Moorland grouse - Flubendazole use for parasitic worm control: preliminary environmental assessment

4. Effects data

No harmonised EU classification is available for flubendazole. A majority of notifiers to the EU classification database list the substance as toxic for reproduction cat.2 (H361d; Suspected of damaging fertility or the unborn child). There are no notified classifications for the environment^[3].

4.1. Aquatic organisms

Although limited, there are data available on the toxicity of flubendazole for invertebrates, aquatic plants and bacteria. Notably, no data could be found for effects on fish. Data are summarised in appendix A. Although a thorough review of reliability of the studies has not been undertaken, all the studies retrieved appear to have been conducted to accepted laboratory and scientific principles.

For acute data, the most sensitive species were invertebrates: flatworm (Dugesia gonocephala, 96 hour-EC50 21.9 µg/l, Bundschuh et al., 2016), tubicified worm (Tubifex tubifex, 96hour-EC50 22.1 µg/l, Bundschuh et al., 2016) and water flea (Daphnia magna, 48 hour-EC50 55.4 µg/l (mean of four studies; Wagil et al., 2015, Oh et al 2006, Bundschuh et al 2016, & Puckowski et al 2017). Tests on other trophic levels were limited, but no effects on green algae or marine bacteria were found at the maximum concentrations tested (>1000 µg/l and >300 µg/l respectively, Bundschuh et al., 2016).

There are only chronic data available for Daphnia magna. The lowest effect concentration was a 21 day NOEC for growth of 2.5 µg/l (Oh et al., 2006).

In the absence of data on the toxicity of flubendazole to fish a predicted no effect concentration (PNEC) has not been derived in this assessment.

4.2. Sediment dwelling organisms

Flubendazole has a log Koc of 4.00 (log Kow 2.91) which, following WFD Common Implementation Strategy Guidance Document 27 (EC, 2018), means sediment dwelling organisms are relevant receptors. The literature search returned no relevant sediment toxicity data, but it is possible to use the equilibrium partitioning approach with the aquatic toxicity data and partitioning data to determine a screening level threshold for sediment toxicity. It should be noted that Koc values are highly dependent on the test system used to generate them, and for this reason amongst others assessments based on equilibrium partitioning are generally used to assess the need for further testing to refine the risk assessment rather than give conclusive information on levels of risk.

Equilibrium partitioning calculations are presented in Appendix B. The lowest chronic aquatic toxicity endpoint of 2.5 µg/l translates to 0.482 mg/kg in sediment.

4.3. Soil dwelling organisms

No data could be found on the impacts of flubendazole on soil dwelling organisms. As for the assessment of sediment dwelling organisms, equilibrium partitioning can be used to estimate toxicity in soil dwelling organisms based on aquatic toxicity data (EC 2008 & EC 2012). The same caveats apply for the approach used for this compartment, with the additional caution that the estimated toxicity level is if anything more uncertain than that for sediment (the REACH guidance from where this approach is taken states that aquatic toxicity may only be applicable to organisms with a water permeable epidermis, and for certain species direct exposure to soil may be of greater importance than exposure via food). Appendix B details the calculation that relates the lowest chronic aquatic toxicity endpoint of 2.5 µg/l to a value of 0.653 mg/kg in soil.

4.4. Higher organisms (Secondary Poisoning)

There are three potential exposure pathways for higher organisms; those that predate on soil dwelling organisms like earthworms or, in the aquatic environment, fish, and scavengers/predators of treated birds.

i) worm-eating predators and fish-eating predators: under the REACH Regulation (EC,2008) and WFD guidance (EC, 2018) a cut off Log Kow of 3 is used to assess the need for a secondary poisoning assessment in the absence of data on bioaccumulation potential. This value is used to indicate that exposure via accumulation in the foodchain is low. Flubendazole has a Log Kow of 2.91 and therefore does not meet the criterion for secondary poisoning assessment.

ii) scavengers/predators that may consume treated birds: exposure via this route is likely to be low because much of the administered dose is excreted in faeces or metabolised in the liver. In addition, flubendazole is of low acute oral toxicity in poultry, rats and dogs (EMEA, 2006). Sub-chronic and chronic studies found equivocal or limited effects for relevant endpoints. The WHO/FAO Joint Expert Committee on Food Additives (JECFA) calculated an average daily intake (ADI) for humans of 0-12 μg/kg bw per day by applying a safety factor of 200 to the NOEL of 2.5 mg/kg bw per day which was established in the 3-month study in dogs (EMEA, 2006).

Hazards to higher organisms are therefore deemed to be low.

In summary, flubendazole is likely to pose the greatest hazard to aquatic and sediment dwelling invertebrates. There may also be a relevant hazard to soil dwelling invertebrates given flubendazole’s properties. No relevant terrestrial or sediment-dwellers’ ecotoxicity data were found to allow a definitive conclusion on these hazards.