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8.6 Occupational health

8.6 Occupational health
Oxford Textbook of Public Health

8.6
Occupational health

David Koh and Jerry Jeyaratnam

Introduction
History and development
The Industrial Revolution and occupational health
Development of occupational health legislation
Occupational health today
Health protection of workers
Assessing the risk of work

Hazard and risk

Risk assessment process

An example of assessment of psychosocial factors

Risk management
Prevention of occupational diseases

Control of new hazards

Control of known hazards
Control of hazards at the workplace

Total elimination of the hazard

Substitution of the hazard

Engineering controls

Redesign of the workstation or process

Administrative controls

Education of workers

Use of personal protective devices

Environmental monitoring

Pre-employment or pre-placement examinations

Biological monitoring

Periodic medical examinations

Notification of occupational diseases
Tertiary prevention
Disaster planning
Post-illness or injury evaluation
Rehabilitation
Worker’s compensation
Work-related diseases
Health promotion at the workplace
Worksite health promotion programmes

The worksite as a setting for health promotion

Components of worksite health promotion programmes
Limitations of workplace health promotion

Limitations of prevention and health promotion

Health promotion as a crusade

Does health promotion really work?

Impact of health promotion on occupational health

Problems of implementation, sustainability, and evaluation

Further development
From occupational health to environmental health
Conclusion
Further reading
Chapter References

Introduction
Occupational health, as defined by a joint committee of the World Health Organization (WHO) and the International Labour Organization in 1950, involves the ‘promotion and maintenance of the highest degree of physical, mental and social well being of workers in all occupations’ (Forsmann 1983). This definition emphasizes the term health rather than disease, and further implies a multidisciplinary responsibility as well as a mechanism for the provision of health services for the working population.
History and development
Historically, the existence of diseases related to work has been documented since antiquity. Imhotep (2780BC) was the chief vizier to the Pharaoh Zoser, the first king of the Third Dynasty of the Old Kingdom. He was also an engineer and architect of the step pyramid at Sakkara, as well as a physician and priest. He described cases of occupational injuries and ‘sprain of the vertebrae’ among the pyramid builders (Brandt Rauf and Brandt Rauf 1987).
Hippocrates (460–377 BC) emphasized the importance of environmental factors in disease causation in his treatise on Air, Waters, Places (Hunter 1969). Both Hippocrates and Galen (AD 130–201) described the diseases of certain occupations, including metallurgists, fullers, tailors, horsemen, farmhands, fishermen, miners, tanners, chemists, and other craftsmen. However, Hippocratic medicine in general did not concern itself with health hazards of occupations. One reason was because of the low social status of the worker. The most hazardous and laborious jobs, for example, mining, were done by the lowest strata of society, such as slaves, prisoners of war, and convicted criminals. The Athenian philosopher Socrates (469–399 BC) offers this description of workers:
What are called the mechanical arts, carry a social stigma and are rightly dishonored in our cities… Furthermore, the workers at these trades simply have not got the time to perform the offices of friendship or citizenship. Consequently, they are looked upon as bad friends and bad patriots. And in some cities…, it is not legal for a citizen to ply a mechanical trade.
After stagnating for several centuries, occupational health developed further in the Middle Ages. Georgius Agricola (1494–1555), a physician–scholar in the mountains of Silesia and Bohemia wrote extensively on the diseases of miners and smelters of gold and silver. In a 12-volume work, De Re Metallica, he described a consumptive lung disease of miners (Hunter 1969).
Paracelsus (1493–1541), a Tyrolean physician, produced a three-volume work On Miners’ Sickness and Other Miners’ Diseases, in which he wrote about pulmonary diseases of miners, diseases of smelters and metallurgists, and diseases caused by mercury (Hunter 1969).
One of the great pioneers in occupational medicine was the Italian physician Bernardino Ramazzini (1633–1714) (Fig. 1). He is often described as the ‘Father of Occupational Medicine’. Ramazzini graduated from the University of Parma in 1659, and held the Chairs at Modena (1670) and Padua (1700). His publication De Morbis Artificum Diatriba, which appeared in 1700 with a second edition in 1713, was the seminal text in occupational medicine (Felton 1997). He wrote:

Fig. 1 Bernardino Ramazzini (1633–1714).

I for one have done all that lay in my power, and have not thought it beneath me to step into workshops of the meaner sort now and again and study the obscure operations of the mechanical arts; all the more that nowadays medicine has been almost entirely converted into a mechanical art, and in the schools they chatter continually about automatism.
One of Ramazzini’s most significant aphorisms is the important addition to the teachings of Hippocrates to physicians. Hippocrates taught physicians that ‘When you come to a patient’s house, you should ask him what sort of pains he has, what caused them, how many days he has been ill, whether the bowels are working and what sort of food he eats.’ Following this citation, Ramazzini wrote: ‘I may venture to add one more question: What occupation does he follow?’
In his writings, Ramazzini described many occupational illnesses that are still seen today, and furthermore, described the principles for their control. He condemned the lack of ventilation and unsuitable temperatures, he urged labourers in dusty trades to work in spacious, ventilated rooms, he recommended rest intervals in prolonged work and advocated exercise and correct working postures.
The Industrial Revolution and occupational health
The one major event that profoundly influenced and shaped the development of occupational health was the Industrial Revolution in the eighteenth century (Hunter 1969). Dramatic social changes during this period occurred in the Western world. These transformations were related to newly introduced industrial processes. Basically, the change entailed the setting up of factories, which set in motion a variety of social changes to almost resemble a revolution. Formerly, most work was done by craftsmen in rural cottage industries. The industrial revolution resulted in work being carried out in factories in urban centres.
Effects were seen both within the community, as well as in the individual worker. In fact, many consider the most significant health impact of industrialization to be on the community. Family life was disrupted, with men leaving their families and moving to work in new industrial areas. In the industrial areas, health and social problems emerged—such as poor housing and sanitation, alcoholism, prostitution, and poverty. The individual workers too, were victim to the process of industrialization. Inside the factories, individuals were exposed to long hours of work and uncontrolled occupational hazards; and faced the risk of accidents at work. Very often the workers were not familiar with the industrial process and so exposed themselves to greater dangers than necessary. Child labour and apprenticeship of young children were commonplace, and there was an absence of labour legislation.
As problems of industrialization grew, people of influence and political power campaigned to improve working conditions of workers. Occupational health legislation began to appear towards the end of the eighteenth century, and progressively developed to protect the health and rights of workers.
The industrial revolution occurred later in other parts of the world. Japan, in the Far East, experienced a similar phenomenon from the nineteenth century (Tsuchiya 1991).
Even today, some centuries after the Industrial Revolution, we are able to observe the same phenomena in some of the developing nations. Even in the industrialized nations, the very same problems are encountered by migrant workers and other deprived sectors of their society. In the United States, there was a resurgence in child labour in the 1980s, following waves of immigration as well as participation of school children in the service sector (Postol 1993).
In a commentary on prevention in occupational and environmental health, Axelson (1997) noted that throughout history, many examples of rational efforts for prevention can be found. However, he states that ‘preventive measures have often been, and still are, neglected or even counteracted for economic reasons.’ Thus, some form of legislation is needed to ensure the protection of workers’ health.
Development of occupational health legislation
The first environmental cancer was described by Percival Pott over 200 years ago (Doll 1975). This cancer (skin cancer of the scrotum), occurred in chimney sweeps, and was caused by exposure to polycyclic aromatic hydrocarbon compounds in the soot generated by combustion of organic material. This particular cancer could be prevented by improved personal hygiene.
An early piece of legislation in England was the Act for Better Regulations of Chimney Sweeps and their Apprentices 1788. This act stipulated a minimum age of 8 years for chimney sweeps; provided for inspections and hearing of complaints, and required that the master not ‘misuse or evil treat’ the apprentice. It further stated that the master ‘shall at least once in every week, cause the said apprentice to be thoroughly washed and cleansed from soot and dirt’, and provided for prosecutions and penalties for violation.
The Health and Morals of Apprentices Act, 1802 (Hunter 1969) applied to apprentices in the cotton and woollen industry. It limited work to a maximum of 12 h a day, and specified that factory walls were to be washed twice a year, and for rooms to be ventilated. This legislation also allowed voluntary factory inspections by visitors.
The Factory Act 1819 set 9 years as a minimum age for the worker, and limited work hours. It extended the law to cover workers other than bound apprentices, but still did not apply to all factories. A later Act in 1833 enforced the appointment of factory inspectors and stated that the age of the worker be certified by a medical person. Other work environments were covered by other legislation, such as the Mines Act 1842, which prohibited women and girls from work in mines, and allowed for government inspection and state interference (Hunter 1969).
Subsequent legislation extended occupational health coverage to all occupations, and many countries today have such comprehensive legislation. However, some countries still retain the Factories Act. One possible reason for this situation is to allow for the allocation and concentration of limited occupational health resources to serve the target population at highest risk, namely, factory workers.
Occupational health legislation has also developed to list requirements for the provision of occupational health services to certain occupations. This has been spelt out in the legislation of some of the more developed countries.
Another recent development of occupational health legislation has been to ensure that employers do not discriminate against applicants and employees with disabilities. One example of this type of legislation is the Disability Discrimination Act 1995 in the United Kingdom (SOM 1997). Employers should also make reasonable accommodations for a known impairment; unless it would cause undue hardship, such as incurring significant difficulty or expense.
Occupational health today
From the humble beginnings outlined above, occupational health has kept pace with developments in society. It remains relevant today. For example, in spite of much improved working conditions compared with two centuries ago, modern day chimney sweeps still experience increased morbidity and mortality. Studies among Scandinavian chimney sweeps show that they have more chest symptoms (Hansen 1990), and have increased mortality from cancers, notably of the lung, bladder, and oesophagus (Evanoff et al. 1993).
In 1991, the Commission of the European Communities (1992) conducted a survey of a survey of 12 500 people, representing the national working populations of 12 countries of the European Union. The main findings of the survey are as follows:

42 per cent of all workers thought their health was or could be affected by their work

40 per cent felt that they ran the risk of an accident at work

one worker in four was concerned for both his health and his safety

27 per cent used potentially dangerous equipment/machinery for more than a quarter of their working hours

84 per cent considered industrial accidents and occupational diseases to be common or very common in their country

14 per cent of workers reported they have had an industrial accident or occupational disease recognized as such by their competent national body.
Comparable data from the developing and less developed countries are not so easily available. However, it would not be unreasonable to presume that poorer working conditions and greater health risks would be encountered.
As practised today, the cornerstones of occupational health practice are health protection and health promotion of those who work. In many countries, such activities extend beyond the worker to include his or her family members.
Health protection of workers
The protection of the health of the working population is the primary concern of the occupational health practitioner. Occupational injuries and diseases are largely preventable. They unnecessarily affect the health of the working population and have effects on work productivity and on the economic and social well being of workers, their families, and society.
According to recent estimates, the cost of work-related health loss and associated productivity loss may amount to several per cent of the total gross national product of a country. For example, the Health and Safety Executive (HSE) in the United Kingdom has estimated that the real costs of personal injury, work accidents, and work-related ill health amount to between 5 and 10 per cent of Britain’s gross trading profit (Davies and Teasedale 1994).
In the United States, the total corporate health and safety costs in 1997 were estimated to be $418 billion in direct costs, and over $837 billion in indirect costs (Brady et al. 1997).
Assessing the risk of work
Health protection begins with an assessment of risk. Risk assessment is a structured and systematic procedure that is dependent upon the correct identification of hazards and an appropriate estimation of the risks arising from them, with a view to making inter-risk comparisons for purposes of their control of avoidance (HSE 1995). It can be either a qualitative or quantitative process. The reason for risk assessment is to ensure that a valid decision can be made for measures necessary to control exposure to substances hazardous to health arising in the workplace. Such risk assessments in the workplace are legal requirements in many countries.
The expertise, effort, and detail required for risk assessment depends on the nature and degree of risk, and the complexity of the work process. Adequate controls are determined based on several factors: such as the toxicity of substance, numbers exposed, acceptability of risk, the legal requirements, costs, and availability of control measures.
Hazard and risk
There is a distinction between the terms ‘hazard’ and ‘risk’.
A hazard is a substance, agent, or physical situation with a potential for harm in terms of injury or ill health, damage to property, damage to the environment, or a combination of these. Hazards can be physical, chemical, biological, ergonomic, or psychosocial in nature (Table 1). Hazard identification is the process of recognizing that a hazard exists and defining its characteristics.

Table 1 Types of hazards at the workplace and their health effects

Risk relates to the likelihood of the harm or undesired event occurring, and the consequences of its occurrence. It is the probability that the substance or agent will cause adverse effects under the conditions of use and/or exposure, and the possible extent of harm. It is thus a function of both exposure to the hazard and the likelihood of harm from the hazard. Extent of risk covers the population that might be affected by the risk, the numbers exposed, and the consequences. Risk assessment is the process of estimating the magnitude of risk, and deciding if the risk is tolerable or acceptable. A tolerable risk may not always be acceptable. It merely refers to a willingness to live with a risk to secure certain benefits, and in the confidence that the risk is being properly controlled (Sadhra and Rampal 1999). The levels of tolerability of risk are different for different countries, and in different working populations and the general public.
Risk assessment process
The process of risk assessment and management should take into account both routine and non-routine activities and conditions, including foreseeable emergency situations. Hazards that are intrinsic to these situations, or generated by such activities should be identified.
Exposed persons should be identified, including non-employees and those who are susceptible and therefore at higher risk because of illness or other medical conditions. Existing control measures, if any, should be evaluated.
The health risks from the hazards should next be determined and assessed, and a decision made if the risk is acceptable or tolerable. Unacceptable risks should be eliminated or reduced with new or improved control measures, and their effectiveness monitored. If needed, further corrective actions should be implemented. At the same time, workers should be informed of the hazards, risks, and appropriate measures that can be taken to protect themselves.
The steps for risk assessment for chemical, biological, ergonomic, and psychosocial hazards may differ, as illustrated by the following examples. The assessments for chemical or physical exposures are generally more objective and precise than the assessment for psychic stressors.
An example of an initial assessment for a chemical exposure is given in Table 2.

Table 2 An example of an initial assessment for chemical exposure

An example of assessment of psychosocial factors
The assessment of psychosocial factors at work is more complex. It may include the evaluation of organizational dysfunction, work conditions, as well as a study of indicators such as sickness absence, staff turnover, and measurement of stress-related illness among employees. The identification of work stressors should review design of tasks, management style, interpersonal relationships, work roles, career concerns, and environmental conditions. Questionnaires to staff can be carried out using validated instruments such as the Occupational Stress Inventory and Occupational Stress Indicator (Wall 1999).
An example of a structured method for an assessment of psychic stressors in the workplace, developed by the Finnish Institute of Occupational Health (Elo 1986), is given in Table 3.

Table 3 Assessment for psychosocial stressors (Elo 1986)

Risk management
Once the degree of risk is assessed, and a decision made that the risk of exposure is unacceptable, some form of control is necessary. There are a wide variety of methods of prevention.
The basic aim of preventive medicine is to prevent the occurrence of disease in an individual or a specific population sector, such as the working population. This is usually achieved by attempts to reduce the risk or contracting a disease. If this is not always possible, another way is by undertaking activities targeted at early detection of disease, namely screening procedures. Customarily several levels of prevention are recognized.
Primary prevention aims to reduce the occurrence of disease by eliminating the cause of disease or reducing exposure to safe levels that prevent it from causing damage, for example banning the use of blue asbestos and reducing noise at its source to levels that do not cause noise-induced deafness.
Secondary prevention aims to detect situations of early effects of disease before they manifest as clinical symptoms and signs in order take corrective action, for example regular monitoring of blood lead levels among lead exposed workers, regular audiograms among workers exposed to high levels of noise in the work environment.
Tertiary prevention aims to minimize the consequences in persons who already have disease. This activity is largely a curative and rehabilitative procedure and depends on proper and appropriate treatment.
Thus, it is evident that primary and secondary prevention are the major domains of preventive medicine and would thus be the focus of attention in this chapter.
Prevention of occupational diseases
Prevention of occupational disease can take place at various levels, such as at the national level, or at the level of the workplace itself. The main aim is to reduce the occurrence of occupational disease by eliminating the cause or by controlling exposure to safe levels in order to prevent it from causing damage to the health of workers.
Control of new hazards
Animal toxicity studies of chemicals to be used in industry are a reasonable predictor of potential health hazards to humans. On the basis of such studies, legislation in manufacturing nations would control the usage of such chemicals in industrial processes. One limitation is that such controls apply only to the new chemicals that are to be introduced into the market. For instance, it is estimated that only 10 per cent of pesticides in current usage have undergone such toxicological evaluation (Jeyaratnam and Koh 1996).
Control of known hazards
Several countries have legislation to ban the use of substances known to be harmful to human health. At the international level, the United Nations in 1991 compiled a consolidated list of products whose consumption and sale have been banned, withdrawn, severely restricted, or not approved by governments. This publication constitutes a tool that helps governments to keep up to date with regulatory decisions taken by other governments and assists them in considering the scope for eventual regulatory action.
The United Nations Environment Program in 1989 has evolved a procedural mechanism of Prior Informed Consent to inform government of banned agents such that these governments could take appropriate action for their control. The relevant document for this procedure is the London Guidelines for the Exchange of Information on Chemicals in International Trade. Chemicals that have been banned or severely restricted in at least five countries have further information made available through Decision Guidance Documents.
At present such documents are available for aldrin, dieldrin, DDT, dinoseb and dinoseb salts, fhroroacetamide, HCH (mixed isomers), polychlorinated biphenyl, polychlorinated terphenyl, polybrominated biphenyl, tris-(2,3-dibromopropyl) phosphate crocidolite, chlordane, chlorodimeform, cyhexatin, heptachlor, and mercury compounds.
By means of such documents, the United Nations system attempts to prevent importing countries from unknowingly using substances banned in countries for health reasons. This type of export of hazardous chemicals also raises an ethical consideration. For instance, is there any justification to manufacture solely for export a chemical banned in the country of manufacture as being hazardous to human health? Surely the answer to this must be a resounding ‘No’. Thus the best safeguard would be to ensure that chemicals banned for health reasons in the country of manufacture should not be manufactured solely for export.
At the national level, there may be rules that regulate the import, storage, sale, and transport of legislated substances through a licensing system, for example, for pesticides. Some substances may be subjected to import controls. For instance, in some countries, the use of chlorofluorocarbons and asbestos is limited by a quota system.
Control of hazards at the workplace
Successful prevention of occupational disease could be achieved by controlling exposure to harmful agents to what are considered as safe and permissible levels. This is a form of primary prevention as it is directed at efforts to prevent damage by controlling exposure to safe levels. There are several mechanisms for the control of exposure at the workplace.
Total elimination of the hazard
This method eliminates the health risk completely, and has been used for substances that are carcinogenic, for example asbestos, benzene, or those that can cause serious health effects, such as cadmium. In the United Kingdom, the HSE had regulated that solder should be substituted with solder low in cadmium or cadmium free in the mid-1980s (Mason et al. 1999). Other successful examples of total elimination of the hazard include the use of asbestos-free products, benzene-free solvents, or solvent-free paints (powdered paints or water-based paints).

Case study 1: Elimination of the hazard from the work process Brazing is a process where a filler metal is melted and allowed to flow into a close fitting joint of two metals. A common filler metal is a copper–zinc–silver–cadmium alloy. Torch brazing was performed in a factory that manufactured compressors. A review of the material safety data sheet of the filler revealed that it contained a significant amount of cadmium. Cadmium is a nephrotoxic agent that is used in the filler metal to reduce its melting point. While cadmium-free alloys are available, these cost more, as a higher silver content is needed to achieve an equivalent melting temperature. Environmental monitoring showed that cadmium in air levels were above the recommended threshold limit values. Biological monitoring of exposed workers showed that a large proportion of exposed workers had blood cadmium values higher than 10 µg/l, the recommended biological exposure index in that country. (Note: the Biological Exposure Index (BEI) for cadmium in blood recommended by the American Conference of Governmental Industrial Hygienists (ACGIH) is 5 µg/l.) The health risk was found to be unacceptable, and as a result, the brazing alloy used was replaced with a cadmium-free substitute. (Source: Jeyaratnam and Koh 1996.)

Substitution of the hazard
Substitution of the hazard with a less toxic alternative is another feasible option. In the case of operations that use solvents, such as degreasing operations, a less toxic solvent such as 1,1,1-trichloroethane can be used, instead of the more toxic trichloroethylene or tetrachloroethane. Another method could be the substitution of the hazard to a form that reduces risk of exposure.

Case study 2: Substitution of the hazard to a different form to reduce exposure A factory that produced a powdered plastic stabilizer chemical that contained inorganic lead. During statutory medical examinations of the workers, it was found that there was a problem of high lead exposure among its employees. The problem was reduced drastically when the production process was changed so that the end product was in granular form, as compared with the original powdered form. The improvement resulted because granules of lead containing stabilizer were less likely to be airborne, and as a result, airborne contamination was reduced dramatically.

Engineering controls
Designing and redesigning of the process to minimize exposure are some possible control measures. Automation, enclosure, or segregation of a work process, the use of dampeners or mufflers to reduce vibration or noise, reducing the open surface area for the evaporation of volatile toxic agents have been some of the successful measures used. Suppressing the substance by processes such as ‘wetting’ of dusty operations, or reducing hazardous emissions in the workplace by use of exhaust ventilation are other examples of engineering controls.
Redesign of the workstation or process
Redesign of the workstation to reduce unnecessary and repetitive bending, or to prevent excessive stretching to the limit of the range of movement of the workers, can minimize ergonomic hazards (Fig. 2).

Fig. 2 Ergonomic improvements to this workplace can reduce the risk of musculoskeletal disorders among the workers.

In the case of computer operators, the use of adjustable equipment, the positioning of the workstation to reduce glare, and appropriate work rest pauses can prevent the development of eye strain and musculoskeletal complaints.
Administrative controls
Administrative controls may be a viable alternative or an additional measure to reduce worker exposure to occupational hazards. This could take the form of job enlargement or job rotation, restriction of hours of work at a hazardous operation, or even temporary job reassignment.
The worker in Fig. 3 is exposed to numerous hazards, such as heat, noise, dust, fumes, and risk of burns and other injuries. In this work situation, his total exposure for the hazardous work conditions can be limited by administratively reducing this particular exposure to an hour or so, during the entire work shift. At other times, the worker is in an air-conditioned and enclosed control room. A better solution would be to automate the process, by use of a robotic arm to feed the oxygen to the furnace.

Fig. 3 Worker in an iron and steel mill feeding oxygen to the furnace.

Education of workers
The training of workers in how to recognize work hazards, how to work safely, and what to do in the event of an emergency or when occupational diseases occur, is another important aspect of prevention. For example, metalworkers are often exposed to skin contact with coolants and soluble oils. Different workers performing the same job can have variable skin contact with coolants, ranging from almost negligible exposure to almost total constant skin contact with the coolants (Wassenius et al. 1998). This variation can be explained by differences in hazard awareness, attitude, and practice of safe working techniques in different workers.
Use of personal protective devices
The use of personal protective equipment is often widely practised. It has its merits, a major one being its relative inexpense, and is especially useful for situations of short-term or occasional exposure to occupational hazards. However, protective devices have to be properly selected to be effective against specific hazards, for example, the choice of an appropriate glove for use with a particular solvent. The use of a modern firefighting uniform made of improved thermal protective textile and the inclusion of overpants, resulted in dramatic reductions of thermal injury to firefighters in New York (Prezant et al. 1999).
Workers have to be trained to use the equipment correctly and to ensure that it is working effectively, such as respirator fit testing in the use of respirators (Fig. 4). Worker compliance in the use of these devices has to be high, or its protective effects may be less than desired. Finally, protective devices have to be properly maintained and replaced when necessary.

Fig. 4 Fit testing to ensure that the respirator will protect the worker.

The Occupational Safety and Health Administration (OSHA 1995) stipulates that personal protective equipment should not be used as a substitute for engineering, work practice, and/or administrative controls. Instead, personal protective equipment should be used in conjunction with these controls to provide for employee safety and health in the workplace.
Environmental monitoring
Environmental or ambient monitoring in the workplace is undertaken to measure external exposure to harmful agents. The monitoring is to ensure that exposure is kept within ‘permissible levels’ so as to prevent the occurrence of disease. The concept of permissible levels assumes that for each substance there is a level of exposure at or below which the exposed worker does not suffer any health impairment.
It must be recognized that permissible levels have their limitations. As such every effort must be made to keep exposure levels as low as possible and the permissible level is a level above which exposure should not occur. This level could also be set for the enforcement of legislation. Furthermore, such levels may be based on incomplete information and previously unsuspected health risks have arisen from substances assumed to be comparatively safe; for example, glycol ethers used in the electronic industry have caused spontaneous abortions.
Permissible levels or occupational exposure limits
Permissible levels, or occupational exposure limits (OELs), are standards that are available for many of the common hazards found in workplaces. Standards are available for the commonly encountered physical, as well as chemical hazards. Standards can also be found for some substances of biological origin, including cellulose, some wood, cotton and grain dusts, proteolytic enzymes, and vegetable oil mists. Permissible levels are based on the following considerations:

the physical and chemical properties of substance, including the nature and amount of impurities

toxicological studies

available human data.
The use of environmental standards for working conditions depends a great deal on good professional judgement, and hence should be used and interpreted only by trained persons. All standards will have imperfections in their derivation and therefore should have their limitations appreciated by the professionals who utilize them.
The earliest OELs were derived for the chemical industry in the nineteenth century in Germany. These standards were often for acute effects from short-term and very high exposures. With the development of industrial hygiene methods of measuring environmental contaminants and exposures, more and more OELs were developed. Different countries have different exposure limits. The process of standard setting, nomenclature, and applicability would necessarily differ.
For example, different approaches were taken in setting standards in the USSR and the United States in the 1970s (Levy 1999). The USSR standards, which were lower than standards set in the United States at that time, were maximum allowable concentrations that were based on an absence of development of any disease or deviation from normal. In contrast, the United States approach allowed for minor physiological adaptive changes. In addition, the principle in the USSR was that standards should be based entirely on health and not on technological and economic feasibility. In the United States, economic and technological feasibility were important considerations in the development of the standards.
Another consideration would be to take into account the situation for which the standards were set. For example, standards that are set for an 8-h working day would not be applicable for a 12-h workday.
Furthermore, exposure to several hazards simultaneously may occur. In such situations, there may be interactions, with possible synergistic or additive effects. This would then require more stringent control of each individual hazard.
The method of environmental monitoring is also of utmost importance. The choice of the correct collecting devices, sampling strategy, and analysis of the collected samples in accredited laboratories with proper quality control are important considerations that have to be addressed.
Individual variation among exposed persons should also be considered. Age, sex, pre-existing disease, genetic make-up, and social habits, such as smoking; would influence individual susceptibility. Some permissible limits, such as the threshold limit values of the ACGIH, are derived to protect the majority of, but not all exposed persons. Susceptible individuals may still suffer health effects even at levels below the recommended permissible levels. In spite of these preconditions, the sensible use of environmental standards can often result in practical and pragmatic control of many common workplace hazards so that the majority of workers are protected. Supplementary measures, such as biological monitoring, will ensure a safety net to identify workers with excessive body burdens or who have early health impairments.
An example of an environmental standard
One of the best known and widely used of the OELs is the proprietary threshold limit value (TLV) system developed by the ACGIH, which will be discussed in some detail.
The concept of ‘time-weighted averages’ (TWAs) and the stated philosophy of protecting ‘nearly all workers’ (in view of individual variation) are important considerations in the interpretation of the TLVs. TLVs are available for only about several chemicals. TLVs have not been established for a large number of recognized toxic materials.
As stated by the ACGIH, TLVs refer to ‘airborne concentrations of substances and represent conditions under which it is believed that nearly all workers may be repeatedly exposed day after day without adverse health effects.’ The ACGIH is aware of the wide variation in individuals, due to factors such as age, sex, pre-existing disease, genetic predisposition, and lifestyle habits, such as smoking. This variation would account for a small percentage of workers experiencing discomfort, or even developing illness from some substances at concentrations at or below the TLV.
The TLVs are updated and published annually. They are derived from information from industrial experience, as well as studies in both animal and human populations. The health outcomes of interest vary with different substances. This may range from definite health impairment, to an absence of irritation, narcosis, nuisance; or other forms of stress, as specified.
The ACGIH stresses that the TLVs ‘are not fine lines between safe and dangerous concentrations, nor are they a relative index of toxicity.’ While serious adverse health effects are not believed likely as a result of exposure to the TLVs, the ACGIH further adds that the ‘best practice is to maintain oncentrations of all atmospheric contaminants as low as is practical’.
Some definitions
Three categories of TLVs are given. These are to be used for different situations (ACGIH 1999).

1.
Threshold limit value time-weighted average (TLV-TWA). The TLV-TWA refers to the time-weighted average concentration for an 8-h workday and 40-h workweek. Nearly all workers can be repeatedly exposed to these levels, day after day, without adverse effects. Throughout the workday, excursions above the TLV-TWA are permitted (provided they are below the TLV ceiling), if these are compensated by equivalent excursions below the TLV-TWA. TLVs are not recommended for simple asphyxiants, where the most important consideration is the available oxygen.

2.
Threshold limit value short-term exposure limit (TLV-STEL). This is a 15-min limit TWA exposure, which should not be exceeded at any time during a workday even if the 8-h TWA is within the TLV-TWA. As defined by the ACGIH, the TLV-STEL is the concentration to which it is believed that ‘workers can be exposed continuously for a short period of time without suffering from irritation, chronic or irreversible tissue damage, or narcosis of sufficient degree to increase the likelihood of accidental injury, impair self-rescue, or materially reduce work efficiency,’ and provided that the daily TLV-TWA is not exceeded. The STEL supplements the TWA limit for substances with primarily chronic effects, but which also have recognized acute effects.

3.
Threshold limit value ceiling (TLV-C). The TLV-C is the concentration that should not be exceeded during any part of the working exposure. For some fast-acting substances, such as irritant gases, the TLV-C might be the only relevant TLV. Environmental measurements for the TLV-C should preferably be instantaneous. In some situations, it is however, permitted to sample over a period not exceeding 15 min.
Notations
Some chemicals with listed TLVs may have a ‘skin’ or ‘sensitizer’ notation.
The skin notation highlights the potential significant contribution to the overall exposure by absorption through the cutaneous route, including mucous membranes. Often this occurs via direct skin contact. Workers with impaired skin barrier function, for example from injured or diseased skin, face a higher risk. Important examples of substances with the skin notation include organic solvents and pesticides such as malathion and lindane.
The sensitizer notation refers to the confirmed potential for worker sensitization as a result of dermal contact and/or inhalation exposure. An example of a chemical with a sensitizer notation is n-butyl acrylate, which is both an irritant and a sensitizer. The lack of a sensitizer notation does not necessarily mean that the substance is not a sensitizer.
Carcinogens
The carcinogenic potential of the chemical is denoted by its carcinogenic designation, which ranges from A1 (confirmed human carcinogen), A2 (suspected human carcinogen), A3 (confirmed animal carcinogen with unknown relevance to humans), A4 (not classifiable as a human carcinogen), to A5 (not suspected as a human carcinogen).
Exposures to carcinogens should be kept as low as possible. Many carcinogens act by genotoxic mechanisms, and thus, in theory at least, there may not be a safe level.
The TLVs of some chemicals, with their accompanying notations, are listed in Table 4.

Table 4 Threshold limit values of selected agents (ACGIH 1999)

Exposure limits for combined exposures
The toxicity of substances of variable composition, for example, welding fumes (Fig. 5), are dependent on factors such as the welding process and electrodes used, and the particular alloy that is welded. The TLV given, which is based on total particulate concentration, would be adequate only if no toxic elements are present in the welding rod, metal or its coating, and the welding conditions are not conducive to the formation of toxic gases.

Fig. 5 Welding fumes can contain particulate concentration as well as toxic materials from the welding rod or welded metals.

Threshold limit values for chemical mixtures can be computed if components in the mixture have either similar toxic effects or independent toxic effects, using the appropriate correction formulas. Details can be found in the TLV and BEI Handbook of the ACGIH.
Exposure limits for physical agents
The threshold limit values for physical agents such as acoustic exposure, electromagnetic radiation, and ergonomic, mechanical, and thermal factors; are also presented.
Different methods of assessment of acoustic exposure are used for different situations, for example, continuous versus impact noise, infrasound and ultrasound. For example, the threshold limit values for noise, measured on the use of the A-weighted network with slow meter response, are as follows (Table 5).

Table 5 Threshold limit values for noise

Personal or area monitoring can also be performed (Fig. 6 and Fig. 7).

Fig. 6 Personal monitoring for noise exposure.

Fig. 7 Area monitoring of noise in the workplace.

Other considerations
In some instances, other considerations are important. Working and weather conditions (e.g. light or heavy work, indoor or outdoor work, solar load present or absent) are considered in the interpretation of the TLV for heat stress.
Exposures to a combination of factors, such as physical and chemical agents, may result in interaction of these agents, and place added stress on the exposed person. For example, among exposed workers, interactions between physical and psychosocial risk factors can increase the risk of developing work-related musculoskeletal disorders (Devereux et al. 1999).
Pre-employment or pre-placement examinations
Pre-placement/employment medical examinations are undertaken to achieve proper job placement according to the mental and physical capabilities of the worker. By such examination and job placement it is hoped to prevent damage to susceptible workers. It must be recognized that such tests are also undertaken with different objectives, for example: to protect other workers and the general public, for insurance purposes, and to obtain baseline information on fitness.
Education of workers should be given during these assessments. Those who work have a right to know the potential hazards and risks in their work and workplaces. They should be educated on these matters and be given information on how to safeguard their health.
Immunization against diseases that may possibly be contracted on the job, and for which an effective vaccine is available, should also be given. An example is the immunization of health-care personnel exposed to the hepatitis B virus.
There are genetic disorders that can be identified that may make a worker more vulnerable to certain workplace exposures. As an example, people with a deficiency in red cell glucose-6-phosphate dehydrogenase are more susceptible to haemolytic anaemia. As such, persons with this condition are likely to be more susceptible to haemolytic agents. Persons with serum total a1-antitrypsin deficiency may be considered as susceptible to respiratory irritants (Koh and Jeyaratnam 1998).
Similarly, evidence of other behaviours (e.g. smoking, alcohol consumption) and diseases (e.g. chronic bronchitis, liver, kidney disease), may increase the susceptibility of workers exposed to certain intoxicants.
Biological monitoring of the worker ideally begins at the pre-employment examination stage and can be continued periodically.
Biological monitoring
Biological monitoring complements environmental monitoring in the assessment of health risk in the exposed worker. It is a useful tool in the prevention and management of ill health among workers (Morgan 1997).
One major feature of biological monitoring, as compared with environmental monitoring, is that, for a particular individual, it takes into account exposure from all routes of absorption. As an example, consider the case of workplace exposure to organic solvents. In this instance, skin absorption may be a significant route of entry of the solvent into the body, and ambient environmental air monitoring might be less useful as an indicator of exposure than biological monitoring.
Furthermore, environmental monitoring at the workplace would not account for non-occupational or extra-occupational exposures. A person working in a noisy environment could be additionally exposed to noise in a second job, or as part of the hobby or non-occupational activity of the worker, for instance, reserve military service.
The following case study illustrates how the results of biological monitoring can complement environmental monitoring.

Case study 3: Biological monitoring for carboxyhaemoglobin A worker uses paint stripper in an enclosed workplace, where there are running engines. He can have increased blood carboxyhaemoglobin due to several sources of exposure. Environmental monitoring of carbon monoxide in the poorly ventilated workplace would detect carbon monoxide levels from the exhaust of the running engines. It would not take into consideration the fact that methylene chloride in the paint stripper is metabolized to produce carboxyhaemoglobin. The worker could also be a smoker, and this would further contribute to total carboxyhaemoglobin, which is detected in biological monitoring. (Source: Aw 1995.)

Validation of the biological monitoring marker
A major challenge that has to be addressed is the question of validation. To be useful, an exposure marker must be shown to be able to (in terms of presence and magnitude) reflect accurately past exposure to the agent, and a risk marker should accurately reflect risk of disease outcome. There are many factors to be considered, among which are properties of the biomarker itself, its lifespan and hence the period of exposure reflected, and its stability during collection and processing.
In addition, the importance of understanding intra-individual variability cannot be overemphasized. This variability may be a function of the timing of sample collection, or the sampling procedure itself. Other sources of intra-individual variability could arise from errors in handling, processing, and storing of specimens. Variation in instrumental analysis, such as inherent day to day variation in the assay method, may affect validity of readings. Quality control in the laboratory is important.
Terminology
While some consider any procedure (e.g. periodic radiographs, blood tests, symptom enquiry, etc.) used to monitor exposed workers as biological monitoring, others make a distinction between biological monitoring, and effects monitoring.
Biological monitoring
Biological monitoring refers to the measurement and assessment of workplace agents or their metabolites either in tissues, secreta, excreta, expired air, or any combinations of these to evaluate exposure and health risk compared with an appropriate measure (Aw 1995).
The specific chemical, or its breakdown product, can be measured, to detect the total body burden of the substance. The method of measurement of these substances must be validated and there should be a means to interpret the results obtained in terms of the extent of exposure, and risk to health.
Biological effect monitoring
This refers to the measurement and assessment of early biological effects, of which the relationship to health impairment has not yet been established, in exposed workers to evaluate exposure and/or other health risk compared with an appropriate reference (Zeilhuis and Hendersen 1986). Some examples of include detection of alterations in enzyme levels (e.g. cholinesterase for workers exposed to organophosphorus or carbamate pesticides), or other biochemical changes such as delta aminolaevulinic acid in urine of workers exposed to inorganic lead, or b2-microglobulin in the urine of cadmium exposed workers.
In the early stages, these changes need not necessarily cause any direct pathological damage to the individual, but rather, reflect situations of excessive exposure. These changes are often reversible on removal of the worker from further exposure.
Health effects monitoring (health surveillance)
Health effects monitoring is ‘the periodic physiological or clinical examination of exposed workers with the objective of protecting and preventing occupationally related diseases’ (Aw 1995). These examinations detect early clinical effects in exposed workers. Examples of the tests conducted include audiometry for noise-exposed workers, clinical examination for skin lesions in workers exposed to polycyclic aromatic hydrocarbon compounds in tar, pitch, and bitumen, and chest radiographs for workers exposed to pneumoconiosis-producing dusts.
Figure 8 illustrates and summarizes the terminology and levels of prevention that are used in occupational health practice.

Fig. 8 Summary of terminology and levels of prevention in occupational disease.

An example of a biological exposure limit value
The measurement value obtained by biological monitoring is evaluated as a health risk by comparing it with the corresponding biological exposure limit value. A set of values have been developed by the ACGIH, which include results of biological monitoring as well as biological effects monitoring (ACGIH 1999).
The BEI is described as in general representing the ‘levels of determinants which are most likely to be observed in specimens collected from a healthy worker who has been exposed to chemicals in the same extent as a worker with inhalation exposure to the TLV’ (ACGIH 1999). Exceptions would be made for chemicals for which TLVs are based on non-systemic effects, for example irritation, and for chemicals with significant routes of entry via additional routes of entry (usually percutaneous absorption).
The ACGIH cautions that ‘BEIs do not indicate a sharp distinction between hazardous and non-hazardous exposures. Due to biological variability, it is possible for an individual’s measurements to exceed the BEI without incurring an increased health risk.’ It is further stated that BEIs are not intended for use as a measure of adverse effect or diagnosis of occupational disease. However, if measurements of the individual or group of workers persistently exceed the BEIs, the cause of the excessive values should be investigated, and measures should be taken to reduce the exposure.
BEIs (as used by ACGIH) for some intoxicants are shown in Table 6.

Table 6 Biological exposure indices (BEIs) of some chemical intoxicants (ACGIH 1999)

Recent advances in biological monitoring
Technological advances in molecular biology over the last two decades have offered more sophisticated techniques that can be used to study the role of specific exogenous agents and host factors in causing ill health.
These advances have resulted in the development of newer molecular biomarkers of exposure, response, and genetic susceptibility. These include measurements for structural gene damage, gene variation, and gene products in cells and body fluids, for example, oncogenes and tumour suppressor genes, DNA adducts, gene products and genetic polymorphisms, and metabolic phenotypes in environmentally exposed populations (Koh et al. 1999).
An understanding of biochemistry and genetics at the molecular level, specific knowledge on metabolism and mechanisms of action, and epidemiology has become increasingly important. This is necessary in order to address the major question of validation and relevance of these molecular biomarkers. For example, the availability of genetic tests to identify susceptible workers raises issues of ethics, individual privacy, right to work, and the relevance of such tests. Several studies have presented data on the association of environmental measurements and various biomarkers for internal and biologically effective doses, genetic polymorphisms, and early response markers (Table 7).

Table 7 Examples of molecular biomarkers measured in occupational health studies

Given the limitations of individual molecular biomarkers in assessing health risk, and the multifactorial nature of environmental disease, it is likely that a combined approach which examines several of these biomarkers simultaneously, will increase our understanding of the complex issue of disease mechanisms and further refine the process of risk assessment.
Periodic medical examinations
Periodic medical examinations may be required for some occupational groups in order to effect primary or, failing that, secondary prevention of disease. In many countries, certain categories of employees must undergo statutory periodic medical examination. These examinations are usually for workers exposed to known hazards such as noise, radiation, asbestos, silica, heavy metals, and specific toxic chemicals. In some countries, only properly qualified health personnel, with additional postgraduate training in occupational health, are empowered to perform the examinations, and issue fitness to work certificates. The results of the examinations have to be kept for a specified period of time, and copies sent to the relevant government body.
The objectives of such statutory medical examinations would be to prevent special groups of ‘at-risk’ workers from developing serious occupational diseases. Regular health examinations, which are specific for the type of hazard the worker is exposed to, are conducted. Workers who are found to show signs of overexposure to any hazard or have early signs of disease can be removed from further exposure. They can be given alternative work until they are fit to return to their former jobs. Furthermore, if signs of overexposure are detected, further control measures can be taken to reduce the exposure and prevent other workers from being similarly affected.
Sometimes, special groups of workers are required to undergo periodic medical examinations for other reasons, such as to certify ongoing fitness to work. Examples of these workers include professional drivers and food handlers.
Notification of occupational diseases
Most countries require the statutory notification of occupational diseases to the government. Notification should be done on the suspicion of occupational disease. The notified case is subsequently investigated and confirmed by the relevant government specialists. Either the employer or health practitioner who sees the worker can notify. In many countries, a list of notifiable occupational diseases is available.
Notification serves as an additional means of control of occupational diseases, undertaken by occupational health and safety professionals in the public sector. It initiates a chain of events, which often includes investigation and confirmation of the index case, and active case finding of other affected persons.
Recommendations for specific preventive measures at the workplace are then prescribed. The authorities would follow up by ensuring that the recommendations have been implemented. If necessary, further evaluation of the effectiveness of the preventive measures can be made.
An example of a notification form is given in Fig. 9 (Ministry of Manpower, Singapore 1999). Figure 10 summarizes the continuum of various means of prevention in occupational health practice.

Fig. 9 An example of a notification form for occupational disease.

Fig. 10 Continuum of preventive actions in occupational health practice.

Tertiary prevention
Tertiary prevention activities are largely curative and rehabilitative procedures. Workers should be removed from further exposure, and the appropriate medical treatment given if indicated. Examples of appropriate treatment include the rendering of first aid promptly after an injury, chelation for severe cases of overexposure to heavy metals, and hyperbaric treatment for cases of compressed air illness.
Disaster planning
Occupational health personnel can also assist in planning for disasters in the workplace and community. Services such as the fire and emergency response services are essential in dealing with disasters at the workplace that may affect the community. As such, planning and practice drills should be done jointly with the relevant local community agencies.
Post-illness or injury evaluation
An evaluation of the health status of the employee returning to work after a prolonged absence from work due to illness or injury is important. The aim is to ensure that the worker has sufficiently recovered from the illness or injury, and that he or she is fit to return to work. The following two issues should be considered.

Can the worker perform his or her duty without adverse health and safety risks to himself/herself or fellow workers?

Should he or she return to full-time unrestricted duty, or should some modified, restricted, or alternative duty be given?
Rehabilitation
The rehabilitation of workers is another important aspect of occupational health care. Management, fellow workers, occupational health professionals, and the injured worker have to work together to ensure that suitable alternative duties are provided, and that any work restrictions or physical limitations are understood. There should be clear short- and long-term goals in rehabilitation, and alternative duties should be meaningful and contribute to production (ACOM, ACRM 1987). Sometimes, the use of external rehabilitation resources may be needed.
Worker’s compensation
In many countries, workers who are injured at work, or fall ill from hazardous work exposures are eligible for compensation. Employers who carry out economic activities through labour and machines create an environment that may be likely to cause ill health in the employees. Thus employers should be liable for payment of compensation to workers if they are injured or fall sick because of their work.
Legislation concerning employment injury benefits is often called a Workmen’s Compensation Act, as in the United States. Employers may be required to insure against their liability under the Act. The workmen’s compensation system is designed to minimize litigation and facilitate payment of compensation to injured workers. It is based on a ‘no fault’ principle. In different countries, certain categories of workers (e.g. domestic helpers) may be excluded.
Other countries may have social insurance to give protection to employment injury victims. The principle of social insurance is that of sharing of risks and pooling financial resources. A social insurance scheme establishes a public channel through a government department or government supervised body, which oversees procedures of screening, determination of award, and payment of benefits.
In the early development of such schemes, only injuries from industrial accidents were covered. This was subsequently enlarged to include occupational diseases. In countries where this is practised, the national legislation would contain a list of those diseases that could be compensated for. The nature of the occupation in relation to each disease may also be prescribed. The worker who suffers from the disease has the advantage of not having to prove that the disease was of occupational origin. Some countries have a more flexible system—any disease that could be shown to be due to an occupation could be considered as compensatable.
Benefits are payable for temporary incapacity or permanent incapacity for workers, and survivors’ benefits for those killed at work. Guidelines for the assessment of disability are available in most countries. The final assessments for disability are made when the workers’ medical condition has stabilized, and not likely to improve or deteriorate further.
Besides Workmen’s Compensation and social insurance schemes, injured workers can sue their employer through common law and claim benefits. This was the only avenue for action in the days before the introduction of Workmen’s Compensation schemes. This can be a long process, and the worker has to prove negligence on the part of the employer. In general, workers who have claimed benefits from Workmen’s Compensation are not allowed further recourse through this action.
Work-related diseases
The term ‘work-related diseases’ has been used to describe not only recognized occupational diseases, but also other disorders in which the work environment and performance of work contribute significantly as one of several causative factors (Lesage 1998). These are diseases in which workplace factors may be associated in their occurrence but need not be the only risk factor in each case. Common work-related diseases include: hypertension, ischaemic heart disease, psychosomatic illnesses, musculoskeletal disorders, and chronic non-specific respiratory disease/chronic bronchitis. In these diseases, work may be associated with their causation or may aggravate a pre-existing condition.
In terms of frequency of occurrence, work-related diseases are often more common than pure ‘occupational diseases’. While prevention of occupational diseases is possible by the elimination of the workplace hazard, work-related diseases cannot be entirely prevented by only addressing occupational hazards.
Thus, at the workplace, three categories of diseases may be noted in workers.

1.
Occupational diseases—these are caused by exposure to specific hazards at the workplace. However, in some situations these occupational diseases may also occur among the general community as a consequence of contamination of the environment from the workplace, for example, lead and pesticides. Occupational diseases are cause specific; for example, asbestos causes asbestosis.

2.
Work-related diseases—these are ‘multifactorial’ in origin, where factors in the work environment may play a part, together with other risk factors in the development or aggravation of such diseases. These diseases have a complex aetiology.

3.
General diseases affecting the working population—these are medical conditions prevalent in the community, such as malaria, hereditary haemolytic anaemia, or diabetes mellitus, without a causal relationship with work. The unhealthy worker may not be able to be as productive as his healthy counterpart. Furthermore, work may have a deleterious or aggravating effect on the medical condition.
Table 8 shows the differences between occupational and work-related diseases.

Table 8 Differences between occupational and work-related diseases

Health promotion at the workplace
Occupational health practitioners have long recognized health promotion to be an integral part of a comprehensive occupational health-care system (ACOM 1983). However, the definition of what really constitutes ‘health promotion’ is sometimes unclear, as definitions of health promotion differ consequent to the continual evolution of the basic concept of health.
The WHO defines health promotion in its broadest sense as ‘the process of enabling people to increase control over, and to improve their health.’ Health promotion is seen as a continuum ranging from the treatment of disease, to the prevention of disease, including protection against specific risks, to the promotion of optimal health (WHO 1988).
This definition appears somewhat vague but it does highlight the essence of health promotion. It involves the population as a whole, in the context of their everyday life, rather than focusing on people at risk for specific diseases. Health promotion is, in brief, the social action dimension of health development, other dimensions being biomedical and technological interventions embodied in public health practice (WHO 1991).
It is a process of activating communities, policy-makers, professionals, and the public for health supportive policies, systems, and ways of living. It is manifested by promoting healthy lifestyles and community action for health, and by creating conditions that make it possible to live a healthy life.
Worksite health promotion programmes
Worksite health promotion programmes are common in industrialized countries. Among the developing nations, there is also growing interest in the workplace as a site with great potential for health promotion. Existing occupational health services now face the challenge of adapting to a wider scope of responsibility than its traditional role.
A major reason for the introduction of worksite health promotion programmes is financial in nature. This is especially pressing in the developed countries. As an example, the American health system passes the burden of costs on to the consumer, which would be the employer, as most American companies offer medical benefits as a matter of right to their employees. These medical benefits have become a serious financial burden to the employer in the face of rapidly rising costs of health care. However, the effect of rising health-care costs is now a fairly global concern. There are several reasons for this escalation of health-care costs.

1.
There has been a shift in disease profile from communicable diseases to non-communicable diseases. At present, non-communicable diseases are responsible for 70 to 80 per cent of deaths in the developed countries and about 40 per cent in the developing world. The emergent non-communicable diseases are consequent to the successful control of communicable diseases as well as the cultivation of unhealthy lifestyles. In addition, improved life expectancy that follows an enhanced standard of living has led to a rise in chronic degenerative diseases. Curative care for such diseases is limited and expensive, requiring repeated medical consultation and follow-up.

2.
An ageing work force is emerging due to declining birth rates and enhanced life expectancy in many developed and rapidly developing countries. An increased prevalence of chronic degenerative diseases, with its attendant treatment costs, is a natural consequence.

3.
Easy availability and constant evolution of high-technology diagnostic and therapeutic aids that are expensive, but are extensively requested by doctors and patients alike. A climate of high medical litigation consciousness and greater health literacy among the general public would increase the demand for high-technology health care significantly.
Industry’s response to this serious financial consideration is often to adopt a ‘cost-containment’ policy, arguing that if companies could reduce their medical insurance and disability claims, they would be able to lower health costs and potentially reduce their operating costs. Worksite health promotion programmes, with their goal of keeping employees healthy and reducing medical utilization, are a part of this cost containment policy. Thus the motivating factor here is financial savings, with good health as the means to the end.
The worksite as a setting for health promotion
The increasing interest in worksite health promotion programme is certainly healthy and the workplace has several factors that make it a unique setting for health promotion. Firstly, the workplace is where the worker spends the greater part of their waking hours. The work force also constitutes a captive population and any health promotion programme at the workplace would very likely invite encouraging response. The employer has the luxury of having at their disposal already well-established communications channels. They have existing physical facilities and resources from which they may adapt and expand upon. There is ease of administration and feedback, and the target population identified can be easily followed up. In addition, larger companies have in-house health personnel who can direct and run the programmes. There may be possible savings in health-care dollars as a result, but regardless of financial gain, the employer enjoys the image of being caring, in providing attractive staff welfare schemes.
The worker also benefits significantly. They have the convenience of not needing to expend time and expense in travelling to locations of community-based facilities. In addition, they are part of a homogeneous group that provides strong peer support and influence. They may also enjoy incentives from participating in worksite health promotion programmes (if the company offers any).
Worksite health promotion programmes inevitably leave an impact on society as a whole as well, because workers form a large proportion of the general population. The male worker is often the head of the household, with a strong influence on the family unit. Hence knowledge and benefits obtained from his participation in the programme will also permeate into his family.
Components of worksite health promotion programmes
The nature of the health promotion programmes offered differs greatly among the various companies. There is clearly great breadth and diversity of these worksite health promotion programmes among the companies that do implement them. One reason for this is the large variety of individuals who design and conduct them. Another reason would be the different motivating factors behind the initiation of worksite health promotion programme for each company, for example, cost containment, staff welfare, positive corporate image, and increased productivity. Fielding and Piserchia (1989) reported that 65 per cent of workplaces in America had one or more areas of health promotion activities. Common types of activities included individual health risk assessment, smoking cessation, control and treatment of hypertension, exercise and fitness, weight control, nutrition education, stress management, back problem prevention and care, and of the job accident prevention. Broadly speaking, the components that make up health promotion programmes include medical care, involving early detection and control of conditions that represent illness or are biological precursors to illnesses such as diabetes mellitus or hypertension. Worksite health promotion programme would aim to screen participants using appropriate techniques and subsequently intervene medically if warranted.
Another component would be the modification of high-risk behaviours with known or suspected negative health consequences such as smoking, inactivity, and poor nutrition. Methods to bring about successful behaviour modification include health information, education, counselling, and incentives.
The third component of worksite health promotion programme is overall corporate culture. Healthy behaviour has a better chance of being sustained if it becomes the norm. This would involve initiating company policies such as smoking restrictions, making time and facilities available for exercise and healthy diets, and positive role modelling by top management personnel.
Limitations of workplace health promotion
Despite the exciting possibilities that health promotion holds, it would still be prudent to consider some of the limitations of health promotion at the work place and the problems faced in the planning, implementation, and evaluation of such programmes.
Limitations of prevention and health promotion
Many people automatically assume that prevention is better than cure. However, prevention does have a price, which may sometimes be exorbitant, and is thus not necessarily always better. For illnesses with low prevalence, preventive measures that are directed at large numbers of persons would result in low yields. The costs involved in prevention then would far outweigh the benefits gained in prevention. While it is true that ‘a stitch in time saves nine’; this axiom might not apply to every person and every preventive measure (Skrabanek and McCormick 1990). They cautioned that, if the ‘one stitch’ has to be inserted one hundred times to save one individual from ‘nine’, it might be unwise to queue for stitching.
The goal of disease prevention, as referred to in most of the worksite health promotion programmes, usually refers to delay, rather than prevention of the disease. This is because many of the target diseases are multifactorial in origin, and while worksite health promotion programmes are mainly directed at the behavioural aspects of lifestyle change, less can be done about the other factors, such as heredity and social class.
Another major limitation to health promotion is the difficulty that exists in arriving at a commonly acceptable and precise definition of health that allows for objective quantification.
Health promotion as a crusade
The zeal for worksite health promotion programmes may sometimes border upon religious fervour, dependent more on faith than facts. This zeal may result in the ‘moralization of health’ (Conrad 1987a), where an individual’s character and moral standing are judged on his state of health, based on the premise of individual responsibility for health. This premise is, of course, not true for the diseases of unknown or multifactorial aetiology. In this scenario, ‘health deviants’ may be stigmatized by their peers for their unhealthy lifestyles, and ‘victim-blaming’ responses may easily emerge. Employers may blame some workers, such as the high-risk individuals who do not participate in worksite health promotion programmes, for their ‘deviant’ health behaviour and not doing something about it.
While participation in worksite health promotion programmes may be voluntary, some employees may well be ‘coaxed’ into participation, and incentives as well as disincentives (such as higher insurance premiums for the overweight and smokers) might be included. Nevertheless, there have been reports (Baun et al. 1986; Conrad 1987b; Lewis et al. 1996) that suggest that worksite health promotion programme participants are relatively ‘healthier’ and more health conscious that non-participants. This means that to some extent, the worksite health promotion programmes are preaching to the already converted.
A more recent review by Grosch et al. (1998) suggested that compared with availability of activities, participation depended less on individual and organizational characteristics. They reported that healthy employees were not consistently more likely to participate in worksite health promotion programme than non-healthy employees.
Conrad (1987a) has warned of the expansion of the boundaries of corporate jurisdiction via worksite health promotion programmes. Citing workplace programmes that screen for drugs, HIV/AIDS, or genetic make-up as the more obvious manifestations of this phenomenon, he cautions that worksite health promotion programmes, with their focus on smoking, diet, exercise, and blood pressure are entering the domain of what has been long regarded as private life. This concern might even be extrapolated further, to the (presently unlikely) point of corporate off-site surveillance programmes. One has to be wary of the extension of these boundaries of corporate jurisdiction. At its worst, ‘wellness’ might become a condition of employment or promotion, which is a type of job discrimination based on lifestyle and health.
Does health promotion really work?
Although there have been some favourable studies to suggest great benefits in health promotion, most authorities would agree that there is a paucity of rigorous scientific proof that addresses this literally multimillion dollar question. Bias in reporting further obscures the truth, as negative results after the input of large sums of money on worksite health promotion programmes, are unlikely to be reported by the persons responsible for the worksite health promotion programmes. Published results may overinflate claims of benefits, and many reports tend to be based on anecdotal evidence or have serious flaws in assumptions, data, or methodology (Warner et al. 1988; Conrad et al. 1991).
While cost containment may be a primary goal for employers providing worksite health promotion programmes, not all employers would benefit equally from worksite health promotion programmes. An economic model (Patton 1991) suggests that establishments employing highly productive, difficult to replace, and older employees are most likely to benefit. The majority of the economic benefit accrue from productivity gains, while effect on health-care expense, worker mortality, or retiree health expenses are small. The benefits may also appear after a period of time from the start of the worksite health promotion programme. A study of employees at Procter and Gamble (Goetzel et al. 1998) showed that in the third year of a worksite health promotion programme, participants had 29 per cent lower health-care costs as compared with non-participants. Overall, recent reviews on worksite health promotion programmes (Anderson and Staufacker 1996; Glanz et al. 1996; Heaney and Goetzel 1997; Pelletier 1997) are cautiously optimistic.
Worksite health promotion programmes are often one of the most visible and popular employee benefits. Some employers might use the introduction of worksite health promotion programmes as an excuse for cost shifting and reductions in other health benefit, such as reduced coverage and increased employee cost-sharing for the treatment of illnesses.
Health professionals may be equally quick to jump on the bandwagon of worksite health promotion programmes. As screening activities are often a part of many worksite health promotion programmes, there is certainly the potential of offering costly, profitable and opportunistic screening procedures, many of which have unproven benefits. The Australian College of Occupational Medicine (1983) believes that a conservative approach should be adopted, bearing in mind that no harm should result to the individual. Another requirement for screening procedures is that there should be conclusive evidence that the procedure can alter the natural history of disease in a significant proportion of those screened.
Impact of health promotion on occupational health
As mentioned earlier, occupational health practitioners have long recognized health promotion as an integral part of a comprehensive occupational health-care system. While the main thrust of occupational health is on the identification and control of physical, chemical, biological, and psychosocial hazards in the work environment, the main target of intervention in worksite health promotion programmes is often the individual, rather than the organization or the environment.
Thus there is concern that undue emphasis on worksite health promotion programmes might focus preventive efforts on the worker and divert attention, funding, and action from efforts directed at the work environment—as an example, focusing on individual stress reduction rather than altering a stressful work environment may help people adapt to unhealthy environments. Conrad (1987b) commented ‘One virtually never hears wellness people discussing occupational disease or hazardous working conditions. Whether they view it as someone else’s domain or as simply too downbeat for upbeat wellness programmes is difficult to know. This may in part explain why worksite health promotion has been greeted with scepticism by occupational health veterans.’ This diversion of attention from the work environment to the worker and the blurring of the occupational health focus might occur in both management as well as the work force. Care must be taken in implementing worksite health promotion programme to incorporate traditional occupational health concerns into the planning process so that a more complete programme may be developed that truly promotes workplace health in terms of the worker as well as their environment.
Problems of implementation, sustainability, and evaluation
The methodological approaches to health promotion are far less developed and more difficult than the epidemiological methods of planning, implementation, and evaluation of programmes of disease prevention. As an example, even the definition of what constitutes a programme has not been universally accepted (Golaszewski 1992).
There are several reasons for these difficulties. Firstly, there is still lack of knowledge on factors conducive to positive health. Very little research has been undertaken on the determinants of positive health, as it is very difficult to develop measurements of health as opposed to disease. Thus most scientific work has focused on the causes of disease and on its pathogenesis, rather than on positive health.
Secondly, health behaviour is very complex as it is influenced by economic, ecological, social, and political conditions. Thus strategies of health promotion programmes are far broader than those of disease prevention as they involve politics, advertising, health education, advocacy for health and healthy living, economics, community development, and ways to affect changes in peoples’ behaviour.
A properly implemented worksite health promotion programme should have written goals or objectives, have person(s) accountable for the achievement of objectives, a budget, and have continuity over time. It should also be a sustainable effort, as compliance with lifestyle changes, a common target of worksite health promotion programmes, has to be sustained to be effective. This may be difficult to achieve. As an example, a review of the literature on the compliance to exercise following worksite health promotion programmes showed that over 50 per cent of participants had dropped out after 6 months (Stoffelmayr et al. 1992). This problem of sustainability is a real one for many aspects of worksite health promotion programmes, and requires further research and attention.
Finally, all good worksite health promotion programmes should have evaluation built in as one of their components from the start of the programme. To facilitate proper evaluation, potential evaluators should keep in mind three points.

1.
Wherever possible, the evaluator should be independent of the persons who are conducting the health programme in question. This would prevent bias due to vested interest.

2.
Proper evaluation requires knowledge of the state-of-the-art on the health problem in question, so that the health evaluator will know what had been done, what can be done, and how it should be done.

3.
Design and resources for evaluation should be incorporated into the planning of a health programme. Otherwise, no documentation will be obtained on who was served, how well they were served, or what changes had occurred from exposure to the programme, which would render subsequent evaluation difficult or impossible.
There are two levels of evaluation that would need to be considered when assessing a programme’s effectiveness. These are process and outcome evaluations.
A process evaluation is a quality assessment review of the programme (Koh et al. 1994). This concept is not really new in either health care or in health education and promotion. In order to improve programme effectiveness, there is a need to examine continually the processes and skills of personnel who plan and deliver health-related programmes, and the compliance and acceptance of programmes by participants. This is the role of process evaluation. It compares what happened to what is supposed to have happened.
Outcome evaluation seeks to assess the effectiveness of the health programme on the target group (Koh et al. 1994). It is concerned predominantly with internal validity, which is the degree to which an outcome can be attributed to a particular intervention, namely did the programme work in this particular setting and did it produce the observed change?
Further development
Health promotion at the workplace is still developing, and much has still to be learnt. The dearth of sound evidence on the merits of worksite health promotion programmes should not be interpreted as a negative assessment of the potential of such programmes, but instead it recommends a healthy scepticism in reading the literature and in the development of a new research-based body of understanding (Warner et al. 1988). Pelletier (1997) has more optimistically suggested that ‘rather than interpreting the methodological flaws and diversity as inherently negative, we may consider it as indicative of a robust phenomena evident in many types of worksites, with diverse employees, differing interventions, and varying degrees of methodological sophistication’.
Over time, research and development will unravel much concerning the true capabilities and limitations of health promotion in the workplace. It is still worth remembering, however, that the pursuit of health in itself is a worthy goal. Even if nothing else, the incorporation of health promotion into the workplace context will certainly serve to provide a somewhat more balanced perspective of life for the worker.
From occupational health to environmental health
The recent rapid growth in interest in environmental health has created a dilemma as to its identity as a speciality in the field of health. The public interest in environmental health was not matched by a well developed speciality in the health field that could respond to its needs and concerns. Increasingly, occupational health practice today has evolved to encompass environmental health issues as well. This is because of several reasons. Firstly, many sources of pollution originate from the workplace. Secondly, in many other instances, the distinction between the work environment and the home environment may not be clearly defined. This is particularly seen in agriculture and small-scale industries, where a clear demarcation does not exist between the workplace and home.
Furthermore, there are several areas of common ground between occupational and environmental health (Jeyaratnam 1994). A comparison of the factors in the work environment influencing the health of the working population (occupational health) and that of the general environment affecting the health of the community (environmental health), is shown in Table 9. It is evident that there are several areas of similarity between the work environment and the general environment which affect health.

Table 9 Comparison of occupational health and environmental health

Occupational health practitioners have the necessary skills in clinical medicine, toxicology, hygiene, epidemiology, and preventive health to position themselves for the management of environmental health concerns, as illustrated in the following case study.

Case study 4: From occupational health to environmental health Villagers living along a river complained of skin disorders a few months after a paper pulp mill was sited upstream from their villages. The residents, who were mainly fishermen and farmers, bathed in the river and used river water for many of their domestic activities. They claimed that pollutants discharged from the paper pulp mill caused the skin disorders. An occupational health team was consulted to resolve the matter. Workplace assessment revealed some occupational health and safety issues that needed to be addressed. The plant utilized modern state-of-the-art technology, with a closed mill system. Monitoring of the effluent from the mill revealed that quality of the discharge was within internationally accepted limits. Examination of a group of the most severely affected villagers revealed that the main skin disorders were fungal infections of the skin, endogenous eczema, and irritant contact dermatitis at specific sites (e.g. from application of topical medicaments, hand dermatitis from use of detergents). A comparison of the existing health records of the village showed no increase in the proportion of cases of skin disorders before and after the paper pulp mill commenced operations. The main health problems were malaria and gastroenteritis. The conclusion was that the villagers’ health concerns (with regard to dermatological disorders) were unrelated to the paper pulp mill. However, the mill management provided supplementary community health care through its health-care department, in conjunction with the local health authorities. This gesture was appreciated by the villagers.

Conclusion
This chapter has traced the history and development of occupational health and its related legislation. In the practice of occupational health, prevention of work-related and occupational disease is a major objective. The priority in prevention of occupational diseases should be to effect primary prevention. When this fails, secondary prevention activities are undertaken to contain damage. However, health protection is not the only occupational health concern. Health promotion in the working population is another important activity. The workplace is an ideal setting for health promotion activities, and appropriate lifestyle interventions can prevent many of the common causes of morbidity in society. Finally, the practice of occupational health today has extended beyond the domain of the workplace, into the general environment. Hence the term occupational and environmental health might more accurately describe this important aspect of public health.
Further reading
Baxter, P.J., et al. (ed.) (2000). Hunter’s diseases of occupations (9th edn). Arnold, London.
Herzstein, J.A., et al. (ed.) (1998). International occupational and environmental medicine. Mosby, St Louis, MO.
Rom, W.M. (ed.) (1998). Environmental and occupational medicine (3rd edn). Lippincott–Raven, Philadelphia, PA.
Stellman, J.M. (ed.) (1998). ILO encyclopaedia of occupational safety and health (4th edn), Vols 1–4. International Labour Organization, Geneva.
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