Singapore and China are the highest-profile countries to ban the use of open-loop scrubbers, but the list of countries joining them is growing, according to Gard.

The Norwegian protection and indemnity club says that while the IMO has set out the criteria for discharging scrubber washwater into the sea, some coastal states and ports have implemented local regulations with more stringent requirements that restrict or completely prohibit its discharge or prohibit the use of scrubbers.