Adapted from 3rd edition, “Encyclopaedia of Occupational Health and Safety”.
The manufacture of foodstuffs from starches and sugars is done in bakeries and biscuit-, pastry- and cake-making establishments. The safety and health hazards presented by the raw materials, the plant and equipment and the manufacturing processes in these plants are similar. This article deals with small-scale bakeries and covers bread and various related products.
There are three main stages in breadmaking—mixing and moulding, fermentation and baking. These processes are carried out in different work areas—the raw materials store, the mixing and moulding room, cold and fermentation chambers, the oven, the cooling room and the wrapping and packaging shop. The sales premises are frequently attached to the manufacturing shops.
Flour, water, salt and yeast are mixed together to make dough; hand mixing has been largely replaced by the use of mechanical mixing machines. Beating machines are used in the manufacture of other products. The dough is left to ferment in a warm, humid atmosphere, after which it is divided, weighed, moulded and baked (see figure 1).
Figure 1. Bread production for a supermarket chain in Switzerland
Small-scale production ovens are of the fixed-hearth type with direct or indirect heat transfer. In the direct type, the refractory lining is heated either intermittently or continuously before each charge. Off-gases pass to the chimney through the adjustable orifices at the rear of the chamber. In the indirect type, the chamber is heated by steam passing through tubes in the chamber wall or by forced hot-air circulation. The oven may be fired by wood, coal, oil, town gas, liquefied petroleum gas or electricity. In rural areas, ovens with hearths heated directly by wood fires are still found. Bread is charged into the oven on paddles or trays. The oven interior can be illuminated so that the baking bread can be observed through the chamber windows. During baking, the air in the chamber becomes charged with water vapour given off by the product and/or introduced in the form of steam. The excess usually escapes up the chimney, but the oven door may also be left open.
Hazards and Their Prevention
The working conditions in artisanal bakehouses can have the following features: night work starting at 2:00 or 3:00 a.m., especially in Mediterranean countries, where the dough is prepared in the evening; premises often infested with parasites such as cockroaches, mice and rats, which may be carriers of pathogenic micro-organisms (suitable construction materials should be used to ensure that these premises are maintained in an adequate state of hygiene); house-to-house bread delivery, which is not always carried out in adequate conditions of hygiene and which may entail an excess workload; low wages supplemented by board and lodging.
Premises are often old and dilapidated and lead to considerable safety and health problems. The problem is particularly acute in rented premises for which neither the lessor nor the lessee can afford the cost of renovation. Floor surfaces can be very slippery when wet, although reasonably safe when dry; non-slip surfaces should be provided whenever possible. General hygiene suffers owing to defective sanitary facilities, increased hazards of poisoning, explosions and fire, and the difficulty of modernizing heavy bakehouse plant owing to the terms of the lease. Small premises cannot be suitably divided up; consequently traffic aisles are blocked or littered, equipment is inadequately spaced, handling is difficult, and the danger of slips and falls, collisions with plant, burns and injuries resulting from overexertion is increased. Where premises are located on two or more storeys there is the danger of falls from a height. Basement premises often lack emergency exits, have access stairways which are narrow, winding or steep and are fitted with poor artificial lighting. They are usually inadequately ventilated, and consequently temperatures and humidity levels are excessive; the use of simple cellar ventilators at street level merely leads to the contamination of the bakehouse air by street dust and vehicle exhaust gases.
Knives and needles are widely used in artisanal bakeries, with a risk of cuts and puncture wounds and subsequent infection; heavy, blunt objects such as weights and trays may cause crush injuries if dropped on the worker’s foot.
Ovens present a number of hazards. Depending on the fuel used, there is the danger of fire and explosion. Flashbacks, steam, cinders, baked goods or uninsulated plant may cause burns or scalds. Firing equipment which is badly adjusted or has insufficient draw, or defective chimneys, may lead to the accumulation of unburnt fuel vapours or gases, or of combustion products, including carbon monoxide, which may cause intoxication or asphyxia. Defective electrical equipment and installations, especially of the portable or mobile type, may cause electric shock. The sawing or chopping of wood for wood-fired ovens may result in cuts and abrasions.
Flour is delivered in sacks weighing up to 100 kg, and these must often be lifted and carried by workers through tortuous gangways (steep inclines and staircases) to the storage rooms. There is the danger of falls while carrying heavy loads, and this arduous manual handling may cause back pain and lesions of intervertebral discs. The hazards may be avoided by: providing suitable access ways to the premises; stipulating a suitable maximum weight for sacks of flour; using mechanical handling equipment of a type suitable for use in small undertakings and at a price within the range of most artisanal workers; and by wider use of bulk flour transport, which is, however, suitable only when the baker has a sufficiently large turnover.
Flour dust is also a fire and explosion hazard, and proper precautions should be taken, including fire and explosion suppression systems.
In mechanized bakeries, dough which is in an active state of fermentation may give off dangerous amounts of carbon dioxide; thorough ventilation should therefore be provided in confined spaces wherever the gas is likely to accumulate (dough chutes and so on). Workers should be trained in confined-space procedures.
A wide variety of machines are used in bread manufacture, particularly in industrial bakeries. Mechanization can bring serious accidents in its wake. Modern bakery machines are usually equipped with built-in guards whose correct operation often depends upon the functioning of electrical limit switches and positive interlocks. Feed hoppers and chutes present special hazards which can be eliminated by extending the length of the feed opening beyond arm’s length to prevent the operator from reaching the moving parts; hinged double gates or rotary flaps are sometimes used as feeding devices for the same purpose. Nips on dough brakes can be protected by either fixed or automatic guards. A variety of guards (covers, grids and so on) can be used on dough mixers to prevent access to the trapping zone while permitting insertion of additional material and scraping of the bowl. Increasing use is made of bread-slicing and wrapping machines with alternating saw blades or rotary knives; all moving parts should be completely enclosed, interlocking covers being provided where access is necessary. There should be a lockout/tagout programme for maintenance and repair of machinery.
Bakehouse workers are usually lightly clothed and sweat profusely; they are subject to draughts and pronounced variations in ambient temperature when changing, for example, from oven charging to cooler work. Airborne flour dust may cause rhinitis, throat disorders, bronchial asthma (“baker’s asthma”) and eye diseases; sugar dust may cause dental caries. Airborne vegetable dust should be controlled by suitable ventilation. Allergic dermatitis may occur in persons with special predisposition. The above health hazards and the high incidence of pulmonary tuberculosis amongst bakers emphasize the need for medical supervision with frequent periodic examinations; in addition, strict personal hygiene is essential in the interests of both workers and the public in general.