The term footwear covers a vast range of products made from many different materials. Boots, shoes, sandals, slippers, clogs and so forth are made wholly or partly of leather, rubber, synthetic and plastics materials, canvas, rope and wood. This article deals with the footwear industry as generally understood (i.e., based on traditional manufacturing methods). The manufacture of rubber boots (or their synthetic equivalents) is essentially a section of the rubber industry, which is covered in the chapter Rubber industry.
Shoes, boots and sandals made from leather, felts and other materials have been made by hand over the centuries. Fine shoes are still made wholly or partly by hand, but in all the industrialized countries there are now large mass-production plants. Even so, some work may still be given out to be done as home work. Child labour continues as one of the more serious problems in the footwear industry, although several countries have taken action against child labour with the help of various international programmes in this area.
Boot and shoe plants usually locate close to leather-producing areas (i.e., near cattle-raising country); some slipper and light-shoe making developed where there was a plentiful supply of felts from the textile trade, and in most countries the industry tends to be localized in its original centres. Leathers of different type and quality, and some reptile skins, formed the original materials, with a tougher quality skin for the soles. In recent years leather has been increasingly displaced by other materials, in particular rubber and plastics. Linings may be made of wool or polyamide (nylon) fabric or sheepskin; laces are made of horsehair or synthetic fibres; paper, cardboard and thermoplastics are used for stiffening. Natural and coloured wax, aniline dyes and colouring agents are used in finishing.
Economic and other factors have transformed the footwear industry in recent years. Tennis shoe manufacturing is one of the major growth sectors of the industry and has moved from production in predominantly one country to worldwide production, especially in developing countries in Asia and South America, in order to increase production and reduce costs. This migration of production to developing countries has also occurred in other sectors of the footwear industry.
There may be over a hundred operations in the making of a shoe, and only a brief summary is possible here. Mechanization has been applied at all stages, but the pattern of the hand process has been closely followed. Introduction of new materials has modified the process without changing its broad outline.
In the making of the uppers (tops of shoes), the leather or other material is sorted and prepared, and the uppers are then cut out on stitching (or dinting) presses by shaped, loose-knife tools. The parts, including the linings, are then “closed” (i.e., sewn or stuck together). Perforating, eyeletting and button-holing may also be carried out.
For making the bottom stock, soles, insoles, heels and welts, pieces are cut out in revolving presses using loose-knife cutters, or in sole-moulding presses; heels are made by compression of leather or wood strips. The stock is trimmed, shaped, scoured and stamped.
The uppers and bottom stock are assembled and then stitched, glued, nailed or screwed together. These operations are followed by shaping and levelling between rollers. The final finishing of the shoe includes waxing, colouring, spraying, polishing and packaging.
Among the raw materials used in the manufacturing process, the most important from the point of view of occupational hazards are the adhesives. These include natural solid and liquid adhesives and adhesive solutions based on organic solvents.
Hazards and Their Prevention
The intensive use of flammable liquids constitutes a considerable fire hazard, and the widespread use of presses and assembling machines has introduced an increased risk of mechanical accidents into this industry. The main health hazards are toxic solvents, high atmospheric dust concentrations, ergonomic risks and noise from the machines.
The solvents and sprays used in adhesives and finishing materials may be highly flammable. Precautions include:
- using the lowest flash point solvents possible
- using good general ventilation and local exhaust ventilation in spray booths and drying racks to reduce the concentration of flammable vapours
- removing combustible residues from cabinets and workbenches and provide closed containers for solvent-containing and oily wastes
- maintaining unobstructed exits and gangways
- minimizing the amount of stored flammable liquids; keep them in approved containers, cabinets and storage rooms
- ensuring that all electrical equipment and wiring near flammable solvents meets appropriate electrical codes
- grounding adequately polishing machines and other sources of static electricity.
Many of the operating parts of the machines present serious hazards, in particular presses, stampers, rollers and knives. The loose-knife cutters at stitching and revolving presses can cause serious injury. The appropriate precautions minimally include two-hand controls (a photo-electric cell device for automatically cutting power may be preferable), the reduction of stroke rate to a safe level in relation to the size of the cutter, and the use of well-designed, stable cutters of adequate height, with flanges fitted perhaps with handles. Sole-moulding and heel presses should be guarded to prevent hand access. Stamping machines can cause burns as well as crushing injuries unless hand access is prevented by guarding. Nips of rollers and knives of milling and shaping machines should be fitted with suitable machinery guarding. The shading and polishing wheels of finishing machines and the spindles on which they are mounted should also be guarded. There should be an effective lockout/tagout programme for repair and maintenance work.
Organic solvents can cause acute and chronic effects on the central nervous system. Benzene, which was formerly used in adhesives and solvents, has been replaced by toluene, xylene, hexane, methyl ethyl ketone (MEK) and methyl butyl ketone (MBK). Both n-hexane and MBK can cause peripheral neuropathy and should be replaced by heptane or other solvents.
Outbreaks of a disease known popularly as “shoemakers’ paralysis” have appeared in a number of factories, presenting a clinical picture of a more or less severe form of paralysis. This paralysis is of the flaccid type, it is localized in the limbs (pelvic or thoracic) and gives rise to osteo-tendinous atrophy with areflexia and no alteration in superficial or deep sensitivity. Clinically, it is a syndrome resulting from functional inhibition or injury of the lower motor neurons of the voluntary motor system (pyramidal tract). The common outcome is neurological regression with extensive proximo-distal functional recuperation.
Good general ventilation and exhaust ventilation at the point of origin of the vapours should be provided to maintain concentrations well below maximum permissible levels. If these levels are observed, the fire risk will also be diminished. Minimizing the amount of solvent used, enclosure of solvent-using equipment and closing solvent containers are also important precautions.
Finishing machines produce dust, which should be removed from the atmosphere by exhaust ventilation. Some of the polishes, stains, colours and polychloroprene glues may carry a dermatitis risk. Good washing and sanitary facilities should be maintained and personal hygiene encouraged.
The increased intensive use of machines and equipment creates a significant noise hazard, necessitating source control of the noise or other preventive measures to prevent hearing loss. There should also be a hearing conservation programme.
Prolonged work on nailing machines which produce high levels of vibration may produce “dead hand” (Raynaud’s phenomenon). It is advisable to restrict the time spent at these machines.
Low-back pain and repetitive strain injuries are two musculoskeletal diseases that are major problems in the footwear industry. Ergonomic solutions are essential for prevention of these problems. Pre-placement and periodic medical examinations linked to workplace hazards are an effective factor for protection of employees’ health.
Environmental and Public Health Hazards
Earth Summit 1992, held in Rio de Janeiro, dealt with environmental concerns, and its proposals for future action, known as Agenda 21, could transform the footwear industry with its emphasis on recycling. In general, however, most waste materials are disposed of in landfills. Without proper precautions, this can result in contamination of the ground and groundwater.
Although home work has social advantages in decreasing unemployment and in the formation of cooperatives, the problems of ensuring proper precautions and working conditions in the home are enormous. In addition, other family members can be at risk if they are not already involved in the work. As discussed previously, child labour remains a serious problem.