A recent Right to Information request with TasWater, has raised concerns regarding pesticide monitoring in domestic water supplies in Tasmania. TasWater was punctual in responding to the request, with the process only taking 32 days, however the information provided leaves more questions than answers.

Trevallyn Dam, located 5km west of Launceston's CBD. What was the source of the Atrazine that was detected in the Dam on August 8 2018 and were the public informed? Why was there no investigation to identify the source of the pollution?  Was the entire dam contaminated? If so for how long?

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Information requested from TasWater included results of all pesticide monitoring in Tasmanian water supplies between 2016 to 2023. TasWater provided 149 positive results, between Feb 2016 and August 2018 only. No information was provided for the past 5 years, which is odd considering that between 2013-2018, pesticide detections averaged 29 per year. It seems implausible that detections immediately ceased in August 2018, just 22 days after Tasmania's most serious pesticide in a domestic water supply incident (ever?). That occurred in Launceston's Trevallyn Dam on August 8 2018, when the herbicide Atrazine was detected at 27µg/L (27 parts per billion), 35% higher than the Australian drinking water guideline. The last TasWater positive detection occurred on August 30 2018 at the Macquarie River at Longford. Since then there apparently have been no pesticide detections in Tasmanian water supplies. Really? What's going on?

To put the Trevallyn Dam incident into some context, pesticide breaches to the ADWG's (Australian Drinking Water Guidelines) are relatively rare events. FoE has recorded only 27 such incidents throughout Australia. The Trevallyn Dam incident is the 22nd most "serious" in relation to Australian drinking water guidelines. In terms of the infamous herbicide Atrazine, levels detected at Trevallyn Dam were the 6th highest recorded in an Australian water supply. Interestingly, the levels were 270 times higher than European Guidelines (any pesticide detection >0.1µg/L is regarded as a breach and is supposed to be investigated to determine the source) and 9 times higher than equivalent Atrazine guidelines in the United States.

The drop off in TasWater detections can partly be explained by TasWater themselves. According to the RTI letter from TasWater dated 4/10/23, "TasWater now test for 21 pesticides on a quarterly* basis. The pesticides are: 2,4 D, Alpha-cypermethrin, Atrazine, Dimethoate, Boscalid, Chlorpyrifos, Chlorothalonil, Clopyralid, Cyanazine, Glyphosate, Dicamba, Haloxyfop, Hexazinone, MCPA, Metribuzin, Metsulfuron methyl, Pendimethalin, Prometryn, Simazine, Sulfometuron-methyl, Terbacil. "For the period 1 January 2016 – 1 September 2023, TasWater carried out over 53,000 tests for pesticides. In 149 cases, pesticides were detected".

(* Note quarterly means once every three months or only 1.12% of days per year).

This could imply a 0.28% chance of detecting a pesticide, with a 0.002% chance of detecting a pesticide above Australian Drinking Water Guidelines. Perhaps the cost of testing outweighed the information gained from such testing? Perhaps funding for the tests has gone elsewhere? Perhaps TasWater have actually substantially reduced or eliminated pesticide testing in most catchments entirely? It appears to FoE that they have indeed decreased testing by at least 50%+ from what had occurred prior to September 1 2018.

According to TasWater on August 14 2018 (6 days after the Trevallyn dam incident!!!): "Historically, we have had few detections of pesticides and therefore the only time we would test for pesticides within the distribution network as if we are undertaking a specific investigation or whether we have had pesticide detections in the source water (raw water) above historical levels (i.e. if we notice a change)...We have a comprehensive water quality monitoring program that is routinely reviewed and to date we have not identified pesticides in our systems above (or approaching) the health limits in the ADWG."

The RTI data also reveals that at some locations in 2016 (eg Bothwell, Bridport, Tunbridge) TasWater appear to have tested fortnightly at some times of the year. It is also entirely plausible that many locations were not tested at all.

TasWater can't be entirely be blamed for not wanting to embark on more strenuous and frequent pesticide testing.  Nine years ago the Tasmanian Government raised eyebrows by axing their decade-long pesticide testing program conducted by the Department of Primary Industries, Parks, Water and Environment (DPIPWE). The program was axed just when results started revealing the highest amounts of pesticides. Up until that time, it was the most comprehensive pesticide testing regime in Australia. TasWater are mainly concerned about monitoring domestic water supplies. It would appear that the bulk of Tasmanian waterways, similar to the rest of Australia (outside of GBR catchments in Queensland), remain untested for. Why?

Pesticide detections were dominated by the herbicide MCPA, almost all of which occurred in 2016. 2018 detections however were dominated by the herbicides Sulfometuron Methyl and Metsulfuron Methyl.

Apart from the incident at Trevallyn Dam, the most serious raw water incidents, at 30% of the Australian Drinking Water Guidelines, occurred in 2018 in raw water at Pats River Weir Whitemark (Atrazine at 6µg/L), Cornwall in an unnamed stream (Metsulfuron Methyl 12µg/L) and Lake Barron Creek Weir, just upstream of National Park east of Mount Field National Park where Simazine was detected at 6µg/L. The small community of Lake Barron, on Lake Barron island recorded an MCPA detection of 11µg/L in 2016 (27.5% of ADWG), Cannes Hill Reservoir near the community of Whitemark recorded Atrazine at 3µg/L (15% of ADWG) and MCPA at 5.3µg/L (13.25% of ADWG) in 2018 and 2016. Also of interest was the contamination of all 5 bores at Lady Barron with the herbicide Clopyralid with levels in one bore at 180µg/L.

In terms of supplied water (coming through customers taps), an MCPA detection of 2.7µg/L in March 2016 (7% of ADWG) occurred at Whitemark Depot, and two detections of Metsulfuron Methyl of 2µg/L (5% of ADWG) at Herrick Reservoir in May 2018 and another of 1µg/L (2.5% of ADWG) in June 2018. Other water supply detections at Bridport, Lady Barron Police Station, Prospect Vale, Launceston, Bothwell and Longford were below 1% of the Australian Drinking Water Guidelines.

Whilst the most frequently pesticide detected was MCPA, 20 detections of Sulfometuron Methyl occurred over a 43 day period between April 30 and June 11 2018. According to FoE records, the only detections of Sulfometuron Methyl in domestic water supplies in Australia occurred in Tasmania during this period, with the highest levels 75µg/L recorded at Adventure Bay on Bruny Island on 25/5/18. Sulfometuron Methyl is registered for use in commercial and industrial areas and rights of way such as roads, powerlines and telephone lines). How did this herbicide impact so many water supplies over a 6 week period? There are no drinking water guidelines for Sulfometuron Methyl.

Tasmanian pesticide detections recorded mainly over the past 30 years from a number of sources according to the Australian Pesticide Map. ~89% of all detections are located in the northern half of the state.

31 different locations recorded pesticide detections between 2016-2018, with the most occurring at Bothwell (16), Tunbridge (11), Whitemark (11), Bridport 10, Gladstone 10, Lady Barron 10, Cornwall 8, Yolla 8, Herrick 7 and Trevallyn Dam 7.

Although communities such as Bothwell and Tunbridge may have recorded the most detections of pesticides, many of their detections were low in comparison to drinking water guideline levels. By accumulating all detections as a percentage of ADWG's, it becomes apparent that the highest risk location for breaches to ADWG's was Trevallyn Dam, due mainly to the Atrazine incident of August 2018. These events are however sporadic and to be a major concern for water authorities, events would have to be ongoing and above ADWG's.

Potential Environmental Impacts

Drinking water is the main focus of TasWater's testing regimes. However there is another aspect that has to be considered, and that is the ecological impact to species within the waterways themselves. Ecological guideline levels are generally much lower than drinking water guideline levels. Ecological impacts of toxicants in waterways are explained in the ANZECC Guidelines, which specify guideline/trigger levels for a number of pesticides. The ANZECC guidelines do not cover all pesticides. In fact FoE found in 2017 that ~11% of pesticides detected in Australian waterways, had ANZECC Guidelines and that only 3.5% of pesticides registered for use in Australia had ANZECC guidelines. Most of these guidelines date back to 2000, although a handful of pesticides have been granted guideline levels since 2020, the most notable, in terms of Tasmanian waterways being Metsulfuron Methyl.

In simple terms, toxicants have 4 trigger levels specified under the ANZECC Guidelines. High quality environmental streams, eg those with little environmental degradation warrant the highest protection level of 99%. This means that a toxicant entering such a waterway has a guideline level that supposedly will protect 99% of the species within that waterway. The more degraded the waterway, the less species protection. In many degraded urban streams for example the ecological trigger level will be 80%. Guideline levels are therefore are much "stricter" the more pristine the waterway. For example for Metsulfuron Methyl the 99% trigger level is 0.0037µg/L. The 95% trigger level is 0.018µg/L, the 90% trigger level is 0.048µg/L and the 80% trigger level is 0.18µg/l, 48 times higher than the guideline in pristine waterways.

State's then define what level of protection is warranted for waterways throughout their areas of jurisdiction. National Parks and high conservation value areas would warrant the highest level of protection, whereas slightly to moderately disturbed waterways (eg agricultural areas) generally warrant a 95% trigger level. Deriving ecological guideline levels can be an extremely complicated undertaking. Generally speaking pollution events may also occur over a short duration, during flood events, where "pulses" of contaminants may enter waterways for a limited time period.

In terms of 99% and 95% trigger levels, by the far the most breaches to ecological guideline trigger levels relate to detections of Metsulfuron Methyl. All detections of Metsulfuron Methyl breached both the 99% and 95% trigger levels implying that this particular herbicide is of most concern regarding the ecological impacts upon waterways in Tasmania. Although MCPA was the most frequently detected herbicide by TasWater testing, only 8% of MCPA samples breached ecological guidelines. Metsulfuron Methyl is used on pastures, rights of way, commercial and industrial areas and forest plantations.

95% trigger level pesticide breaches 2016-2018, based on TasWater pesticide test regimes. 90% of breaches occur in the north of the state, with the majority in the north east of the state, including Launceston.

Curries Dam, drinking water supply for George Town and popular fishing location near centre of image. Tamar River and George Town/Bell Bay on the left of image.

TasWater recorded a detection of the organophosphate insecticide Chlorpyrifos at the Curries River offtake of 1µg/L in August 2017. Chlorpyrifos has an exceedingly low 99% guideline level of 0.00004µg/L. This means that the detection of this insecticide at the Currie River was 25,000 times above the 99% ecological trigger level and ten times the 95% ecological trigger level. The same location also recorded Metsulfuron Methyl in May 2018 at 67 times the 99% trigger level and almost 14 times the 95% trigger level. What was the source of the Chlorpyrifos and Metsulfuron Methyl? Why was an investigation not carried out? TasWater's main role is to provide safe drinking water to consumers, the ecological impacts of toxicants in water supplies is not apparently the agencies priority. Was the EPA informed?

Average levels of the 18 Metsulfuron Methyl detections across Tasmania were 65 times higher than the 99% trigger level and 12 times higher than the 95% trigger level. The most detections occurred in the states north west at Yolla (Dowling Creek). Metsulfuron Methyl was detected over a two month period in 2016 at an average of nine times the 99% trigger level and almost two times the 95% trigger level at Dowling Creek.

Metsulfuron Methyl only "gained" an ecological guideline level in 2021, meaning that when the herbicide was detected by TasWater in 2016 and 2018 barely anyone would have "batted an eyelid". It also appears that the recent guideline levels have not led to any restrictions of the Metsulfuron Methyl label, despite the exceedingly small ecological guideline level. Pesticide labels specify what amounts of the particular chemical can be sprayed on specific crops and land uses.

Any heavy rainfall events that occur after recent spraying can lead to offsite pollution events. This is particularly the case when many hectares of land in logged plantations for example are left exposed with limited vegetation to lessen soil and pesticide movement off site. If TasWater testing picked up many breaches to ANZECC guidelines in their limited testing regimes in 2016 and 2018 what is going on in terms of Metsulfuron Methyl pollution in other waterways throughout the state since then? No data No Problem?

In terms of the Tasmanian detections in an Australian context, based on FoE pesticide records.

Atrazine: Lake Trevallyn 8/8/18 27µg/L. Australia's 6th highest detection of Atrazine in a domestic water supply and 22nd highest detection of any pesticide in a domestic water supply. (Atrazine Australian Drinking Water Guideline 20µg/L. ANZECC trigger levels 99% 0.7µg/L, 95% 13µg/L).

Chlorpyrifos: Curries River 10/8/17 1µg/L: Australia's 2nd highest detection of Chlorpyrifos in a domestic water supply. (Chlorpyrifos Australian Drinking Water Guideline 10µg/L. ANZECC trigger levels 99% 0.00004µg/L, 95% 0.01µg/L).

Clopyralid: Lady Barron Bores 14/12/16 22-180µg/L: Australia's 5 highest detections of Clopyralid in a domestic water supply and in any water source. (Clopyralid Australian Drinking Water Guideline 2000µg/L. No ANZECC trigger levels).

Dicamba: Lady Barron 7/5/18, Whitemark 7/5/18, Cornwall 8/5/18 0.6µg/L - 0.7µg/L: Australia's 3rd, 4th and 5th highest detections of Dicamba in a domestic water supply. (Dicamba Australian Drinking Water Guideline 100µg/L. No ANZECC trigger levels).

Hexazinone: Ringarooma WTP 3/7/18 9.5µg/L. Australia's 4th highest detection of Hexazinone in a domestic water supply. (Hexazinone Australian Drinking Water Guideline 400µg/L. ANZECC trigger levels 99% 0.31µg/L, 95% 1.1µg/L).

MCPA: Lady Barron 2/3/16 5.3µg/L. Australia's 2nd highest detection of MCPA in a domestic water supply and 4th highest detection in any water source. 11µg/L. Whitemark 2/3/16. (MCPA Australian Drinking Water Guideline 40µg/L. ANZECC trigger levels 99% 1.4µg/L, 95% 1.4µg/L).

Metsulfuron Methyl: Australia's 9 highest detections of Metsulfuron Methyl in domestic water supplies. 8/5/18 Cornwall 12µg/L (max) highest detection in any Australian waterway. (Metsulfuron Methyl Australian Drinking Water Guideline 40µg/L. ANZECC trigger levels 99% 0.0037µg/L, 95% 0.18µg/L).

Simazine: Lady Barron Creek Weir 26/7/18 6µg/L. Australia's 5th highest detection of Simazine in a domestic water supply. (Simazine Australian Drinking Water Guideline 20µg/L. ANZECC trigger levels 99% 0.2µg/L, 95% 3.2µg/L).

Sulfometuron-methyl: Australia's 10 highest detections of Sulfometuron Methyl in Australian domestic water supplies and Australian waterway. 25/5/18 Adventure Bay 75µg/L (max). (Sulfometurn Methyl has no Australian Drinking Water Guideline and no ANZECC trigger levels).

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