Definition and Scope

Ergonomics means literally the study or measurement of work. In this context, the term work signifies purposeful human function; it extends beyond the more restricted concept of work as labour for monetary gain to incorporate all activities whereby a rational human operator systematically pursues an objective. Thus it includes sports and other leisure activities, domestic work such as child care and home maintenance, education and training, health and social service, and either controlling engineered systems or adapting to them, for example, as a passenger in a vehicle.

The human operator, the focus of study, may be a skilled professional operating a complex machine in an artificial environment, a customer who has casually purchased a new piece of equipment for personal use, a child sitting in a classroom or a disabled person in a wheelchair. The human being is highly adaptable but not infinitely so. There are ranges of optimum conditions for any activity. One of the tasks of ergonomics is to define what these ranges are and to explore the undesirable effects which occur if the limits are transgressed—for example if a person is expected to work in conditions of excessive heat, noise or vibration, or if the physical or mental workload is too high or too low.

Ergonomics examines not only the passive ambient situation but also the unique advantages of the human operator and the contributions that can be made if a work situation is designed to permit and encourage the person to make the best use of his or her abilities. Human abilities may be characterized not only with reference to the generic human operator but also with respect to those more particular abilities that are called upon in specific situations where high performance is essential. For example, an automobile manufacturer will consider the range of physical size and strength of the population of drivers who are expected to use a particular model to ensure that the seats are comfortable, that the controls are readily identifiable and within reach, that there is clear visibility to the front and the rear, and that the internal instruments are easy to read. Ease of entry and egress will also be taken into account. By contrast, the designer of a racing car will assume that the driver is athletic so that ease of getting in and out, for example, is not important and, in fact, design features as a whole as they relate to the driver may well be tailored to the dimensions and preferences of a particular driver to ensure that he or she can exercise his or her full potential and skill as a driver.

In all situations, activities and tasks the focus is the person or persons involved. It is assumed that the structure, the engineering and any other technology is there to serve the operator, not the other way round.

History and Status

About a century ago it was recognized that working hours and conditions in some mines and factories were not tolerable in terms of safety and health, and the need was evident to pass laws to set permissible limits in these respects. The determination and statement of those limits can be regarded as the beginning of ergonomics. They were, incidentally, the beginning of all the activities which now find expression through the work of the International Labour Organization (ILO).

Research, development and application proceeded slowly until the Second World War. This triggered greatly accelerated development of machines and instrumentation such as vehicles, aircraft, tanks, guns and vastly improved sensing and navigation devices. As technology advanced, greater flexibility was available to allow adaptation to the operator, an adaptation that became the more necessary because human performance was limiting the performance of the system. If a powered vehicle can travel at a speed of only a few kilometres per hour there is no need to worry about the performance of the driver, but when the vehicle’s maximum speed is increased by a factor of ten or a hundred, then the driver has to react more quickly and there is no time to correct mistakes to avert disaster. Similarly, as technology is improved there is less need to worry about mechanical or electrical failure (for instance) and attention is freed to think about the needs of the driver.

Thus ergonomics, in the sense of adapting engineering technology to the needs of the operator, becomes simultaneously both more necessary and more feasible as engineering advances.

The term ergonomics came into use about 1950 when the priorities of developing industry were taking over from the priorities of the military. The development of research and application for the following thirty years is described in detail in Singleton (1982). The United Nations agencies, particularly the ILO and the World Health Organization (WHO), became active in this field in the 1960s.

In immediate postwar industry the overriding objective, shared by ergonomics, was greater productivity. This was a feasible objective for ergonomics because so much industrial productivity was determined directly by the physical effort of the workers involved—speed of assembly and rate of lifting and movement determined the extent of output. Gradually, mechanical power replaced human muscle power. More power, however, leads to more accidents on the simple principle that an accident is the consequence of power in the wrong place at the wrong time. When things are happening faster, the potential for accidents is further increased. Thus the concern of industry and the aim of ergonomics gradually shifted from productivity to safety. This occurred in the 1960s and early 1970s. About and after this time, much of manufacturing industry shifted from batch production to flow and process production. The role of the operator shifted correspondingly from direct participation to monitoring and inspection. This resulted in a lower frequency of accidents because the operator was more remote from the scene of action but sometimes in a greater severity of accidents because of the speed and power inherent in the process.

When output is determined by the speed at which machines function then productivity becomes a matter of keeping the system running: in other words, reliability is the objective. Thus the operator becomes a monitor, a trouble-shooter and a maintainer rather than a direct manipulator.

This historical sketch of the postwar changes in manufacturing industry might suggest that the ergonomist has regularly dropped one set of problems and taken up another set but this is not the case for several reasons. As explained earlier, the concerns of ergonomics are much wider than those of manufacturing industry. In addition to production ergonomics, there is product or design ergonomics, that is, adapting the machine or product to the user. In the car industry, for example, ergonomics is important not only to component manufacturing and the production lines but also to the eventual driver, passenger and maintainer. It is now routine in the marketing of cars and in their critical appraisal by others to review the quality of the ergonomics, considering ride, seat comfort, handling, noise and vibration levels, ease of use of controls, visibility inside and outside, and so on.

It was suggested above that human performance is usually optimized within a tolerance range of a relevant variable. Much of the early ergonomics attempted to reduce both muscle power output and the extent and variety of movement by way of ensuring that such tolerances were not exceeded. The greatest change in the work situation, the advent of computers, has created the opposite problem. Unless it is well designed ergonomically, a computer workspace can induce too fixed a posture, too little bodily movement and too much repetition of particular combinations of joint movements.

This brief historical review is intended to indicate that, although there has been continuous development of ergonomics, it has taken the form of adding more and more problems rather than changing the problems. However, the corpus of knowledge grows and becomes more reliable and valid, energy expenditure norms are not dependent on how or why the energy is expended, postural issues are the same in aircraft seats and in front of computer screens, much human activity now involves using videoscreens and there are well-established principles based on a mix of laboratory evidence and field studies.

Ergonomics and Related Disciplines

The development of a science-based application which is intermediate between the well-established technologies of engineering and medicine inevitably overlaps into many related disciplines. In terms of its scientific basis, much of ergonomic knowledge derives from the human sciences: anatomy, physiology and psychology. The physical sciences also make a contribution, for example, to solving problems of lighting, heating, noise and vibration.

Most of the European pioneers in ergonomics were workers among the human sciences and it is for this reason that ergonomics is well-balanced between physiology and psychology. A physiological orientation is required as a background to problems such as energy expenditure, posture and application of forces, including lifting. A psychological orientation is required to study problems such as information presentation and job satisfaction. There are of course many problems which require a mixed human sciences approach such as stress, fatigue and shift work.

Most of the American pioneers in this field were involved in either experimental psychology or engineering and it is for this reason that their typical occupational titles—human engineering and human factors—reflect a difference in emphasis (but not in core interests) from European ergonomics. This also explains why occupational hygiene, from its close relationship to medicine, particularly occupational medicine, is regarded in the United States as quite different from human factors or ergonomics. The difference in other parts of the world is less marked. Ergonomics concentrates on the human operator in action, occupational hygiene concentrates on the hazards to the human operator present in the ambient environment. Thus the central interest of the occupational hygienist is toxic hazards, which are outside the scope of the ergonomist. The occupational hygienist is concerned about effects on health, either long-term or short-term; the ergonomist is, of course, concerned about health but he or she is also concerned about other consequences, such as productivity, work design and workspace design. Safety and health are the generic issues which run through ergonomics, occupational hygiene, occupational health and occupational medicine. It is, therefore, not surprising to find that in a large institution of a research, design or production kind, these subjects are often grouped together. This makes possible an approach based on a team of experts in these separate subjects, each making a specialist contribution to the general problem of health, not only of the workers in the institution but also of those affected by its activities and products. By contrast, in institutions concerned with design or provision of services, the ergonomist might be closer to the engineers and other technologists.

It will be clear from this discussion that because ergonomics is interdisciplinary and still quite new there is an important problem of how it should best be fitted into an existing organization. It overlaps onto so many other fields because it is concerned with people and people are the basic and all-pervading resource of every organization. There are many ways in which it can be fitted in, depending on the history and objectives of the particular organization. The main criteria are that ergonomics objectives are understood and appreciated and that mechanisms for implementation of recommendations are built into the organization.

Aims of Ergonomics

It will be clear already that the benefits of ergonomics can appear in many different forms, in productivity and quality, in safety and health, in reliability, in job satisfaction and in personal development.

The reason for this breadth of scope is that its basic aim is efficiency in purposeful activity—efficiency in the widest sense of achieving the desired result without wasteful input, without error and without damage to the person involved or to others. It is not efficient to expend unnecessary energy or time because insufficient thought has been given to the design of the work, the workspace, the working environment and the working conditions. It is not efficient to achieve the desired result in spite of the situation design rather than with support from it.

The aim of ergonomics is to ensure that the working situation is in harmony with the activities of the worker. This aim is self-evidently valid but attaining it is far from easy for a variety of reasons. The human operator is flexible and adaptable and there is continuous learning, but there are quite large individual differences. Some differences, such as physical size and strength, are obvious, but others, such as cultural differences and differences in style and in level of skill, are less easy to identify.

In view of these complexities it might seem that the solution is to provide a flexible situation where the human operator can optimize a specifically appropriate way of doing things. Unfortunately such an approach is sometimes impracticable because the more efficient way is often not obvious, with the result that a worker can go on doing something the wrong way or in the wrong conditions for years.

Thus it is necessary to adopt a systematic approach: to start from a sound theory, to set measurable objectives and to check success against these objectives. The various possible objectives are considered below.

Safety and health

There can be no disagreement about the desirability of safety and health objectives. The difficulty stems from the fact that neither is directly measurable: their achievement is assessed by their absence rather than their presence. The data in question always pertain to departures from safety and health.

In the case of health, much of the evidence is long-term as it is based on populations rather than individuals. It is, therefore, necessary to maintain careful records over long periods and to adopt an epidemiological approach through which risk factors can be identified and measured. For example, what should be the maximum hours per day or per year required of a worker at a computer workstation? It depends on the design of the workstation, the kind of work and the kind of person (age, vision, abilities and so on). The effects on health can be diverse, from wrist problems to mental apathy, so it is necessary to carry out comprehensive studies covering quite large populations while simultaneously keeping track of differences within the populations.

Safety is more directly measurable in a negative sense in terms of kinds and frequencies of accidents and damage. There are problems in defining different kinds of accidents and identifying the often multiple causal factors and there is often a distant relationship between the kind of accident and the degree of harm, from none to fatality.

Nevertheless, an enormous body of evidence concerning safety and health has been accumulated over the past fifty years and consistencies have been discovered which can be related back to theory, to laws and standards and to principles operative in particular kinds of situations.

Productivity and efficiency

Productivity is usually defined in terms of output per unit of time, whereas efficiency incorporates other variables, particularly the ratio of output to input. Efficiency incorporates the cost of what is done in relation to achievement, and in human terms this requires the consideration of the penalties to the human operator.

In industrial situations, productivity is relatively easy to measure: the amount produced can be counted and the time taken to produce it is simple to record. Productivity data are often used in before/after comparisons of working methods, situations or conditions. It involves assumptions about equivalence of effort and other costs because it is based on the principle that the human operator will perform as well as is feasible in the circumstances. If the productivity is higher then the circumstances must be better. There is much to recommend this simple approach provided that it is used with due regard to the many possible complicating factors which can disguise what is really happening. The best safeguard is to try to make sure that nothing has changed between the before and after situations except the aspects being studied.

Efficiency is a more comprehensive but always a more difficult measure. It usually has to be specifically defined for a particular situation and in assessing the results of any studies the definition should be checked for its relevance and validity in terms of the conclusions being drawn. For example, is bicycling more efficient than walking? Bicycling is much more productive in terms of the distance that can be covered on a road in a given time, and it is more efficient in terms of energy expenditure per unit of distance or, for indoor exercise, because the apparatus required is cheaper and simpler. On the other hand, the purpose of the exercise might be energy expenditure for health reasons or to climb a mountain over difficult terrain; in these circumstances walking will be more efficient. Thus, an efficiency measure has meaning only in a well-defined context.

Reliability and quality

As explained above, reliability rather than productivity becomes the key measure in high technology systems (for instance, transport aircraft, oil refining and power generation). The controllers of such systems monitor performance and make their contribution to productivity and to safety by making tuning adjustments to ensure that the automatic machines stay on line and function within limits. All these systems are in their safest states either when they are quiescent or when they are functioning steadily within the designed performance envelope. They become more dangerous when moving or being moved between equilibrium states, for example, when an aircraft is taking off or a process system is being shut down. High reliability is the key characteristic not only for safety reasons but also because unplanned shut-down or stoppage is extremely expensive. Reliability is straightforward to measure after performance but is extremely difficult to predict except by reference to the past performance of similar systems. When or if something goes wrong human error is invariably a contributing cause, but it is not necessarily an error on the part of the controller: human errors can originate at the design stage and during setting up and maintenance. It is now accepted that such complex high-technology systems require a considerable and continuous ergonomics input from design to the assessment of any failures that occur.

Quality is related to reliability but is very difficult if not impossible to measure. Traditionally, in batch and flow production systems, quality has been checked by inspection after output, but the current established principle is to combine production and quality maintenance. Thus each operator has parallel responsibility as an inspector. This usually proves to be more effective, but it may mean abandoning work incentives based simply on rate of production. In ergonomic terms it makes sense to treat the operator as a responsible person rather than as a kind of robot programmed for repetitive performance.

Job satisfaction and personal development

From the principle that the worker or human operator should be recognized as a person and not a robot it follows that consideration should be given to responsibilities, attitudes, beliefs and values. This is not easy because there are many variables, mostly detectable but not quantifiable, and there are large individual and cultural differences. Nevertheless a great deal of effort now goes into the design and management of work with the aim of ensuring that the situation is as satisfactory as is reasonably practicable from the operator’s viewpoint. Some measurement is possible by using survey techniques and some principles are available based on such working features as autonomy and empowerment.

Even accepting that these efforts take time and cost money, there can still be considerable dividends from listening to the suggestions, opinions and attitudes of the people actually doing the work. Their approach may not be the same as that of the external work designer and not the same as the assumptions made by the work designer or manager. These differences of view are important and can provide a refreshing change in strategy on the part of everyone involved.

It is well established that the human being is a continuous learner or can be, given the appropriate conditions. The key condition is to provide feedback about past and present performance which can be used to improve future performance. Moreover, such feedback itself acts as an incentive to performance. Thus everyone gains, the performer and those responsible in a wider sense for the performance. It follows that there is much to be gained from performance improvement, including self-development. The principle that personal development should be an aspect of the application of ergonomics requires greater designer and manager skills but, if it can be applied successfully, can improve all the aspects of human performance discussed above.

Successful application of ergonomics often follows from doing no more than developing the appropriate attitude or point of view. The people involved are inevitably the central factor in any human effort and the systematic consideration of their advantages, limitations, needs and aspirations is inherently important.

Conclusion

Ergonomics is the systematic study of people at work with the objective of improving the work situation, the working conditions and the tasks performed. The emphasis is on acquiring relevant and reliable evidence on which to base recommendation for changes in specific situations and on developing more general theories, concepts, guidelines and procedures which will contribute to the continually developing expertise available from ergonomics.

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In the 3rd edition of the ILO’s Encyclopaedia, published in 1983, ergonomics was summarized in one article that was only about four pages long. Since the publication of the 3rd edition, there has been a major change in emphasis and in understanding of interrelationships in safety and health: the world is no longer easily classifiable into medicine, safety and hazard prevention. In the last decade almost every branch in the production and service industries has expended great effort in improving productivity and quality. This restructuring process has yielded practical experience which clearly shows that productivity and quality are directly related to the design of working conditions. One direct economical measure of productivity—the costs of absenteeism through illness—is affected by working conditions. Therefore it should be possible to increase productivity and quality and to avoid absenteeism by paying more attention to the design of working conditions.

In sum, the simple hypothesis of modern ergonomics can be stated thus: Pain and exhaustion cause health hazards, wasted productivity and reduced quality, which are measures of the costs and benefits of human work.

This simple hypothesis can be contrasted to occupational medicine which generally restricts itself to establishing the aetiology of occupational diseases. Occupational medicine’s goal is to establish conditions under which the probability of developing such diseases is minimized. Using ergonomic principles these conditions can be most easily formulated in the form of demands and load limitations. Occupational medicine can be summed up as establishing “limitations through medico-scientific studies”. Traditional ergonomics regards its role as one of formulating the methods where, using design and work organization, the limitations established through occupational medicine can be put into practice. Traditional ergonomics could then be described as developing “corrections through scientific studies”, where “corrections” are understood to be all work design recommendations that call for attention to be paid to load limits only in order to prevent health hazards. It is a characteristic of such corrective recommendations that practitioners are finally left alone with the problem of applying them—there is no multidisciplinary team effort.

The original aim of inventing ergonomics in 1857 stands in contrast to this kind of “ergonomics by correction”:

... a scientific approach enabling us to reap, for the benefit of ourselves and others, the best fruits of life’s labour for the minimum effort and maximum satisfaction (Jastrzebowski 1857).

The root of the term “ergonomics” stems from the Greek “nomos” meaning rule, and “ergo” meaning work. One could propose that ergonomics should develop “rules” for a more forward-looking, prospective concept of design. In contrast to “corrective ergonomics”, the idea of prospective ergonomics is based on applying ergonomic recommendations which simultaneously take into consideration profitability margins (Laurig 1992).

The basic rules for the development of this approach can be deduced from practical experience and reinforced by the results of occupational hygiene and ergonomics research. In other words, prospective ergonomics means searching for alternatives in work design which prevent fatigue and exhaustion on the part of the working subject in order to promote human productivity (“... for the benefit of ourselves and others”). This comprehensive approach of prospective ergonomics includes workplace and equipment design as well as the design of working conditions determined by an increasing amount of information processing and a changing work organization. Prospective ergonomics is, therefore, an interdisciplinary approach of researchers and practitioners from a wide range of fields united by the same goal, and one part of a general basis for a modern understanding of occupational safety and health (UNESCO 1992).

Based on this understanding, the Ergonomics chapter in the 4th edition of the ILO Encyclopaedia covers the different clusters of knowledge and experiences oriented toward worker characteristics and capabilities, and aimed at an optimum use of the resource “human work” by making work more “ergonomic”, that is, more humane.

The choice of topics and the structure of articles in this chapter follows the structure of typical questions in the field as practised in industry. Beginning with the goals, principles and methods of ergonomics, the articles which follow cover fundamental principles from basic sciences, such as physiology and psychology. Based on this foundation, the next articles introduce major aspects of an ergonomic design of working conditions ranging from work organization to product design. “Designing for everyone” puts special emphasis on an ergonomic approach that is based on the characteristics and capabilities of the worker, a concept often overlooked in practice. The importance and diversity of ergonomics is shown in two examples at the end of the chapter and can also be found in the fact that many other chapters in this edition of the ILO Encyclopaedia are directly related to ergonomics, such as Heat and Cold, Noise, Vibration, Visual Display Units, and virtually all chapters in the sections Accident and Safety Management and Management and Policy.

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The complex merchant vessels, passenger ships and ships of war of the 1990s comprise tons of steel and aluminium as well as a variety of materials that range from the most common to the very exotic. Each vessel may contain hundreds or even thousands of kilometres of pipe and wire equipped with the most sophisticated power plants and electronic equipment available. They must be constructed and maintained to survive the most hostile of environments, while providing comfort and safety for the crews and passengers aboard and reliably completing their missions.

Ship construction and repair rank among the most hazardous industries in the world. According to the US Bureau of Labor Statistics (BLS), for example, shipbuilding and repair is one of the three most hazardous industries. While materials, construction methods, tools and equipment have changed, improved radically over time and continue to evolve, and while training and emphasis on safety and health have significantly improved the lot of the shipyard worker, the fact remains that throughout the world each year workers die or are seriously injured while employed in the construction, maintenance or repair of ships.

Despite advances in technology, many of the tasks and conditions associated with constructing, launching, maintaining and repairing today’s vessels are essentially the same as they were when the very first keel was laid thousands of years ago. The size and shape of the components of a vessel and the complexity of the work involved in assembling and outfitting them largely preclude any kind of automated processes, although some automation has been made possible by recent technological advances. Repair work remains largely resistant to automation. Work in the industry is very labour intensive, requiring highly specialized skills, which often must be utilized under less than ideal circumstances and in a physically challenging situation.

The natural environment in itself poses a significant challenge for shipyard work. While there are a few shipyards that have the capability to construct or repair vessels under cover, in most cases shipbuilding and repairing is done largely out of doors. There are shipyards located in every climatic region of the world, and while the more extreme northern yards are dealing with winter (i.e., slippery conditions wrought by ice and snow, short daylight hours and the physical effects on workers of long hours on cold steel surfaces, often in uncomfortable postures), the yards in more southerly climes are faced with the potential for heat stress, sunburn, working surfaces hot enough to cook on, insects and even snake bites. Much of this work is done over, in, under or around the water. Often, swift tidal currents may be whipped by the wind, causing a pitching and rolling working surface on which workers must perform very exacting tasks in a variety of positions, with tools and equipment that have the potential for inflicting serious physical injury. That same often unpredictable wind is a force to be reckoned with when moving, suspending or placing units often weighing in excess of 1,000 tons with a single or multiple crane lift. The challenges presented by the natural environment are manifold and provide for a seemingly endless combination of situations for which safety and health practitioners must design preventive measures. A well-informed and trained workforce is critical.

As the ship grows from the first steel plates which comprise the keel, it becomes an ever-changing, ever-more-complex environment with a constantly changing subset of potential hazards and hazardous situations requiring not only well-founded procedures for accomplishing the work, but mechanisms for recognizing and dealing with the thousands of unplanned situations which invariably arise during the construction process. As the vessel grows, scaffolding or staging is added continuously to provide access to the hull. While the very construction of this staging is highly specialized and at times inherently hazardous work, its completion means that workers are subjected to greater and greater risk as the height of the staging over the ground or water increases. As the hull begins to take form, the interior of the ship is also taking shape as modern construction methods permit large subassemblies to be stacked on one another, and enclosed and confined spaces are formed.

It is at this point in the process that the labour-intensive nature of the work is most apparent. Safety and health measures must be well coordinated. Worker awareness (for the safety of both the individual worker and those nearby) is fundamental to accident-free work.

Each space within the confines of the hull is designed for a very specialized purpose. The hull may be a void which will contain ballast, or it may house tanks, cargo holds, sleeping compartments or a highly sophisticated combat control centre. In every case building it will require a number of specialized workers to perform a variety of tasks within close proximity of one another. A typical scenario may find pipefitters brazing valves into position, electricians pulling wire cable and installing circuit boards, brush painters doing touch-up, shipfitters positioning and welding deckplates, crews of insulators or carpenters and a test crew verifying that a system is activated in the same area at the same time. Such situations, and others even more complex, take place all day, every day, in an ever-changing pattern dictated by schedule or engineering changes, personnel availability and even the weather.

The application of coatings presents a number of hazards. Spray-painting operations must be accomplished, often in confined spaces and with volatile paints and solvents and/or a variety of epoxy-type coatings, notorious for their sensitizing characteristics.

Enormous progress in the area of safety and health for the shipyard worker has been made over the years through the development of improved equipment and construction methods, safer facilities and a highly-trained workforce. However, the greatest gains have been made and continue to be made as we turn our attention toward the individual worker and focus on eliminating behaviour which contributes so significantly to accidents. While this could be said of almost any industry, the labour-intensive character of shipyard work makes it especially important. As we move toward safety and health programmes which more actively involve the worker and incorporate his or her ideas, not only does the worker’s awareness of the hazards inherent in the job and how to avoid them increase, he or she begins to feel ownership for the programme. It is with this ownership that true success in safety and health can be realized.

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General Profile

Distinct segments of the automobile and transportation equipment industry produce:

• cars and light trucks
• medium and heavy trucks
• buses
• farm and construction equipment
• industrial trucks
• motorcycles.

The characteristic assembly line for the finished vehicle is supported by separate manufacturing facilities for various parts and components. Vehicle components may be manufactured within the parent enterprise or purchased from separate corporate entities. The industry is a century old. Production in the North American, European and (since the Second World War) Japanese sectors of the industry became concentrated in a few corporations which maintained branch assembly operations in South America, Africa and Asia for sales to those markets. International trade in finished vehicles has increased since the 1970s, and trade in original equipment and replacement auto parts from facilities in the developing world is increasingly important.

Manufacture of heavy trucks, buses and farm and construction equipment are distinct businesses from car production, although some auto producers manufacture for both markets, and farm and construction equipment are also made by the same corporations. This line of products uses large diesel engines rather than gasoline engines. Production rates are typically slower, volumes smaller and processes less mechanized.

The types of facilities, the production processes and the typical components in car production are shown in table 1. Figure 1provides a flow chart for the steps in automobile production. The standard industrial classifications that are found in this industry include: motor vehicles and car body assembly, truck and bus body assembly, motor vehicle parts and accessories, iron and steel foundries, non-ferrous foundries, automotive stampings, iron and steel forgings, engine electrical equipment, auto and apparel trimmings and others. The number of people employed in the manufacture of parts exceeds that employed in assembly. These processes are supported by facilities for design of the vehicle, construction and maintenance of plant and equipment, clerical and managerial functions and a dealer and repair function. In the United States, car dealers, service stations and wholesale auto parts facilities employ about twice as many workers as the manufacturing functions.

Table 1. Production processes for automobile production.  

Figure 1. Flow chart for automobile production. 

The workforce is predominantly male. In the United States, for example, it is about 80% male. Female employment is higher in trim and other lighter manufacturing processes. There is limited opportunity for job transfer from hourly work to clerical work or to technical and professional employment. Assembly line supervisors do, however, often come from the production and maintenance units. About 20% of hourly employees are employed in the skilled trades, although the fraction of employees in any particular facility who are in skilled trades varies greatly, from less than 10% in assembly operations to almost 50% in stamping operations. Because of contractions in employment levels over the decade of the 1980s, the average age of the workforce in the late 1990s exceeds 45 years, with hiring of new workers appearing only since 1994.

Major Sectors and Processes

Ferrous casting

Founding or metal casting involves the pouring of molten metal into a hollow inside a heat-resistant mould, which is the outside or negative shape of the pattern of the desired metal object. The mould may contain a core to determine the dimensions of any internal cavity in the final metal object. Foundry work consists of the following basic steps:

• making a pattern of the desired article from wood, metal, plastic or some other material
• making the mould by pouring sand and a binder around the pattern and compacting or setting it
• removing the pattern, inserting any core and assembling the mould
• melting and refining the metal in a furnace
• pouring the molten metal into the mould
• cooling the metal casting
• removing the mould and core from the metal casting by the “punch-out” process (for small castings) and by vibrating screens (shakeout) or hydro-blasting
• removing extra metal (e.g., the metal in the sprue—the pathway for molten metal to enter the mould) and burnt-on sand from the finished casting (fettling) by blasting with steel shot, hand chipping and grinding.

Ferrous foundries of the production type are a characteristic auto industry process. They are used in the automobile industry to produce engine blocks, heads and other parts. There are two basic types of ferrous foundries: gray iron foundries and ductile iron foundries. Gray iron foundries use scrap iron or pig iron (new ingots) to make standard iron castings. Ductile iron foundries add magnesium, cerium or other additives (often called ladle additives) to the ladles of molten metal before pouring to make nodular or malleable iron castings. The different additives have little impact on workplace exposures.

Typical automobile foundries use cupola or induction furnaces to melt the iron. A cupola furnace is a tall vertical furnace, open at the top, with hinged doors at the bottom. It is charged from the top with alternate layers of coke, limestone and metal; the molten metal is removed at the bottom. An induction furnace melts the metal by passing a high electric current through copper coils on the outside of the furnace. This induces an electric current in the outer edge of the metal charge, which heats the metal due to the high electrical resistance of the metal charge. Melting progresses from the outside of the charge to the inside.

In ferrous foundries, moulds are traditionally made from green sand (silica sand, coal dust, clay and organic binders), which is poured around the pattern, which is usually in two parts, and then compacted. This can be done manually or mechanically on a conveyor belt in production foundries. The pattern is then removed and the mould assembled mechanically or manually. The mould must have a sprue.

If the metal casting is to have a hollow interior, a core must be inserted into the mould. Cores can be made from thermosetting phenol-formaldehyde resins (or similar resins) mixed with sand which is then heated (hot box method) or from amine-cured urethane/sand mixtures which cure at room temperature (cold box method). The resin/sand mixture is poured into a core box which has a cavity in the desired shape of the core.

The products produced in gray iron castings are typically of a large size, such as engine blocks. The physical size increases the physical hazards on the job and also presents more difficult dust control problems.

Atmospheric contaminants in foundry processes

Silica-containing dusts. Silica-containing dusts are found in finishing, in shakeout-knockout, in moulding, in core making and in sand system and melt department maintenance activities. Air sampling studies during the 1970s typically found severalfold overexposures to silica, with the highest levels in finishing. Exposures were higher in mechanized production foundries than job shops. Improved control measures including enclosure and exhaust of sand systems and shakeout, mechanization and periodic industrial hygiene measurements have reduced levels. Standard ventilation designs are available for most foundry operations. Exposures above current limits persist in finishing operations due to inadequate sand removal after shakeout and silica burn-in on casting surfaces.

Carbon monoxide. Acutely dangerous carbon monoxide levels are encountered during cupola furnace maintenance and during upsets in process ventilation in the melt department. Excessive levels can also be encountered in cooling tunnels. Carbon monoxide exposures have also been associated with cupola melting and with the combustion of carbon material in green sand moulds. Exposure to sulphur dioxide of unknown origin can also occur, perhaps from sulphur contaminants in the mould.

Metal fumes. Metal fumes are found in melting and pouring operations. It is necessary to use compensating hoods over pouring stations in order to exhaust both metal fumes and combustion gases. Excessive exposures to lead fumes are occasionally encountered in iron foundries and are pervasive in brass foundries; lead fumes in gray iron arise from lead contamination of the scrap iron starting materials.

Other chemical and physical hazards. Formaldehyde, amine vapours and isocyanate pyrolysis products can be found in coremaking and core burn-off products. High-production coremaking is characteristic of the auto industry. Hot box phenol-formaldehyde coremaking replaced oil-sand cores in the mid-1960s and brought substantial formaldehyde exposures, which, in turn, increased the risks of respiratory irritation, lung function abnormalities and lung cancer. Protection requires local exhaust ventilation (LEV) at the core machine, core check stations and conveyor and low emission resins. When the phenol-formaldehyde coremaking has been replaced by cold box amine-cured polyurethane systems, effective maintenance of seals at the core box, and LEV where the cores are stored prior to insertion in the mould, are needed to protect employees against ocular effects of amine vapours.

Workers who are employed in these areas should undergo pre-placement and periodic medical examinations, including a chest x ray reviewed by an expert reader, a lung function test and a symptoms questionnaire, which are essential to detect early signs of pneumoconiosis, chronic bronchitis and emphysema. Periodic audiograms are needed, as hearing protection is often ineffective.

High levels of noise and vibration are encountered in processes such as furnace loading, mechanical de-coring, stripping and knockout of castings and fettling with pneumatic tools.

Foundry processes are heat intensive. The radiant heat load in melting, pouring, shakeout, core knockout and sprue removal requires special protective measures. Some of these measures include increased relief time (time away from the job), which is a common practice. Still extra relief during hot, summer months is also commonly provided. Workers should be outfitted with heat-protective clothing and eye and face protection in order to prevent the formation of cataracts. Climatized break areas near the work area improve the protective value of heat relief.

Aluminium casting

Aluminium casting (foundry and die-casting) is used to produce cylinder heads, transmission cases, engine blocks and other automotive parts. These facilities typically cast the products in permanent moulds, with and without sand cores, although the lost foam process has been introduced. In the lost foam process, the polystyrene foam pattern is not removed from the mould but is vaporized by the molten metal. Die casting involves the forcing of molten metal under pressure into metal moulds or dies. It is used to make large numbers of small, precise parts. Die-casting is followed by trim removal on a forge press and some finishing activities. Aluminium may be melted onsite or it can be delivered in molten form.

Hazards can arise because of significant pyrolysis of the core. Silica exposures may be found in permanent mould foundries where large cores are present. Local exhaust on shakeout is needed to prevent hazardous levels of exposure.

Other non-ferrous casting

Other non-ferrous die casting and electroplating processes are used to produce the trim on automotive products, the hardware and the bumpers. Electroplating is a process in which a metal is deposited onto another metal by an electrochemical process.

Bright metal trim traditionally was die-cast zinc, successively plated with copper, nickel and chrome, and then finished by polishing. Carburettor and fuel-injector parts are also die cast. Manual extraction of parts from die-casting machines is increasingly being replaced by mechanical extraction, and bright metal parts are being replaced by painted metal parts and plastic. Bumpers had been produced by pressing steel, followed by plating, but these methods are increasingly being replaced by the use of polymer parts in passenger vehicles.

Electroplating with chrome, nickel, cadmium, copper and so on is normally carried out in separate workshops and involves exposure to, inhalation of or contact with vapours from the acid plating baths. An increased incidence of cancer has been associated with both chromic acid and sulphuric acid mists. These mists are also extremely corrosive to the skin and respiratory tract. Electroplating baths should be labelled as to contents and should be fitted with special push-pull local exhaust systems. Anti-foaming surface tension agents should be added to the liquid in order to minimize mist formation. Workers should wear eye and face protection, hand and arm protection and aprons. Workers need periodic health checks as well.

Inserting and removing components from open-surface tanks are very hazardous operations which are increasingly becoming more mechanized. The buffing and polishing of plated components on felt belts or discs is strenuous and entails exposure to cotton, hemp and flax dust. This hazard can be minimized by providing a fixture or by mechanizing with transfer-type polishing machines.

Forging and heat treatment

Hot forging and cold forging followed by heat treatment are used to produce engine, transmission and suspension parts and other components.

Historically, automotive forging involved heating iron billets (bars) in individual oil-fired furnaces set close to individually operated steam hammer forges. In these drop hammer forges, the heated iron is placed in the bottom half of a metal die; the top half of the die is attached to the drop hammer. The iron is formed into the desired size and shape by multiple impacts of the dropping hammer. Today, such processes are replaced by induction heating of billets, which are worked in forging presses, which use pressure instead of impact to form the metal part, and drop hammer forges (upsetters) or by cold forging followed by heat treatment.

The forging process is extremely noisy. Noise exposure can be abated by replacing oil furnaces with induction heating devices, and the steam hammers with forging presses and upsetters. The process is also smoky. Oil smoke can be reduced by modernizing the furnace.

Forging and heat treatment are heat-intensive operations. Spot cooling using make-up air that circulates over workers in process areas is needed to reduce heat stress.

Machining

High production machining of engine blocks, crankshafts, transmissions and other components is characteristic of the auto industry. Machining processes are found within various parts manufacturing facilities and are the dominant process in engine, transmission and bearing production. Components such as camshafts, gears, differential pinions and brake drums are produced in machining operations. One-person machining stations are increasingly replaced by multiple station machines, machining cells and transfer lines which may be up to 200 metres in length. Soluble oils and synthetic and semi-synthetic coolants increasingly predominate over straight oils.

Foreign body injuries are common in machining operations; increased mechanical material handling and personal protective equipment are key preventive measures. Increased automation, particularly long transfer lines, increases the risk of severe acute trauma; improved machine guarding and energy lockout are preventive programmes.

The highest level of control measures for coolant mist include full enclosure of machining stations and fluid circulation systems, local exhaust directed outside or recirculated only through a high-efficiency filter, coolant system controls to reduce mist generation and coolant maintenance to control micro-organisms. Addition of nitrite to amine-containing fluids must be prohibited due to risk of nitrosamine production. Oils with substantial polynuclear aromatic hydrocarbon (PAH) content must not be used.

In case-hardening, tempering, nitrate salt baths and other metal heat-treatment processes using furnaces and controlled atmospheres, the microclimate may be oppressive and various airborne toxic substances encountered (e.g., carbon monoxide, carbon dioxide, cyanides).

Machine attendants and workers handling swarf and centrifuging cutting oil prior to filtration and regeneration are exposed to the risk of dermatitis. Exposed workers should be provided with oil-resistant aprons and encouraged to wash thoroughly at the end of each shift.

Grinding and tool sharpening may present a danger of hard metal disease (interstitial lung disease) unless cobalt exposure is measured and controlled. Grinding wheels should be fitted with screens, and eye and face protection and respiratory protective equipment should be worn by grinders.

Machined parts are typically assembled into a finished component, with attendant ergonomic risks. In engine facilities engine testing and running-in must be carried out at test stations fitted with equipment for removing exhaust gases (carbon monoxide, carbon dioxide, unburned hydrocarbons, aldehydes, nitrogen oxides) and with noise-control facilities (booths with sound-absorbent walls, insulated bedplates). Noise levels may be as high as 100 to 105 dB with peaks at 600 to 800 Hz.

Stamping

Pressing of sheet metal (steel) into body panels and other components, often combined with subassembly by welding, is done in large facilities with large and small mechanical power presses. Individual load and unload presses were successively replaced by mechanical extraction devices and now shuttle transfer mechanisms which can load as well, yielding fully automated press lines. Fabrication of subassemblies such as hoods and doors is accomplished with resistance welding presses and is increasingly performed in cells with robot transfer of parts.

The main process is the pressing of steel sheet, strip and light sections on mechanical power presses ranging in capacity from roughly 20 to 2,000 tonnes.

Modern press safety requires effective machinery guarding, prohibition of hands in dies, safety controls including anti-tie down two-hand controls, part revolution clutches and brake monitors, automatic feed and ejection systems, collection of press scrap and the use of personal protective equipment such as aprons, foot and leg protection and hand and arm protection. Outmoded and hazardous full-revolution clutch machines and pull-back devices must be eliminated. Handling rolled steel with cranes and loading of decoilers prior to blanking at the head of a press lines poses a severe safety hazard.

Press operators are exposed to substantial mist levels from drawing compounds which are similar in composition to machining fluids such as soluble oils. Welding fumes are present in fabrication. Noise exposures are high in stamping. Control measures for noise include mufflers on air valves, lining metal chutes with vibration-damping equipment, quieting parts carts, and isolation of presses; the point of operation of the press is not the main site of noise generation.

Following pressing, the pieces are assembled into sub-groups such as hoods and doors using resistance welding presses. Chemical hazards include welding fumes from primarily resistance welding and pyrolysis products of surface coatings, including drawing compound and sealers.

Plastic body panels and trim components

Metal trim parts such as chrome strips are being increasingly replaced by polymer materials. Hard body parts may be made from fibrous glass-reinforced polyester polystyrene systems, acrylonitrile-butadiene-styrene (ABS) thermosetting systems or polyethylene. Polyurethane systems may be high density for body parts, such as nose cones, or low-density foam for seats and interior padding.

Polyurethane foam moulding presents severe respiratory sensitization problems from inhalation of di-isocyanate monomer and possibly catalysts. Complaints persist in operations which are in compliance with limits for toluene di-isocyanate (TDI). Methylene chloride exposures from gun flushing can be substantial. Pouring stations need enclosure and LEV; spills of isocyanate should be minimized by safety devices and cleaned promptly by trained crews. Fires in curing ovens are also a problem in these facilities. Seat manufacture has severe ergonomic stresses, which can be reduced by fixtures, especially for stretching upholstery over cushions.

Styrene exposure from fibrous glass lay-up should be controlled by enclosing storage of mats and local exhaust. Dusts from grinding cured parts contain fibrous glass and should also be controlled by ventilation.

Vehicle assembly

Assembly of components into the finished vehicle typically takes place on a mechanized conveyor involving upwards of a thousand employees per shift, with additional support personnel. The largest segment of employees in the industry are in this process type.

A vehicle assembly plant is divided into distinct units: the body shop, which can include subassembly activities also found in a stamping; paint; chassis assembly; cushion room (which can be outsourced); and final assembly. Paint processes have evolved toward lower-solvent, more reactive formulations in recent years, with increasing use of robot and mechanical application. The body shop has become increasingly automated with reduced arc welding and replacement of hand-operated spot-welding guns with robots.

Light truck assembly (vans, pickups, sport utility vehicles) is similar in process to car assembly. Heavy truck, farm and construction equipment manufacture involves less mechanization and automation, longer cycle jobs, heavier physical labour, more arc welding and different paint systems.

The body shop of an assembly plant assembles the shell of the vehicle. Resistance welding machines may be transfer type, robotic or individually operated. Suspended spot welding machines are heavy and cumbersome to manipulate even when fitted with a counterbalance system. Transfer machines and robots have eliminated many manual jobs and removed workers from close, direct exposure to hot metal, sparks and combustion products of the mineral oil which contaminates the sheet metal. However, increased automation carries increased risk of severe injury to maintenance workers; energy lockout programmes and more elaborate and automatic machine guarding systems, including presence-sensing devices, are needed in automated body shops. Arc welding is employed to a limited degree. During this work, employees are exposed to intense visible and ultraviolet radiation and risk inhalation of combustion gases. LEV, protective screens and partitions, welding visors or goggles, gloves and aprons are needed for arc welders.

The body shop has the greatest laceration and foreign body injury hazards.

In past years assembly techniques and body panel defect retouching processes entailed soldering with lead and tin alloys (also containing traces of antimony). Soldering and especially the grinding away of excess solder produced a severe risk of lead poisoning, including fatal cases when the process was introduced in the 1930s. Protective measures included an isolated solder grind booth, respirators supplying positive-pressure air for solder grinders, hygiene facilities and lead-in-blood monitoring. Nevertheless, increased body burdens of lead and occasional cases of lead poisoning among workers and families persisted into the 1970s. Lead body solder has been eliminated in US passenger vehicles. In addition, noise levels in these processes may range up to 95 to 98 dB, with peaks at 600 to 800 Hz.

Automobile bodies from the body shop enter the paint shop on a conveyor where they are degreased, often by the manual application of solvents, cleaned in a closed tunnel (bonderite) and undercoated. The undercoat is then rubbed down by hand with an oscillating tool using wet abrasive paper, and the final layers of paint are applied and then cured in an oven. In paint shops, workers may inhale toluene, xylene, methylene chloride, mineral spirits, naphtha, butyl and amyl acetate and methyl alcohol vapours from body, booth and paint gun cleaning. Spray painting is carried on in downdraft booths with a continuously filtered air supply. Solvent vapour at painting stations is typically well controlled by down-draft ventilation, which is needed for product quality. Inhalation of paint particulate was formerly less well controlled, and some paints in the past contained salts of chromium and lead. In a well controlled booth, the workers should not have to wear respiratory protective equipment to achieve compliance with exposure limits. Many voluntarily wear respirators for overspray. Recently introduced two-component polyurethane paints should be sprayed only when air-supplied helmets are used with suitable booth re-entry times. Environmental regulations have spurred the development of high-solids paints with lower solvent content. Newer resin systems may generate substantial formaldehyde exposure, and powdered paints now being introduced are epoxy formulations which may be sensitizers. Recirculation of paint booth and oven exhaust from roof ventilating units into work areas outside the booth is a common complaint; this problem can be prevented by exhaust stacks of sufficient height.

In the production of commercial vehicles (lorries (trucks), trams, trolley buses) and farm and construction equipment, manual spray painting is still widely employed due to the large surfaces to be covered and the need for frequent retouching. Lead and chromate paints may still be employed in these operations.

The painted body work is dried in hot air and infra-red ovens fitted with exhaust ventilation and then moves on to join the mechanical components in the final assembly shop, where the body, engine and transmission are joined together and the upholstery and internal trim are fitted. It is here that conveyor belt work is to be seen in its most highly developed version. Each worker carries out a series of tasks on each vehicle with cycle times of about 1 minute. The conveyor system transports the bodies gradually along the assembly line. These processes demand constant vigilance and may be highly monotonous and act as stressors on certain subjects. Although normally not imposing excessive metabolic lead, these processes virtually all involve moderate to severe risk factors for musculoskeletal disorders.

The postures or movements the worker is obliged to adopt, such as when installing components inside the vehicle or working under the body (with hands and forearms above head level) are the most readily abated hazards, although force and repetition must also be reduced to abate risk factors. After final assembly the vehicle is tested, finished and dispatched. Inspection can be limited to roller tests on a roller bed (where ventilation of exhaust fumes is important) or can include track trials on different types of surface, water and dust tightness trials and road trials outside the factory.

Parts depots

Parts depots are integral to distributing the finished product and supplying repair parts. Workers in these high-production warehouses use order pickers to retrieve parts from elevated locations, with automated parts-delivery systems in three-shift operations. Manual handling of packaged parts is common. Painting and other production processes may be found in parts depots.

Testing of prototypes

Testing of automobile prototypes is specialized to the industry. Test drivers are exposed to a variety of physiological stresses, such as violent acceleration and deceleration, jolting and vibration, carbon monoxide and exhaust fumes, noise, work spells of prolonged duration and different ambient and climatic conditions. Endurance drivers endure special stresses. Fatal vehicle accidents occur in this occupation.

Assembly of heavy trucks and farm and construction equipment

The processes in these industry sectors are essentially the same as in the assembly of cars and light trucks. Contrasts include: slower pace of production, including non-assembly-line operations; more arc welding; riveting of truck cabs; movement of components by crane; use of chromate-containing pigments; and diesel on drive-off at the end of the assembly line. These sectors include more producers relative to volume and are less vertically integrated.

Manufacture of locomotives and rail cars

Distinct segments of railroad equipment manufacture include locomotives, passenger cars, freight cars and electric self-propelled passenger cars. Compared to car and truck manufacture, assembly processes involve longer cycles; there is more reliance on cranes for material handling; and arc welding is more heavily used. The large size of the products makes engineering control of spray paint operations difficult and creates situations where workers are completely enclosed in the product while welding and spray painting.

Health Problems and Disease Patterns

Production processes are not unique to the auto industry, but often the scale of production and the high degree of integration and automation combine to present special hazards to employees. Hazards to employees in this complex industry must be arrayed in three dimensions: process type, job classification group and adverse outcome.

Adverse outcomes with distinct cause and prevention methods can be distinguished as: fatal and severe acute injuries; injuries generally; repeated trauma disorders; short-onset chemical effects; occupational disease from long-term chemical exposure; service sector hazards (including infectious disease and client- or customer-initiated violence); and work environment hazards such as psychosocial stress.

Job classification groups in the automobile industry can usefully be divided by divergent hazard spectra: skilled trades (maintenance, service, fabrication and installation of production equipment); mechanical material handling (powered industrial truck and crane operators); production service (including non-skilled maintenance and cleaners); fixed production (the largest grouping, including assemblers and machine operators); clerical and technical; and executive and managerial.

Health and safety outcomes common to all processes

According to the US Bureau of Labor Statistics, the auto industry has one of the highest injury rates overall, with 1 in 3 employees hurt each year, 1 in 10 seriously enough to lose time from work. Lifetime risk of occupational fatality from acute traumatic injury is 1 in 2,000. Certain hazards are generally characteristic of occupational groupings throughout the industry. Other hazards, particularly chemicals, are characteristic of specific production processes.

Skilled trades and mechanical material-handling occupations are at high risk for fatal and severe acute traumatic injuries. The skilled trades are less than 20% of the workforce, yet suffer 46% of fatal occupational injuries. Mechanical material-handling occupations suffer 18% of fatalities. The skilled-trades fatalities largely occur during maintenance and service activities, with uncontrolled energy as the leading cause. Preventive measures include energy lockout programmes, machine guarding, fall prevention and industrial truck and crane safety, all based on directed job safety analysis.

By contrast, fixed production occupations suffer higher rates of injuries generally and repeated trauma disorders, but are at reduced risk to fatal injury. Musculoskeletal injuries, including repeated trauma disorders and closely related strains and sprains caused by overexertion or repetitive motion are 63% of disabling injuries in assembly facilities and about half the injuries in other process types. The chief preventive measures are ergonomics programmes based on risk factor analysis and structured reduction in force, frequency and postural stresses of high-risk jobs.

Production service occupations and skilled trades face the majority of acute and high-level chemical hazards. Typically these exposures occur during routine cleaning, response to spills and process upsets and in confined space entry during maintenance and service activities. Solvent exposures are prominent among these hazardous situations. The long-term health consequences of these intermittent high exposures are not known. High exposures to carcinogenic coal tar pitch volatiles are experienced by employees tarring wood block floors in many facilities or torching floor bolts in stamping plants. Excess mortality from lung cancer has been observed in such groups. Preventive measures focus on confined space entry and hazardous waste and emergency response programmes, although long-term prevention depends on process change to eliminate exposure.

Effects of chronic exposure to chemicals and some physical agents are most evident among fixed production workers, principally because these groups can more feasibly be studied. Virtually all the process-specific adverse effects described above arise from exposures in compliance with existing occupational exposure limits, so protection will depend on reduction of allowable limits. In the near term, best practices including well designed and maintained exhaust systems serve to reduce exposures and risks.

Noise-induced hearing loss is pervasive in all segments of the industry.

All sectors of the workforce are subject to psychosocial stress, although these are more apparent in the clerical, technical, administrative support, managerial and professional occupations because of their generally less intense exposure to other hazards. Nevertheless, job stress is likely more intense among production and maintenance employees, and stress effects are likely greater. No effective means of reducing stresses from night work and rotating shift work have been implemented, although shift preference agreements allow for some self selection, and shift premiums compensate those employees assigned to off shifts. Acceptance of rotating shifts by the workforce is historical and cultural. Skilled trades and maintenance employees work substantially more overtime and during holidays, vacations and shutdowns, compared to production employees. Typical work schedules include two production shifts and a shorter maintenance shift; this provides flexibility for overtime in periods of increased production.

The discussion which follows groups chemical and some specific physical hazards by production type and addresses injury and ergonomic hazards by job classification.

Foundries

Foundries stand out among auto industry processes with a higher fatality rate, arising from molten metal spills and explosions, cupola maintenance, including bottom drop, and carbon monoxide hazards during relining. Foundries report a higher fraction of foreign body, contusion and burn injuries and a lower fraction of musculoskeletal disorders than other facilities. Foundries also have the highest noise exposure levels (Andjelkovich et al. 1990; Andjelkovich et al. 1995; Koskela 1994; Koskela et al. 1976; Silverstein et al. 1986; Virtamo and Tossavainen 1976).

A recent review of mortality studies including the American auto industry showed that foundry workers experienced increased rates of deaths from lung cancer in 14 of 15 studies (Egan-Baum, Miller and Waxweiller 1981; Mirer et al. 1985). Because high lung cancer rates are found among cleaning room workers where the primary exposure is silica, it is likely that mixed silica-containing dust exposure is a major cause (IARC 1987, 1996), although polynuclear aromatic hydrocarbon exposures are also found. Increased mortality from non-malignant respiratory disease was found in 8 of 11 studies. Silicosis deaths were recorded as well. Clinical studies find x-ray changes characteristic of pneumoconiosis, lung function deficits characteristic of obstruction and increased respiratory symptoms in modern production foundries with the highest levels of controls. These effects arose from exposure conditions which prevailed from the 1960s onward and strongly indicate that health risks persist under current conditions as well.

Asbestos effects are found on x ray among foundry workers; victims include production as well as maintenance workers with identifiable asbestos exposures.

Machining operations

A recent review of mortality studies among workers in machining operations found apparent exposure-related increased stomach, oesophageal, rectal, pancreatic and laryngeal cancer in multiple studies (Silverstein et al. 1988; Eisen et al. 1992). Known carcinogenic agents historically present in coolants include polynuclear aromatic compounds, nitrosamines, chlorinated paraffins and formaldehyde. Present formulations contain reduced amounts of these agents, and exposures to coolant particulate are reduced, but cancer risk may still occur with present exposures. Clinical studies have documented occupational asthma, increased respiratory symptoms, cross-shift lung function drop and, in one case, legionnaire’s disease associated with coolant mist exposure (DeCoufle 1978; Vena et al. 1985; Mallin, Berkeley and Young 1986; Park et al. 1988; Delzell et al. 1993). Respiratory effects are more prominent with synthetics and soluble oils, which contain chemical irritants such as petroleum sulphonates, tall oils, ethanolamines, formaldehyde and formaldehyde donor biocides, as well as bacterial products such as endotoxin. Skin disorders are still common among machining workers, with greater problems reported for those exposed to synthetic fluids.

Pressed metal operations

The characteristic injury hazards in mechanical power presswork are crushing and amputation injuries, especially of the hands, due to trapping in the press, and hand, foot and leg injuries, caused by scrap metal from the press.

Pressed metal facilities have twice the proportion of laceration injuries of auto industry facilities generally. Such operations have a higher proportion of skilled workers than typical for the industry, especially if die construction is pursued onsite. Die change is an especially hazardous activity.

Mortality studies in the metal-stamping industry are limited. One such study found increased mortality from stomach cancer; another found increased mortality from lung cancer among maintenance welders and millwrights exposed to coal tar pitch volatiles.

Hardware and electroplating

A mortality study of employees at an automotive hardware plant found excess mortality from lung cancer among workers in departments which integrated zinc die-cast and electroplating. Chromic and sulphuric acid mist or die-cast smoke were likely causes.

Vehicle assembly

Injury rates, including cumulative trauma disorders (CTDs), are now the highest in assembly of all processes in the auto sector, due largely to the high rate of musculoskeletal disorders from repetitive work or overexertion. Musculoskeletal disorders account for more than 60% of disabling injuries in this sector.

Several mortality studies in assembly plants observed increased deaths from lung cancer. No specific process within the assembly sector has been shown responsible, so this issue remains under investigation.

Testing of prototypes

Fatal vehicle accidents occur in this occupation.

Design work

The design staffs of auto companies have been the subject of health and safety concern. Prototype dies are made by first constructing the pattern of wood, using extremely hard wood, laminates and particleboard. Plastic models are made by fibrous glass lay-up with polyester-polystyrene resins. Metal models are essentially dies constructed by precision machining. Wood, plastic and metal model and pattern makers have been shown to suffer excess incidence and mortality from colon and rectal cancer in repeated studies. A specific agent has not been identified.

Environmental and Public Health Issues

Environmental regulation aimed at stationary sources in the auto industry principally addresses volatile organic compounds from spray painting and other surface coatings. Pressure to reduce solvent content of paints has actually changed the nature of the coatings used. These rules affect supplier and parts plants as well as vehicle assembly. Foundries are regulated for air emissions of particulates and sulphur dioxide, while spent sand is treated as hazardous waste.

Vehicle emissions and vehicle safety are critical public health and safety issues regulated outside the occupational arena.

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