Ecotoxicity Study gives Open Loop Scrubbers the All-Clear

A recent independent ecotoxicity study undertaken in accordance with the IMO GESAMP guidelines gives open loop scrubbers the all-clear. The study indicated that both in a standard OECD port and in a highly trafficked seaway the operation of open loop scrubbers did not create an unwarranted risk. The study is freely accessible on the EGCSA website at


Don Gregory, Director of the EGCSA commented that “the results of the study were not unexpected. The study puts to bed the myth and unsubstantiated claims of some NGOs who are simply seeking to ban the use of residual fuel oil. They have used rhetoric, sensationalism and unsubstantiated claims or pseudo studies to attempt to discredit scrubbers.” Gregory went on to say; “the fact is that the forecast for scrubber uptake in IMO’s 2016 Fuel Availability Study by CE Delft Consortium ensured that Administrations agreed to introduce the global sulphur cap in 2020. Without scrubbers the world would be facing another 3.5 years of high sulphur emissions.”


The ecotoxicity study addresses the concerns that the discharge water from scrubbers, whilst infinitely low in concentrations of substances that might be considered hazardous, “might” produce an unexpected toxic cocktail. 


EGCSA appointed research group DHI to undertake the ecotoxicity assessment in accordance with GESAMP guidelines. This premier independent and not for profit organisation specialises in water quality assessments and operates globally. To date, DHI has dealt with over 50% of the USCG requirements for ballast water management systems approvals. Ecotoxicity is a GESAMP requirement for assessing the risk arising from toxic substance preparations in BWMS and also in anti-fouling systems. 


Discharge water was taken from four ships operating in northern Europe with open loop scrubbers. The samples were homogenised and presented to different levels of marine organisms including algae & crustaceans in a step-wise process, culminating in testing the toxicity with fish. The steps towards assessing the possible toxicity to fish were possible because at no stage were the measured assessment parameters exceeded. 


The final step in the risk assessment is the translation of the data to the real-life situations of several scrubbers discharging into a port or into a busy sea lane. In all cases, the risk of ecotoxicity was well below the unacceptable level.


Gregory commented that the study gives certainty to ports, harbours and other authorities about the acceptability of operating open loop scrubbers in their jurisdictions. Nevertheless, EGCSA will be seeking partnerships with ports to undertake more studies to provide on-going assurance that ecotoxicity of the open loop scrubber wash water remains at a safe level to discharge into the marine environment.

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