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Occupational Hazards and Controls

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Table 1 provides an overview of the types of exposures which may be expected in each area of pulp and paper operations. Although exposures may be listed as specific to certain production processes, exposures to employees from other areas may also occur depending on weather conditions, proximity to sources of exposure, and whether they work in more than one process area (e.g., quality control, general labour pool and maintenance personnel).

Table 1. Potential health and safety hazards in pulp and paper production, by process area

Process area

Safety hazards

Physical hazards

Chemical hazards

Biological hazards

Wood preparation


Log pond

Drowning; mobile equipment;
slipping, falling

Noise; vibration; cold; heat

Engine exhaust


Wood room

Nip points; slipping, falling

Noise; vibration

Terpenes and other wood extracts; wood dust

Bacteria; fungi

Chip screening

Nip points; slipping, falling

Noise; vibration

Terpenes and other wood extracts; wood dust

Bacteria; fungi

Chip yard

Nip points; mobile equipment

Noise; vibration; cold; heat

Engine exhaust; terpenes and other wood extracts; wood dust

Bacteria; fungi



Stone groundwood

Slipping, falling

Noise; electric and magnetic fields; high humidity



Slipping, falling

Noise; electric and magnetic fields; high humidity

Cooking chemicals and by-products; terpenes and other wood extracts; wood dust


Sulphate pulping

Slipping, falling

Noise; high humidity; heat

Acids and alkalis; cooking chemicals and by-products; reduced sulphur gases; terpenes
and other wood extracts; wood dust


Sulphate recovery

Explosions; nip points; slipping,

Noise; heat; steam

Acids and alkalis; asbestos; ash; cooking chemicals and by-products; fuels; reduced
sulphur gases; sulphur dioxide


Sulphite pulping

Slipping, falling

Noise; high humidity; heat

Acids and alkalis; cooking chemicals and by-products; sulphur dioxide; terpenes and other wood extracts; wood dust


Sulphite recovery

Explosions; nip points; slipping,

Noise; heat; steam

Acids and alkalis; asbestos; ash; cooking chemicals and by-products; fuels; sulphur dioxide



Slipping, falling


Acids and alkalis; bleaching chemicals and by- products; dyes and inks; pulp/paper dust; slimicides; solvents



Slipping, falling

Noise; high humidity; heat

Bleaching chemicals and by-products; slimicides; terpenes and other wood extracts


Sheet forming and


Pulp machine

Nip points; slipping, falling

Noise; vibration; high
humidity; heat; steam

Acids and alkalis; bleaching chemicals and by-products; flocculant; pulp/paper dust; slimicides; solvents


Paper machine

Nip points; slipping, falling

Noise; vibration; high
humidity; heat; steam

Acids and alkalis; bleaching chemicals and by-products; dyes and inks; flocculant; pulp/paper
dust; paper additives; slimicides; solvents



Nip points; mobile equipment


Acids and alkalis; dyes and inks; flocculant;
pulp/paper dust; paper additives; slimicides; solvents



Mobile equipment


Fuels; engine exhaust; pulp/paper dust


Other operations


Power generation

Nip points; slipping, falling

Noise; vibration; electric and
magnetic fields; heat; steam

Asbestos; ash; fuels; terpenes and other wood extracts; wood dust

Bacteria; fungi

Water treatment



Bleaching chemicals and by-products


Effluent treatment



Bleaching chemicals and by-products; flocculant; reduced sulphur gases


Chlorine dioxide

Explosions; slipping, falling


Bleaching chemicals and by-products


Turpentine recovery

Slipping, falling


Cooking chemicals and by-products; reduced sulphur gases; terpenes and other wood extracts


Tall oil production


Acids and alkalis; cooking chemicals and by-products; reduced sulphur gases; terpenes and other wood extracts


RMP = refining mechanical pulping; CMP = chemi-mechanical pulping; CTMP = chemi-thermomechanical pulping.


Exposure to the potential hazards listed in table 1 is likely to depend on the extent of automation of the plant. Historically, industrial pulp and paper production was a semi-automatic process which required a great deal of manual intervention. In such facilities, operators would sit at open panels adjacent to the processes to view the effects of their actions. The valves at the top and bottom of a batch digester would be manually opened, and during the filling stages, gases in the digester would be displaced by the incoming chips (figure 1). Chemical levels would be adjusted based on experience rather than sampling, and process adjustments would be dependent on the skill and knowledge of the operator, which at times led to upsets. For example, over-chlorination of pulp would expose workers downstream to increased levels of bleaching agents. In most modern mills, progress from manually controlled to electronically controlled pumps and valves allows for remote operation. The demand for process control within narrow tolerances has required computers and sophisticated engineering strategies. Separate control rooms are used to isolate the electronic equipment from the pulp and paper production environment. Consequently, operators usually work in air-conditioned control rooms which offer refuge from the noise, vibration, temperature, humidity and chemical exposures inherent to mill operations. Other controls which have improved the working environment are described below.

Figure 1. Worker opening cap on manually controlled batch digester.


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Safety hazards including nip points, wet walking surfaces, moving equipment and heights are common throughout pulp and paper operations. Guards around moving conveyors and machinery parts, quick clean-up of spills, walking surfaces which allow drainage, and guard-rails on walkways adjacent to production lines or at height are all essential. Lock-out procedures must be followed for maintenance of chip conveyors, paper machine rolls and all other machinery with moving parts. Mobile equipment used in chip storage, dock and shipping areas, warehousing and other operations should have roll-over protection, good visibility and horns; traffic lanes for vehicles and pedestrians should be clearly marked and signed.

Noise and heat are also ubiquitous hazards. The major engineering control is operator enclosures, as described above, usually available in wood preparation, pulping, bleaching and sheet-forming areas. Air-conditioned enclosed cabs for mobile equipment used in chip pile and other yard operations are also available. Outside these enclosures, workers usually require hearing protection. Work in hot process or outdoor areas and in vessel maintenance operations requires workers to be trained to recognize symptoms of heat stress; in such areas, work scheduling should allow acclimatization and rest periods. Cold weather may create frostbite hazards in outdoor jobs, as well as foggy conditions near chip piles, which remain warm.

Wood, its extracts and associated micro-organisms are specific to wood preparation operations and the initial stages of pulping. Control of exposures will depend on the particular operation, and may include operator booths, enclosure and ventilation of saws and conveyors, as well as enclosed chip storage and low chip inventory. Use of compressed air to clear wood dust creates high exposures and should be avoided.

Chemical pulping operations present the opportunity for exposures to digestion chemicals as well as gaseous by-products of the cooking process, including reduced (kraft pulping) and oxidized (sulphite pulping) sulphur compounds and volatile organics. Gas formation may be influenced by a number of operating conditions: the wood species used; the quantity of wood pulped; the amount and concentration of white liquor applied; the amount of time required for pulping; and maximum temperature attained. In addition to automatic digester capping valves and operator control rooms, other controls for these areas include local exhaust ventilation at batch digesters and blow tanks, capable of venting at the rate the vessel’s gases are released; negative pressure in recovery boilers and sulphite-SO2 acid towers to prevent gas leaks; ventilated full or partial enclosures over post-digestion washers; continuous gas monitors with alarms where leaks may occur; and emergency response planning and training. Operators taking samples and conducting tests should be aware of the potential for acid and caustic exposure in process and waste streams, and the possibility of side reactions such as hydrogen sulphide gas (H2S) production if black liquor from kraft pulping comes into contact with acids (e.g., in sewers).

In chemical recovery areas, acidic and alkaline process chemicals and their by-products may be present at temperatures in excess of 800°C. Job responsibilities may require workers to come into direct contact with these chemicals, making heavy duty clothing a necessity. For example, workers rake the spattering molten smelt that collects at the base of the boilers, thereby risking chemical and thermal burns. Workers may be exposed to dust when sodium sulphate is added to concentrated black liquor, and any leak or opening will release noxious (and potentially fatal) reduced sulphur gases. The potential for a smelt water explosion always exists around the recovery boiler. Water leaks in the tube walls of the boiler have resulted in several fatal explosions. Recovery boilers should be shut down at any indication of a leak, and special procedures should be implemented for transferring the smelt. Loading of lime and other caustic materials should be done with enclosed and ventilated conveyors, elevators and storage bins.

In bleach plants, field operators may be exposed to the bleaching agents as well as chlorinated organics and other by-products. Process variables such as bleaching chemical strength, lignin content, temperature and pulp consistency are constantly monitored, with operators collecting samples and performing laboratory tests. Because of the hazards of many of the bleaching agents used, continuous alarm monitors should be in place, escape respirators should be issued to all employees, and operators should be trained in emergency response procedures. Canopy enclosures with dedicated exhaust ventilation are standard engineering controls found at the top of each bleaching tower and washing stage.

Chemical exposures in the machine room of a pulp or paper mill include chemical carry-over from the bleach plant, the papermaking additives and the chemical mixture in the waste water. Dusts (cellulose, fillers, coatings) and exhaust fumes from mobile equipment are present in the dry-end and the finishing operations. Cleaning between product runs may be done with solvents, acids and alkalis. Controls in this area may include complete enclosure over the sheet drier; ventilated enclosure of the areas where additives are unloaded, weighed and mixed; use of additives in liquid rather than powder form; use of water-based rather than solvent-based inks and dyes; and eliminating the use of compressed air to clean up trimmed and waste paper.

Paper production in recycled paper plants is generally dustier than conventional paper production using newly produced pulp. Exposure to micro-organisms can occur from the beginning (paper collection and separation) to the end (paper production) of the production chain, but exposure to chemicals is less important than in conventional paper production.

Pulp and paper mills employ an extensive maintenance group to service their process equipment, including carpenters, electricians, instrument mechanics, insulators, machinists, masons, mechanics, millwrights, painters, pipefitters, refrigeration mechanics, tinsmiths and welders. Along with their trade-specific exposures (see the Metal processing and metal working and Occupations chapters), these tradespeople may be exposed to any of the process-related hazards. As mill operations have become more automated and enclosed, the maintenance, cleaning and quality assurance operations have become the most highly exposed. Plant shutdowns to clean vessels and machines are of special concern. Depending on mill organization, these operations may be carried out by in-house maintenance or production personnel, although subcontracting to non-mill personnel, who may have less occupational health and safety support services, is common.

In addition to process exposures, pulp and paper mill operations entail some noteworthy exposures for maintenance personnel. Because pulping, recovery and boiler operations involve high heat, asbestos was used extensively to insulate pipes and vessels. Stainless steel is often used in vessels and pipes throughout pulping, recovery and bleaching operations, and to some extent in papermaking. Welding this metal is known to generate chromium and nickel fumes. During maintenance shut-downs, chromium-based sprays may be applied to protect the floor and walls of recovery boilers from corrosion during start-up operations. Process quality measurements in the production line are often made using infrared and radio-isotope gauges. Although the gauges are usually well shielded, instrument mechanics who service them may be exposed to radiation.

Some special exposures may also occur among employees in other mill-support operations. Power boiler workers handle bark, waste wood and sludge from the effluent treatment system. In older mills, workers remove ash from the bottom of the boilers and then reseal the boilers by applying a mixture of asbestos and cement around the boiler grate. In modern power boilers, this process is automated. When material is fed into the boiler at too high a moisture level, workers may be exposed to blow-backs of incomplete combustion products. Workers responsible for water treatment may be exposed to chemicals such as chlorine, hydrazine and various resins. Because of the reactivity of ClO2, the ClO2 generator is usually located in a restricted area and the operator is stationed in a remote control room with excursions to collect samples and service the saltcake filter. Sodium chlorate (a strong oxidizer) used to generate ClO2 can become dangerously flammable if it is allowed to spill on any organic or combustible material and then dry. All spills should be wetted down before any maintenance work may proceed, and all equipment should be thoroughly cleaned afterward. Wet clothing should be kept wet and separate from street clothing, until washed.



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Paper and Pulp Industry References

Canadian Pulp and Paper Association. 1995. Reference Tables 1995. Montreal, PQ: CPPA.

Food and Agriculture Organization (FAO) of the United Nations. 1995. Pulp and Paper Capacities, Survey 1994-1999. Rome: FAO.

Henneberger, PK, JR Ferris, and RR Monson. 1989. Mortality among pulp and paper workers in Berlin. Br J Ind Med 46:658-664.

International Agency on the Research of Cancer (IARC). 1980. Monographs on the Evaluation of Carcinogenic Risks to Humans: Wood, Leather and Some Associated Industries. Vol. 25. Lyon: IARC.

—.1987. Monographs on the Evaluation of Carcinogenic Risks to Humans, Overall Evaluations of Carcinogenicity: An Updating of IARC Monographs. Vol. 1-42 (supplement 7). Lyon: IARC.

—.1995. Monographs on the Evaluation of Carcinogenic Risks to Humans: Wood Dust and Formaldehyde. Vol. 62. Lyon: IARC.

International Labour Organization (ILO). 1992. Social and Labour Issues in the Pulp and Paper Industry. Geneva: ILO.

Jäppinen, P. 1987. Exposure to Compounds, Cancer Incidence and Mortality in the Finnish Pulp and Paper Industry. Thesis, Helsingfors, Finland.

Jäppinen, P and S Tola. 1990. Cardiovascular mortality among pulp mill workers. Br J Ind Med 47:259-261.

Jäppinen, P, T Hakulinen, E Pukkala, S Tola, and K Kurppa. 1987. Cancer incidence of workers in the Finnish pulp and paper industry. Scand J Work Environ Health 13:197-202.

Johnson, CC, JF Annegers, RF Frankowski, MR Spitz, and PA Buffler. 1987. Childhood nervous system tumors—An evaluation of the association with paternal occupational exposure to hydrocarbons. Am J Epidemiol 126:605-613.

Kuijten, R, GR Bunin, and CC Nass. 1992. Parental occupation and childhood astrocytoma: Results of a case-control study. Cancer Res 52:782-786.

Kwa, SL and IJ Fine. 1980. The association between parental occupation and childhood malignancy. J Occup Med 22:792-794.

Malker, HSR, JK McLaughlin, BK Malker, NJ Stone, JA Weiner, JLE Ericsson, and WJ Blot. 1985. Occupational risks for pleural mesothelioma in Sweden, 1961-1979. J Natl Cancer Inst 74:61-66.

—. 1986. Biliary tract cancer and occupation in Sweden. Br J Ind Med 43:257-262.

Milham, SJ. 1976. Neoplasias in the wood and pulp industry. Ann NY Acad Sci 271:294-300.

Milham, SJ and P Demers. 1984. Mortality among pulp and paper workers. J Occup Med 26:844-846.

Milham, SJ and J Hesser. 1967. Hodgkin’s disease in woodworkers. Lancet 2:136-137.

Nasca, P, MS Baptiste, PA MacCubbin, BB Metzger, K Carton, P Greenwald, and VW Armbrustmacher. 1988. An epidemiologic case-control study of central nervous system tumors in children and parental occupational exposures. Am J Epidemiol 128:1256-1265.

Persson, B, M Fredriksson, K Olsen, B Boeryd, and O Axelson. 1993. Some occupational exposures as risk factors for malignant melanomas. Cancer 72:1773-1778.

Pickle, L and M Gottlieb. 1980. Pancreatic cancer mortality in Louisiana. Am J Public Health 70:256-259.
Pulp and Paper International (PPI). 1995. Vol. 37. Brussels: Miller Freeman.

Robinson, C, J Waxweiller, and D Fowler. 1986. Mortality among production workers in pulp and paper mills. Scand J Work Environ Health 12:552-560.

Schwartz, B. 1988. A proportionate mortality ratio analysis of pulp and paper mill workers in New Hampshire. Br J Ind Med 45:234-238.

Siemiatycki, J, L Richardson, M Gérin, M Goldberg, R Dewar, M Désy, S Campell, and S Wacholder. 1986. Association between several sites of cancer and nine organic dusts: Results from an hypothesis-generating case control study in Montreal, 1979-1983. Am J Epidemiol 123:235-249.

Skalpe, IO. 1964. Long-term effects of sulfur dioxide exposure in pulp mills. Br J Ind Med 21:69-73.

Solet, D, R Zoloth, C Sullivan, J Jewett, and DM Michaels. 1989. Patterns of mortality in pulp and paper workers. J Occup Med 31:627-630.

Torén, K, S Hagberg, and H Westberg. 1996. Health effects of working in pulp and paper mills: Exposure, obstructive airways diseases, hypersensitivity reactions, and cardiovascular diseases. Am J Ind Med 29:111-122.

Torén, K, B Järvholm, and U Morgan. 1989. Mortality from asthma and chronic obstructive pulmonary diseases among workers in a soft paper mill: A case referent study. Br J Ind Med 46:192-195.

Torén, K, B Persson, and G Wingren. 1996. Health effects of working in pulp and paper mills: Malignant diseases. Am J Ind Med 29:123-130.

Torén, K, G. Sällsten, and B Järvholm. 1991. Mortality from asthma, chronic obstructive pulmonary disease, respiratory system cancer among paper mill workers: A case referent study. Am J Ind Med 19:729-737.

US Department of Commerce. 1983. Pulp and Paper Mills. (PB 83-115766). Washington, DC: US Department of Commerce.

—.1993. Selected Occupational Fatalities Related to Pulp Paper and Paperboard Mills as Found in Reports of OSHA Fatality/Catastrophe Investigations. (PB93-213502). Washington, DC: US Department of Commerce.

Weidenmüller, R. 1984. Papermaking, the Art and Craft of Handmade Paper. San Diego, CA: Thorfinn International Marketing Consultants Inc.

Wingren, G, H Kling, and O Axelson. 1985. Gastric cancer among paper mill workers. J Occup Med 27:715.

Wingren, G, B Persson, K Torén, and O Axelson. 1991. Mortality patterns among pulp and paper mill workers in Sweden: A case-referent study. Am J Ind Med 20:769-774.

Workers’ Compensation Board of British Columbia. 1995. Personal communication.