There is no standard definition for the term herb, and the distinction between the herbs and spice plants is unclear. This article provides an overview of general aspects of some herbs. There are more than 200 herbs, which we are here considering to be those plants originally grown mainly in temperate or Mediterranean climates for their leaves, stems and flowering tops. The primary use for herbs is to flavour foods. Important culinary herbs include basil, bay or laurel leaf, celery seed, chervil, dill, marjoram, mint, oregano, parsley, rosemary, sage, savory, tarragon and thyme. The major demand for culinary herbs comes from the retail sector, followed by the food processing and food service sectors. The United States is by far the major consumer of culinary herbs, followed by the United Kingdom, Italy, Canada, France and Japan. Herbs are also used in cosmetics and pharmaceutical products to impart desirable flavours and odours. Herbs are used medicinally by the pharmaceutical industry and in the practice of herbal medicine.
Ginseng root is used in the practice of herbal medicine. China, the Republic of Korea and the United States are major producers. In China, most operations have historically been plantations owned and run by the government. In the Republic of Korea, the industry is made up of more than 20,000 family operations, most of which are smallholdings, family operations that plant less than an acre each year. In the United States, the largest proportion of producers work on smallholdings and plant less than two acres per year. However, the largest proportion of the US crop is produced by a minority of growers with a hired workforce and mechanization that allows them to plant as much as 60 acres per year. Ginseng is usually grown in open field plots covered by artificial shade structures that simulate the effects of the forest canopy.
Ginseng is also grown in intensively cultivated forest plots. A few per cent of the world’s production (and most organic ginseng) is gathered by wild collectors. The roots take 5 to 9 years to reach marketable size. In the United States, bed preparation for either forest plot or open field methods is typically accomplished by a tractor-towed plow. Some hand labour may be required to clear ditches and give the beds their final shape. Mechanized planters pulled behind a tractor are often used for seeding, although the more labour-intensive practice of transplanting nursery seedlings into beds is common in the Republic of Korea and China. Constructing the 7- to 8-foot-high pole and wood lath or cloth shade structures over open field plots is labour intensive and involves considerable lifting and overhead work. In Asia, locally available woods and thatch or woven reeds are used in the shade structures. In mechanized operations in the United States, mulching the plants is accomplished with straw shredders which are adapted from machines used in the strawberry industry and pulled behind a tractor.
Depending on the adequacy and condition of machine guarding, contact with the tractor PTO shaft, the straw shredder’s intake or other moving machinery parts can present a risk of entanglement injury. For each year until harvest, three hand weedings are required, which involve crawling, bending and stooping to work at crop level and which place high demands on the musculoskeletal system. Weeding, especially for the first- and second-year plants, is intensive work. One acre of field-grown ginseng may require more than 3,000 total hours of weeding over the 5 to 9 years preceding harvest. New chemical and non-chemical weed control methods, including better mulching, may be able to reduce the musculoskeletal demands posed by weeding. New tools and mechanization also hold promise for reducing the demands of weeding work. In Wisconsin, US, some herb growers are testing an adapted pedal cycle that allows weeding in a seated posture.
Artificial shade creates an especially humid environment susceptible to fungus and mould infestation. Fungicides are routinely applied at least monthly in the United States with tractor-towed application machinery or backpack garden sprayers. Insecticides are also spray applied as needed, and rodenticides put out. The use of lower-toxicity chemicals, improvements in application machinery and alternative pest management practices are strategies for reducing the repeated, low-dose pesticide exposures experienced by employees.
When the roots are ready for harvest, the shade structures are disassembled and stored. Mechanized operations utilize digging machinery adapted from the potato industry which is towed behind a tractor. Here again, inadequate machine guarding of the tractor PTO and moving machinery parts may present a risk of entanglement injuries. Picking, the last step in harvesting, involves hand labour and bending and stooping to gather roots from the soil surface.
On smaller holdings in the United States, China and the Republic of Korea, most or all of the steps in the production process are typically done by hand.
Mint and Other Herbs
There is considerable diversity in herb production methods, geographical locations, work methods and hazards. Herbs can be collected in the wild or grown under cultivation. Cultivated plant production has the advantages of greater efficiency, more consistent quality and timing of the harvest, and the potential for mechanization. Much of the mint and other herb production in the United States is highly mechanized. Soil preparation, planting, cultivation, pest control and harvesting are all done from the seat of a tractor with towed machinery.
Potential hazards resemble those in other mechanized crop production and include motor vehicle collisions on public roads, traumatic injuries involving tractors and machinery and agricultural chemical poisonings and burns.
More labour-intensive cultivation methods are typical in Asia, North Africa, the Mediterranean and other areas (e.g., mint production in China, India, the Philippines and Egypt). Plots are ploughed, often with animals, and then beds are prepared and fertilized by hand. Depending on the climate, a network of irrigation trenches is excavated. Depending on the type of herb produced, seeds, cuttings, seedlings or rhizome portions are planted. Periodic weeding is especially labour intensive and the day-long shifts of stooping, bending and pulling place high demands on the musculoskeletal system. Despite extensive use of manual labour, weed control in herb cultivation is sometimes inadequate. For a few crops, chemical weeding with herbicides, sometimes followed by manual weeding, is used, but herbicide use is not widespread since herb crops are often herbicide sensitive. Mulching crops can reduce weeding labour needs as well as conserve soil and soil moisture. Mulching also generally aids plant growth and yield, since mulch adds organic matter to soils as it decomposes.
Aside from weeding, labour-intensive soil preparation methods, planting, construction of shade or support structures, harvesting and other operations can also result in high musculoskeletal demands for prolonged periods. Modifications in production methods, specialized hand tools and techniques, and mechanization are possible directions to explore for reducing musculoskeletal and labour demands.
The potential for pesticide and other agricultural chemical burns and poisonings can be a concern on labour-intensive operations since backpack sprayers and other manual application methods may not prevent adverse exposures via the skin, mucous membranes or breathing air. Work in greenhouse production poses special hazards due to the confined breathing atmosphere. Substituting lower toxicity chemicals and alternative pest management strategies, improving application equipment and application practices, and making better PPE available may be ways to reduce risks.
The extraction of volatile oils from the harvested crop is common for certain herbs (e.g., mint stills). Cut and chopped plant material is loaded into an enclosed wagon or other structure. Boilers produce live steam which is forced into the sealed structure through low-pressure hoses, and the oil is floated and extracted from the resulting vapour.
Possible hazards associated with the process include burns from live steam and, less frequently, boiler explosions. Preventive measures include regular inspections of boilers and live steam lines to ensure structural integrity.
Herb production with low levels of mechanization may require prolonged close contact with plant surfaces and oils and, less often, associated dusts. Some reports are available in the medical literature of sensitization reactions, occupational dermatitis, occupational asthma and other respiratory and immunological problems associated with a number of herbs and spices. The available literature is small and may reflect underreporting rather than a low likelihood of health problems.
Occupational dermatitis has been associated with mint, laurel, parsley, rosemary and thyme, as well as cinnamon, chicory, cloves, garlic, nutmeg and vanilla. Occupational asthma or respiratory symptoms have been associated with dust from Brazilian ginseng and parsley as well as black pepper, cinnamon, cloves, coriander, garlic, ginger, paprika and red chillies (capsaicin), along with bacteria and endotoxins in dusts from grains and herbs. However, most cases have occurred in the processing industry, and only a few of these reports have described problems arising directly from exposures incurred in herb cultivation work (e.g., dermatitis after parsley picking, asthma after chicory root handling, immunologic reactivity after greenhouse work with paprika plants). In most reports, a proportion of the workforce develops problems while other employees are less affected or asymptomatic.
The herb and spice crop processing industry represents a higher order of magnitude exposure to certain hazards than herb crop cultivation. For example, the grinding, crushing and mixing of leaves, seeds and other plant materials can involve work in noisy, extremely dusty conditions. Hazards in herb processing operations include hearing loss, traumatic injuries from inadequately guarded moving machinery parts, dust exposures in breathing air, and dust explosions. Closed processing systems or enclosures for machinery can reduce noise. Feed openings of grinding machines should not permit the entry of hands or fingers.
Health conditions including skin diseases, irritation of the eyes, mouth and gastrointestinal tract, and respiratory and immunological problems have been linked to dusts, fungi and other air contaminants. Self selection based on ability to tolerate health effects has been noted in spice grinders, usually within the first 2 weeks of work. Segregation of the process, effective local exhaust ventilation, improved dust collection, regular mopping and vacuuming of work areas, and personal protective equipment can help reduce risks from dust explosions and contaminants in breathing air.