The chlor-alkali industry produces chlorine gas and alkali (sodium hydroxide) by a process that applies electrolysis to saltwater. Some chlor-alkali plants use a mercury-cell process in which mercury is used as the electrolysis cathode. This occurs at both of the facilities named above. Arnika organized new monitoring of mercury in fish in Labe (Elbe) River. Its results were published in this report published as part of broader IPEN project.