Jämsänkoski sawmills were criticised as early as the 1800s about allowing the logs intended for the sawmill to stand in the Jämsänjoki river, polluting the water and hindering passage of boats. The pulp mill brought new problems. Contemporaries say that the air was filled with the stink of sulphur, and the emissions belched out by the mill stripped the leaves from trees in the vicinity. In 1896, the district physician of Jämsä was concerned about pollution of the Jämsänjoki river, as people who lived on its banks drew their drinking water from it. The river water was also polluted by the tanneries of Jämsä and the riverside residents themselves.

The evaporation and incineration plant for lye effluent was completed in 1969.Thus, the environmental impacts of pulp mills were acknowledged early on, but they were seen as a necessary evil. Most of the debate at the time centred on the smell pollution from the sulphate pulp mills. People of sulphate mill towns tried to take a humorous view of the issue, saying "Money smells". Pulp production in Finland had multiplied by the 1950s, and during the next decade factory emissions became the subject of heated public debate. Many of the old pulp mills were by small waterways, which became badly polluted. Particular criticism was directed at sulphite pulp mills. United’s old sulphite mills were in Valkeakoski and Jämsänkoski, which also operated a bleaching plant.

Pollution of Jämsänjoki river also damaged the company's own operation, as the Kaipola mill drew its service water from Lake Päijänne, from an area into which the river ran. Kaipola also discharged its own effluent into Lake Päijänne. As early as the end of the 1950s, the surroundings of the factory drain were full of waste pulp. The pollution spread in the late 1960s and early 1970s to cover almost the whole of Päijänne.

Jämsänjoki and Päijänne were indirectly saved by the service water needs of the city of Helsinki. Helsinki wanted to draw its raw water from Päijänne. For this reason, pollution of the lake had to be halted and its cleansing got under way. The water needs of the capital region resolved granting of the loan needed to build a waste liquor evaporation and incineration plant at the Jämsänkoski mill. The plant was completed in 1969. Cleansing of the river was finally under way only when the pulp mill ceased operation in 1981. Technological advances in methods of purifying effluent have also improved the situation.