21bb3034 Bijlage 1 behorende bij 21bb437 - Phoslock toxicity evaluation

In Lake De Kuil and Lake Rauwbraken (the Netherlands), macrophytes flourished and colonisation depth increased after interventions with Phoslock® (Waajen et al., 2016a; van Oosterhout et al., in revision). In Phoslock® treated compartments in ponds in Dongen and Eindhoven, macrophytes also grew to very high biomass and coverage (Waajen et al., 2016b). In addition, in two other Dutch lakes (Groote Melanen and Kleine Melanen) after a Phoslock® application, submerged and floating macrophytes grew to higher biomass compared to previous years (Aquon, 2019a, 2019b, 2016). Also, in lake Eichbaumsee where around 10.8 tons of Phoslock per ha were applied, more aquatic plants were found afterward (Spieker et al., 2014). These case studies demonstrate that the improved water transparency observed in Phoslock® treated water bodies increases the macrophyte colonisation depth as well as the plant coverage of the lake beds, which promotes the successful re-establishment of macrophytes. A pilot study was undertaken in a popular Austrian swimming lake, in which Phoslock® treatments were combined with active planting of Characean macrophyte species. On one occasion, Phoslock® was applied in spring after the Characeans had been planted several months previously without causing any negative effect on the plants.

During this restoration project, the Characeans were successfully established in the lake, leading to an improved ecological state and an increase in the lake's recreational value (Epe et al., in prep.; Systema GmbH personal communication). The results from these case studies demonstrate that an application of Phoslock® has a beneficial effect on macrophytes due to an improvement in light conditions, geo-physical sediment properties and by counteracting the growth of benthic cyanobacteria. Macroinvertebrates A range of studies has been conducted to investigate the impact of Phoslock® on the resident benthic macroinvertebrate community. Bishop et al. (2014) found no differences in the pre- and post-application benthic macroinvertebrate biometrics tested (taxa richness, diversity, tolerance, functional feeding groups). Reitzel et al. (2013) found no difference in chironomids abundance in the control and Phoslock® treatments in a lab experiment. A study conducted in Lake Rauwbraken (The Netherlands) reports slightly increased post-treatment densities of chironomid larvae (van Oosterhout et al., 2020). In Lake De Kuil (The Netherlands), the application of a low dose flocculant (FeCl3) combined with Phoslock® resulted in a shift of the lake from a hypertrophic to a mesotrophic state (Waajen et al., 2017a).

This study shows a short-term impact on the macroinvertebrate numbers and taxa during the first month following the application. However, one year after the application, the macroinvertebrate community structure (number and taxa) exceeded the pre-application situation. The adverse impact one month after the application is most likely due to the chemical effects caused by the FeCl3 and, to some minor extent, due to the bentonite's physical impact. The positive effects one year after the application can most probably 15

be attributed to the shift in the lake's trophic state. Meis (2012) found a reduction in Oligochaeta, Chironomidae and Sphaeriidae groups in Loch Flemington (UK) after a Phoslock® application. The author discussed that it could be argued that the reduction was due to an increase of La content in the sediment caused by Phoslock®; however, other studies also found a reduction in macroinvertebrate (i.e., Oligochaeta and Sphaeriidae) abundance after external nutrient load reduction (Gunn et al., 2012; Köhler et al., 2005). As a result, it is not possible to say definitively that the reduction in Oligochaeta, Chironomidae and Sphaeriidae groups in Loch Flemington was due to possible toxic effects, a reduction in nutrient availability or the change in the trophic state. However, acute tests performed with extremely high Phoslock® concentrations have shown no toxic effect, indicating that Phoslock® toxicity is low or null. Fish Several studies have reported increased macrophyte coverage and higher macroinvertebrate diversity after a Phoslock® treatment (Bishop et al., 2014; van Oosterhout et al., 2020; Waajen et al., 2017a; Epe et al, in prep). This change in the ecological structure is expected to positively influence the fish stock by creating a diversified habitat with favourable spawning conditions and improved refuge from predation.

In Lake De Kuil (The Netherlands), pike biomass and mainly carp increased after the treatment. The increase of carp in the lake can be attributed to an increased appreciation of the improved water quality by fishermen which resulted in uncontrolled carp stocking. The increased biomass of pike in the lake can be directly related to the improved water clarity and enhanced macrophyte cover (Waajen et al., 2016a). Also in compartments in ponds in Dongen and Eindhoven no adverse effects on fish biomass were observed (Waajen et al., 2016b). 2.1.5. Conclusion Ecotoxicological Assessment on aquatic biota Tests from acute and chronic toxicity studies support the conclusion that the use of Phoslock® is safe for the aquatic environment (paragraph 2.1.1). The low ecotoxicological profile of Phoslock® is further confirmed in several studies in which an extensive post-treatment monitoring was conducted after whole lake applications (Spears et al., 2016; Waajen et al., 2016a,b; 2017a,b; van Oosterhout et al. 2020; in revision) (paragraph 2.2.4). The use of Phoslock® as a tool for eutrophication management improves the trophic state of a waterbody and thereby induces a biological recovery process in formerly impaired aquatic systems.

2.2. Exposure scenario – Waterbirds and terrestrial mammals (particularly pets) Avian fauna could potentially be impacted by short-term localised disturbances during an application, however this will be limited to a small area. In addition, applications can be timed to avoid disturbance to breeding avian species or overwintering bird species if present. For waterbirds, an exposure to Phoslock® is likely to be restricted to the consumption of aquatic organisms, e.g., macrophytes, invertebrates, and fish. It is known that the trophic transfer of compounds such as La via food uptake to higher biotic levels such as birds is assumed to be limited (Campbell et al., 2005). When given as lanthanum carbonate the oral bioavailability of lanthanum is reported to be 0.0007 % and 0.00084 % in rats and humans, respectively, and almost all administered lanthanum is excreted via the faeces, even after i.v. injection of a soluble lanthanum compound (D’Haese et al., 2019). Thus, as with humans and other mammals, it is most likely that the amount of lanthanum absorbed by waterbirds after ingestion will be excreted via the faeces (e.g., (Lürling and van Oosterhout, 2012). In this context, it is also worth mentioning that lanthanum and other REE elements have been introduced as feed additives in livestock breeding to improve animal health and production.

Amongst bird species, body weight gains have been observed in broilers, while egg production, egg-shell breaking strength and food conversion rates have increased in egg-laying hens. Overall improvements in general health and performance parameters have also been observed (Abdelnour et al., 2019). Although there is no research on the effect of Phoslock® on waterbirds, from the available information it seems unlikely that waterbirds will suffer any toxicity caused by 16

Phoslock®. Furthermore, no adverse effects on the resident avian fauna have been observed during the numerous field applications undertaken with Phoslock®. Domestic animals such as cats and dogs could be exposed to Phoslock® treated water by swimming or drinking water from a treated lake. Any risk from this exposure is related to the lanthanum and can be evaluated from a range of data available for veterinary drugs and food additives using lanthanum carbonate (Lantharenol®, active ingredient lanthanum carbonate octahydrate) to prevent chronic renal malfunction in ageing animals. About the dermal and respiratory exposure pathways, Lantharenol® is not considered to pose a risk by inhalation. It is not an irritant to skin or eyes and is not a dermal sensitizer. Concerning oral exposure, the supplementation of regular feed with Lantharenol® is safe and welltolerated by healthy animals up to a concentration of 75 g/kg complete feed. For dogs, this concentration corresponds to a daily intake of 9.3–12.4 g of Lantharenol® (corresponding to 4.3-5.7 g of elemental lanthanum). Considering that the intended dose of Lantharenol® in the feed of adult dogs and cats ranges from 1.5-7.5 g/kg complete feed, it can be concluded that this food additive is safe for adult dogs and cats at the highest dose proposed with a safety margin of at least ten (Schmid et al., 2009; EFSA 2012, EFSA 2019).

Given the minimal daily intake concentration of 4.3 g that is considered to be safe and the peak concentration for total lanthanum in the water after a Phoslock® application (Spears et al., 2013a; cf. Table 1), a dog would need to drink about 2000 L of lake water per day to ingest a similar nominal safe concentration. Even when applying a safety factor of ten, the water volume that an animal has to drink is about 200 L per day, a quantity that could not possibly be consumed in a day by, for instance, a dog. Therefore, even water consumption directly after the application would not pose a risk to animal health. 2.3. Toxicological assessment – Human exposure to Phoslock® treated water Theoretically, humans may be exposed to Phoslock® during recreational activities in Phoslock® treated water bodies. The main exposure pathways could be dermal contact and oral uptake by swallowing water during swimming or consuming fish from treated water bodies. The following summary describes the most important studies and the conclusions that can be drawn from them. 2.3.1.

Toxicological studies with Phoslock® – Oral toxicity and tissue distribution patterns In two studies conducted with Phoslock®, the potential to induce toxic effects and the gastrointestinal absorption of Phoslock® derived lanthanum was tested in rats: • A 28-Day Repeated Dose Oral Toxicity Study in Wistar Rats was conducted with Phoslock® following the strict requirements of the OECD 407 Test Guideline and the OECD principles of GLP (Good Laboratory Practice). This study aimed to assess the possible health hazards which could arise from repeated exposure to Phoslock® via oral administration to rats over 28 days. A total of four dose groups were used in the study. According to the test guideline, the highest administered dose was 1000 mg of Phoslock®/kg body weight/day. No test-item related mortality was observed and no adverse effects of the test item were found for male and female clinical observations, functional observations, body weight development, food consumption, haematology and coagulation, clinical biochemistry, urinalysis, gross macroscopic findings at necropsy, organ weights and histopathology in all treated dose groups. Hence, according to the OECD 407 Test Guideline, the no observed adverse effect level (NOAEL) of Phoslock® is considered to be > 1000 mg/kg body weight/day (Schmid et al. 2019). • Behets et al.

(2020) conducted a study with Wistar Rats evaluating the gastrointestinal absorption and tissue distribution of lanthanum after oral administration of lanthanum chloride, lanthanum carbonate or Phoslock® over 10 weeks. Considering all possible exposure pathways, the authors evaluated the safety margins and concluded that the uptake of lanthanum through exposure to Phoslock® treated water is unlikely to pose a health risk to animals and/or humans.

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2.3.2. Phoslock® human health risk assessment As suggested by Behets et al. (2020), a further approach for a human health risk assessment for Phoslock® is to focus on its active ingredient lanthanum. Unlike aquatic ecotoxicity studies, where the chemical nature of the lanthanum added is of paramount importance, in the acid environment of the human stomach such aquatic speciation effects are minimized. All lanthanum compounds, such as lanthanum chloride, lanthanum carbonate and Phoslock®, dissociate in the acidic stomach where after liberated La precipitates with phosphate and other oxyanions (e.g. oxalate) from food. Lanthanum is an ingredient in topical formulations in concentrations of up to 30% to treat several skin disorders to reduce irritation and inflammation. Based on a comparison of these concentrations with the highest measured TLa concentration in Phoslock® treated water (Spears et al., 2013a; cf. Table 1), it can be concluded that no adverse effects are expected through dermal exposure. For oral exposure pathways, a huge amount of data from pre-clinical and clinical studies are available due to the use of lanthanum carbonate (trade name Fosrenol®, Shire Pharmaceuticals) for the treatment of hyperphosphatemia in renal failure (Stewart, 2002; D’Haese et al., 2003; Behets et al., 2004; Hutchison, 2009; Hutchison et al., 2009, 2016, 2018; Damment, 2011).

Lanthanum carbonate is administered daily at doses containing 375 to 3000 mg/day of elemental lanthanum over many years. Hutchison et al. (2016) recently showed that after 10 years of lanthanum carbonate treatment in dialysis patients, corresponding to more than 850,000 personyears of worldwide patient exposure, there is no evidence that lanthanum carbonate is associated with adverse safety outcomes in patients with end-stage renal disease. The potential for any adverse effects to humans related to the use of Phoslock® in water bodies is further discussed in detail by Copetti et al. (2016) and D’Haese et al. (2019). Given an average therapeutic dose of Fosrenol® of 1500 mg per day (~900 mg lanthanum/day) without toxicity to the patients after up to 10 years of treatment, consumers would have to ingest at least 390 L of the surface water per day to attain a similar, nominally safe dose. It is not possible for such large volumes of water to be drunk by a person in a day and therefore, an application of Phoslock® would never deliver as much as lanthanum as a single Fosrenol® tablet. Therefore, even ingestion of Phoslock® treated water directly after an application would not pose a risk to human health. A similar estimation can be carried out for the consumption of fish from Phoslock® treated water bodies.

Taking the highest lanthanum concentrations measured in fish muscles (0.81 mg lanthanum/g dry weight), a person would have to consume more than 1000 kg of fish per day to reach the nominally safe recommended therapeutic dose of lanthanum in adults (D’Haese et al., 2019). Again, given this high margin of safety, it can be concluded that there are no adverse effects associated with the consumption of fish from Phoslock® treated water bodies. 2.3.3. Conclusion – Toxicological assessment for human exposure Over the past 15 years, Phoslock® has been widely researched and scrutinized by the international scientific community and until now 92 scientific peer-review publications about Phoslock® have been published. For the human exposure assessment, a vast amount of data is available from mammalian toxicity studies with Phoslock® and long term clinical studies with lanthanum carbonate. The available data show a wide margin of safety associated with Phoslock® applications at predicted use rates and environmentally relevant concentrations.

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3. Reality check 3.1. Kralingse Plas This section aims to discuss potential direct and indirect effects a Phoslock® application might cause in Kralingse Plas based on the specific biotic and abiotic factors of the lake, the dose selected, and the scientific literature discussed above. Phoslock® dose for Kralingse Plas The maximum Phoslock® dose calculated for Kralingse Plas was 813 tons (Phoslock Europe, 2020); this dose will yield to around 288 mg Phoslock® per L or 7.2 tons per ha. This is a realistic dose and similar to other systems. For instance, in the paper cited above which reported peak TLa concentrations in Phoslock® treated lakes, the dosage range was 0.06 to 6.7 tons/ha (Spears et al., 2013a). Applications have also been reported in the literature where Phoslock® doses were higher: 10.8 tons/ha and 16.7 tons/ha (Novak and Chambers, 2014; Yasseri and Epe, 2016). Amongst the 16 treated lakes described in Spears et al. (2013a), Loch Flemington, Lake Blankensee and Lake Bärensee are shallow lakes and comparable to Kralingse Plas. The maximum TLa concentration (2.3 mg/L) was measured during a Phoslock application in Loch Flemington (max depth 2.5 and average depth 1m).

The peak in TLa concentration will mainly depend on the application method; for instance, if the application takes place over several weeks across alternating areas (as has been proposed), the TLa concentrations are unlikely to be higher than already measured and reported by Spears et al. (2013a). The application design should be planned once the final dose for each area is defined. 3.1.1. Direct and indirect changes Physico-chemical changes Phoslock® will inactivate phosphate (Douglas, 2002) which can be expected to result in a reduced algal biomass, particularly cyanobacteria, in the following growing seasons. This is likely to shift the system from a eutrophic to a more mesotrophic state which in turn should result in several ecological changes (Fig. 4). Phoslock® will increase turbidity for a short period during the application, however in the longer term water transparency should increase as a result of the reduced algal biomass, particularly during summer, and light will reach deeper in the water column (i.e., Lürling and van Oosterhout, 2013; Waajen et al., 2016; Mucci 2019). The Phoslock® application will not directly affect temperature, pH, conductivity, alkalinity or oxygen concentrations (Spears et al., 2013b; van Oosterhout and Lürling, 2013).

Due to the reduction in the phytoplankton biomass as a result of reduced phosphate availability, there may be an increase in oxygen concentrations in the water column in the summer after the application due to less bacterial decay and less oxygen consumption (van Oosterhout et al., in revision) and anoxic events can be expected to be less or absent as lake productivity will be lower. Phoslock® will increase the total lanthanum concentration in the water column. Based on a dose of 288 mg Phoslock®/L, a maximum total lanthanum (TLa) concentration of 14 mg TLa/L is theoretically possible, however this value is unrealistic as Phoslock® sinks to the bottom of the lake after application and it is not logistically possible to apply the 813 tons at the same time in all locations. Applications are usually spread over several days or weeks, targeting different locations each day. Such a strategy has also been proposed for Kralingse Plas. Therefore, the maximum concentration of total lanthanum in the water column is expected to be similar to that described by Spears et al. (2013a) in the 16 other aquatic systems (0.026 to 2.3 mg TLa/L). Nearly all of the lanthanum applied to the lake will remain embedded within the clay matrix and not be in a soluble form.

Based on the water chemistry of Kralingse Plas, estimated free La3+ ions concentrations are predicted to be very low (less than 6x10-8 mg La /L) (Fig. 1A-Appendix) and no direct toxic effects from free La3+ ions are expected. 19

Lanthanum concentrations will also increase in the sediment of Kralingse Plas following a Phoslock® application. If the La incorporated in Phoslock were to be homogeneously mixed into the first 10 cm of the sediment following the application, the proposed dose would result in a concentration of 319 mg La/kg dry weight of sediment. Post-treatment monitoring undertaken on previous applications has shown however that lanthanum distribution is not vertically homogenous (van Oosterhout et al., 2020) and it is expected that most of the lanthanum added to Kralingse Plas will be found in the top few centimetres of the sediment in the first years. If we assume therefore that 100% of the lanthanum applied will be in the top three centimetres of the sediment, a La concentration of 1063 mg/ kg DW of sediment would be expected. This concentration does not exceed the maximum permissible concentration of lanthanum in Dutch sediments (4700 mg/ kg DW) (Sneller et al., 2000). Furthermore, it is also to be expected that the La contained in the Kralingse Plas sediments will be mixed deeper in the sediment over time.

For instance, La has been found in sediment depths below 10 cm in a number of lakes treated with Phoslock® (Dithmer et al., 2016b; van Oosterhout et al., 2020), with the result that the La concentrations in the sediment become even more diluted over time and phosphorus in deeper sediment layers is bound. It is also important to note that La has been measured in water, sediment, macrophytes and chironomid larvae in other Dutch lakes prior to Phoslock® applications (van Oosterhout et al., 2020; Waajen et al., 2017b). In the Kralingse Plas, there is already lanthanum present in the sediment as well (Data B-WARE Research Centre). An application of Phoslock® to the lake does therefore not result in the introduction of a new element to the system but merely an increase in the concentration of an existing element. 3.2. Biological changes Phytoplankton Phoslock® will decrease the phosphate concentration (Douglas, 2002) and this can be expected to result in a reduction in algal biomass (mainly the cyanobacterial biomass) in the ensuing growing seasons as well as a decline in concentrations of cyanotoxins (e.g., Mucci et al., in review.) and a concomitant increase in phytoplankton diversity (e.g., Robb et al., 2003; Bishop et al., 2014; Bishop & Richardson 2018; Epe, 2014; Barçante et al., 2020).

Macrophytes The dominant macrophyte species in Kralingse Plas in 2019 were Elodea nuttallii, Ceratophyllum demersum, and Chara globularis. Toxic effects, reduced growth and germination issues have not been observed in any of the macrophytes tested until now, including E. nuttallii and Chara sp., both of which are present in Kralingse Plas (Waters-Hart, 2020; Epe et al., in prep.). The abundance of E. nuttallii and Chara sp. tripled in Lake de Kuil (The Netherlands) after a Phoslock® application, while similar increases in other macrophytes species occurred in 17 other lakes where Phoslock® was added (Spears et al., 2016; Waajen et al., 2016a). Based on the studies conducted, no toxic effects caused by Phoslock® are expected on the aquatic plants in Kralingse Plas. On the contrary, an increase in aquatic plants in the following years after the intervention is expected due to water quality improvement (i.e., reduced incidence of cyanobacterial blooms) (e.g., Waajen et al., 2016). Zooplankton The main group of zooplankton present in Kralingse Plas is Daphnia sp. (van Giels and Kleppe, 2020), and the EC50 value that has been measured for this group was 3 and > 173 times higher than the Phoslock® dose proposed for Kralingse Plas (288 mg/L).

Thus, based on laboratory tests done with different zooplankton species and the Phoslock® dose chosen for Kralingse Plas, no direct toxic effects caused by Phoslock® are expected (Fig 3). Zooplankton may be affected by an increase in water turbidity during the application; however, these effects are considered temporary and not long-lasting (i.e., van Oosterhout and Lurling, 2011; 20

Waajen et al., 2016). Once the algal biomass is reduced, an indirect effect through a lower availability of food (lower phytoplankton biomass) for zooplankton can be expected. This indirect effect should be contrasted however with the impact that the persistent blooms of cyanobacteria would otherwise have on zooplankton. Cyanobacteria blooms are commonly made up of large, inedible filaments or colonies that also produce toxins or grazing-repellent compounds and these traits (morphological and chemical) can act as an anti-grazing defence (Ger et al., 2016a; Lürling, 2020). Thus, a higher phytoplankton biomass does not automatically imply a higher availability of edible food or a greater zooplankton biomass (e.g., Josué et al., 2018). Cyanobacterial blooms also affect the type of zooplankton that are present. For instance, blooms typically lead to the exclusion of large generalist grazers, which are often replaced by smaller and selective grazers (Ger et al., 2016b). Thus, it is difficult to predict what will happen with the zooplankton community in Kralingse Plas after a change in trophic state as plankton interactions are dynamic, and several factors (predation, grazing, competition, presence of macrophytes, and abiotic factors) are involved.

However, based on previous whole lake applications and laboratory experiments, no toxic effects of Phoslock® on zooplankton are expected in Kralingse Plas, nor a food shortage for fish. Macroinvertebrates The effect of Phoslock® on insect larvae (also present in Kralingse Plas) has been evaluated using a dose 12 times higher than the one that is proposed for Kralingse Plas with no adverse effect on growth or survival rates being observed. The effect of Phoslock® on freshwater shrimp (also present in Kralingse plas as Mysida sp.) has been evaluated using a dose that is between 2 to 173 times higher than that proposed for Kralingse Plas, with no effect on survival being observed. Based on the available literature and laboratory experiments, the macroinvertebrate community after a Phoslock® application may (or may not) change in Kralingse Plas. However, if a change does occur, the change will not be caused by a toxic effect but will be due to a change in water quality. For instance, if macrophyte abundance increases, as has been observed in other systems treated with Phoslock®, macrofauna abundance may also increase as a result of improved habitat complexity (Spears et al., 2016 and Waajen, unpublished data). Fish A reduction in the fish biomass in Kralingse Plas occurred several years ago and the biomass has remained very low since.

Data from van Giels (2016) showed that in 2016 the main fish species in Kralingse Plas were perch, roach, pike, ruffe, bream and eel, totalling 12.7 kg/ha. No literature was found relating to toxicological studies concerning these specific species, although acute tests conducted on two other species of fish yielded EC50 values that were between 95 and 1087 times higher than the total La concentration expected in Kralingse Plas (2.3 mg TLa/L based on Spears et al., 2013a; Fig 3 and Table 7). Prior to a Phoslock® application, the fish population of Lake de Kuil (The Netherlands) consisted of similar species as the Kralingse Plas (perch, bream, eel, roach, pike, ruffe, besides other species such as tench, carp, and spined loach), totalling 50.2 kg/ha. No fish kill occurred during the application and five years after the Phoslock® application, the fish stock was similar in species diversity and an increase in fish biomass to 131.8 kg/ha had been observed (Fig. 2A-Appendix). Eight years after the application, the fish stock was still similar (136.9 kg/ha) (Waajen et al., 2016a). The large increase in fish stock was due to the improvement in water quality but also carp stocking by anglers (Waajen et al., 2016a).

In addition, in two urban ponds in the Netherlands (Pond Dongen and Pond Eindhoven) the fish stock after a Phoslock® application developed well and increased in biomass (Waajen et al., 2016b). Based on the field observations, acute tests done in different fish species (Table 7) and the lack of a recorded fish kill after more than 200 solo application of Phoslock®, no direct damage to the fish in Kralingse Plas following a Phoslock® application based on the proposed dose is expected. The fish community may change due to a change in trophic state; for instance, more aquatic plants/macroinvertebrates and less anoxic events, however this can be expected to create a more suitable environment for fish. 21

Mammals and water-birds Kralingse Plas is a foraging area for certain bat species in the riparian zones (Grutters et al., 2018). No research has been undertaken on the effect of Phoslock® or lanthanum in bats, however no direct effects are expected as there will be no direct contact between the bats and Phoslock®. More insects are to be expected due to more underwater vegetation which can serve as a food source for some bats (Grutters et al., 2018). The act of applying Phoslock® may cause some disturbance to fish, birds and bats due to water movement, light and sound, however as recreational activities already occur in the lake, the disturbance caused by a Phoslock® application will be limited. Based on the Phoslock® dose proposed for Kralingse Plas and toxicological tests done with the medicine used for pets (Lantharenol®), it can be concluded that the amount of lanthanum that could be ingested by a dog or a cat would be safe even if the animal consumes 300 litres of lake water (considering a worst-case scenario of total lanthanum around 14 mg/L). Clearly, it is not possible for a dog to drink 300 litres of water per day, therefore the consumption of lake water will not pose a risk to animal health even during the application.

Human patients have been taking 900 mg La per day to treat hyperphosphatemia in renal failure without toxicity for more than ten years (Hutchison et al., 2016). A person would need to drink more than 63 litres of water from Kralingse Plas to reach a similar safe dose of Fosrenol®. This is also considering a worst case scenario that the TLa concentration is 14 mg/L. As humans are unable to drink this quantity of water per day, the proposed Phoslock dose does not pose any risks to humans. Summary As of 7 October 2020, Phoslock® is mentioned in the title, keywords or abstract in ninety-two peerreviewed (accessed via Scopus). Among these 92 papers, 38 evaluate Phoslock® in the presence of live organisms however none of these 38 papers report a direct toxic effect from Phoslock® under realistic conditions and dosage. Overall, based on the scientific literature discussed in this report and the proposed Phoslock® dose for Kralingse plas, no toxic effects on any of the aquatic organisms present in Kralingse Plas are expected to be seen as a result of a Phoslock® application. Similarly, no adverse effect on pets or humans are to be expected either. Of the 92 papers published, 29 studies cover whole field applications or enclosure experiments using Phoslock® with most of these cases resulting in an improvement in water quality.

These changes are summarized in Figure 4 and presented in more detail in Table 1A in the appendix. The use of Phoslock® has generally resulted in a number of positive ecological changes in the treated systems with lakes moving towards a more mesotrophic state. Observed effects include a reduction in cyanobacteria and an increase in phytoplankton diversity, macrophytes and macroinvertebrates abundance. At the same, no long-term negative effects on zooplankton have been seen while fish habitats have improved.

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Figure 4. Scheme showing from left to right (a) untreated system with cyanobacterial bloom in spring/summer (b) system undergoing Phoslock® treatment in autumn/winter and (c) treated system in following spring/summer with clear water, less P released from the sediment, eukaryote algae dominance, more macrophytes and macroinvertebrates. Secchi disks represent water transparency. Scheme adapted from Lürling et al., (2016) and Mucci, (2019). Numbers are the references. 1 to 6: (Epe et al., 2017; Lürling and van Oosterhout, 2013; Meis, 2012; Spears et al., 2015; Waajen et al., 2016a) 6 to 11 (Robb et al., 2003; Bishop et al., 2014; Bishop & Richardson 2018; Epe, 2014; Barçante et al., 2020 and Mucci et al. in review.12 and 13 van Oosterhout and Lurling, 2011; Waajen et al., 2016a. 14 and 15: Spears et al., 2016; Waajen et al., 2016. 16: Waajen et al., 2016. 17: Waajen et al 2017.18: Mucci et al., in review).

3.3. Deferred eutrophication management Eutrophication is threatening freshwater ecosystems worldwide by stimulating excess phytoplankton growth, triggering the risk of nuisance cyanobacteria blooms and inducing the shift of shallow lakes from clear water to a turbid state. These changes in the ecological structure in aquatic systems also include the biogeochemical processes of the lake sediments and changes in the habitat of the benthic community (Scheffer & van Nes 2007; Downing 2014; Lürling et al. 2016). The increased demand for eutrophication management measures is mainly driven by water quality, human and public health risk thresholds for cyanobacteria biomass and by the ecosystem services of waterbodies related to recreational use, drinking water supply and biodiversity conservation. Various estimates have been made for both the costs for eutrophication management as well as the costs of non-intervention, with the costs of “doing nothing” being often higher than the costs of taking pro-active measures aimed at reducing eutrophication.

The costs of this ‘do nothing’ approach include the reduced values to waterfront dwellings, additional drinking water treatment costs, reduced amenity of waterbodies, removal of algal toxins and decomposition products from drinking waters, ecological effects such as fish kills, increased public health risk due to cyanobacteria toxins and tourist industry losses (Douglas et al., 2016). Cyanobacteria blooms pose a serious health risk for humans and animals (WHO 2003). Deaths of cattle and dogs have been reported worldwide after the ingestion of cyanobacteria infested water or benthic cyanobacteria mats (Mez et al., 1997; Wood et al., 2010; Lürling & Faassen, 2013). During summer, news reports regularly refer to cases of human and animal poisoning, with the latter often having lethal consequences as was recently reported for the Lake Neuchâtel (Switzerland), where several dogs died after the ingestion of lake water (Republique et Canton de Neuchâtel, 2020). Likewise, in the Dutch

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lakes Amstelmeer and IJmeer dogs died from cyanobacterial intoxication (Faassen et al., 2012; Lürling & Faassen, 2013). In situ lake measures as part of an effective eutrophication management plan for the restoration of impaired lacustrine systems are often associated by the stakeholder community with adverse effects on the ecosystem itself and potential risks for the public health. The consequences, costs and risks related to the decision to ‘do nothing’ are most often not considered or underestimated. From a cost-benefit point of view an effective management of eutrophication based on a so called “system analysis” (Lürling et al., 2016) should be the method of choice and less expensive than the non-implementation of restoration measures.

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4. Conclusion The aim of this report has been to provide comprehensive information about the potential risks for the environment and public health related to the use of Phoslock® as a eutrophication management tool. Phoslock® is a lanthanum modified bentonite clay designed to bind excess phosphorus in aquatic environments suffering from eutrophication. The potential risks associated with its use are related to its active ingredient lanthanum and, in the aquatic environment, to the temporary increase of suspended solids in the water column. Data from a range of ecotoxicological studies undertaken with organisms belonging to different trophic levels demonstrate that the risk for the aquatic life associated with the use of Phoslock® can be rated low in Kralingse Plas. Extensive post-application monitoring conducted in several field studies confirms the low ecotoxicological profile in terms of bioaccumulation, biodiversity and trophic state improvement. Lanthanum carbonate is used as a food additive (Lanthanrenol®) for dogs and cats suffering from renal malfunction and thus, the risks for any adverse effects on domestic animals or other vertebrates are negligible. Human exposure to Phoslock® might occur from recreational activities or from consumption of fish from treated waterbodies.

Due to the use of lanthanum carbonate (Fosrenol®) as a drug given to renal failure patients, a huge amount of data is available from the preclinical and clinical drug development phase. For the human exposure assessment, the available data show a wide margin of safety associated with Phoslock® applications at predicted use rates and environmentally relevant concentrations.

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