Legend tells us that tea may have been discovered in China by Emperor Shen-Nung, “The Divine Healer”. Observant of the fact that people who drank boiled water enjoyed better health, the wise Emperor insisted on this precaution. When adding branches to the fire, some tea leaves accidentally fell into the boiling water. The Emperor approved of the pleasing aroma and delightful flavour and tea was born.
From China, tea spread throughout Asia, soon becoming the national beverage of China and Japan. It was not until the 1600s that Europe became familiar with the beverage. Shortly thereafter, tea was introduced to North America. In the early 1900s, Thomas Sullivan, a New York wholesaler, decided to package tea in small silk bags rather than in tins. People started brewing the tea in the silk bag rather than removing its contents. Thus the tea bag was first introduced.
Tea is the world’s second most popular drink; only water is consumed more often. Consumers can choose from a wide variety of tea products—instant tea, iced tea mixes, specialty and flavoured teas, herbal teas, ready-to-drink teas decaffeinated teas and tea bags. The packaging of tea products has changed significantly; most of the small shops that once dispensed tea from wooden crates into individual tins have given way to sophisticated high-speed production lines which process, package, and/or bottle thousands of pounds of tea and ready-to-drink mixes per hour.
Process Overview
Production of tea bags consists of the blending of various cut and dried leaf teas from a number of regions around the world. Tea is usually received in wooden crates or large bags. The tea is blended and sent to tea packaging machines, where it is packaged either as individual tea bags or in bulk packages. Instant powdered tea requires blended tea in cut leaf form to be brewed using hot water. The liquid tea concentrate is then spray dried into a fine powder and placed in drums. The tea powder may be sent to the packaging lines where it is packaged into canisters or jars, or blended with other ingredients such as sugar or sugar substitutes. Flavouring such as lemon and other fruit flavors may also be added during the blending stage prior to packaging.
Hazards
There are a number of common safety hazards and health issues associated with the blending, processing and packaging of tea. Safety hazards such as machine guarding, noise, slips and falls and lifting-related injuries are quite common within the beverage industry. Other hazards, such as dust in the blending and packaging areas, are not usually found in wet-process bottling and canning operations.
Machine hazards
The blending and packaging of tea involves equipment and machinery where workers are exposed to chains and sprockets, belts and pullies, rotating shafts and equipment and high-speed packaging lines containing a number of dangerous pinch points. Most injuries are the result of lacerations and bruises to the fingers, hands or arms. Guarding of this equipment is critical to protect workers from getting caught in, under or between moving parts. Guards and/or interlocks should be installed to protect workers from moving parts where the potential of injury exists. Whenever a guard is removed (such as for maintenance), all energy sources should be isolated and maintenance and repair of equipment should be with an effective lockout/tagout programme in effect.
Dust hazards
Tea dust can be present in blending and packaging operations. Tea dust may also be present in high concentrations during clean-up or blow-down operations. Tea dust with a diameter greater than 10 micrometers can be classified as “nuisance dust”. Nuisance dust has little adverse effect on the lungs and should not produce significant organic disease or toxic effects when exposures are kept under reasonable control. Excessive concentrations of nuisance dust in the workroom air, however, may cause unpleasant deposits in the eyes, ears and nasal passages. Once inhaled, these particles may become entrapped in the nasal and pharyngeal region of the respiratory system, until they are expelled through the body’s own cleaning mechanisms (e.g., coughing or sneezing).
Respirable dust particulates are those that are less than 10 micro-meters in diameter and therefore small enough to pass through the nasal and pharyngeal regions and enter the lower respiratory tract. Once in the lungs, they may become embedded in the alveolar region, where scar tissue could develop. Respirable particulates can be respiratory irritants, especially in asthmatics. Effective seals and closures will help contain dust particles.
Exhaust ventilation or other types of dust-control equipment should be provided at the site of dust production to maintain dust levels below generally recognized standards (10 mg/m3) or other government regulations that may apply. Dust masks should be worn by workers who may be highly sensitive to dusts and by workers exposed to large concentrations of dust at any one time. Persons with chronic bronchitis or asthma are at higher risk. Workers who suffer from hypersensitivity to tea dust should be removed from the area.
Although there is little information on actual tea dust explosions, test data indicate that the explosion characteristics of tea dust are relatively weak. It appears that the greatest potential for a tea dust explosion exists with storage bins and dust collectors where concentrations and particle size are optimized. Minimizing dust concentration within a room or process will reduce the potential of a dust explosion. Electrical equipment designed for dust hazard areas may also be desirable in some operations.
Although tea and tea dust may not always burst into flames, large quantities of tea will almost always smoulder if ignited. Large quantities of water in a fine mist can be used to cool the smouldering tea below its ignition temperature.
Noise
As in most high-speed packaging operations, high noise levels are almost always present in the tea industry. High noise levels can be generated from vibrating blenders, air-operated and other packaging machines, air conveying systems, dust collectors and box cutters. The noise levels in many of these areas can range from 85 dBA to over 90 dBA. The major potential health hazard associated with exposure to noise lies in the possibility of producing permanent hearing loss. The severity of hearing loss is dependent on the noise levels within the workplace, duration of the exposure and the individual’s personal susceptibility. Noise and hearing conservation programmes are discussed further elsewhere in this Encyclopaedia.
Chemical hazards
Although most of the production processes and packaging operations do not expose workers to hazardous chemicals, sanitation operations use chemicals to clean and sanitize equipment. Some cleaning chemicals are handled in bulk quantities through fixed pipe systems, while other chemicals are applied by hand using predetermined mixtures. Exposure to these chemicals can cause respiratory problems, dermatitis or skin irritation and chemical burns to the skin. Severe burns to the eyes and/or loss of vision are also hazards associated with the handling of cleaning chemicals. Proper evaluations as to the hazards of the chemicals being used are essential. Proper selection and use of PPE should be part of routine job procedure. PPE such as splash-proof goggles or face shields, chemical-resistant gloves, aprons, boots and a respirator should be considered. Emergency eye and body wash stations should be provided where hazardous chemicals are either stored, mixed or used.
Material handling
Tea arrives on pallets in either bags or crates and is stored in warehouses to await blending and packaging. These bags and crates are moved either by hand or by material-handling devices such as fork-lifts or vacuum lifts. Once blended, the tea is conveyed to hoppers for packaging. Packaging operations can vary from using highly automated equipment to labour-intensive hand packaging operations (figure 1). Injuries to the lower back resulting from lifting tasks are quite common when handling bags weighing 100 pounds (45.5 kg) or more. Repetitive motions on packaging lines can result in cumulative trauma to the wrist, arm and/or shoulder area.
Figure 1. Packing of tea at the Brooke Bond tea and coffee factory in Dar-es-Salaam, Tanzania.
Mechanical devices such as vacuum lifts can aid in reducing heavy lifting tasks. Assigning two workers to a heavy lifting task can help reduce the chances of a serious back injury. Modifying work stations to be more ergonomically correct and/or automating equipment on packaging lines can reduce worker exposure to repetitive tasks. Rotating workers to light duty tasks can also reduce worker exposure to such tasks.
Personal aids such as back belts and wrist bands are also used by some workers to assist them in their lifting tasks or for temporary relief of minor strains. However, these have not been shown to be effective, and they may even be harmful.
Most warehouse operations require the use of fork-lift trucks. Failure to drive at safe speeds, sharp turns, driving with raised forks, failure to observe or yield to pedestrians and loading/ unloading accidents are the leading causes of injuries involving fork-lift operators. Only trained and competent operators should be permitted to drive fork-lifts. Training should consist of formal classroom training and a driving test where operators can demonstrate their skills. Proper maintenance and daily pre-use inspections also help ensure the safe operation of these vehicles.
Slips, trips and falls
Slips, trips and falls are a major concern. In dry blending and packaging operations, fine tea dust will accumulate on walking and working surfaces. Good housekeeping is important. Floors should be swept clean of tea dust on a regular basis. Debris and other items left on the floor should be picked up immediately. Slip-resistant, rubber-soled shoes appear to provide the best traction. Wet-process areas also provide slip and fall hazards. Floors should be kept as dry as possible. Adequate floor drainage should be provided within all wet-process areas. Standing water should not be permitted to accumulate. Where standing water exists, it should be mopped into floor drains.
Exposure to high temperatures
Contact with hot water, steam lines and process equipment can result in serious injury from burns. Most burns occur on the hands, arms and face. Hot water used for clean-up or wash-down has also been known to cause burns on feet and legs.
Heat sealers and glue operations on packaging lines also can cause burns. Guarding of exposed hot points on equipment is important. The proper evaluation of the hazards, and selection and use of personal protective equipment, will also help reduce or eliminate worker exposure to high temperatures and burns. Use of pipeline breaking and lockout procedures will protect workers from the unexpected release of hot liquids and steam.
Safe Practices
A general safety programme which addresses the use and selection of PPE, entry into confined spaces, isolation of energy sources, identification and communication of hazardous chemicals, self-inspection programmes, hearing conservation programmes, the control of infectious materials, process management and emergency response programmes should also be included as part of the work process. Training of workers in safe work practices is important in reducing worker exposure to hazardous conditions and injuries.