" DISCLAIMER: The ILO does not take responsibility for content presented on this web portal that is presented in any language other than English, which is the language used for the initial production and peer-review of original content. Certain statistics have not been updated since the production of the 4th edition of the Encyclopaedia (1998)."

Thursday, 10 March 2011 15:28

Bark and Sap Production

Written by
Rate this item
(0 votes)

Some text was revised from the articles “Hemp”, by A. Barbero-Carnicero; “Cork”, by C. de Abeu; “Rubber cultivation”, by the Dunlop Co.; “Turpentine”, by W. Grimm and H. Gries; “Tanning and leather finishing”, by V.P. Gupta; “Spice industry”, by S. Hruby; “Camphor”, by Y. Ko; “Resins”, by J. Kubota; “Jute”, by K.M. Myunt; and “Bark”, by F.J. Wenzel from the 3rd edition of this “Encyclopaedia”.

The term bark refers to the multilayered protective shell covering a tree, shrub or vine. Some herbaceous plants, such as hemp, are also harvested for their bark. Bark is composed of inner and outer bark. Bark starts at the vascular cambium in the inner bark, where cells are generated for the phloem or conductive tissue that transports sugar from the leaves to the roots and other parts of the plant and the sap wood inside the bark layer with vessels that carry water (sap) up from the roots to the plant. The primary purpose of the outer bark is to protect the tree from injury, heat, wind and infection. A great variety of products are extracted from bark and tree sap, as shown in table 1.

Table 1. Bark and sap products and uses


Product (tree)


Resins (inner bark)

Pine resin, copal, frankincense, myrrh, red resin (climbing palm)

Varnish, shellac, lacquer

Incense, perfume, dye

Oleoresins (sapwood)




Camphor (camphor laurel tree)

Solvent, thinner, perfume feedstock, disinfectant, pesticide

Violin bow treatment, varnish, paint, sealing wax, adhesive, cement, soap

Gymnast’s powder

Perfume, incense, plastic and film feedstock, lacquers, smokeless powder explosives, perfumes, disinfectants, insect repellents




Tyres, balloons, gaskets, condoms, gloves

Insulators, underground and marine cable coatings, golf balls, surgical appliances, some adhesives, chicle/base for chewing gum

Medicines and poisons (bark)

Witch hazel


Quinine (cinchona)


Pacific yew


Caffeine (yoco vine)

Lonchocarpus vine



Anti-malaria medicinal

Cough medicine

Ovarian cancer treatment

Arrow poison

Amazonian soft drink

Fish asphyxiate

Flavours (bark)

Cinnamon (cassia tree)

Bitters, nutmeg and mace, cloves, sassafras root

Spice, flavouring

Root beer (until linked to liver cancer)

Tannins (bark)

Hemlock, oak, acacia, wattle, willow, mangrove, mimosa, quebracho, sumach, birch

Vegetable tanning for heavier leathers, food processing, fruit ripening, beverage (tea, coffee, wine) processing, ink colouring ingredient, dyeing mordants

Cork (outer bark)

Natural cork (cork oak), reconstituted cork

Buoy, bottle cap, gasket, cork paper, cork board, acoustic tile, shoe inner sole

Fibre (bark)

Cloth (birch, tapa, fig, hibiscus, mulberry)

Baobab tree (inner) bark

Jute (linden family)

Bast from flax, hemp (mulberry family), ramie (nettle family)

Canoe, paper, loincloth, skirt, drapery, wall hanging, rope, fishing net, sack, coarse clothing


Hessians, sackings, burlap, twine, carpets, clothing

Cordage, linen


Sugar maple syrup (sapwood)

Gur (many palm species)

Condiment syrup

Palm sugar

Waste bark

Bark chips, strips

Soil conditioner, mulch (chips), garden pathway covering, fiberboard, particleboard, hardboard, chipboard, fuel


Trees are grown for their bark and sap products either by cultivation or in the wild. Reasons for this choice vary. Cork oak groves have advantages over wild trees, which are contaminated by sand and grow irregularly. The control of a rubber tree leaf rust fungus in Brazil is more effective in the sparse tree spacing of the wild. However, in locations free of this fungus, such as in Asia, plantation groves are very effective for cultivating rubber trees.


Three broad processes are used in harvesting bark and sap: stripping of bark in sheets, debarking for bulk bark and bark ingredients and the extraction of tree fluids by cutting or tapping.

Bark sheets

Stripping sheets of bark from standing trees is easier when the sap is running or after steam injection between the bark and the wood. Two bark stripping technologies are described below, one for cork and the other for cinnamon.

The cork oak is cultivated in the western Mediterranean basin for cork, and Portugal is the largest cork producer. The cork oak, as well as other trees such as the African baobab tree, share the important feature of regrowing outer bark after its removal. Cork is part of the outer bark that lies beneath the hard outer shell called the rhytidome. The thickness of the cork layer increases year-by-year. After an initial bark removal, harvesters cut regrown cork every 6 to 10 years. Stripping the cork involves cutting two circular and one or more vertical cuts without damaging the inner bark. The cork worker uses a bevelled hatchet handle to remove the cork sheets. The cork is then boiled, scraped and cut into marketable sizes.

Cinnamon tree cultivation has spread from Sri Lanka to Indonesia, East Africa and the West Indies. An ancient tree management technique is still used in cinnamon cultivation (as well as willow and cascara tree cultivation). The technique is called coppicing, from the French word couper, meaning to cut. In neolithic times, humans discovered that when a tree is cut close to the ground, a mass of similar, straight branches would sprout from the root around the stump, and that these stems could be regenerated by regular cutting just above ground. The cinnamon tree can grow to 18 m but is maintained as 2-metre-high coppices. The main stem is cut at three years, and the resulting coppices are harvested every two to three years. After cutting and bundling the coppices, the cinnamon gatherers slit the bark sides with a sharp, curved knife. They then strip the bark off and after one to two days separate the outer and inner bark. The outer corky layer is scraped off with a broad, blunt knife and discarded. The inner bark (phloem) is cut into 1-metre lengths called quills; these are the familiar cinnamon sticks.

Bulk bark and ingredients

In the second major process, bark may also be removed from cut trees in large rotating containers called debarking drums. Bark, as a byproduct of lumber, is used as fuel, fibre, mulch or tannin. Tannin is among the most important bark products and is used to produce leather from animal skins and in food processing (see the chapter Leather, fur and footwear). Tannins are derived from a variety of tree barks around the world by open diffusion or percolation.

In addition to tannin, many barks are harvested for their ingredients, which include witch hazel and camphor. Witch hazel is a lotion extracted by steam distillation of twigs from the North American witch hazel tree. Similar processes are used in harvesting camphor from branches of the camphor laurel tree.

Tree fluids

The third major process includes the harvesting of resin and latex from the inner bark and oeloresins and syrup from the sapwood. Resin is found especially in the pine. It oozes out of bark wounds to protect the tree from infection. To commercially obtain resin, the worker must wound the tree by peeling off a thin layer of the bark or piercing it.

Most resins thicken and harden when exposed to the air, but some trees produce liquid resins or oleoresins, such as turpentine from conifers. Severe wounds are made into one side of the tree wood to harvest turpentine. The turpentine runs down the wound and is collected and hauled to storage. Turpentine is distilled into turpentine oil with a colophony or rosin residue.

Any milky sap exuded by plants is called latex, which in rubber trees is formed in the inner bark. Latex gatherers tap the rubber trees with spiral cuts around the trunk without damaging the inner bark. They catch the latex in a bowl (see the chapter Rubber industry). The latex is kept from hardening either through coagulation or with an ammonium hydroxide fixative. Acid wood smoke in the Amazon or formic acid is used to coagulate raw rubber. Crude rubber is then shipped for processing.

In the early spring in the cold climates of the United States, Canada, and Finland, a syrup is harvested from the sugar maple tree. After the sap starts to run, spouts are placed into drilled holes in the trunk through which sap runs either into buckets or through plastic piping for transport to storage tanks. The sap is boiled to 1/40th of its original volume to produce maple syrup. Reverse osmosis may be used to remove much of the water prior to evaporation. The concentrated syrup is cooled and bottled.

Hazards and Their Prevention

The hazards related to producing bark and sap for processing are natural exposures, injuries, pesticide exposures, allergies and dermatitis. Natural hazards include snake and insect bites and the potential for infection where vector-borne or water-borne diseases are endemic. Mosquito control is important on plantations, and pure water supply and sanitation is important at any tree farm, grove or plantation.

Much of the work with bark stripping, cutting and tapping involves the possibility of cuts, which should be promptly treated to prevent infection. Hazards exist in the manual cutting of trees, but mechanized methods of clearing as well as planting have reduced injury hazards. The use of heat for “smoking” rubber and evaporating oils from bark, resins and sap expose workers to burns. Hot maple syrup exposes workers to scalding injuries during boiling. Special hazards include working with draught animals or vehicles, tool-related injuries and the lifting of bark or containers. Bark stripping machines expose workers to potentially serious injury as well as to noise. Injury control techniques are needed, including safe work practices, personal protection and engineering controls.

Pesticide exposures, especially to the herbicide sodium arsenite on rubber plantations, are potentially hazardous. These exposures can be controlled by following manufacturer recommendations for storage, mixing and spraying.

Allergic proteins have been identified in natural rubber sap, which has been associated with latex allergy (Makinen-Kiljunen et al. 1992). Substances in pine resin and sap can cause allergic reactions in persons sensitive to balsam-of-Peru, colophony or turpentine. Resins, terpenes and oils may cause allergic contact dermatitis in workers handling unfinished wood. Dermal exposures to latex, sap and resin should be avoided through safe work practices and protective clothing.

The disease hypersensitivity pneumonitis is also known as “maple stripper’s lung”. It is caused by exposure to the spores of Cryptostroma corticate, a black mould that grows under the bark, during bark removal from stored maple. Progressive pneumonitis may also be associated with sequoia and cork oak woods. Controls include eliminating the sawing operation, wetting the material during debarking with a detergent and ventilation of the debarking area.



Read 3619 times Last modified on Saturday, 13 August 2011 19:15


Part I. The Body
Part II. Health Care
Part III. Management & Policy
Part IV. Tools and Approaches
Part V. Psychosocial and Organizational Factors
Part VI. General Hazards
Part VII. The Environment
Part VIII. Accidents and Safety Management
Part IX. Chemicals
Part X. Industries Based on Biological Resources
Agriculture and Natural Resources Based Industries
Farming Systems
Food and Fibre Crops
Tree, Bramble and Vine Crops
Specialty Crops
Beverage Crops
Health and Environmental Issues
Beverage Industry
Food Industry
Livestock Rearing
Paper and Pulp Industry
Part XI. Industries Based on Natural Resources
Part XII. Chemical Industries
Part XIII. Manufacturing Industries
Part XIV. Textile and Apparel Industries
Part XV. Transport Industries
Part XVI. Construction
Part XVII. Services and Trade
Part XVIII. Guides

Agriculture and Natural Resources Based Industries Additional Resources

Click the Button below to view additional resources for this topic.


Agriculture and Natural Resources Based Industries References

AgSafe—Coalition for Health and Safety in Agriculture. 1992. Occupational Injuries in California Agriculture 1981–1990. Berkeley, CA: University of California.

Alexandratos, N. 1995. World Agriculture: Towards 2010. An FAO Study. New York: John Wiley & Sons.

Bean, TL and TS Lawrence. 1992. Vehicles on Public Highways. National Institute for Farm Safety Paper No. 92-04.
Myrtle Beach, SC: National Institute for Farm Safety.

Bonsall, JL. 1985. Measurement of occupational exposure to pesticides. In Occupational Hazards of Pesticide Use, edited by GJ Turnbull. London: Taylor and Francis.

Boxer PA, C Burnett, and N Swanson. 1995. Suicide and occupation: A review of the literature. J Occup Med 37(4):442–452.

Bringhurst, LS, RN Byrne, and J Gershon-Cohen. 1959. Respiratory disease of mushroom workers. Farmer’s lung. JAMA 171:15–18.

Brown, LR, N Lenssen, and H Kane. 1995. Vital Signs 1995: The Trends that Are Shaping Our Future. New York: WW Norton & Company.

Bull, D. 1982. A Growing Problem: Pesticides and the Third World Poor. Washington DC: Oxfam.

Campbell, WP. 1987. The Condition of Agricultural Driveline System Shielding and Its Impact on Injuries and Fatalities. MS Thesis. West Lafayette, IN: Purdue University.

Chang, S. 1993. Mushroom biology: The impact on mushroom production and mushroom products. In Mushroom Biology and Mushroom Products, edited by S Chang, JA Buswell, and S Chiu. Hong Kong: Chinese University Press.

Christiani, DC. 1990. Occupational health in developing countries: Review of research needs. Am J Ind Med 17:393–401.

Connally LB, PA Schulte, RJ Alderfer, LM Goldenhar, GM Calvert, KE Davis-King, and WT Sanderson. 1996. Developing the National Institute for Occupational Safety and Health’s cancer control demonstration projects for farm populations. Journal of Rural Health suppl 12(4):258–264.

Cox, A, HTM Folgering, and LJLD Van Griensven. 1988. Extrinsic allergic alveolitis caused by the spores of the Oyster mushroom Pleurotus ostreatus. Eur Respir J 1:466–468.

—. 1989. Allergische Alveolitis verursacht durch Einatmung von Sporen des Pilzes Shii-take (Lentinus edodes). Atemwegs Lungenkr 15:233–234.

Dankelman, I and J Davidson. 1988. Women and Environment in the Third World: Alliance for the Future. London: Earthscan Publications.

Davies DR. 1995. Organophosphates, affective disorders, and suicide. Journal of Nutritional and Environmental Medicine 5:367–374.

Deere & Co. 1994. Farm and Ranch Safety Management. Moline, IL: Deere & Company.

Dufaut, A. 1988. Women carrying water: How it affects their health. Waterlines 6:23–25.

Eicher, LC. 1993. State Codes for Road Travel of Agricultural Machinery. American Society of Agricultural Engineering (ASAE) Paper No. 931513. St. Joseph, MI: ASAE.

Estlander T, L Kanerva and P Piirilä. 1996. Allergic dermatoses and respiratory diseases caused by decorative plants. Afr Newslttr Occup Health Saf 6(1):11–13.

Etherton, JR, JR Myers, RC Jensen, JC Russell, and RW Broddee. 1991. Agricultural machine-related deaths. Am J Public Health 81(6):776–768.

Food and Agriculture Organization (FAO) of the United Nations. 1987. African Agriculture: The Next 25 Years. Rome: FAO.

—. 1995. The State of World Fisheries and Aquaculture. Rome: FAO.

—. 1997. FAOSTAT Statistics Database (http://apps.fao.org/Default.htm). Accessed 22 January.

Forget, G. 1991. Pesticides and the third world. J Toxicol Environ Health 32:11–31.

—. 1992. Occupational health and development: An overview of the situation. IDRC Reports: Perils in the Workplace 20:4–7.

Franck IM and DM Brownstone. 1987. Harvesters. New York: Facts on File Publications.

Freivalds, A. 1984. Evaluation of the lift angle in spade work. Ergonomics 27 suppl:128–133.

Gerrits, JPG and LJLD Van Griensven. 1990. New developments in indoor composting (tunnel process). Mushroom J 205:21–29.

Gite, LP. 1991. Optimum handle height for animal drawn mould board plough. Appl Ergon 22:21–28.

Gite, LP and BG Yadav. 1990. Optimum handle height for a push-pull type manually operated dryland weeder. Ergonomics 33:1487–1494.

Glascock, LA, TL Bean, RK Wood, TG Carpenter, and RG Holmes. 1993. Characteristics of SMV Accidents. American Society of Agricultural Engineering (ASAE) Paper No. 931618. St. Joseph, MI: ASAE.

Griffin, GA. 1973. Combine Harvesting. Moline, IL: Deere & Company.

Gunderson, PD. 1995. An analysis of suicides on the farm or ranch within five north central United States, 1980 to 1988. In Agricultural Health and Safety: Workplace, Environment, Sustainability, edited by HH McDuffie, JA Dosman, KM Semchuk, SA Olenchock, and A Senthilselvan. Boca Raton, FL: CRC Press.

Hanrahan, LP, HA Anderson, LK Haskins, J Olson, K Lappe, and D Reding. 1996. Wisconsin farmer cancer mortality, 1981 to 1990: Selected malignancies. Journal of Rural Health suppl 12(4):273–277.

Hausen, BM, KH Schulz, and U Noster. 1974. Allergic disease caused by the spores of an edible fungus Pleurotus florida. Mushr Sci 9:219–225.

Horner, WE, MD Ibanez, V Liengswangwong, JE Salvaggio, and SB Lehrer. 1988. Characterization of allergens from spores of the Oyster mushroom Pleurotus ostreatus. J Allergy Clin Immunol 82:978–986.

International Labour Organization (ILO). 1994. Recent Developments in the Plantation Sector. Geneva: ILO.

International Organization for Standardization (ISO). 1985. ISO 263. Evaluation of Human Exposure to Whole-body Vibration: Part I: General Requirements. Geneva: ISO.

Jones, TH. 1978. How to Build Greenhouses, Garden Shelters, and Sheds. New York: Harper & Row.

Kelley, KA. 1996. Characteristics of flowing grain-related entrapments and suffocations with emphasis on grain transport vehicles. Journal of Agricultural Safety and Health 96(3):143–151.

Klincewicz, S, AT Fidler, G Siwinski, and A Fleeger. 1990. Health Hazard Report: Penick Corporation, Newark, New Jersey. No. HETA -87-311-2087. Cincinnati, OH: NIOSH.

Kundiev, YI. 1983. Conditions of labor in agriculture. In Occupational Diseases of Agricultural
Workers, edited by YI Kundiev and EP Krasnyu. Kiev: Zdorovye.

Loftas, T (ed.). 1995. Dimensions of Need: An Atlas of Food and Agriculture. Santa Barbara, CA: ABC-CLIO, Inc.

Makinen-Kiljunen, S, K Turjanmaa, T Palosuo, and T Reunala. 1992. Characterization of latex antigens and allergens in surgical gloves and natural rubber by immunoelectrophoretic methods. Journal Allergy Clin Immunol 90(2):230_235.

McDuffie, HH, JA Dosman, KM Semchuk, SA Olenchock, and A Senthilselvan (eds.). 1994. Agricultural Health and Safety: Workplace, Environment, Sustainability. Boca Raton, FL: CRC Press.

Merchant. JP, BA Boehlecke, G Taylor, and M Pickett-Harner (eds.). 1986. Occupational Respiratory Diseases. DHHS (NIOSH) Publication No. 86-102. Washington, DC: GPO.

Meridian Research, Inc. 1994. Occupational Safety and Health Hazards in Agriculture: A Review of the Literature. Silver Spring, MD: Meridian Research.

Meyers, JR. 1997. Injuries among Farm Workers in the United States, 1993. DHHS (NIOSH) Publication No. 97-115. Cincinnati, OH: NIOSH.

Meyers, JR and DL Hard. 1995. Work-related fatalities in the agricultural production and services sectors, 1980–1989. Am J Ind Med 27:51–63.

Miles, J. 1996. Personal communication.

Mines, R and PL Martin. 1986. A Profile of California Farmworkers. Giannini Information Series 86-2, Berkeley: University of California, Division of Agriculture and Natural Resources.

Mohan D and R Patel. 1992. Design of safer agricultural equipment: Application of ergonomics and epidemiology. Int J Ind Erg 10: 301–310.

Murphy, DJ and RC Williams. 1983. Safe Forage Harvesting. Agricultural Engineering Fact Sheet No. 21. State College, PA: Pennsylvania State University Cooperative Extension Service.

Murphy, DJ. 1992. Safety and Health for Production Agriculture. St. Joseph, MI: American Society of Agricultural Engineering.

Myers, ML. 1992. Sustainable Agriculture as a Strategy in Agricultural Safety. American Society of Agricultural Engineers (ASAE) Paper No. 928510. St. Joseph, MI: ASAE.

Nag, PK and SK Chatterjeee. 1981. Physiological reactions of female workers in Indian agricultural work. Hum Factors 23:607–614.

Nag, PK and P Dutt. 1979. Effectiveness of some simple agricultural weeders with reference to physiological responses. J Hum Ergol 8:13–21.

—. 1980. Circulo-respiratory efficiency in some agricultural work. Appl Ergon 11:81–84.

Nag, PK and CK Pradhan. 1992. Ergonomics in the hoeing operation. Int J Ind Erg 10:341–350.

Nag, PK, NC Sebastian, and MG Marlankar. 1980. Occupational workload of Indian agricultural workers. Ergonomics 23:91–102.

Nag, PK, A Goswami, SP Ashtekar, and CK Pradhan. 1988. Ergonomics in sickle operation. Appl Ergon 19:233–239.

Nakazawa, T, K Kanatani and Y Umegae. 1981. Mushroom workers lung due to the inhalation of spores of Cortinus shii-take. Jpn J Chest Dis 40:934–938.

National Committee for Childhood Agricultural Injury Prevention. 1996. Children and Agriculture: Opportunities for Safety and Health. Marshfield, WI: Marshfield Clinic.

National Research Council (NRC). 1989. Alternative Agriculture. Washington, DC: National Academy Press.

—. 1993. Sustainable Agriculture and the Environment in the Humid Tropics. Washington, DC: National Academy Press.

National Safety Council (NSC). 1942. Accident Facts. Chicago, IL: NSC.

—. 1986. Grain Harvest Safety. Chicago, IL: NSC.

—. 1993. Accident Facts. Chicago, IL: NSC.

—. 1995. Accident Facts. Chicago, IL: NSC.

Nomura, S. 1993. Studies on the work load and health management in agricultural workers. Journal of Japanese Association of Rural Medicine 42:1007–1011.

Olson, J.A. 1987. Pleurotus spores as allergens. Mushr J 172:115–117.

Organization for Economic Cooperation and Development (OECD). 1994. Farm Employment and Economic Adjustment in OECD Countries. Paris: OECD.

Parrón, T, AF Hernández, and E Villanueva. 1996. Increased risk of suicide with exposure to pesticides in an intensive agricultural area: A 12-year retrospective study. Forensic Science International 79:53–63.

Partanen, T. 1996. Improving the work environment by means of risk surveys. Afr Newslttr Occup Health Saf 6(2):28–29.

Pearce, N and JS Reif. 1990. Epidemiologic studies of cancer in agricultural workers. Am J Ind Med 18:133–148.

Pepys, J. 1967. Hypersensitivity against inhaled organic antigens. J Roy Coll Phys London 2:42–48.

Popendorf, W and KJ Donham. 1991. Agricultural hygiene. In Patty’s Industrial Hygiene and Toxicology, 4th edition, edited by GD Clayton and FE Clayton. New York: John Wiley & Sons, Inc.

Pradhan, CK, A Goswami, SK Ghosh, and PK Nag. 1986. Evaluation of working with spade in agriculture. Indian J Med Res 84:424–429.

Raffle, PAB, PH Adams, PJ Baxter, and WR Lee. 1994. Hunter’s Diseases of Occupations, 8th edition, London: Edward Arnold.

Recht, C and MF Wetterwald. 1992. Bamboos. Portland, OR: Timber Press.

Rowntree, RA. 1987. Contemplating the urban forests. In Our American Land: 1987 Yearbook of Agriculture. Washington, DC: USDA.

Rylander, R. 1986. Lung diseases caused by organic dusts in the farm environment. Am J Ind Med 10:221–227.

Sakula, A. 1967. Mushroom-worker’s lung. Brit Med J 3:708–710.

Sastre, J, MD Ibanez, M Lopez, and SB Lehrer. 1990. Respiratory and immunological reactions among Shii-take (Lentinus edodes) workers. Clin Exp Allergy 20:13–20.

Scherf, BD. 1995. World Watch List for Domestic Animal Diversity. Rome: FAO.

Sen, RN and PK Nag. 1975. Work organization of heavy load handling in India. J Hum Ergol 4:103–113.

Shutske, JM, WE Field, LD Gaultney, and SD Parsons. 1991. Agricultural machinery fire losses: A preventative approach. Applied Engineering in Agriculture 6(5):575–581.

Skillicorn, P, W Spira, and W Journet. 1993. Duckweed Aquaculture: A New Aquatic Farming System for Developing Countries. Washington, DC: World Bank.

Snyder, K and T Bobick. 1995. Safe Grain and Silage Handling. DHHS (NIOSH) Publication No. 95-109. Cincinnati, OH: NIOSH.

Sonnenberg, ASM, PCC Van Loon, and LJLD Van Griensven. 1996. Het aantal sporen dat Pleurotus
spp. in de lucht verspreidt (with an English summary). De Champignoncultuur 40:269–272.

Steinke, WE. 1991. Farm Labor, Tractor Use, and Farm Work Injury Survey. Unpublished data. Davis, CA: University of California.

Stewart, CJ. 1974. Mushroom worker’s lung—Two outbreaks. Thorax 29:252–257.

Stolz, JL, PH Arger, and JM Benson. 1976. Mushroom worker’s lung disease. Radiology 119:61–63.

Storch, G, JG Burford, RB George, L Kaufman, and L Ajello. 1980. Acute histoplasmosis: Description of an outbreak in Northern Louisiana. Chest 77(1):38–42.

Sullivan JB, M Gonzales, GR Krieger, and CF Runge. 1992. Health-related hazards of agriculture. In Hazardous Material Toxicology: Clinical Principles of Environmental Health, edited by JB Sullivan and GR Kreiger. London: Williams & Wilkins.

Tannahill, R. 1973. Food in History. New York: Stein and Day.

Toner, M. 1996. Debugging king cotton. Atlanta Journal-Constitution 47(50):G1.

United Nations Development Programme (UNDP). 1996. Urban Agriculture: Food, Jobs, and Sustainable Cities. New York: UNDP.

US Department of Agriculture (USDA). 1996. Foreign Agricultural Service Circular Series FTROP 2-96. Washington, DC: USDA.

US Department of Labor (DOL). 1968. Fair Labor Standards Act—The Hazardous Occupations Order for Agriculture. Washington, DC: US DOL.

US Department of State. 1996. International Narcotics Control Report. Washington, DC: US Department of State.

Van den Bogart, HGG. 1990. De champignonkwekerslong: een onderzoek naar voorkomen en etiologie in Nederland. PhD dissertation. Nijmegen, Netherlands: University of Nijmegen.

Van den Bogart, HGG, G Van den Ende, PGG Van Loon, and LJLD Van Griensven. 1993. Mushroom worker’s lung: serologic reactions to thermophilic actinomycetes in the air of compost tunnels. Mycopathologia 122:21–28.

Van Haaren, JPM. 1988. Occupational diseases. In The Cultivation of Mushrooms, edited by LJLD Van Griensven. Rustington, UK: Darlington Mushroom Laboratories.

Van Loon, PCC, AL Cox, OPJM Wuisman, SLGE Burgers, and LJLD Van Griensven. 1992. Mushroom worker’s lung. Detection of antibodies against shii take (Lentinus edodes) spore antigens in shii take workers. J Occup Med 34:1097–1101.

Villarejo, D. 1995. Issues for farm employees in the United States. In Agricultural Health and Safety: Workplace, Environment and Sustainability, edited by HH McDuffie, JA Dosman, KM Semchulk, SA Olenchock, and A Senthilselvan. Boca Raton, FL: CRC Press.

Viten VPh, EP Krashyyuh, and OV Ilyna. 1994. Ergonomic and health aspects of pesticide exposure in greenhouses. In Health, Safety and Ergonomic Aspects in Use of Chemicals in Agriculture and Forestry: Proceedings of the XII Joint GIGR; IAAMRH, IUFRP International Symposium, edited by Y Kundiev. Kiev: Institute for Occupational Health.

Wallerstein N and M Weinger. 1992. Health and safety education for worker empowerment. Am J Ind Med 22:619–635.

Weinger, J and M Lyons. 1992. Problem-solving in the fields: An action-oriented approach to farmworker education about pesticides. Am J Ind Med 22:677–690.

Weinger, M and N Wallerstein. 1990. Education for action: An innovative approach to training hospital employees. In Essentials of Modern Hospital Safety, edited by W Charney and J Whirmer. Chelsea, MI: Lewis Publishers.

Zejda. JE, HH McDuffie, and JA Dosman. 1993. Epidemiology of health and safety risks in agriculture and related industries: Practical applications for rural physicians. West J Med 158:56–63.