Weaving and knitting are the two primary textile processes for manufacturing fabrics. In the modern textile industry, these processes take place on electrically powered automated machines, and the resulting fabrics find their way into a wide range of end-uses, including wearing apparel, home furnishings and industrial applications.

Weaving

The weaving process consists of interlacing straight yarns at right angles to one another. It is the oldest technology of manufacturing fabric: hand-powered looms were used in pre-Biblical times. The basic concept of interlacing the yarns is still followed today.

Warp yarns are supplied from a large reel, called a warp beam, mounted at the back of the weaving machine. Each warp yarn end is threaded through a heddles harness. The harness is used to lift or depress the warp yarns to allow the weaving to be done. The simplest weaving requires two harnesses, and more intricate woven fabrics require as many as six harnesses. Jacquard weaving equipment is used to manufacture the most decorative fabrics and has features to enable each individual warp yarn to be lifted or depressed. Each yarn end then is threaded through a reed of closely spaced thin parallel metal pieces mounted on the machine’s lay, or sley. The lay is designed to move in a reciprocating arc around a pivotal anchor point. The yarn ends are attached to the take-up roll. The woven fabric is wound on this roll.

The oldest technology for feeding the filling yarn across the width of the warp yarns is the shuttle, which is propelled in a free-flight fashion from one side of the warp yarn to the other side and pays out the filling yarn from a small bobbin mounted in it. New and faster technology, shown in figure 1, called shuttleless weaving, uses air jets, water jets, small projectiles that ride in a guidetrack, or small, sword-like devices called rapiers to carry the filling yarn.

Figure 1. Air-jet weaving machines

Tsudakoma Corp

Employees in weaving are typically grouped into one of four job functions:

1. machine operators, commonly called weavers, who patrol their assigned production area to check on fabric production, correct some basic machine malfunctions such as yarn breaks and restart stopped machines
2. machine technicians, sometimes called fixers, who adjust and repair the weaving machines
3. direct production service workers, who transport and load raw materials (warp and filling yarn) onto the weaving machines and who unload and transport finished products (fabric rolls)
4. indirect production service workers, who perform cleaning, machine lubrication and so on.

Safety risks

Weaving presents only a moderate worker safety risk. However, there are a number of typical safety hazards and minimization measures.

Falls

Objects on the floor that cause worker falls include machine parts and oil, grease and water spots. Good housekeeping is particularly important in weaving, since many of the process workers spend most of their workday patrolling the area with eyes directed to the production process rather than toward objects on the floor.

Machinery

Power transmission devices and most other pinch points are typically guarded. The machine lay, harnesses and other parts that must be frequently accessed by weavers, however, are only partially enclosed. Ample walking and working space must be provided around the machines, and good work procedures help workers avoid these exposures. In shuttle weaving, guards mounted on the lay are needed to prevent the shuttle from being thrown out, or to deflect it in a downward direction. Lockouts, mechanical blocks and so on are also required in order to prevent the introduction of hazardous energy into areas when technicians or others are performing job duties on stopped machines.

Materials handling

These can include lifting and moving heavy cloth rolls, warp beams and so on. Hand-trucks to help unload, or doff, and transport small cloth rolls from take-ups on the weaving machine reduce the risk of worker strain injuries by alleviating the need to lift the full weight of the roll. Powered industrial trucks can be used to doff and transport large cloth rolls from bulk take-ups placed at the front of the weaving machine. Wheeled trucks with powered or manual hydraulic assists can be used to handle warp beams, which usually weigh several hundred kg. Warp-handling workers should wear safety shoes.

Fires and ignition

Weaving creates a fair amount of lint, dust and fibre flyings which can represent fire hazards if the fibres are combustible. Controls include dust-collection systems (located under the machines in modern facilities), regular machine cleanings by service workers and use of electrical equipment designed to prevent sparking (e.g., Class III, Division 1, Hazardous Locations).

Health risks

Health risks in modern weaving are generally limited to noise-induced hearing loss and to pulmonary disorders associated with some types of fibres used in the yarn.

Noise

Most weaving machines, operating in the numbers found in a typical production facility, produce noise levels that generally exceed 90 dBA. In some shuttle and high-speed shuttleless weaving, levels may even exceed 100 dBA. Appropriate hearing protectors and a hearing conservation programme are nearly always necessary for weaving workers.

Fibre dust

Pulmonary disorders (byssinosis) have long been linked with dusts associated with the processing of raw cotton and flax fibres, and are discussed elsewhere in this chapter and this Encyclopaedia. Generally, ventilation and room air filtration cleaning systems with dust collection points under the weaving machines and at other points in the weaving area maintain dusts at or below required maximum levels (e.g., 750 mg/m³ of air in the OSHA cotton dust standard) in modern facilities. Additionally, dust respirators are needed for temporary protection during cleaning activities. A worker medical surveillance programme should be in place to identify workers who might be especially sensitive to the effects of these dusts.

Machine Knitting

There is a major cottage industry for the production of hand-knitted items. There are inadequate data on numbers of workers, generally women, thus engaged. The reader is referred to the chapter Entertainment and the arts for an overview of likely hazards. Editor.

The mechanical knitting process consists of interconnecting loops of yarn on powered automated machines (see figure 2). The machines are equipped with rows of small, hooked needles to draw formed yarn loops through previously formed loops. The hooked needles have a unique latch feature that closes the hook to easily allow the loop drawing and then opens to allow the yarn loop to slide off the needle.

Figure 2. Circular-knitting machine

Sulzer Morat

Circular-knitting machines have needles arranged in a circle, and the fabric produced on them comes off the machine in the shape of a large tube that is wound onto a take-up roll. Flat-knitting machines and warp-knitting machines, on the other hand, have needles arranged in a straight row, and fabric comes off the machine in a flat sheet for roll take-up. Circular- and flat-knitting machines are generally fed from yarn cones, and warp-knitting machines are generally fed from warp beams that are smaller but similar to those used in weaving.

Employees in knitting are grouped into job functions with duties similar to those in weaving. Job titles appropriately parallel the process name.

Safety risks

Safety risks in knitting are similar to those in weaving though generally of a lesser degree. Oil on the floor often is a little more prevalent in knitting due to the high lubrication needs of the knitting needles. Machine entrapment risks are less in knitting since there are fewer pinch points on the machines than those found in weaving, and much of the machinery lends itself well to enclosure guarding. Energy-control lockout procedures remain a must.

Cloth roll handling still presents a worker strain injury risk, but the heavy warp-beam handling risks are not present except in warp knitting. Risk control measures are similar to those in weaving. Knitting does not produce the levels of lint, flyings and dust that are found in weaving, but the oil from the process helps keep the fire fuel load at a level that needs attention. Controls are similar to those in weaving.

Health risks

Health risks in knitting are also generally lower than those in weaving. Noise levels range in the mid-80-dBA to low-90-dBA levels. Respiratory disorders for knitting workers processing raw cotton and flax do not appear to be especially prevalent, and regulatory standards for these materials are often not applicable in knitting.

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The Carpet and Rug Institute

Hand-woven or hand-knotted carpets originated several centuries BC in Persia. The first US woven carpet mill was built in 1791 in Philadelphia. In 1839, the industry was reshaped with Erastus Bigelow’s invention of the power loom. The majority of carpet is machine-made in modern mills by one of two processes: tufted or woven.

Tufted carpet is now the predominant method of carpet production. In the United States, for example, approximately 96% of all carpet is machine tufted, a process that developed from tufted bedspread manufacturing centred in northwest Georgia. Tufted carpet is made by inserting a pile yarn into a primary backing fabric (usually polypropylene) and then attaching a secondary backing fabric with a synthetic latex to hold the yarns in place and attach the backings to each other, adding stability to the carpet.

Carpet Construction

Machine tufting

The tufting machine is comprised of hundreds of needles (up to 2,400) in a horizontal bar across the width of the machine (see figure 1). The creel, or yarn on cones arranged in racks, are passed overhead through small-diameter guide tubes to the machine needles on a jerker bar. Generally, two yarn spools are provided for each needle. The yarn end of the first spool is spliced together with the leading end of the second one, so that when yarn from the first spool has been used, yarn is supplied from the second without stopping the machine. A guide tube is provided for each yarn end, in order to prevent the yarns from becoming entangled. The yarns pass through a series of vertically aligned, fixed guides attached to the machine body and a guide located on the end of an arm extending from the moving needle bar of the machine. When the needle bar moves up and down, the relationship between the two guides is changed. Tufted product used for residential carpet is shown in figure 2.

Figure 1. Tufting machine

Carpet and Rug Institute

Figure 2. Residential carpet profile

Carpet and Rug Institute

The jerker bar takes up the slack yarn delivered during the upward stroke of the needles. The yarns are threaded through their respective needles in the needle bar. The needles are operated simultaneously at 500 or more strokes per minute in a vertical, reciprocating motion. A tufting machine can produce 1,000 to 2,000 square metres of carpet in 8 hours of operation.

The primary backing into which the yarns are inserted is supplied from a roll located in front of the machine. The speed of the roll of carpet backing controls the stitch length and the number of stitches per inch. The number of needles in the width per inch or cm of the machine determines the gauge of the fabric, such as 3/16 gauge or 5/32 gauge.

Located below the needle plate of the tufting machine are loopers or looper-and-knife combinations, which pick up and hold momentarily the yarns carried by the needles. When forming loop pile, loopers shaped like inverted hockey sticks are positioned in the machine so that the formed pile loops move away from the loopers as the backing is advanced through the machine.

Loopers for cut pile are a reversed “C” shape, with a cutting surface on the top inside edge of the crescent shape. They are used in combination with knives having a ground cutting edge on one end. As the backing advances through the machine toward the cut pile loopers, the yarns picked up from the needles are cut with a scissor-like action between the looper and knife cutting edge. Figure 3 and figure 4 show the tufts on a backing and the kinds of loops available.

Figure 3. Commercial carpet profile

Carpet and Rug Institute

Figure 4. Level loop; cut and loop; velvet plush; saxony

Carpet and Rug Institute

Weaving

Woven carpet has a pile surface yarn woven simultaneously with warp and weft threads that form the integrated backing. Backing yarns are usually jute, cotton or polypropylene. Pile yarns can be wool, cotton or any of the synthetic fibres, such as nylon, polyester, polypropylene, acrylic and so on. A back coating is applied to add stability; however, a secondary back is unnecessary and is rarely applied. Variations of woven carpet include velvet, Wilton and Axminster.

There are other methods of making carpet—knitted, needlepunched, fusion bonded—but those methods are used less often and for more specialized markets.

Fibre and Yarn Production

Carpet is manufactured primarily from synthetic yarns—nylon, polypropylene (olefin) and polyester—with lesser quantities of acrylic, wool, cotton and blends of any of these yarns. In the 1960s, synthetic fibres became predominant because they provide a durable, quality product in an affordable price range.

Synthetic yarns are formed by the extrusion of a molten polymer forced through the tiny holes of a metal plate, or spinneret. Additives to the molten polymer may provide solution-dyed colour or less transparent, whiter, more durable fibres and various other performance attributes. After the filaments emerge from the spinneret, they are cooled, drawn and texturized.

Synthetic fibres can be extruded in different shapes or cross-sections, such as round, trilobal, pentalobal, octalobal or square, depending upon the design and shape of the spinneret holes. These cross-sectional shapes can affect many properties of carpet, including lustre, bulkiness, texture retention, and soil-hiding abilities.

After fibre extrusion, post-treatments, such as drawing and annealing (heating/cooling), increase tensile strength and generally enhance the fibre’s physical properties. The filament bundle then goes through a crimping or texturing process, which converts straight filaments to fibres with a repeating kinked, curled or sawtooth configuration.

Yarn can be produced as either bulked continuous filament (BCF) or staple. The BCF is continuous strands of synthetic fibre formed into yarn bundles. Extruded yarn is made by winding the proper number of filaments for the desired yarn denier directly onto “take-up” packages.

Staple fibres are converted into spun yarns by textile yarn spinning processes. When staple fibre is produced, large bundles of fibre called “tow” are extruded. After the crimping process, the tow is cut into fibre lengths of 10 to 20 cm. There are three critical preparation steps—blending, carding and drafting—before the staple fibres are spun. Blending carefully mixes bales of staple fibre to ensure that the fibres intermingle in a way so that yarn streaking will not occur in subsequent dyeing operations. Carding straightens the fibres and puts them in a continuous sliver (rope-like) configuration. Drafting has three main functions: it blends fibres, places them in a parallel form and continues to decrease the weight per unit length of the total fibre bundle to make it easy to spin into the final yarn.

After spinning, which draws the sliver down to the desired yarn size, the yarn is plied and twisted to provide various effects. The yarn is then wound onto yarn cones to prepare it for the heat-setting and yarn-twisting processes.

Colouration Techniques

Because the synthetic fibres have various shapes, they take dyestuffs differently and may have varying colouration performance characteristics. Fibres of the same generic type can be treated or modified so that their affinity for certain dyes is changed, producing a multicolour or two-toned effect.

Colouration for carpet can be achieved at two possible times in the manufacturing process—either by dyeing the fibre or yarn before the fabric is tufted (pre-dyeing) or by dyeing the tufted fabric (post-dyeing of greige goods) before the application of the secondary backing and the finishing process. Methods of pre-dyeing include solution dyeing, stock dyeing and yarn dyeing. Post-dyeing methods include piece dyeing, the application of colour from an aqueous dye bath onto unfinished carpet; beck dyeing, which handles batches of greige goods of approximately 150 running metres; and continuous dyeing, a continuous process of dyeing almost unlimited quantities by distributing dye with an injection applicator across the full width of the carpet as it moves in open-width form under the applicator. Carpet printing uses machinery that is essentially enlarged, modified textile printing equipment. Both flat-bed and rotary-screen printers are used.

Carpet Finishing

Carpet finishing has three separate purposes: to anchor the individual tufts into the primary backing, to adhere the tufted primary backing to a secondary backing and to shear and clean the surface pile to give an attractive surface appearance. Adding a secondary backing material, such as woven polypropylene, jute or attached cushion material, adds dimensional stability to the carpet.

First, the back of the carpet is coated, usually by means of a roller rotating in a synthetic latex mix, and the latex is spread by a doctor blade. The latex is a viscous solution, usually from 8,000 to 15,000 centipose viscosity. Normally, between 22 and 28 ounces (625–795 g) of latex per square yard is applied.

A separate roll of secondary backing is positioned carefully onto the latex coating. The two materials are then carefully pressed together by a marriage roller. This laminate, remaining flat and unflexed, then passes through a long oven, usually 24 to 49 m long, where it is dried and cured at temperatures from 115 to 150 C for 2 to 5 minutes through three zones of heating. A high rate of evaporation is important for carpet drying, with forced hot air moving along precisely controlled heating zones.

In order to clean the surface yarns that may have developed fuzzing on the tips of the fibre during the dyeing and finishing stages, the carpet is lightly sheared. The shear is a unit that heavily brushes the carpet pile to make it both erect and uniform; it passes the carpet through a series of rotary knives or blades that shear or cut off the fibre tips at a precise, adjustable height. Two or four shear blades operate in tandem. The “double shear” has a double set of hard bristle or nylon brushes and two shear blade heads per unit, used in tandem.

The carpet goes through an intense inspection process and is packaged and stored, or cut, packaged and shipped.

Safe Practices in Carpet Mills

Modern carpet and yarn mills provide safety policies, monitoring of safety performance and, when necessary, prompt and thorough accident investigation. Carpet manufacturing machinery is well guarded to protect employees. Keeping the equipment serviced and safe is of primary importance for enhancing quality and productivity and for protection of the workers.

Workers should be trained in the safe use of electrical equipment and work practices to avoid injuries resulting from the unexpected start-up of machines. They need training to recognize hazardous energy sources, the type and magnitude of the energy available and the methods necessary for energy isolation and control. They also should be trained to distinguish exposed live parts from other parts of electrical equipment; to determine the nominal voltage of exposed, energized parts; and to know the required clearance distances and corresponding voltages. In areas where lockout/tagout will be in effect, employees are instructed in the prohibition against restarting or re-energizing equipment.

Where older equipment is in use, careful inspections should be frequent and upgrades made when advisable. Rotating shafts, v-belts and pulley drives, chain and sprocket drives, and overhead hoists and rigging should be periodically inspected, and guards installed whenever possible.

Because hand-pushed yarn buggies are used to move material in a yarn mill, and because yarn fly waste or lint (the scrap from yarn production) accumulates on the floor, the wheels of the yarn buggies must be kept clean and free to roll.

Employees should be trained in the safe use of compressed air, which is frequently used in clean-up procedures.

Fork-lift trucks, either electric- or propane-powered, are used throughout the carpet manufacturing and warehouse facilities. Proper maintenance and attention to safe refuelling, battery changing and so on are essential. Because fork-lift trucks are used where other personnel are working, various ways may be employed to avoid accidents (e.g., walkways reserved exclusively for workers, in which the trucks are prohibited); portable stop signs where employees are required to work in aisles with heavy fork-lift truck traffic; limiting the warehouse/shipping-dock areas to fork-lift truck operators and shipping personnel; and/or instituting a one-way traffic system.

Redesign of machines to minimize repetitive motions should help to reduce the incidence of repetitive-motion injuries. Encouraging workers to regularly practise simple hand and wrist exercises along with adequate work breaks and frequent changes in work tasks may also be helpful.

Musculoskeletal injuries from lifting and carrying may be reduced by the use of mechanical lifting devices, hand-trucks and rolling carts, and by stacking materials on platforms or tables and, where possible, keeping their bulk and weight to more easily manageable dimensions. Training in proper lifting techniques and muscle strengthening exercises can also be helpful, especially for workers returning after an episode of back pain.

A hearing conservation programme is advisable to avoid injury from the noise levels created in some mill operations. Sound-level surveys of the manufacturing equipment will identify those areas in which engineering controls are not sufficiently effective and in which workers may be required to wear hearing-protection equipment and have annual audiometric testing.

Contemporary standards of ventilation and exhaust of heat, lint and dust should be met by the mills.

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Adapted from 3rd edition, Encyclopaedia of Occupational Health and Safety.

All “oriental” carpets are hand woven. Many are made in family workplaces, with all the members of the household, often including very small children, working long days and often into the night on the loom. In some cases it is only a part-time occupation of the family, and in some areas the carpet weaving has been moved from the home into factories that are usually small.

Processes

The processes involved in the manufacture of a carpet are: yarn preparation, consisting of wool sorting, washing, spinning and dyeing; designing; and the actual weaving.

Yarn preparation

In some cases the yarn is received at the weaving place already spun and dyed. In others, the raw fibre, usually wool, is prepared, spun and dyed at the weaving place. After the sorting of the wool fibre into grades, usually done by women sitting on the floor, it is washed and spun by hand. The dyeing is carried out in open vessels using mostly aniline-based or alizarine dyestuffs; natural dyestuffs are no longer being used.

Designing and weaving

In handicraft weaving (or tribal weaving, as it is sometimes called), the designs are traditional, and no new designs need to be made. In industrial establishments employing a number of workers, however, there may be a designer who first sketches the design of a new carpet on a sheet of paper and then transfers it in colours onto squared paper from which the weaver can ascertain the number and arrangement of the various knots to be woven into the carpet.

In most cases the loom consists of two horizontal wooden rollers supported on uprights, one about 10 to 30 cm above floor level and the other about 3 m above it. The warp yarn passes from the top roller to the bottom roller in a vertical plane. There is usually one weaver working at the loom, but for wide carpets there may be as many as six weavers working side by side. In about 50% of the cases, the weavers squat on the floor in front of the bottom roller. In other cases, they may have a narrow horizontal plank on which to sit, which is raised up to 4 m above the floor as weaving proceeds. The weaver has to tie short pieces of woollen or silk yarn into knots around pairs of warp threads and then move the thread by hand across the whole length of the carpet. Picks of weft are beaten up into the fibre of the carpet by means of a beater or hand comb. The tufts of yarn protruding from the fibre are trimmed or cut down by scissors.

As the carpet is woven, it is usually wound onto the lower roller, which increases its diameter. When the workers squat on the floor, the position of the lower roller prevents them from stretching their legs, and as the diameter of the rolled-up carpet increases, they have to sit further back but must still lean forward to reach the position in which they tie in the knots of yarn (see figure 1). This is avoided when the weavers sit or squat on the plank, which may be raised as high as 4 m above the floor, but there may still not be enough room for their legs, and they are often forced into uncomfortable positions. In some instances, however, the weaver is provided with a back rest and a pillow (in effect, a legless chair), which may be moved horizontally along the plank as the work progresses. Recently, improved types of elevated looms have been developed that allow the weaver to sit on a chair, with ample room for his or her legs.

Figure 1. Squat loom

In some parts of the Islamic Republic of Iran, the warp in the carpet loom is horizontal instead of being vertical, and the worker sits on the carpet itself whilst working; this makes the task even more difficult.

Hazards of Carpet Weaving

As a largely cottage industry, carpet weaving is fraught with the hazards imposed by impoverished homes with small, crowded rooms that have poor lighting and inadequate ventilation. The equipment and processes are passed along from generation to generation with little or no opportunity for the education and training that might spark a break with the traditional methods. Carpet weavers are subject to skeletal deformations, eyesight disorders and mechanical and toxic hazards.

Skeletal deformation

The squatting position that the weavers must occupy on the old type of loom, and the need for them to lean forward to reach the place into which they knot the yarn, may, over time, lead to some very serious skeletal problems. These are often compounded by the nutritional deficiencies associated with poverty. Especially among those who start as young children, the legs may become deformed (genu valgum), or a crippling arthritis of the knee may develop. The constriction of the pelvis that sometimes occurs in females may make it necessary for them to have a Cesarean delivery when giving birth. Lateral curvature of the spinal column (scoliosis) and lordosis are also common maladies.

Vision disorders

The constant close focus on the point of weaving or knotting may cause considerable eyestrain, particularly when the lighting is inadequate. It should be noted that electric lighting is not available in many home workplaces, and the work, which is often continued into the night, must be performed by the light of oil lamps. There have been cases of almost total blindness occurring after only about 12 years of employment at this work.

Hand and finger disorders

The constant tying of small knots and the threading of the weft yarn through the warp threads may result in swollen finger joints, arthritis and neuralgia causing permanent disabilities of the fingers.

Stress

The high degree of skill and constant attention to detail over long hours are potent psychosocial stressors, which may be compounded by exploitation and harsh discipline. Children are often “robbed of their childhood”, while adults, who often lack the social contacts essential for emotional balance, may develop nervous illness manifested by trembling of the hands (which may hamper their work performance) and sometimes mental troubles.

Mechanical hazards

As no power machinery is used, there are practically no mechanical hazards. If the looms are not properly maintained, the wooden lever tensioning the warp may break and strike the weaver as it falls. This hazard may be avoided by using special thread tensioning gears.

Chemical hazards

The dyestuffs used, particularly if they contain potassium or sodium bichromate, may cause skin infections or dermatitis. There is also the risk from the use of ammonia, strong acids and alkalis. Lead pigments are sometimes used by designers, and there have been cases of lead poisoning due to their practice of smoothing the tip of the paintbrush by placing it between the lips; lead pigments should be replaced by non-toxic colours.

Biological hazards

There is a danger of anthrax infection from contaminated raw wool from areas where the bacillus is endemic. The appropriate governmental authority should ensure that such wool is properly sterilized before it is delivered to any workshops or factories.

Preventive Measures

The sorting of the raw material—wool, camel hair, goat hair and so on—should be done over a metal grid fitted with exhaust ventilation to draw any dust into a dust collector located outside the workplace.

The rooms in which the wool-washing and dyeing processes take place should be adequately ventilated, and the workers provided with rubber gloves and waterproof aprons. All waste liquors should be neutralized before being discharged into waterways or sewers.

Good lighting is required for the designing room and for weaving work. As noted above, inadequate light is a serious problem where there is no electricity and when the work is continued after sundown.

Perhaps the most important mechanical improvement would be mechanisms that raise the lower roller of the loom. This would obviate the necessity of weavers having to squat on the floor in an unhealthy and uncomfortable fashion and allow them to sit in a comfortable chair. Such an ergonomic improvement will not only improve the health of the workers but, once adopted, will increase their efficiency and productivity.

The workrooms should be kept clean and well ventilated, and properly boarded or covered floors substituted for earth floors. Adequate heating is required during cold weather. Manual manipulation of the warp places great strain on the fingers and may cause arthritis; wherever possible, hooked knives should be used for holding and weaving operations. Pre-employment and annual medical examinations of all workers are highly desirable.

Hand-tufted Carpets

The manufacture of carpets by the tying of knots of yarn by hand is a very slow process. The number of knots varies from 2 to 360 per square centimetre according to the quality of the carpet. A very large carpet with an intricate design may take over a year to make and involve the tying of hundreds of thousands of knots.

Hand tufting is an alternative method of rug manufacture. It uses a special kind of hand tool fitted with a needle through which the yarn is threaded. A sheet of coarse cotton cloth on which the design of the carpet has been traced is suspended vertically, and when the weaver places the tool against the cloth and presses a button, the needle is forced through the cloth and retracts, leaving a loop of yarn about 10 mm deep on the reverse side. The tool is moved horizontally about 2 or 3 mm, leaving a loop on the face of the cloth, and the trigger button is pressed again to form another loop on the reverse side. With acquired dexterity, as many as 30 loops on each side can be made in 1 minute. Depending on the design, the weaver has to stop from time to time to change the colour of yarn as called for in different parts of the pattern. When the looping operation has been finished, the carpet is taken down and placed reverse side up on the floor. A rubber solution is applied to the back and a covering or backing of stout jute canvas placed over it. The carpet is then placed face upwards and the protruding loops of yarn are trimmed by portable electric clippers. In some cases the design of the carpet is made by cutting or trimming the loops to varying depths.

Hazards in this type of carpet making are considerably less than in the manufacture of hand-knotted carpets. The operator usually sits on a plank in front of the canvas and has plenty of leg room. The plank is raised as the work proceeds. The weaver would be made more comfortable by provision of a backrest and a cushioned seat which could be moved horizontally along the plank as work proceeds. There is less visual strain, and no hand or finger movements that are likely to cause trouble.

The rubber solution used for this carpet usually contains a solvent which is both toxic and highly flammable. The backing process should be carried out in a separate workroom with good exhaust ventilation, at least two fire exits, and with no open flames or lights. Any electrical connections and equipment in this room should be certified as meeting sparkproof/flameproof standards. No more than a minimum amount of the flammable solution should be kept in this room, and appropriate fire extinguishers should be provided. A fire-resistant storage facility for the flammable solutions should not be situated inside any occupied building, but preferably in an open yard.

Legislation

In most countries, the general provisions of factory legislation cover the necessary standards required for the safety and health of workers in this industry. They may not be applicable, however, to family undertakings and/or home work, and they are difficult to enforce in the scattered small enterprises which, in the aggregate, employ many workers. The industry is notorious for the exploitation of its workers and for its use of child labour, often in defiance of existing regulations. A nascent worldwide trend (mid-1990s) among purchasers of hand-woven and tufted carpets to refrain from buying products produced by illegal or overly exploited workers will, it is hoped by many, eliminate such servitude.

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For nearly 300 years, work in the textile industry has been recognized as hazardous. Ramazzini (1964), in the early 18th century, described a peculiar form of asthma among those who card flax and hemp. The “foul and poisonous dust” which he observed “makes the workmen cough incessantly and by degrees brings on asthmatic troubles”. That such symptoms did in fact occur in the early textile industry was illustrated by Bouhuys and colleagues (1973) in physiological studies at Philipsburg Manor (a restoration project of life in the early Dutch colonies in North Tarrytown, New York, in the United States). While numerous authors throughout the 19th and early 20th centuries in Europe described the respiratory manifestations of work-related illness in textile mills with increasing frequency, the disease remained essentially unrecognized in the United States until preliminary studies in the middle of the 20th century under the direction of Richard Schilling (1981) indicated that, despite pronouncements to the contrary by both industry and government, characteristic byssinosis did occur (American Textile Reporter 1969; Britten, Bloomfield and Goddard 1933; DOL 1945). Many subsequent investigations have shown that textile workers around the world are affected by their work environment.

Historical Overview of Clinical Syndromes in the Textile Industry

Work in the textile industry has been associated with many symptoms involving the respiratory tract, but by far the most prevalent and the most characteristic are those of byssinosis. Many but not all vegetable fibres when processed to make textiles may cause byssinosis, as discussed in the chapter Respiratory system. The distinguishing feature of the clinical history in byssinosis is its relationship to the work week. The worker, typically after having worked a number of years in the industry, describes chest tightness beginning on Monday (or the first day of the work week) afternoons. The tightness subsides that evening and the worker is well for the remainder of the week, only to re-experience the symptoms on the following Monday. Such Monday dyspnoea may continue unchanged for years or may progress, with symptoms occurring on subsequent workdays, until chest tightness is present throughout the work week, and ultimately also while away from work on weekends and during vacation. When the symptoms become permanent, dyspnoea is described as effort dependent. At this stage a non-productive cough may be present. Monday symptoms are accompanied by across-shift decreases in lung function, which may be present on other workdays even in the absence of symptoms, but the physiological changes are not so marked (Bouhuys 1974; Schilling 1956). Baseline (Monday pre-shift) lung function deteriorates as the disease progresses. The characteristic respiratory and physiological changes seen in byssinotic workers have been standardized into a series of grades (see table 1) which currently form the basis of most clinical and epidemiological investigations. Symptoms other than chest tightness, particularly cough and bronchitis, are frequent among textile workers. These symptoms probably represent variants of the airway irritation brought on by dust inhalation.

Table 1. Grades of byssinosis

Source: Bouhuys 1974.

There is unfortunately no simple test capable of establishing the diagnosis of byssinosis. The diagnosis must be made on the basis of worker symptoms and signs as well as on the physician’s awareness of and familiarity with the clinical and industrial settings in which the disease is likely to occur. Lung function data, although not always specific, may be very helpful in establishing the diagnosis and in characterizing the degree of impairment.

In addition to classic byssinosis, textile workers are subject to several other symptom complexes; in general, these are associated with fever and not related to the initial day of the work week.

Mill fever (cotton fever, hemp fever) is associated with fever, cough, chills and rhinitis which occurs with the worker’s first contact with the mill or with return after a prolonged absence. Chest tightness does not appear to be associated with this syndrome. The frequency of these findings among workers is quite variable, from as low as 5% of the workers (Schilling 1956) to a majority of those employed (Uragoda 1977; Doig 1949; Harris et al. 1972). Characteristically, symptoms subside after a few days despite continued exposure in the mill. Endotoxin in vegetable dust is thought to be a causative agent. Mill fever has been associated with an entity now commonly described in industries using organic materials, the organic dust toxic syndrome (ODTS), which is discussed in the chapter Respiratory system.

“Weaver’s cough” is primarily an asthmatic condition characteristically associated with fever; it occurs in both new and senior workers. The symptoms (unlike mill fever) can persist for months. The syndrome has been associated with materials used to treat the yarn—for example, tamarind seed powder (Murray, Dingwall-Fordyce and Lane 1957) and locust bean gum (Vigliani, Parmeggiani and Sassi 1954).

The third non-byssinotic syndrome associated with textile processing is “mattress maker’s fever” (Neal, Schneiter and Caminita 1942). The name refers to the context in which the disease was described when it was characterized by an acute outbreak of fever and other constitutional symptoms, including gastrointestinal symptoms and retrosternal discomfort in workers who were using low-grade cotton. The outbreak was attributed to contamination of the cotton with Aerobacter cloacae.

In general, these febrile syndromes are thought to be clinically distinct from byssinosis. For example, in studies of 528 cotton workers by Schilling (1956), 38 had a history of mill fever. The prevalence of mill fever among workers with “classic” byssinosis was 10% (14/134), compared to 6% (24/394) among workers who did not have byssinosis. The differences were not statistically significant.

Chronic bronchitis, as defined by medical history, is very prevalent among textile workers, and in particular among non-smoking textile workers. This finding is not surprising since the most characteristic histological feature of chronic bronchitis is mucous gland hyperplasia (Edwards et al. 1975; Moran 1983). Chronic bronchitis symptomatology should be carefully distinguished from classic byssinosis symptoms, although byssinotic and bronchitic complaints frequently overlap and in textile workers are probably different pathophysiological manifestations of the same airway inflammation.

Pathology studies of textile workers are limited, but reports have shown a consistent pattern of disease involving the larger airways (Edwards et al. 1975; Rooke 1981a; Moran 1983) but no evidence suggestive of destruction of lung parenchyma (e.g., emphysema) (Moran 1983).

Clinical Course of Byssinosis

Acute versus chronic disease

Implicit in the grading system given in table 1 is a progression from acute “Monday symptoms” to chronic and essentially irreversible respiratory disease in workers with byssinosis. That such a progression occurs has been suggested in cross-sectional data beginning with the early study of Lancashire, United Kingdom, cotton workers, which found a shift toward higher byssinosis grades with increasing exposure (Schilling 1956). Similar findings have since been reported by others (Molyneux and Tombleson 1970). Moreover, this progression may begin relatively soon after employment (e.g., within the first few years) (Mustafa, Bos and Lakha 1979).

Cross-sectional data have also shown that other chronic respiratory symptoms and symptom complexes, such as wheeze or chronic bronchitis, are much more prevalent in older cotton textile workers than in similar control populations (Bouhuys et al. 1977; Bouhuys, Beck and Schoenberg 1979). In all cases the cotton textile workers have displayed more chronic bronchitis than the controls, even when adjusting for sex and smoking status.

Grade 3 byssinosis indicates that, in addition to symptoms, textile workers demonstrate changes in respiratory function. The progression from early byssinosis (grade 1) to late byssinosis (grade 3) is suggested by the association of lung function loss with the higher grades of byssinosis in cross-sectional studies of textile workers. Several of these cross-sectional studies have given support to the concept that across-shift changes in lung function (which correlate with the acute findings of chest tightness) are related to chronic irreversible changes.

Underlying the association between acute and chronic disease in textile workers is a dose-response relationship in acute symptoms, which was first documented by Roach and Schilling in a study reported in 1960. These authors found a strong linear relation between biological response and total dust concentrations in the workplace. Based on their findings they recommended 1 mg/m³ gross dust as a reasonably safe level of exposure. This finding was later adopted by the ACGIH and was, until the late 1970s, the value used as the threshold limit value (TLV) for cotton dust in the United States. Subsequent observations demonstrated that the fine dust fraction (<7 μm) accounted for practically all of the prevalence of byssinosis (Molyneux and Tombleson 1970; Mckerrow and Schilling 1961; McKerrow et al. 1962; Wood and Roach 1964). A 1973 study by Merchant and colleagues of respiratory symptoms and lung function in 1,260 cotton, 803 blend (cotton-synthetic) and 904 synthetic-wool workers was undertaken in 22 textile manufacturing plants in North Carolina (United States). The study confirmed the linear association between byssinosis prevalence (as well as decrements in lung function) and concentrations of lint-free dust.

The validation of changes in respiratory function suggested by cross-sectional studies has come from a number of longitudinal investigations which complement and extend the results of the earlier studies. These studies have highlighted the accelerated loss of lung function in cotton textile workers as well as the high incidence of new symptoms.

In a series of investigations involving several thousand mill workers examined in the late 1960s over a 5-year span of time, Fox and colleagues (1973a; 1973b) found an increase in byssinosis rates which correlated with years of exposure, as well as a sevenfold greater annual decrease in forced expired volume in 1 second (FEV₁) (as a per cent of predicted) when compared to controls.

A unique study of chronic lung disease in textile workers was initiated in the early 1970s by the late Arend Bouhuys (Bouhuys et al. 1977). The study was novel because it included both active and retired workers. These textile workers from Columbia, South Carolina, in the United States, worked in one of four local mills. The selection of the cohort was described in the original cross-sectional analysis. The original group of workers consisted of 692 individuals, but the analysis was restricted to 646 whites aged 45 years or older as of 1973. These individuals had worked an average of 35 years in the mills. The control group for the cross-sectional results consisted of whites aged 45 years and older from three communities studied cross-sectionally: Ansonia and Lebanon, Connecticut, and Winnsboro, South Carolina. In spite of geographic, socio-economic and other differences, the community residents did not differ in lung function from textile workers who held the least dusty jobs. Since no differences in lung function or respiratory symptoms were noted between the three communities, only Lebanon, Connecticut, which was studied in 1972 and 1978, was used as the control for the longitudinal study of textile workers studied in 1973 and in 1979 (Beck, Doyle and Schachter 1981; Beck, Doyle and Schachter 1982).

Both symptoms and lung function have been extensively reviewed. In the prospective study it was determined that the incidence rates for seven respiratory symptoms or symptom complexes (including byssinosis) were higher in textile workers than in controls, even when controlling for smoking (Beck, Maunder and Schachter 1984). When textile workers were separated into active and retired workers, it was noted that those workers retiring during the course of the study had the highest incidence rates of symptoms. These findings suggested that not only were active workers at risk for impairing respiratory symptoms but retired workers, presumably because of their irreversible lung damage, were at continuing risk.

In this cohort, loss of lung function was measured over a 6-year period. The mean decline for male and female textile workers (42 ml/yr and 30 ml/yr, respectively) was significantly greater than the decline in male and female controls (27 ml/yr and 15 ml/yr). When classified by smoking status, the cotton textile workers in general still had greater losses in FEV₁ than did the controls.

Many authors have previously raised the potential confounding issue of cigarette smoking. Because many textile workers are cigarette smokers, it has been claimed that the chronic lung disease associated with exposure to textile dust can in large part be attributed to cigarette smoking. Using the Columbia textile-worker population, this question was answered in two ways. One study by Beck, Maunder and Schachter (1984) used a two-way analysis of variance for all lung function measurements and demonstrated that the effects of cotton dust and smoking on lung function were additive—that is, the amount of lung function loss due to one factor (smoking or cotton dust exposure) was not changed by the presence or absence of the other factor. For FVC and FEV₁ the effects were similar in magnitude (average smoking history 56 pack-years, average mill exposure 35 years). In a related study, Schachter et al. (1989) demonstrated that using a parameter which described the shape of the maximum expiratory flow volume curve, angle beta, distinct patterns of lung function abnormalities could be shown for a smoking effect and for a cotton effect, similar to conclusions reached by Merchant earlier.

Mortality

Studies of cotton-dust exposure on mortality have not consistently demonstrated an effect. Review of experience in the late 19th and early 20th centuries in the United Kingdom suggested an excess of cardiovascular mortality in older textile workers (Schilling and Goodman 1951). By contrast, review of the experience in New England mill towns from late in the 19th century failed to demonstrate excess mortality (Arlidge 1892). Similar negative findings were observed by Henderson and Enterline (1973) in a study of workers who had been employed in Georgia mills from 1938 to 1951. By contrast, a study by Dubrow and Gute (1988) of male textile workers in Rhode Island who died during the period 1968 to 1978, showed a significant increase in proportionate mortality rate (PMR) for non-malignant respiratory disease. The elevations in PMR were consistent with increased dust exposure: carding, lapping and combing operatives had higher PMRs than did other workers in the textile industry. An interesting finding of this and other studies (Dubrow and Gute 1988; Merchant and Ortmeyer 1981) is the low mortality from lung cancer among these workers, a finding that has been used to argue that smoking is not a major cause of mortality in these groups.

Observations from a cohort in South Carolina suggest that chronic lung disease is indeed a major cause (or predisposing factor) for mortality, since among those workers aged 45 to 64 who died during a 6-year follow-up, lung function measured as residual FEV₁ (observed-to-predicted) showed marked impairment at the initial study (mean RFEV₁ = -0.9l) in male non-smokers who died during the 6-year follow-up (Beck et al. 1981). It may well be that the effect of mill exposure on mortality has been obscured by a selection effect (healthy worker effect). Finally, in terms of mortality, Rooke (1981b) estimated that of the average 121 deaths he observed annually among disabled workers, 39 had died as a result of byssinosis.

Increased Control, Decreased Disease

Recent surveys from the United Kingdom and the United States suggest that the prevalence as well as the pattern of lung disease seen in textile workers has been affected by the implementation of stricter air-quality standards in the mills of these countries. In 1996, Fishwick and his colleagues, for example, describe a cross-sectional study of 1,057 textile spinning operatives in 11 spinning mills in Lancashire. Ninety-seven per cent of the workforce was tested; the majority (713) worked with cotton and the remainder with synthetic fibre). Byssinosis was documented in only 3.5% of the operatives and chronic bronchitis in 5.3%. FEV₁, however, was reduced in workers exposed to high dust concentrations. These prevalences are much reduced from those reported in earlier surveys of these mills. This low prevalence of byssinosis and related bronchitis appears to follow the trend of decreasing dust levels in the United Kingdom. Both smoking habits and cotton dust exposures contributed to the lung function loss in this cohort.

In the United States, results of a 5-year prospective study of workers in 9 mills (6 cotton and 3 synthetic) was conducted between 1982 and 1987 by Glindmeyer and colleagues (1991; 1994), where 1,817 mill workers who were employed exclusively in cotton yarn manufacturing, slashing and weaving or in synthetics were studied. Overall, fewer than 2% of these workers were found to have byssinotic complaints. Nevertheless, workers in yarn manufacturing exhibited a greater annual loss of lung function than workers in slashing and weaving. The yarn workers exhibited dose-related lung function loss which was also associated with the grade of cotton used. These mills were in compliance with then current OSHA standards, and the mean airborne lint-free respirable cotton dust concentrations averaged over 8 hours were 196 mg/m³ in yarn manufacture and 455 mg/m³ in slashing and weaving. The authors (1994) related across-shift changes (the objective lung function equivalent of byssinotic symptoms) with longitudinal declines in lung function. Across-shift changes were found to be significant predictors of longitudinal changes.

While textile manufacture in the developed world appears now to be associated with less prevalent and less severe disease, this is not the case for developing countries. High prevalences of byssinosis can still be found worldwide, particularly where governmental standards are lax or non-existent. In his recent literature survey, Parikh (1992) noted byssinosis prevalences well above 20% in such countries as India, Cameroon, Ethiopia, Sudan and Egypt. In a study by Zuskin et al. (1991), 66 cotton textile workers were followed in a mill in Croatia where mean respirable dust concentrations remained at 1.0 mg/m³. Byssinosis prevalences doubled, and annual declines in lung function were nearly twice those estimated from prediction equations for healthy non-smokers.

Non-Respiratory Disorders Associated with Work in the Textile Industry

In addition to the well-characterized respiratory syndromes which can affect textile workers, there are a number of risks that have been associated with working conditions and hazardous products in this industry.

Oncongenesis has been associated with work in the textile industry. A number of early studies indicate a high incidence of colorectal cancer among workers in synthetic textile mills (Vobecky et al. 1979; Vobecky, Devroede and Caro 1984). A retrospective study of synthetic textile mills by Goldberg and Theriault (1994a) suggested an association with length of employment in the polypropylene and cellulose triacetate extrusion units. Other associations with neoplastic diseases were noted by these authors but were felt to be “not persuasive” (1994b).

Exposure to azo dyes have been associated with bladder cancer in numerous industries. Siemiatycki and colleagues (1994) found a weak association between bladder cancer and work with acrylic fibres and polyethylene. In particular, workers who dye these textiles were found to be at an increased risk. Long-term workers in this industry presented a 10-fold excess risk (marginal statistical significance) for bladder cancer. Similar findings have been reported by other authors, although negative studies are also noted (Anthony and Thomas 1970; Steenland, Burnett and Osorio 1987; Silverman et al. 1989).

Repetitive-motion trauma is a recognized hazard in the textile industry related to high-speed manufacturing equipment (Thomas 1991). A description of carpal tunnel syndrome (Forst and Hryhorczuk 1988) in a seamstress working with an electrical sewing machine illustrates the pathogenesis of such disorders. A review of hand injuries referred to the Regional Plastic Surgery Unit treating Yorkshire wool workers between 1965 and 1984 revealed that while there was a fivefold decrease in employment in this industry, the yearly incidence of hand injuries remained constant, indicating increased risk in this population (Myles and Roberts 1985).

Hepatic toxicity in textile workers has been reported by Redlich and colleagues (1988) as a result of exposure to the solvent dimethylformanide in a fabric-coating factory. This toxicity was recognized in the context of an “outbreak” of liver disease in a New Haven, Connecticut, factory that produces polyurethane-coated fabrics.

Carbon disulphide (CS₂) is an organic compound used in the preparation of synthetic textiles which has been associated with increased mortality from ischemic heart disease (Hernberg, Partanen and Nordman 1970; Sweetnam, Taylor and Elwood 1986). This may relate to its effects on blood lipids and diastolic blood pressure (Eyeland et al. 1992). Additionally, this agent has been associated with peripheral neurotoxicity, injury to sensory organs and disturbances in hormonal and reproductive function. It is generally believed that such toxicity results from long-term exposure to concentrations in excess of 10 to 20 ppm (Riihimaki et al. 1992).

Allergic responses to reactive dyes including eczema, uticaria and asthma have been reported in textile-dyeing workers (Estlander 1988; Sadhro, Duhra and Foulds 1989; Seidenari, Mauzini and Danese 1991).

Infertility in men and women has been described as a result of exposures in the textile industry (Rachootin and Olsen 1983; Buiatti et al. 1984).

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