 4600 times over the ANZECC 99% DGV in Coochin Creek. If this wasn’t bad enough Chlorpyrifos was detected at 3500 times the DGV at the same time, with Metolachlor at almost 18 times the DGV, Diuron at over 11 times the DGV and Atrazine at three times the DGV. 10 pesticides were detected at the same time! These chemical cocktails are not isolated and appear to be the norm. How are the synergistic impacts of a cocktail of chemicals factored into ecological guidelines?

Sugarcane country: Barratta Creek (above), north of Ayr in centre of image, with Burdekin river on left and Haughton River on the right. The highest levels of Metolachlor detected in Queensland occurred in the Barratta Creek at almost 1200 times the ANZECC DGV in June 2015. Baratta Creek has recorded over 7000 pesticide detections since 2011, including high levels of Atrazine and Diuron. Nine separate pesticides were recorded in Barratta Creek at the same time in early 2023.

Locations

A map of Queensland showing the 39 locations of pesticide sampling locations that FoE sourced from the Pesticide Portal. Average distance from the coast (excluding two locations near Comet) is ~10km, meaning greater potential impacts on the GBR. White pins indicate a location where pesticides were detected, but the average level detected over varying time periods did not exceed 99% or 95% DGV’s. Yellow indicates sites where pesticides breached the 99% DGV and red pins indicate sites where both the 99% and 95% DGV’s were exceeded.

In terms of 99% DGV ecological impacts over the entire length of time when testing occurred (inlcuding zero detection samples),  the key problem in some catchments appears to be application of Metolachlor, Diuron, Imidacloprid, Diazinon, Chlorpyrifos, Metsulfuron Methyl, Tebuthiuron, Imazapic and Atrazine.

Imidacloprid, Diuron, Metsulfuron Methyl, Diazinon and Chlorpyrifos appear to be most problematic in terms of 95% DGV’s.

FoE had accessed ~307,000 pesticide tests via the Pesticide Portal. Almost 72,000 of these tests were positive for pesticides, meaning that around 23% of all samples were positive across 39 locations. Positive detections in comparison to all samples were highest at Barratta Creek at Northcote 49.4% and lowest at the Normanby River 0.8% positive.

The following table helps explain why it is important to understand the issue based on catchment by catchment data, as pesticide use can vary significantly depending on the location and the crops grown.

The following table sheds some useful information based on locational data. What it shows is that 87.2% of waterways flowing into the Great Barrier Reef where pesticide testing occurred breached 99% DGV’s over the time period that those pesticides were tested for. 33.3% of waterways regularly breached 95% ecological trigger levels over the same time period. These averages included negative detections.

Note that although the insecticides Diazinon and Chlorpyrifos are listed at some locations with very high average detections, these averages are ‘skewed’ due to the incredibly low 99% trigger levels for both chemicals. These averages may in some instances be due to a handful of detections only a very short time period, meaning that the impact of the chemicals would be short lived (but intense). It should also be noted that although the dates listed showed that when pesticide data was sourced from the Pesticide Reporting Portal, some of the 24 pesticides may not have been tested for at that particular date, with a variance in frequency at some locations between pesticide test regimes.

Summary of above table. Although Prosperine River, Sandy Creek and Coochin Creek all had the most individual chemicals breaching the long term 99% DGV, Welcome Creek possibly takes the ‘award’ of the most polluted agricultural waterway, in terms of DGV exceedences relating to the misuse of Diazinon. Coochin Creek appears to be the biggest problem area in terms of long term breaches to 95% DGV’s, although Coochin Creek was impacted by short term spikes in detections of Chlorpyrifos and Diazinon.

Screenshot from Australian Pesticide Map showing pesticide detections throughout Queensland, are concentrated along the coast with highest amounts of detections in and around Brisbane region.

For more information regarding this blog contact anthony.amis@foe.org.au