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A sulfite pulp and paper mill visited in 1995 in Everett, Washington appeared to be a relatively clean operation with regard to worker exposure. There was very little smell. The foul smelling mercaptans are not produced in sulfite mills (10 % of US mills), but they are in Kraft mills (60 % of US mills). This mill did not produce its own wood chips, but purchased them from a supplier. The purpose of chemical pulping is to digest the lignin in the wood fibers, a process called cooking. The alkali and lime used in chemical pulping are recovered by evaporation and causticizing. The papermaking starts with the bleaching of the pulp. Various additives are used depending on the type of paper being produced. The cooking process is enclosed, and operating the furnace under negative pressure prevents the escape of gas. Except for spills and accidents, the only workers at risk for significant chemical exposures in the modern mill appear to be the maintenance workers. The Kraft or sulfate process is an alkaline digestion of the lignin with production of hydrogen sulfide and mercaptans. The sulfite process is an acid digestion with the production of SO2 and sulfuric acid. [Burgess, p. 485-91] Hypersensitivity pneumonitis (HP) caused by Aspergillus fumigatus has been identified in chip unloaders. [NIOSHTIC # 191197] Contact dermatitis to slimicides has been reported. Slimicides include mercaptobenzothiazole, glutaraldehyde, and isothiazolinones. Melamine-formaldehyde resin is used to increase water resistance in paper towels. Formaldehyde resins are used in paper money and other specialty papers. [Kanerva, p. 1033-40] Workers in nonproduction departments had high exposures to asbestos, hexavalent Cr, Cu, Hg, NO2, O3, styrene, SO2, trichloroethylene, and welding fumes. [Am Ind Hyg Assoc J 1999 Jan-Feb;60(1):73-83] Operators exposed to aerosols contaminated with bacteria and fungi had significantly higher incidence of fever and gastrointestinal infections compared to controls. [Ann Occup Hyg 2002;46(1):269-71] Pulp and paper manufacture is not classifiable as to carcinogenicity to humans. [IARC] |
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