lymphomas,6 but no study has previously been undertaken to investigate the risk of cancer in the paper recycling industry. De-inking and recycling of paper will become an important industry in the future as paper consumption increases.7 As Denmark has an old paper recycling industry8 and a national compulsory cancer registration, we conducted a historical cohort study of incidence of cancer in Danish paper recycling plants.
Materials and methods
DESCRIPTION OF THE PAPER RECYCLING PLANTSFive Danish paper recycling plants were included. The oldest plant started production in 1956 and the newest in 1969. In three plants, paper waste was mixed with water, and slimicides, sizing agents, flocking chemicals, fillers, and other chemicals were added to the paper stock.Two plants used a de-inking process to remove printing ink from newspapers and magazines. In a flotation de-inking system, paper waste was dissolved in water, fatty acids and other compounds were added, and printing ink and impurities were separated by an air flow in a foam separator.The most common chemicals used in the