The first discharge of up to 100,000 litres of diluted caustic soda was reported at UPM's Kuusanniemi Pulp Mill in Kuusankoski on Friday evening. However, not all of the toxin passed into the river. A second, smaller discharge occurred downstream at the Sunila Mill in Kotka, owned by Myllykoski Paper and Stora Enso.
Groundwater has not been contaminated by the discharges. However, environmental officials urge the public not to use water from the river south of Kuusankoski and to avoid swimming in the waterway. The situation is being constantly monitored. No fish deaths have so far been reported.
Discharges of caustic soda are rare from Finnish pulp mills. The worst incident in recent history was in 2003 when 7,500 cubic litres of the toxin was discharged into the Saimaa waterway. There was considerable pollution with fish deaths, discolouration and deoxidation of the water. UPM Kymmene was forced to pay damages to 470 lakeside land owners.
Caustic soda (sodium hydroxide) is used in the production of pulp, which forms the basis material for the majority of paper and board grades.