Emamectin benzoate (EmBz) - environmental quality standard (EQS) - implementation: consultation

Sets out our directions to the Scottish Environmental Protection Agency (SEPA) on the application of a new environmental quality standard (EQS) for Emamectin benzoate (EmBz). We are seeking views on the timescale SEPA should implement to apply the new EQS reducing the discharge limits for these farms.

Background and rationale for new EQS standards for EmBz

The Scottish Environment Protection Agency derived the previous standards for the EmBz in 1999. The standard was 763 ng/kg of sediment wet weight.[1]

In 2016, SEPA commissioned independent scientific work to review the original EQS for EmBz. The review was prompted by indications from a study by the Scottish Association for Marine Science that the use of the medicine may be affecting crustaceans.

The review was undertaken by the consultancy, WRc and completed in 2017. It recommended a new, tighter EQS of 12ng/kg of sediment dry weight.

In 2017, SEPA conducted a survey of waters around fish farms to trial improved environmental monitoring strategies. Its subsequent analysis of the environmental samples collected identified evidence of impact on crustaceans. Analysis of the results showed that EmBz had a negative effect on the crustacean abundance and richness. The impact was proportional to the concentrations of EmBz in the seabed and present at concentrations substantially below the original EQS of 763 ng/kg.

On the basis of the accumulated evidence, SEPA requested the UK Technical Advisory Group (UKTAG) to develop recommendations on a new EQS for EmBz. In developing the new EQS, UKTAG used the best available scientific information and followed the latest protocols for deriving EQSs.

UKTAG is a partnership between the UK's environment and conservation agencies. It was set up jointly by the devolved administrations to provide scientific advice on EQSs and other matters relating to the protection of the water environment.

As part of the UKTAG process updating the EQS, the sector and the medicine manufacturer were invited to provide any additional information that they may have. UKTAG consulted on its initial proposals for a new EQS in May 2019.

In November 2019, it published its analysis of responses to its consultation on the proposed EQS for EmBz. It concluded that the evidence provided by the aquaculture sector in response to the consultation needed to be reviewed before final recommendations could be made. Also, based on the evidence so far considered, the new standard would not be lower than 23.5 ng/kg of sediment (dry weight).

SEPA then replaced its October 2017 interim regulatory position with a new interim regulatory position based on an interim standard of 23.5ng/kg of sediment dry weight. As with its previous interim regulatory position, the new position only applied to new fish farm applications, or applications to increase discharges at existing fish farms.

UKTAG published its recommendations following independent scientific peer review in July 2022, recommending a new EQS for marine sediments of 131 ng/kg sediment (dry weight).

Subsequently, in January 2023, Salmon Scotland contacted UKTAG, to alert them to a possible error in the calculation to derive the EQS for EmBz. At the same time, the Scottish Government paused the launch of the consultation.

This allowed UKTAG to further consider the advice and confirm the outcome of their investigation into the representation by Salmon Scotland.

UKTAG notified the Scottish Government on 22 March that has further considered the advice received from Salmon Scotland and signed off the report and latest recommendation.

The new recalculated recommended EQS for marine sediment therefore changed from 131 ng/kg dry weight to 272 ng/kg dry weight.

The thresholds and times of when EQS changes took place are set out in the table below:

Table 1: EQS threshold changes over time
  Sediment (ng/kg dwt) EmBz concentration per kilogram of marine sediment (ng)
Existing standard threshold 763 (wet weight) Equivalent to approximately 1,520 (dry weight)
Interim position 12 (dry weight)
Updated interim position 23.5 (dry weight)
UKTAG recommendation, July 2022 131 (dry weight)
UKTAG recalculated recommendation March 2023 272 ng/kg dry weight


Email: waterenvironment@gov.scot

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