OPERATOR FATIGUE MANAGEMENT GUIDE

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OPERATOR FATIGUE MANAGEMENT GUIDE Original contributors (ver 0.1) Alvaro Aliaga, Andre van der Linde, Archie Eksteen, Christo Aspeling, Coenrad Lusse, David Cather, Deane Macpherson, Gerhard Stenzel, Gert McCarthy, Hugo van Dyk, Johan Wepener, John R McEndoo, Mike Kilbride, Nombasa Tsengwa, Judi Sandrock

Editing and expansion (ver 0.2, ver 0.3) Prof Johan Hanekom

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Disclaimer The information contained in this document and associated references are not prescriptive. It indicates good practice and is intended as information for sitespecific interpretation and application by the responsible parties within the Anglo American plc group. The material contained in this document is based on information that is believed to be reliable, however, no representation or warranty, expressed or implied, as to its accuracy or completeness is made. No responsibility is accepted by Anglo American plc or any of its subsidiaries or associated companies for any loss or damage of whatever nature arising out of the use of, adherence to or lack thereof to any part of this information.

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Table of contents Glossary 1. Introduction 1.1 Objective

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2. Causes of operator fatigue 2.1 Consequences of shift work 2.1.1 Fatigue, sleep and biological rhythm 2.1.2 Medical complications 2.1.3 Psychosocial problems 2.2 Other causes of fatigue 2.2.1 Illness and medication 2.2.2 Monotony of task 2.2.3 Age 2.2.4 Nutrition 2.2.5 Fitness 2.2.6 Substance use and abuse 2.2.7 Environmental factors that influence fatigue levels

8 9 12 12 13 13 13 14 14 14 15 15

3. Management of operator fatigue 3.1 A comprehensive approach to fatigue management 3.2 Countermeasures to mitigate operator fatigue 3.2.1 Shift scheduling 3.2.2 The use of food and drugs to mitigate fatigue 3.2.3 The use of environmental stimuli to mitigate fatigue 3.2.4 Specific devices to assist with operator alertness

18 18 21 21 26 26 28

4. Recommendations

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5. References

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6. Contributors

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Appendix 1. Examples of shift scheduling

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Appendix 2. Elements of a healthy diet

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Appendix 3. Biological markers of circadian rhythm and circadian rhythm disruption 38 Appendix 4. Screening and placement

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Glossary Fatigue:

Physical or mental weariness

Backward rotation:

Shifts working against the clock, i.e. first night, then afternoon, and finally morning shifts

Forward rotation:

Working with the clock, i.e. day, followed by afternoon, and finally night shifts

Apnoea:

Severe and recurring disturbed breathing during sleep which is caused by the narrowing or complete closure of the upper airway, resulting in respiratory obstruction

Circadian rhythm:

Normal biological rhythm in the body (sometimes referred to as the body clock), that regulates human sleep/wake cycles and basic bodily functions

Insomnia:

Difficulty in falling asleep or staying asleep (can be transient, short term or chronic)

Time on task:

The number of hours that a worker has been on a shift

Actimetry:

Measurement of wrist activity as an indicator of the phase of the circadian rhythm

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1. Introduction Operator fatigue has been identified within the Anglo American plc group as one of the primary causes of accidents and loss of life, providing a challenge to its Safety Management Programmes. In many different studies in many industries, it has been shown that shift workers are subject to fatigue. It is widely accepted that fatigue of shift workers cannot be eliminated, but can be mitigated to some extent, and can be managed. Some of the problems associated with shift-work fatigue are summarised in the box below1. Problems associated with shift-work fatigue include: • Chronic sleep problems (more than 50% of shift workers) • Gastric ailments (4-5 times increase in occurrence) • Chronic fatigue (80% of workers) • Depression and mood swings • Increased alcohol and drug abuse • Higher incidence of serious accidents • Increased incidence of divorce and spouse abuse

With operations worldwide affected, the group felt a duty to address operator fatigue in shift workers, while acknowledging that each operation will have different risks. The experience of managers from several operations was pooled by sharing knowledge and best practices. This has been supplemented with international experience and research to develop this document towards reducing and managing operator fatigue at operations of the Anglo American group. Case studies highlighting solutions that have been developed for specific operations in the group are available within a web tool specifically designed for this purpose at http://jnbqp1.corporate.aaplc.com/atd_cop.2

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Grey text boxes are used throughout the document to highlight important research findings. This document can be accessed by members of the Anglo American Group through the following sites. • For those who are registered on the Portal - Open the Portal and visit the safety portlet • For those who are registered on the SHE Knowledge Base - Open the SHE Knowledge Base and go to Guidance Documents Those who have access to the Anglo Johannesburg intranet - go to the Tech-Know Link or the ATD (Technical • Documents, AA Best Practice Guidelines) sites • Those who do not have access to either of the above - go to the ATD web site via the internet http://www.anglotechnical.co.za/ (password 6,45main) and follow the path in the ATD site in the previous bullet or search for AAC_OH_000003 (Operator Fatigue Management Guide). • For Kumba divisions, it is also available on the Kumba Intranet &

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1.1 Objective As an ethical employer, Anglo American plc desires to provide a safe working environment for all employees, in which risks are appropriately managed. To protect the health and safety of personnel, combat fatigue, increase productivity and prevent accidents, injury or damage to equipment, it is necessary to develop a management plan to ensure that risks associated with operator fatigue are mitigated appropriately. As a result, this document was developed to: •

increase awareness on operator fatigue,

•

serve as a vehicle to share best practices, and

•

assist Anglo American plc operations in developing their own solutions.

The right solution for each operation should be developed based on each operation’s profile, risks, employees and mine circumstances. It should also be developed in consultation with its stakeholders and should be thoroughly tested before implementation.

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2. Causes of operator fatigue Fatigue is a complex state characterised by a lack of alertness and reduced mental and physical performance, often accompanied by drowsiness. Two main types of fatigue may be distinguished. •

Task-related fatigue This is a function of the number of hours worked, workplace conditions, physically or mentally strenuous work and task risk.

•

Non task-related fatigue This is associated, among others, inability to cope with work conditions or shift work, the disruption of natural sleep rhythms in shift workers, sleep disorders, family conflicts, and ineffective management of shift work by the worker and company alike.

The main causes of workplace fatigue have been identified to be [2-4] the following. • Attempting to work after inadequate sleep (both the duration and the quality of sleep is important) • Attempting to work against the natural biological clock (the circadian rhythm, to be explained below) • Duration of daily duty periods • Duration of time away from work (days off and breaks in duty periods) • Pattern of duty, rest and sleep within the 24 hour cycle • Workload • Monotony of task Some studies have equated the effects of fatigue and alcohol intoxication (e.g. [5]). A shift in the sleep-wake cycle (e.g. working the night shift) initially produces performance deterioration that is greater than the performance deterioration for alcohol intoxication at currently acceptable levels (0.05%). 2.1 Consequences of shift work as primary cause of fatigue Shift-work is a primary cause of fatigue [3], [6]. Nearly 20% of workers worldwide work in shifts. Irrespective of patterns of work scheduling, it has been unequivocally accepted that shift work disrupts biological rhythms, sleep and social interaction [7], [8]. Research shows that sleepiness at work is no issue with daytime workers, but dramatically impacts on shift workers.

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2.1.1 Fatigue, sleep and the biological rhythm To understand what underlies fatigue in shift workers, it is necessary to understand the concept of circadian rhythm. The human body operates on a 24hour internal clock, which is synchronised to the 24-hour day-night cycle. A large number of biological processes can be identified that have a 24-hour cycle (or circadian rhythm). This includes sleepiness, body temperature and hormonal levels in the brain and body. These processes are synchronised in the body. This means that, for example, body temperature is lower at night. People are awake and alert during the high phase of the circadian rhythm, and sleepy during the low phase. Two types of people may be distinguished regarding when they operate best during the 24-hour cycle. Morning people have their circadian high phase in the morning/afternoon, while evening people have their circadian high phase in the afternoon/evening. One set of data [7] shows that the best performance in a mental task fell for the first group in the time slot between 8:00 and 12:00, while for the second group it was between 16:00 and 20:00. Other studies have shown that alertness and performance show a maximum in the late afternoon and a trough in the early morning around 5:00 [6]. Research has proven that shift work strongly affects health and performance by disruption of circadian rhythms [7], [6]. Intolerance to shift work accompanies internal desynchronisation among circadian rhythms. This means that the high and low phases of the different body rhythms do not operate in phase in more, which may result in sleep disorders and health problems. Workers with better tolerance to shift work are less prone to having their circadian rhythms become desynchronised. Circadian rhythms never adjust completely to the night shift, so that workers are always more sleepy, less alert and more accident-prone during the night shift [7], [3]. Evening people (16 % of people in a particular study in a hot climate) adapt better to shift work [7]. However, they also reach circadian lows in the early morning hours. Therefore, as the majority of shift workers work during the night at the low phase of their circadian rhythms, sleepiness and the resulting poorer performance is always expected and cannot be eliminated [6]. It can however be mitigated, as will be explained below.

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a. The importance of sleep As mentioned earlier, research studies have equated the effects of fatigue (caused by sleep deprivation) and alcohol intoxication (e.g. [5]). • •

A period of 18 hours without sleep is equivalent to the legal blood alcohol limit of 0.05%. In many cases, one of four shift workers in the mining industry suffers from some kind of sleeping disorder.

It cannot be stressed enough how important it is for health and performance that workers get quality and quantity of sleep. Sleep has a profound effect on fatigue levels. Many studies show that night shift work results in acute partial sleep deprivation [7]. The importance of sleep, particularly for shift workers, cannot be ignored, as sleep deprivation might result in fluctuating moods, low motivation and low tolerance levels. Research has shown that performance deteriorates during the night time, when night workers operate at their circadian low phase [7]. The most dangerous symptom of being sleep-deprived is that workers have slower reaction time, decreased alertness and decreased performance [7], [9]. These are all factors that influence the ability to make decisions, so that more mistakes are made. Major lapses of performance can occur at higher levels of sleepiness [7]. Many studies have shown that sleep deprivation leads to significantly higher risk of accidents and injury [7], [4]. Fatigue was identified as a significant contributing factor in a number of large scale disasters, for example the Chernobil disaster [10]. Shift workers have problems with sleep management, as they attempt to have sleep at times of the day that do not match their natural biological rhythms. Several studies show that shift workers experience sleepiness during night shift work, while work during the daytime is associated with no or marginal sleepiness [7]. A considerable increase in sleepiness is also evident in workers that return to the day shift after working on the night shift [7]. Morning shift workers have greater difficulties to fall asleep and also sleep less [3] than afternoon shift workers. Many studies have shown the circadian rhythm in subjective sleepiness in humans. The sleepiness rhythm exhibits a peak between 21:00 and 23:00 [7]. An early start to the morning shift (6:00) has a particularly detrimental effect on alertness [7].

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The proportion of shift workers suffering from sleep disturbances is above 50%, while this number is 5-20% for day workers [7]. The problems include difficulty in initiating sleep and staying asleep. Sleep is very difficult to achieve at the high phase of the circadian rhythm and very easy at its low phase [6], [7]. Consideration of both the quantity and the quality of sleep are important when determining whether a person is deprived of sleep. These are discussed next. b. Quantity of sleep Several studies on experienced night-shift workers have revealed that night work decreases sleep length. Day sleep after working the night shift (also, early night sleep before working the morning shift) is 2 to 4 hours shorter than regular night sleep [6]. Shift workers have on average 14 hours less sleep per week than daytime workers because of difficulty to fall asleep while the body is at a high phase of the natural body rhythm during the morning and afternoon.

Studies have shown that sleep duration is dependent on the time of sleep onset. Sleep duration is the shortest if started some hours after the circadian low phase [7]. Morning shifts (starting between 4:00 and 7:00) are usually perceived as extremely fatigue-inducing [7]. Shorter sleep duration is associated with decreased life expectancy [7]. c. Quality of sleep Two problems are associated with poor sleep: •

sleep disturbances, and

•

sleep disorders.

Sleep disturbances. Poor quality of sleep could be due to environmental effects in the sleeping environment. Any disturbance while a person is asleep, including temperature changes, lighting conditions, noise and limited space to sleep may lead to sleep being interrupted or sleep quality being poor. These factors can be mitigated in many situations. Sleeping disorders. There are four types of recognisable sleeping disorders that may result from sleep deprivation and shift work. • Insomnia is caused primarily by disruption of the circadian rhythm. As mentioned before, it is extremely difficult to fall asleep at a natural circadian high phase. Sore joints and arthritis have also been recorded as causes for &

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insomnia. Hypersomnia is poor quality of sleep due to disturbances, resulting in sleepiness in workers. Parasomnia is mainly associated with sleepwalking. Obstructive sleep apnoea is recognisable through heavy snoring, pauses in breathing, restlessness, excessive daytime sleepiness and headaches.

People with higher levels of lifestyle regularity report fewer sleep problems [8]. I.e., it is important to develop a regular pattern in the daily routine, especially regarding bedtime and waketime. 2.1.2 Medical complications of shift work Desynchronisation of circadian rhythms (resulting from shift work) may lead to several medical complications. This includes physical health, impaired metabolism, impaired responsiveness to medication, and longevity. There is higher risk of cardiovascular disease in shift workers as compared to day workers [7]. Other cardiovascular disease risk factors also increase in shift workers: blood cholesterol tends to be significantly higher in shift workers, blood pressure is generally higher, and smoking is more common [7]. Gastrointestinal disorders are significantly correlated to shift work. This is related to (among others) eating food at the wrong time, irregular meal times, eating sandwiches or snack food rather than balanced meals, and higher intake of carbohydrates, caffeine and alcohol [7]. The importance of proper nutrition is discussed in section 2.5. Mental health is affected by shift work as well. Shift workers complain more frequently about depression, anxiety and stress [7]. The adverse effects of shift work on health are aggravated in older individuals (starting at ages between 40 and 50) [7]. 2.1.3 Psychosocial problems associated with shift work Shift workers have been shown to experience a number of psychological disturbances and family dysfunctions, which seriously impacts on the social and family life [7]. Shift workers have higher than normal stress levels, which affect their fatigue levels. In many cases, shift workers finding it difficult to maintain satisfactory social and family lives and may end up neglecting recovery time from work to fulfil other &

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needs and responsibilities. Stress in shift workers is caused by several factors, including the following. • • •

• •

Shift work often isolates the worker in both time (work when others are asleep) and space (work far from home). There is a tendency for shift workers to work more overtime or to do moonlighting. This displacement of workers (in time and space) can result in domestic inconvenience and have detrimental effects on relationships within the family [7], [11]. There is a lack of "normal" family interactions (e.g. rituals, feasts, and birthdays). Duties at home may be neglected. Research indicates that levels of anxiety are much higher in families of shift workers than those of day workers [7]. The above factors result in an increased risk of divorce and suicide in shift workers.

Social needs must be considered and understood when designing shifts. • • • • •

There must be intervals between shifts to allow time for socialising. Timing of shifts of shift should be appropriate, so that socialising is allowed during times at which day workers would normally socialise. The number of weekends off within a 28-day cycle should be appropriate. It should be considered that more consecutive long weekend days give shift workers more time to socialise normally. Arrangements to accommodate the special needs of pregnant and breastfeeding workers, workers with family responsibilities, older workers, disabled workers or workers with health problems are necessary.

2.2 Other causes of fatigue 2.2.1 Illness and medication Illness like clinical depression, flu, diabetes and heart disease can affect the level of fatigue in the workplace. Although these illnesses can be medically treated, medication can affect the alertness of workers. 2.2.2 Monotony of task Repetitive tasks and long hours without physical activity lead to long, undemanding and monotonous work. This in turn leads to tiredness, sleepiness and increases the risk of accidents. Any situation that creates monotony (e.g. absence of stimuli or sequences of similar stimuli) will impair alertness and performance [6]. The risk for perceptual errors is greatest when the task and &

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environmental demands are low, such as driving on a quiet road for a long time [4].

2.2.3 Age As people get older their ability to cope with shift work deteriorates. Their sleep becomes lighter and more awakenings occur during sleep, so that sleep efficiency declines. However, sleep deprivation affect young workers more than older workers. Although young workers have significantly quicker reaction time3 than older workers, reaction times in older workers change less when deprived of sleep (in shift work, for example). It is also interesting to note that older workers are more realistic in their expectations regarding the effect of fatigue on their performance [9]. I.e., younger workers are more likely to expect that sleep deprivation will not affect their performance. 2.2.4 Nutrition Inadequate nutrition contributes to fatigue. A specific illness, chronic fatigue syndrome, is characterised by: • fatigue that is disproportionate to the intensity of effort that is undertaken, • has persisted for 6 months or longer, and • has no obvious cause. Malnutrition has been shown to be one of the primary causes [12] of this syndrome. Proper nutrition is very important in combating fatigue (e.g. [13]). It is abundantly clear from research studies that good nutrition underlies good health. Appendix 2 provides an example of a well-balanced diet. Note that, in addition to requiring a balanced diet, the time of day for meals and the frequency of intake are equally important. Meal timing is one important synchroniser of circadian rhythms [7].

2.2.5 Fitness The relationship between fitness and fatigue has been known for a long time (e.g. [14]). Physical fitness improves performance. It also speeds up the recovery time between shifts. Even moderate levels of exercise, like walking three or four times a week for 30 minutes, can deliver good returns in time. 3

Reaction time testing is a sensitive measure of sustained attention. &

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Exercise has been proven to: • • • • • • •

reduce the risk of cardiovascular disease, increase the quality of sleep, decrease fatigue, reduce muscle tension, counter stress, improve concentration, and improve performance.

2.2.6 Substance use and abuse The two main substances likely to be abused by shift workers are caffeine and alcohol. Caffeine and alcohol intake can prevent workers from having a good night’s rest, contributing to fatigue at work. a. Caffeine It is true that caffeine (e.g. coffee, Coca-Cola) improves alertness and physical function [15], [16]. However, the danger is that (especially if taken in large quantities over time) caffeine may delay sleep onset, lighten sleep, decrease total sleep time, and worsen post-sleep performance [15]. Furthermore, the body will build up a tolerance to it. b. Alcohol Alcohol initially promotes sleep, but then it disrupts the second half of sleep, shortens the total sleep time, aggravates gastro-intestinal problems and aggravates snoring and sleep apnoea.

2.2.7 Environmental factors that influence fatigue levels Various environmental factors have been found to affect fatigue of operators in different environments. If managed properly, operator fatigue may be reduced. a. Thermal stress Heat or excessive cold prevents workers from getting good sleep after a productive shift. In a South African context, this may be especially true for workers who do not stay in a hostel. Heat-related stress is less of a problem for shift workers staying in hostels fitted with air conditioners (which is true for some local mines). Heat tolerance times are documented in [17]. In summary, workers doing physical work can tolerate temperatures of 45 oC for around 15 minutes, 40 oC for about 30 &

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minutes, and 35 oC for 90 minutes. Sedentary workers can tolerate these temperatures for longer. These are the maximum values that can be tolerated before heat stress and fatigue takes its toll and performance declines. For unimpaired mental performance, the maximum exposure times to various temperatures are less than the numbers given above for physical work, e.g. around 60 minutes at 35 oC. Decline in performance can be expected below 20 oC or above 30oC for physical tasks. b. Illumination Illumination (or lack thereof) contributes to fatigue in two ways. First, as . discussed before, excessive illumination in sleeping areas contribute to poor quality of sleep. Second, poor lighting conditions contribute to fatigue levels of night workers. The advantages of illumination on night shift have been demonstrated, especially in critical areas such as intersection and places where equipment has to be manoeuvred. Although there may be limitations to the extent to which such areas can be illuminated due to practical and economical considerations, minimum illumination should be within legal limits. Night audits should be done to identify all working areas that need illumination. c. Noise Long exposure to high noise levels (>95 dBA) may induce irritability, headaches, fatigue and sleep disorders. Noise is detrimental to the performance of difficult tasks and will influence decision-making ability. Levels of 70 to 80 dBA are disruptive to cognitive tasks, such as where short-term memory is required. Variability in performance increases with high levels of noise. High noise levels in the home environment or in sleep areas raise stress levels and disrupt sleep.

d. Vibration Operating equipment that vibrates excessively may be equivalent to doing physical work for an entire shift. Excessive vibration can cause fatigue, whereas certain constant levels of vibration may also induce sleep. The ISO has developed a standard for whole-body vibration that specifies the limits in terms of time of exposure, intensity of vibration (measured as acceleration), and frequency of vibration [17]. In summary, accelerations of around 4 ms-2 can be tolerated for 1 minute before fatigue sets in, while vibrations of 0.4 ms-2 can be tolerated for 8 hours. Vibrations in the 3.5 Hz to 6Hz range can have alerting effects, while vibrations outside this range can have a relaxing effect that may induce sleep. e. Air quality Although poor ventilation is a cause of sleepiness [6], the importance of ventilation does not end there. The air quality that workers breathe, both outdoors and &

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indoors, is of extreme importance in health. The seriousness can be illustrated by the following example. In 1987, 700 workers out of 1250 that worked in a particular building, became ill. They showed many different symptoms, and were off work for periods ranging from 3 months to 3 years. This was ascribed to problems in regulating air quality in the building [1].

Polluted indoor air has been associated with health problems that include asthma, sick building syndrome, multiple chemical sensitivity, and hypersensitivity pneumonitis. Symptoms are often nonspecific and include headache, eye and throat irritation, chest tightness and shortness of breath, and fatigue [18]. Dust and other pollutants may affect fatigue levels directly or indirectly. Any environmental stressor will increase fatigue levels. Pollutants can cause shortness of breath or asthma, which in turn leads to increased levels of fatigue. Initiatives to reduce excessive dust and pollutant levels should be promoted. Generally, the use of dust masks alone is not adequate. Dust mask can only partially protect the individual against inhalation of dust or other pollutants, while they also cause carbon dioxide inhalation that will increase worker drowsiness on the job.

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3. Management of operator fatigue It is important to understand that operator fatigue is the result of factors that cannot be eliminated altogether, but that can certainly be controlled. Operator fatigue cannot be eliminated, but • countermeasures can be put into place to combat fatigue, and • fatigue can be limited by proper management. Management of fatigue is not simply a matter of correct shift scheduling. Rather, a comprehensive fatigue management programme as opposed to prescriptive hours of work is required [2]. The guidelines in the following sections may assist the management of fatigue. When using these guidelines, priority should be given to keeping operators awake, as opposed to waking them up. 3.1 A comprehensive approach to fatigue management A comprehensive approach to shift management will typically incorporate the following aspects. In some of the points to follow, the parallels with safety management plans are obvious. Some aspects of the following is based on [19] and [7]. •

Management commitment. A strong commitment from management to managing fatigue is advisable, reflected by actions (i.e. enforcing of a fatigue management plan; the appointment of a high ranking officer responsible for fatigue management, probably the same individual responsible for safety within the organisation).

•

Communication channels. There must be interaction between workers and managers. Communication on fatigue management, safety and other job matters must be open. Regular meetings should review policies, rules and procedures.

•

Shift planning. The design and improvement of shift schedules should also be based on information obtained from employees during consultations, negotiations or questionnaires and the impact of shift work on their performance, private and social needs should be recorded and analysed. Changes to shift schedules should be managed by a team consisting of employee representatives (trade union), industrial relations, human resources and line management. &

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•

Legal requirements. All relevant legislation should be adhered to in scheduling shifts times and duration.

•

Operational management. A high level of housekeeping is important. Attention should be given to specific fatigue-related hazards. Incident and accident should be documented, and investigations should be conducted after these have occurred. Causes of accidents (which may include fatigue) should be indicated in these reports.

•

Training. Managers and workers should receive training and regular followup sessions to ensure that both groups remain alert regarding operator fatigue. Shift operators and their families should be advised on: o the causes of fatigue o the consequences of shift work o the management of fatigue o good sleeping habits and healthy diets o physical fitness programs and advantages o proper nutrition

•

Pre-shift screening. Screening should ideally take place before shifts commence. Drug and alcohol tests should be undertaken with correctly calibrated instruments before the shift commences, and it should be determined whether workers are not too fatigued to go to work. Depending on circumstances, employees failing any of these pre-shift tests should not be allowed to work the specific shift, or should be denied access to any mobile equipment. Although representing a larger risk, some operations may find it practical to use random screening, rather than to subject every worker to tests at every shift.

•

Screening of circadian rhythm. It is recommended that the natural body rhythm be screened annually to determine the state of the biological clock of each individual (measure whether the circadian rhythm is still synchronised or not). Appendix 3 gives an indication of procedures that may be used. This will also be valuable in establishing which workers are morning or evening types (the latter being more suited to night work). On discovery of a desynchronised circadian rhythm in a worker, it is recommended that this worker be transferred to day work for at least one year.

•

Placement. There should be well-developed selection and placement &

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procedures, keeping in mind that not all individuals are suited for shift-work, as discussed earlier. For example, evening people are more adaptable to night shift work than morning people. Appendix 4 summarises criteria that may assist in selection and placement. Selection and placement procedures are generally to some extent based on the outcomes of preemployment health screening. •

Health screening. Specialist pre-employment medical screening implemented at Anglo American plc operations, in combination with manjob specifications, are generally adequate to identify predisposing factors for general health (e.g. vision, hearing, age, drug use and general fitness). However, shift operators are exposed to stress that may result in inadequate sleep and fatigue. In addition, other medical conditions such as arthritis, cardiovascular disorders, high blood pressure, high blood sugar, gastro-intestinal disorders, respiratory disorders and mental disorders may be caused by or enhanced by disruption of the circadian rhythm and fatigue. Physical and mental health should be screened at least at annual intervals. Identified health disorders should be followed up regularly. All employees with negative health-screening tests should be referred for appropriate therapy or counselling, where appropriate rehabilitation programmes can be put in place for them. These programmes may include personal counselling or group therapy, depending on individual needs.

•

Support services and therapeutic interventions. Employee support services should be available (i.e. counselling, recreational facilities). It is very important to identify when to intervene with therapy to assist shift workers cope with non-task related problems like: o o o o o o

•

family and marriage problems, alcohol and drug problems, trauma counselling, psychological problems, work-related problems, and medical conditions such as HIV/Aids.

Lifestyle. Living patterns and personal lifestyles also have a major impact on operators especially since taking care of extended family and unsuitable living conditions might contribute to poor sleeping and eating habits.

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3.2 Countermeasures to mitigate operator fatigue Several countermeasures to combat fatigue may be considered, these being • appropriate scheduling of shifts, breaks and rest, • appropriate use of drugs and food, and • appropriate use of environmental stimuli. Of these, shift scheduling impacts most strongly on fatigue. This will be discussed first.

3.2.1 Shift scheduling As mentioned earlier, night shift workers get 14 hours less sleep per week than day workers. Apart from the difficulty of falling asleep at inappropriate times (in relation to the biological rhythm), poor shift scheduling aggravates the situation regarding sleep deprivation. Although shift scheduling is a key management action, it should only be one element of each operator fatigue management plan. As discussed above, comprehensive fatigue management programmes are preferred above prescriptive hours of work [2]. Different shift patterns are used in various industries, the most popular being 12hour shifts (night and day shift) and 8-hour shifts (morning, afternoon and night shifts). Although there is no apparent right or wrong way to schedule shifts, there are factors to keep in mind (discussed below). Shift scheduling in each operation should be based on employee and operation circumstances. In the design of a shift schedule, a number of parameters can be manipulated to achieve a balance between the health and safety of the worker and productivity [10]. For example, the time at which a shift starts, the duration of individual shifts, and the direction of shift rotation, all impact on both productivity and the capacity of workers to recover from fatigue. Work schedules can affect absenteeism rates, error rates, incident rates and accident rates. a. Driving principles in shift scheduling The goal of shift scheduling is usually to achieve either of two objectives: • to minimise the shift in circadian rhythm, or • to achieve a complete shift in circadian phase. The first is the objective when rotating shifts are used. The second is the objective &

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when placing a person on permanent night shift.

Rotating shifts should be designed to minimise disruption of the circadian rhythm, and to give the shift worker enough rest periods and periods to socialise at appropriate times.

Workers on permanent night shift should achieve a complete shift in the circadian rhythm, so that their circadian low phase occurs during the daytime when they should sleep.

The general consensus in the scientific literature is that night work should be reduced as much as possible. If this is not possible, rapidly rotating shift systems are preferable to slowly rotating ones. This will be considered in more detail below.

b. Factors to consider in shift scheduling

What follows is a list of factors to consider when scheduling shifts. The list includes a number of results from research studies, which may prove helpful when designing shift schedules.

Permanent night shift •

The nightshift is the critical shift regarding operator fatigue and safety.

•

Permanent night work does not seem to be recommendable for the majority of shift workers [20]. The general consensus is that night work should be reduced as much as possible, or, where appropriate, eliminated. Night work may be reduced by (i) scheduling fewer night shifts for each worker during a four week cycle, (ii) shortening of the night shift [2]. As is discussed in further detail below, where it is not possible to reduce night work, a rapidly rotating shift system may be used.

•

Although permanent night work is not recommended, there is some support for permanent night work, as it will maximise adjustment of the body rhythm to night work. This is opposed to rapidly rotating shift systems, which are designed to minimise circadian disruption [5]. The strongest argument in favour of permanent night work is that there is a lower accident rate in permanent night workers than rotating shift workers [7].

•

Where permanent night work is contemplated, the following considerations need to be taken into account. Initially there is a progressive decline in performance over several consecutive night shifts [7]. A reasonable degree &

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of adaptation to the night shift does occur over a week of consecutive night shifts [5]. However, nighttime performance remains sub-optimal. Shifts in the circadian rhythm will occur at the rate of about one hour per day (e.g. when changing to permanent night shift). The mechanism is exposure to light at a particular circadian phase. This adjustment can be achieved more rapidly by artificial light (see paragraph 3.2.3). The circadian adjustment of shift workers, however, is counteracted by a day-night light pattern in opposition to night work hours [6].

Rotating shifts •

It is not entirely clear from research whether rotating shifts are less safe than stable patterns. This depends on a number of complex individual and organisational factors [4]. However, generally rotating shift systems are preferred to permanent night shift.

•

A primary motivation for this is that research has shown that rapid shift rotation ensures that no shift in circadian rhythm occurs. This system minimises sleep deprivation and circadian rhythm disruption, while it improves social contact, alertness and health compared to working on the night shift only [7].

•

The number of consecutive working days should be limited to around five (with a maximum of seven) [20]. However, a rapid rotation (2 to 4 days) is better than weekly rotation [2], [7]. Desynchronisation of the circadian rhythm is transient under these conditions, and recovery more rapid.

•

Every shift system should include some free weekends with at least two consecutive days off during a four week cycle [20].

•

Clockwise (forward) rotation in shifts is tolerated better than backward rotation [2], [7], [20].

•

Note that there is a progressive decline in performance over several consecutive night shifts [7]. In a rotation shift schedule, it is recommended that there should not be more than three consecutive night shifts.

•

Short duration changeovers (or rapid changeovers) between shifts seriously shorten sleep [21]. Rapid changeovers (e.g. from night shift to afternoon shift on the same day) should be avoided.

•

An early start for the morning shift (before 6:00) should be avoided [20]. Such an early start to the morning shift forces workers to awaken at the circadian low phase, which is particularly fatigue inducing.

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Extended shifts •

Extended shifts (9-12 hours) should only be contemplated when the nature of work and the workload are suitable for extended working hours, and the shift system is designed to minimise the accumulation of fatigue and toxic exposure is limited [20].

•

The impact of extended shifts (12 hours) on employee health and safety is highly dependent on the specific work tasks involved. 12-hour shifts are a viable option to 8-hour shifts. A key provision is that 12-hour shifts should not be extended by overtime. The regulation of overtime is important, as the time for recovery between extended shifts will be greatly reduced when overtime is worked [10]. Furthermore, employees should not be brought in on their off days to work additional shifts.

Alertness and time of day •

The effect of time of day on performance should be taken into consideration when scheduling tasks within a shift, and when scheduling the start and end times of shifts [10]. Studies indicate that the greatest fatigue occurs in the early morning hours. This correlates to findings that indicate that there is a higher rate of adverse incidents during the period 01:00 to 06:00 (peaking perhaps at 03:00) and, to a lesser extent, between 14:00 and 18:00.

•

The scheduling of tasks within shifts should be planned such that high risk tasks are performed during periods of highest alertness. Hours on shift (or time on task) is a significant factor in the rate of incidents and accidents in the workplace. More than nine hours on task can expose the worker to extremely high risk for accidents and incidents [10].

•

Investigations of time on task effects in the transport and mining industries showed increased risk at about four to five hours into the shift. Scheduling of high risk tasks should be minimised around these time points, and breaks should be strategically planned [10].

Provision for breaks and nap taking •

Research suggests that less fatigue problems would be experienced if schedules were created that supported break taking and nap taking.

•

Increased alertness is found after breaks, but in all studies a gradual return to sleepiness begins immediately [6].Therefore, breaks to raise alertness should be inserted at relatively short intervals. It becomes more effective when combined with food intake and physical activity. Breaks as a fatigue countermeasure is primarily valuable to mitigate sleepiness due to time on task, but has no effect on the circadian rhythm. Strategic timing of breaks or shift changeover, to maximise the degree of alertness and minimise &

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performance impairment, may reduce the incident frequency [10]. •

Napping may is probably the most effective countermeasure against sleepiness during night shift work [10], [6]. Effective naps are around 30 minutes to two hours long. It needs to be kept in mind that there will be 5 to 15 minutes of impaired alertness after awakening [6]. Naps should ideally be formally scheduled as part of the shift.

Worker participation in scheduling shifts •

Research studies have shown that subjective fatigue levels perceived by workers is related to the amount of participation that they have in the process of shift scheduling. Increased worker autonomy in deciding schedules is valuable in counteracting fatigue [4]. The process by which changes to shift schedules are implemented within a workplace is important to the resultant effects on employee health and safety [10].

•

Flexible working time arrangements is recommended in shift systems [20].

c. Shift design Using the principles above, the following duty limits should typically be specified in a fatigue management plan [2]. See Appendix 1 for examples. • maximum time for continuous duty (number of days) • minimum time of breaks from duty (number of days) • maximum duration of a shift • minimum off-duty time between consecutive shifts • minimum off duty time following the night shift • maximum number of consecutive shifts • maximum number of consecutive night shifts • maximum average period of duty within any shift cycle • minimum number of actual off-days in a 4 week cycle • maximum night shift duration The scheme should also detail variations for particular situations involving the following. • emergencies • situations where life or property is endangered • unforeseen operational circumstances Procedures should be in place to enforce the above minimum or maximum times. Procedures should be in place to retract operators that are fatigued from service.

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3.2.2 The use of food and drugs to mitigate fatigue a. Caffeine Caffeine is rapidly absorbed and have an almost immediate impact on alertness and fatigue [6], [16], [15]. This impact usually lasts between 5 and 7 hours. However, the increase of alertness by caffeine would not necessarily cause a corresponding improvement of performance, especially in the early morning (circadian trough), and after long (24 hours) sleep deprivation [6]. Also note that the increased alertness induced by caffeine spills over into the sleeping time of workers, resulting in poorer quality of sleep. Thus, caffeine is a valuable remedy if immediate increased in alertness is desired in particular situations, but should not be used as a regular long-term measure to mitigate fatigue. b. Sugar Sleepiness is reduced by an increased intake of sugar. However, heavy food intake leads to an increased risk of sleepiness. Fat and proteins have a less alertness-enhancing effect than sugar. Either way, the effects of food intake on wakefulness is not very strong [6]. c. Drugs Drugs are not commonly used to mitigate fatigue resulting from shift work. It is of interest to note that there has been some research on the possible manipulation of melatonin, a hormone found in the brain. Melatonin level demonstrates a circadian rhythm and changes in this level is associated with the day-night cycle. Research has shown that it may be possible to shift the circadian clock by manipulating melatonin levels. However, it is not used yet to control fatigue resulting from shift work [6]. It is not currently recommended that drugs be considered as way to mitigate shift-work fatigue. 3.2.3 The use of environmental stimuli to mitigate fatigue a. Noise Noise is a definite candidate as a fatigue countermeasure. Research has shown that low frequency noise and monotonous noise can cause tiredness, whereas high-frequency sound has an alerting effect. Listening to the radio increases alertness when tired [6]. b. Activity Although physical work, with associated increase in sensory stimulation, results in increased alertness, it is also true that heavy physical work is followed by aftereffects on alertness, resulting in a more rapid onset of sleepiness [6]. c. Social interaction Social interaction (conversations) is valuable in enhancing alertness in shift &

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workers when sleepy [6]. This may include conversing while on the job (where this will not impede concentration), during breaks, and over two-way radios where workers work in relative isolation (e.g. truck drivers). Radios on trucks and mobile equipment are used in some operations to establish communication between operators and the control room, while two-way radio systems with a dedicated channel for operators to chat with each other is valuable in mitigating fatigue. Note that while some operations require some workers to use cell phones, others have found that these may reduce productivity. d. Environmental temperature The degree of alertness is usually reduced upon exposure to higher temperatures [6], [17]. Alertness drops above 25 degrees when doing sedentary work. In experimental circumstances, a 10 degrees drop in temperature over a period of one minute significantly increased alertness. Once adapted, the temperature drop has to be repeated. It is not as effective as noise in increasing alertness and is also less practical and more unpleasant. However, alertness and performance is enhanced when controlling the temperature appropriately for sedentary work. e. Light Light exposure may be used in two situations to mitigate fatigue. First, light may be used to achieve a rapid shift in the circadian phase of permanent night workers [6], [22]. Second, the use of bright light may be used to decrease sleepiness and increase alertness in night shift workers [23]. Where light exposure is used in practical situations, the duration of exposure is usually around 2 to 5 hours and the intensity may be as low as 1200 lux. The sensitivity to light exposure is at a maximum immediately before and after the circadian trough and the sensitivity disappears 4 to 5 hours away from the trough. Bright light exposure in the first part of the night is not very effective, but does help to a limited extent to alleviate sleepiness in night workers. However, it does not necessarily have a significant impact on alertness [23]. On the other hand, bright light exposure can have powerful immediate physiological and psychological arousing effects when administered in the second part of the night (early morning hours). Different physiological mechanisms apparently underlie these two effects. Bright light exposure in the early morning appears to trigger a day-oriented arousal response. It must be noted that the biological effects of bright light exposure may last for a long time during the following day, which will influence the quality of daytime sleep in night shift workers.

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3.2.4 Specific devices to assist with operator alertness Devices are available on the market to assist with keeping shift workers alert. These should receive a low priority relative to an appropriately designed fatigue management plan. Precedence should be given to measures designed to mitigate fatigue and keep operators awake, as opposed to measures for waking them up. Many operations use operator alertness monitoring devices available on the market. Others use stimulatory practices to counter sleepiness. The following list gives examples of techniques and devices used by different operations. The list is not exhaustive, and no claims are made as to whether these have been found to be effective in research studies. •

The Nap Zapper is a one of a family of similar devices used to awaken operators when it is detected that they are falling asleep. This particular device is worn over the ear and has an electronic position sensor. When the operator' s head nods forward, it sounds a loud alarm. Note that such a device can assist in alerting an operator to sleepiness, it is not designed to keep operators awake.

•

Electronic operator fatigue monitors are used in various situations. Some devices are body-worn, while other devices are vehicle-mounted. Devices may measure different signs of fatigue in isolation, or a combination thereof. One device monitors the duration of time that a driver' s eyelids are closed. Another device measures both eyelid closure and eye position. Other devices measure heart rate, respiration rate, or wrist movement.

•

A particular device used on public roads monitors how many times the driver leaves the lane on freeways, and provides an audible warning when drivers change lanes or cross the middle line without activating a turning signal.

•

Modular Mining Systems (www.mmsi.com) designed the DISPATCH truck allocation system, which is used in some local operations. It optimises and controls the allocation of haul trucks in the pit. Constant communication with the control room is available, and routes are varied to mitigate monotony.

•

Truck cabins may be ergonomically designed for operator comfort to reduce fatigue. Also, a steering system has been designed that dampens vibrations from the road to reducing the physical fatigue of fighting road feedback.

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4. Recommendations Management should understand the causes of operator fatigue as outlined in this document. Shortfalls should be identified and plans should be developed to address the issues relevant to each operation. It is recommended that the following process be followed in developing an operation-specific operator fatigue management plan: •

risk assessment in each operation, including management-worker consultation,

•

development of a draft plan based on the comprehensive approach described in paragraph 3.1 (planning), including shift design based on the considerations in paragraph 3.2.1,

•

test period (implementation),

•

feedback (monitoring),

•

review.

The diagrams on the following page summarise some of the information discussed in this document. These diagrams may be used as a tool to navigate the document when considering the factors contributing to operator fatigue, and methods used to mitigate fatigue. The appendices give examples of typical shift schedules, medical testing, placement procedures, and balanced nutritional programmes, which may assist in the design of operator fatigue management plans.

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Biological rhythm Sleep deprivation

Shift work

Task

Quantity of sleep Quality of sleep Sleep disturbances Sleep disorders

Worker-related physical factors Illness Fitness Nutrition Age Substance use

Medical consequences Operator fatigue Social consequences

Environmental factors Temperature Noise Air quality Illumination

Figure 1 Factors underlying operator fatigue. This figure contains hyperlinks to sections in the text.

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Shift scheduling Principles Considerations Permanent night shift Shift rotation Extended shifts Alertness Breaks and naps Worker participation Design of shifts Foods and drugs Countermeasures Assistive devices

Fatigue management

Stimuli Noise Activity Social interaction Temperature Light

Recommendations

Comprehensive approach

Figure 2. Management of operator fatigue. This figure contains hyperlinks to sections in the text.

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5. References [1] R. A. Fox, D. B. Shires, and H. M. Fox, "Environmentally induced dysfunction: The Camp Hill Medical Centre experience," Journal of Nutritional and Environmental Medicine, vol. 6, no. 4, pp. 351-358, 1996. [2] P. Gander, "Fatigue management in air traffic control: The New Zealand approach," Transportation Research Part F: Traffic Psychology and Behaviour, vol. 4, no. 1, pp. 4962, 2001. [3] M. M. Ohayon, P. Lemoine, V. rnaud-Briant, and M. Dreyfus, "Prevalence and consequences of sleep disorders in a shift worker population," Journal of Psychosomatic Research, vol. 53, no. 1, pp. 577-583, 2002. [4] A. Guppy and J. dams-Guppy, "Truck driver fatigue risk assessment and management: A multinational survey," Ergonomics, vol. 46, no. 8, pp. 763-779, 2003. [5] N. Lamond, J. Dorrian, H. J. Burgess, A. L. Holmes, G. D. Roach, K. McCulloch, A. Fletcher, and D. Dawson, "Adaptation of performance during a week of simulated night work," Ergonomics, vol. 47, no. 2, pp. 154-165, 2004. [6] T. Akerstedt, "Is there an optimal sleep-wake pattern in shift work?," Scandinavian Journal of Work, Environment and Health, vol. 24, no. SUPPL. 3, pp. 18-27, 1998. [7] A. K. Pati, A. Chandrawanshi, and A. Reinberg, "Shift work: Consequences and management," Current Science, vol. 81, no. 1, pp. 32-52, 2001. [8] T. H. Monk, C. F. Reynolds III, D. J. Buysse, J. M. DeGrazia, D. J. Kupfer, and T. H. Monk, "The relationship between lifestyle regularity and subjective sleep quality," Chronobiology International, vol. 20, no. 1, pp. 97-107, 2003. [9] P. Philip, J. Taillard, P. Sagaspe, and C. Valtat, "Age, performance and sleep deprivation," Journal of Sleep Research, vol. 13, pp. 105-110, 2004. [10] A. Baker, K. Heiler, and S. A. Ferguson, "The impact of roster changes on absenteeism and incident frequency in an Australian coal mine," Occupational and Environmental Medicine, vol. 60, pp. 43-49, 2003. [11] R. Fenwick and M. Tausig, "Scheduling stress: Family and health outcomes of shift work and schedule control," American Behavioral Scientist, vol. 44, no. 7, pp. 1179-1198, 2001. [12] R. J. Shephard, "Chronic fatigue syndrome: An update," Sports Medicine, vol. 31, no. 3, pp. 167-194, 2001. [13] P. Salmon, "Nutrition, cognitive performance, and mental fatigue," Nutrition, vol. 10, no. 5, pp. 427-428, 1994. [14] R. J. Shephard, "A brief bibliography on fatigue and fitness," Journal of Occupational Medicine, vol. 16, no. 12, pp. 804-808, 1974. [15] C. M. LaJambe, G. H. Kamimori, G. Belenky, and T. J. Balkin, "Caffeine effects on recovery sleep following 27 h total sleep deprivation," Aviation Space and Environmental Medicine, vol. 76, no. 2, pp. 108-113, 2005. [16] T. M. McClellan, G. H. Kamimori, D. G. Bell, and I. F. Smith, "Caffeine maintains vigilance and marksmanship in simulated urban operations with sleep deprivation," Aviation Space and Environmental Medicine, vol. 76, no. 1, pp. 39-45, 2005. [17] E. J. McCormick and M. S. Sanders, Human factors in engineering and design, 5 ed. Auckland: McGraw-Hill, 1983. &

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[18] L. C. Oliver and B. W. Shackleton, "The indoor air we breathe," Public Health Reports, vol. 113, no. 5, pp. 398-409, 1998. [19] P. K. Arnold and L. R. Hartley, "Policies and practices of transport companies that promote or hinder the management of driver fatigue," Transportation Research Part F: Traffic Psychology and Behaviour, vol. 4, no. 1, pp. 1-17, 2001. [20] P. Knauth, "Designing better shift systems," Applied Ergonomics, vol. 27, no. 1, pp. 3944, 1996. [21] J. Axelsson, T. Akerstedt, G. Kecklund, and A. Lowden, "Tolerance to shift work—how does it relate to sleep and wakefulness," International Archives on Occupational and Environmental Health, vol. 77, pp. 121-129, 2004. [22] S. Bougrine, R. Mollard, G. Ignazi, and A. Coblenz, "Days off and bright light: Effects on adaptation to night work," International Journal of Industrial Ergonomics, vol. 21, pp. 187198, 1998. [23] S. Lavoie, J. Paquet, B. Selamoui, and M. Ruffiange, "Vigilance levels during and after bright light exposure in the first half of the night," Chronobiology International, vol. 20, no. 6, pp. 1019-1038, 2003. [24] C. H. Robinson and M. R. Lawler, Normal and therapeutic nutrition. New York: McMillan, 1990. [25] G. Mazzoccoli, A. Giuliani, S. Carughi, A. De Cata, F. Puzzolante, M. La Viola, N. Urbano, F. Perfetto, and R. Tarquini, "The hypothalamic-pituitary-thyroid axis and melatonin in humans: Possible interactions in the control of body temperature," Neuroendocrinology Letters, vol. 25, no. 5, pp. 368-372, 2004. [26] S. S. Gilbert, C. J. Van Den Heuvel, S. A. Ferguson, and D. Dawson, "Thermoregulation as a sleep signalling system," Sleep Medicine Reviews, vol. 8, no. 2, pp. 81-93, 2004. [27] J. Carrier and T. H. Monk, "Circadian rhythms of performance: New trends," Chronobiology International, vol. 17, no. 6, pp. 719-732, 2000. [28] J. Arendt and D. J. Skene, "Melatonin as a chronobiotic," Sleep Medicine Reviews, vol. 9, no. 1, pp. 25-39, 2005. [29] A. J. Lewy, V. K. Bauer, S. Ahmed, K. H. Thomas, N. L. Cutler, C. M. Singer, M. T. Moffit, R. L. Sack, and A. J. Lewy, "The human phase response curve (PRC) to melatonin is about 12 hours out of phase with the PRC to light," Chronobiology International, vol. 15, no. 1, pp. 71-83, 1998. [30] E. B. Klerman, J. F. Duffy, H. B. Gershengorn, R. E. Kronauer, and E. B. Klerman, "Comparisons of the variability of three markers of the human circadian pacemaker," Journal of Biological Rhythms, vol. 17, no. 2, pp. 181-193, 2002. [31] A. Voultsios, D. J. Kennaway, and D. Dawson, "Salivary Melatonin as a Circadian Phase Marker: Validation and Comparison to Plasma Melatonin," Journal of Biological Rhythms, vol. 12, no. 5, pp. 457-466, 1997. [32] M. E. Quigley and S. S. C. Yen, "A mid-day surge in cortisol levels," Journal of Clinical Endocrinology and Metabolism, vol. 49, no. 6, pp. 945-947, 1979. [33] S. C. Bos, J. Waterhouse, B. Edwards, T. Reilly, and R. Simons, "The Use of Actimetry to Assess Changes to the Rest-Activity Cycle," Chronobiology International, vol. 20, no. 6, pp. 1039-1059, 2003.

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6. Contributors CoP on Fatigue Management Name

Company/Division

Contact details

Alvaro Aliaga

Base Metals, Anglo Mine Manager at El Soldado, Anglo Chile

[email protected]

Andre van der Linde

ATD Mining, Occupational Health Engineering

[email protected] T: 011 638 3508

Archie Eksteen

Base Metals, Anglo Black Mountain

[email protected]

Christo Aspeling

Kumba, Grootegeluk Mine

[email protected] T: 014 763 9103 / C: 083 304 6191

Coenrad Lusse

Base Metals, Anglo Training Co-ordinator

[email protected] T: 09264 63 271 2417

David Cather

Tarmac Group, Anglo Technical Director

[email protected] T: 0944 2076988773

Deane Macpherson

AngloGold Ashanti Section manager, Corporate Safety

[email protected] T: 018 478 6489 / C: 082 452 8333

Gerhard Stenzel

Anglo Coal, Landau Colliery

[email protected] T: 013 6930688

Gert McCarthy

PPRust Mining [email protected] Business Area Manager Mining

Hugo van Dyk

Kumba, Sishen Mine

[email protected] T: 053 739 2149

Johan Wepener

Kumba, Leeuwpan Mine Mine Manager

[email protected] T: 013 664 7600 / C: 083 264 6271

John R McEndoo

AngloGold Ashanti

[email protected] T: 011 637 6262

Mike Kilbride

Kumba, Executive Director, Business Operations

[email protected] T: 012 307 3488

Nombasa Tsengwa

Kumba, GM SHEQ & LM

[email protected] T: 012 307 4316

Judi Sandrock

Kumba, Manager Knowledge Management

[email protected] T: 012 307 4153

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Appendix 1 Examples of shift scheduling A.1.1 Seven day shift pattern Some operations currently use a seven-day morning shift followed by one day off, then a seven-day afternoon shift followed by two days off, and then seven night shifts followed by five days off (dubbed the 7 1 7 2 7 5 system). Some of the potential problems that this shift pattern may present are (i) the worker has to adapt his sleeping cycle within one day (when changing from morning to afternoon shift), which may result in the worker being fatigued when the second cycle starts; (ii) the rotation is slow, allowing the possibility of desynchronisation of the circadian rhythm; (iii) the number of consecutive night shifts may result in decreased performance and high levels of fatigue; (iv) the shift worker has only three days off before he starts working the last night shift (day 21). Enough time is needed to adapt to rotating shift times, so that in this case it is expected that the worker will be sleep deprived and would not be able to operate at the required levels of alertness during the night shifts of the third cycle. Ideally, a number of adaptations to this system should be made. It would be preferable to have two days off between shift cycles, while the number of consecutive workdays should ideally be fewer. The number of consecutive night shifts should preferably be limited to three. A.1.2 A shift pattern used in air traffic control Air traffic control is a mentally strenuous task that requires high levels of alertness. As in the mining industry, errors may be disastrous. The principles of shift design used in air traffic control are similar to the principles that are appropriate in other industries. The following shift pattern design rules are recommended for use in air traffic control in Great Britain [2]. • • • • • • • •

The maximum duration of the night shift is 8.5 hours. There is a maximum of two consecutive night shifts. After two consecutive night shifts, the minimum rest period is 54 hours. The minimum allowed rest period before working the night shift is 14 hours. Busy daytime shifts are limited to 6 hours in duration. The number of consecutive early starts is limited to four (if the morning shift starts before 7:00) or two (if the morning shift starts before 6:00). After 6 consecutive periods of duty or 50 hours of work (whichever comes first), at least 60 hours of rest is required. In a 30-day cycle, there should be at least three rest periods of 60 hours, and a maximum number of 200 hours of duty. &

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Within a duty period, breaks should be taken after each two hours of work (or four hours under light workloads). Breaks should be at least 30 minutes.

Based on these rules, a typical shift pattern that is used is a rapid forward rotating pattern: two morning shifts followed by two afternoon shifts, then two night shifts followed by one sleep day, and finally three days off. Not all these recommendations may be applicable (e.g. the short 6-hours shifts during busy periods) to the designing of shifts for the mining industry.

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Appendix 2 Elements of a healthy diet A healthy diet should contain the following [24]. A large variety of foods should be eaten, including starches, fruit and vegetables, protein and moderate intake of fats. The following is regarded as a basic diet for an adult. One food should be selected from each group. The amounts are per day. Vegetable-fruit group Dark green leafy or deep yellow: ¼ to 1/3 cup Other vegetable: ¼ to 1/3 cup Potato: 1 medium potato Citrus fruit: ½ cup Other fruit: 1 serving Bread-cereal group Cereal, whole grain or enriched: ¾ cup Bread, whole grain or enriched: 3 slices Milk group Milk (2% fat): 2 cups Meat group Meat, fish, poultry, eggs: 5 ounces (cooked) Fats Margarine (soft): one tablespoon Oil: one tablespoon Water It is extremely important to drink enough water. Apart from water contained in other fluids (e.g. coffee, milk or soft drinks), one should drink around 1.5 litres of water per day (6-8 glasses).

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Appendix 3 Biological markers of circadian rhythm and circadian disruption As mentioned in the text, it is recommended that the natural body rhythm be screened annually to determine the state of the biological clock of each individual. The objective is to establish whether the circadian rhythm is still synchronised or has been disrupted. Where the latter is observed, it is recommended that the particular worker be transferred to day work for at least one year. The following measures can be used as markers of the biological rhythm. Core body temperature The body temperature (referring to core temperature, not surface temperature) is synchronised to the day-night cycle. The body temperature is lower during nighttime, and higher during daytime [25]. A lowering of body temperature has been shown to induce sleepiness [26]. There is a parallel between core temperature and circadian fluctuations in performance [27]. The body temperature rhythm is also inversely related to fluctuations in the hormone melatonin (discussed below), of which the levels are associated with the light-dark cycle. Core body temperature can be used as an index of the circadian rhythm phase. I.e., if tracked over a 24-hour period, the high phase and low phase should correspond to respectively low levels and high levels of melatonin. Melatonin and cortisol Melatonin is a hormone that is associated with regulation of the human sleep/wake cycle and lowering of core body temperature [28]. The peak level of melatonin occurs at night, while levels are lower during daytime [29]. Melatonin level can be measured either as concentration in the blood [30], or as salivary melatonin concentration. The latter is more suitable for studies in which the levels have to be tracked over a 24-hour cycle [31]. Cortisol (also a hormone) is another biological marker of circadian rhythm [30]. Corticol secretion peaks around midday [32]. There is a correlation between good performance and high blood cortisol levels [27]. Actimetry A simple measure of the circadian rhythm is the rest-activity cycle measured by actimetry. Activity rhythms are measured with a small wrist-worn piezo-electric accelerometer. Suitable analyses of activity records can provide measures of disruptions to circadian rhythms [33]. They describe the calculation of a series of activity indices that measure the overall activity pattern, (e.g. activity before &

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bedtime, when in bed, when getting up and during the day). In a normal circadian rhythm, wrist activity is low during sleep and high during the day. Research has shown that night work may be associated with lower activity when workers are awake and higher activity when in bed, which indicates disruption of the circadian rhythm. In summary, there are various ways to measure circadian rhythm. These could all be tracked over a 24-hour period, to establish whether they are synchronised (in phase, or 180 degrees out of phase) and whether these phase relationships have changed. Actimetry appears to be the simplest way to track the circadian rhythm.

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Appendix 4 Screening and placement Some considerations in placement of workers are summarised briefly in this appendix. To establish whether a particular worker is suitable for shift work or night work, one needs to consider the following. Most of this information is discussed in more detail in the text. Age Generally, younger workers are more adaptable to shift work or permanent night work. Health Night work or shift work is detrimental to health. Health problems will be aggravated by night work in workers that already exhibit health problems (e.g. cardiovascular disease, gastro-intestinal disorders). Personal circumstances Personal circumstances (e.g. family responsibility) may disincline a worker to perform shift work. Demotivated workers become fatigued more quickly and are more likely to make mistakes. Attitude If a worker is found to be particularly averse to night work, it is advisable to exclude him/her from night shift work. As mentioned, demotivated workers become fatigued more easily. Morning person or evening person It may be of great help to establish whether a worker is of morning type or evening type, or neutral. This may be done by measuring the phase of the natural biological rhythm, for example by measurement of core body temperature over a 24-hour period. Core body temperature will reach its low phase much later at night in evening people than in morning people. People of evening type or neutral type are better suited to shift work or permanent night work. Amplitude of circadian changes Although circadian rhythms (like changes in body temperature) occur in all people, these changes are less pronounced in some people. These people are better suited for shift work or permanent night work.

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