Scrubbers can help shipowners comply with IMO legislation such as emission control areas (ECAs) that require ships to burn fuel with a sulphur content of no more than 1.00% sulphur (effective July 1, 2010).
For vessels operating within an ECA, scrubbers have been cited as a less expensive and more convenient option, as they give the ability to be flexible on fuel supply so that higher sulphur bunker fuels can still be used. This helps tackle issues of supply of lower sulphur fuels and distillates and rising costs that remains a concern to many in the industry. Link: 
Scrubbers have been shown to cut SOx by 90-98%, particulate matter by 50-85% and CO2 by 5%, according to a test by MAN Holeby, Denmark. They could also remove carbon black, which is the latest focus of the IMO as is a short-lived climate enforcer and has been shown to accelerate global warming.
UK-based scrubbing technology company Hamworthy Krystallon Limited (acquired by Wärtsilä in January 2012) claims that its seawater scrubber removes 100% of sulphur and over 80% of particulates from exhaust gas over a 25-year cycle.
The system is also typically robust and maintenance free, according to Ralf Jurgens from the dry exhaust gas system R&D Couple Systems. No operating staff is required and the system can be switched on and off from the bridge.
It has been noted that one side effect of a scrubber is that the process only moves the unwanted substance from the exhaust gases into a liquid solution, solid paste or powder form. This must be disposed of safely, if it cannot be reused.
Danish-based scrubbing technology company Aalborg Industries has said one of the main concerns for scrubbers is retrofitting existing ships. Aalborg is currently executing case studies together with owners to determine the implications of a scrubber on board of their vessels. Owners are being invited to participate in these case studies.
The maturity of marine scrubber technology is constantly being raised as a concern, as well as the size and weight of such equipment.
The International Association of Independent Tanker Owners INTERTANKO has also raised concerns over a current lack of information on the practicality, efficiency and reliability of scrubbing on different types and sizes of ships.
A report carried out by INTERTANKO also highlighted concerns that many scrubbers end up discharging millions of tonnes of sulphur into the sea instead of into the air. The effect of this is unknown.