It is now widely recognised that occupational health and welfare does not tend to receive the attention that is afforded to lack of safety due to more obvious, and usually instant acting, physical hazards. Incidents such as tripping over obstacles, falling objects, bumps and collisions can result in many lost man-shifts, but at least their occurrence can be recorded fairly accurately.
Lost man-shifts, or deterioration in quality of life, due to insidious health hazards are much more difficult to record accurately. Nevertheless, Kevin Minton of the UK Construction Plant Hire Association has stated that a construction worker is 100 times more likely to die of work-related ill health than from an accident.
Dr. Donald Lamont reports that there is a general low-level of concern over occupational health in construction, aggravated by a previous lack of ‘safety culture’ in the industry and a macho image/attitude to working practices. He says, “HSE had little useful data on the numbers affected by ill health. Also the ‘healthy worker’ effect and transient nature of tunnelling make data collection even more difficult making it ‘out of sight out of mind’!”
Since we are talking about underground construction, the intensive training on safety issues of most miners instils an instinctive awareness of physical hazards and some less visible but more familiar hazards such as methane gas. Yet even there an overly macho attitude or too much familiarity with some equipment can undo all the good work of training. Such circumstances include not wearing safety gloves when handling possibly hazardous materials, or riding on belt conveyors not designed for it.
Lamont states that one cause of the problem is a ‘lack of ownership’ of the problem by some clients, designers and contractors. He also lists the transient workforce in tunnelling, and the nature of the work and working environment as contributory causes.
It appears that while attention to more obvious, and better-known health hazards has substantially improved, overall care for occupational health has not. In such circumstances hazards are either ignored (and it is easy to ignore some of these in the relatively short term of a tunneling project) or they are left to another party.
“Occupational health is always the poor relation to ‘safety,’” says Lamont. “Partly it is because of the long period over which problems normally develop and people move on or out of the industry. Partly there is a culture of hiding symptoms for macho reasons.”
“Where countries have poor safety standards they most likely will have very poor occupational health standards. Noise, vibration, manual handling, dust are universal tunnelling hazards. Heat is a problem in deep Alpine tunnels and hot climates.”
There are two aspects of occupational health according to Lamont:
• To ensure fitness for work.
• To address ill health due to work.
Added to this is the need for a plan of welfare to ensure continued good health at work.
Fitness for work
Tunnelling is a physically demanding activity undertaken in and environments that are often hot and humid in a confined space remote from the surface. In addition, many projects can involve working in shifts and/or over long periods. Shift work can affect one’s ‘body clock’ in upsetting sleep and eating patterns. Long hours are physically, as well as, mentally tiring, but in Europe are covered by the Working Time Regulations.
Lamont says that good practice suggests that all those working underground should undergo basic occupational health surveillance. This should indicate both the level of fitness at the start of a work period, and check for any deterioration after working. There also needs to be recognition that some safety critical occupations require a higher level of fitness. These might include working at height installing tunnel supports, or in particularly confined spaces such as in TBM forward chambers or air-locks, perhaps under compressed air atmosphere.
Plant operation, particularly transport work, may require particular abilities as regards fitness including good hearing and lack of colour blindness.
Eligibility for a rescue team is particularly demanding due to physical demands in environments that can easily be more extreme due to high levels of heat, wearing breathing apparatus, etc.
Before a tunneller is employed he or she should undergo screening to assess basic medical fitness for work, covering height, weight, blood pressure, function of heart and lungs, sight, hearing, level of diabetes, and health affecting practices such as smoking, level of alcohol consumption and drug use. The latter may be legitimately health-related, or socio-politically motivated drug abuse, says Lamont. In either case it can affect fitness for work, both physical and mental, for which the time and level of drug retention in the body should be considered.
In addition the screening should be able to identify pre-existing conditions of occupational ill health such as noise-induced hearing loss and hand-arm vibration syndrome (HAVS) from excessive use of power tools, etc. The date collected will not only assess a candidate’s suitability for work, but provide a base level to assess any subsequent deterioration, as can be determined by periodic reassessment.
Going back to compressed air work, the occupation is unusual in being covered by particular health requirements under statute. Only those medically fit can enter a compressed air environment as assessed by the ‘appointed doctor’. Under European regulations checks include periodic MRI or X-ray scans along bones to check for bone necrosis. The frequency of periodic checks depends on the pressure to which the tunneller is exposed: every 28 days for exposure above one bar, and every three months for exposure below one bar. Compressed air and other hyperbaric work in tunnelling will be covered in another editorial feature in T&TI later this year.
Any work is association with asbestos is another particular circumstance covered by law. Under the UK Control of Asbestos Regulations, and worker exposed to asbestos must have had a medical examination in the two years prior to employment.
Ill health due to work
The potential hazards to health on tunnelling projects are many and widespread, but each can have its own combination including, perhaps, some special cases for concern. To put the known potential hazards to health in a list, which may not be comprehensive:
Physical hazards to health
• Noise
• Vibration
• Manual handling
• Heat/cold extremes
• Pressure
Chemical hazards
These may already occur in the environment of the new or existing, or be used in construction materials, and include:
• Asbestos
• Lead
• Silica dust
• Cement dust
• Epoxy resins
• Certain chemical additives
• Certain solvents
• Ground contaminants
Atmospheric contaminants including the above, and radon gas as a radiological hazard.
Biological hazards
• Ground contaminants
• Contaminated water
While each deserves attention Lamont says, “my feeling for health priorities in tunnelling would be noise, vibration, manual handling, dust and the need for good welfare facilities, to concentrate on just a few. These health hazards occur in virtually all tunnels. I am not talking deaths, but ill health starting as loss of quality of life and leading eventually to inability to work and the socio/economic consequences of unemployment.”
Guidance
To learn more about potential health hazards, there is a substantial amount of guidance published by leading safety authorities around the world.
In the UK, the Health & Safety Executive (HSE) offers publications and advice via its website – http://www.hse.gov.uk/. There is a relevant British Standard, BS 614, and the British Tunnelling Society has produced publications on Hand-Arm Vibration Syndrome (HAVS), and the hazards and behaviour of Nitrous Oxide (NO) in tunnels exhaust emissions.
To learn more about the nature of health hazards HSE has conducted a number of research programmes. The subjects tackled include:
• Heat strain in compressed air tunnelling,
• Behaviour of nitrogen monoxide (NO –nitric oxide) in tunnel atmospheres,
• Behaviour of RPE (respiratory protective equipment) under pressure,
• Behaviour of atmospheric monitoring equipment under pressure,
• Monitoring decompression regimes in real time.
Prevention
In his presentation, Lamont sets out a list of the principles of preventing the effects of health hazards, in a recommended sequence of attention according to effectiveness if feasible. This is (with examples):
• Avoid the hazard (preventing interaction, physical removal, etc.)
• Combat risk at source (eg dust suppression)
• Adapt work to the individual (design task safety for worker’s ability)
• Adapt to technical progress
• Substitute by less/non-dangerous means (e.g., replacement of alkaline shotcrete accelerators by non-alkaline types)
• Collective protection over individual protection such as PPE (Personal Protective Equipment) (more effective and less prone to error PPE is NOT first choice)
• Instruction, training and supervision (in otherwise dealing with the hazard)
Leading health hazards
Considered below are the leading, but obviously not the only, hazards to health in tunnelling, as recommend by Lamont:
• Noise
• Vibration
• Manual handling
• Dust
• The need for good welfare facilities
Noise
Major sources of noise in tunnelling are drilling equipment, cutterheads, pneumatic and hydraulic power tools, fans and to a lesser extent transport systems. In the UK sources are controlled under legislation by the Machinery Regulations and the Control of Noise at Work Regulations 2005.
Despite any machismo/bravado exhibited by workers, the consequences of excessive exposure to noise can be severe. There can be hearing impairment with consequent diminished quality of life and possible incapacity for work even though physical disability is not obvious, Lamont points out. Consequently the extent of the problem is not recognized by society. It is understood that 50 per cent of miners have significant hearing impairment.
Prevention being much better than ‘cure’, the measures to be taken, mostly set out in UK legislation, include:
• Set out exposure action and limit values for noise exposure and for peak sound pressure.
• Require risk assessment.
• Elimination or reduction of exposure to noise, including noise enclosures if possible, plus good machinery maintenance, as far as in reasonably practical (SFAIRP).
• Measures (excluding provision of PPE) to be taken at the upper exposure action values.
• Provision of personal hearing protectors. Designation of Hearing Protection Zones. Health surveillance including audiometry. Information, instruction and training.
HAVS and HAV nots
The consequences of excessive vibration from power tools (basically HAVS) have received considerable attention in recent years both in UK tunnelling and elsewhere. This has led to measures such as improved designs of hand-held power tools, greatly limiting the working time when using vibrating tools, and, if possible, replacement with other methods of excavation, etc., including mini-excavators and purely manual tools.
A related hazard is whole body vibration (WBV) caused by ride-on operation of vibrating machinery such as locomotives and hard rock cutting machinery. This may be alleviated by better machinery design to isolate the seat from the rest of the machine by shock absorbers and cushioning.
The relevant UK legislation is the Control of Vibration at Work Regulations 2005.
The consequences of excessive vibrations exposure with HAVS are loss of sensation in the hands with initial tingling and numbness, loss of strength in the hands, discoloration (‘white finger’ – tips of fingers go white and then red, with in on recovery), and eventual incapacity for work. With WBV there is also incapacity for work leading from consequent back pain, and internal organ damage.
Actions to be taken to cut down the hazard include setting exposure limit values (ELV) and exposure action values (EAV) (on an 8-hour average in UK legislation). Various graphical and tabular aids are available to judge actual values against these limits over time.
In line with the principles for action on noise there should be a vibration risk assessment and ensure that exposure risk is eliminated at source (SFAIRP) such as by good tool maintenance, and anyway to maintain that the worker is not exposed to vibration above the ELV. Measures are to be taken, excluding the provision of PPE, at the upper exposure limit. There should also be health surveillance, information, instructions and training about vibration hazards.
Other measures to mitigate the hazard include job rotation, keeping hands warm, and possibly anti-vibration gloves, although Lamont says these are of doubtful value.
Manual handling
Although legislation and safety enforcement has led to the provision of materials handling devices to aid work and to try and prevent injury, basic manual handling seems inevitable in many tasks underground including manual excavation (shovelling, digging and rock handling, etc), erection of (small) segments (unless manipulators available), erection of steel arching, installation of TBM cutters, picks, etc. In many cases the hazard can be from stretching as well as weight, so as may be the case with erecting support mesh without adequate access equipment. This seems to be an area where machismo and perceived convenience are short-term factors in developing long-term problems. Relevant UK legislation is the Manual Handling Operations Regulations 1992.
The consequences of excessive, inappropriate manual handling include musculo-skeletal disorder (including ‘back back’), work-related upper limb disorder, and incapacity for work with probable obvious disability.
Manual handling must be eliminated as far as is reasonably practical, with the mitigation of risk from unavoidable manual handling. Such operations must be assessed, and reassessed if necessary, for possible improvement in methods together with instruction and information n the correct means of lifting, pulling and pushing. Common advice on manual handling includes avoidance of repetitive work, avoid manual handling in confined spaces, and in hot/humid conditions, and avoid twisting and turning when handling.
Mitigation measures that can be undertaken include:
• Make things too heavy to lift manually so that mechanical aids must be used.
• Mechanical excavation aids instead of hand tools.
• Use of segment hoists and erectors.
• Lifting points in cutterheads.
• Handling aids for cutters and picks.
Dust
One of the most insidious hazards underground is dust, particularly when airborne, with some dusts more dangerous than others depending on the interaction with the human body. Dust hazards are normally considered to be due to inhalation, but some fine or unusual chemical dusts can cause skin irritation and inflammation (dermatitis). Many today are still suffering the effects of excessive dust inhalation from when suppression was not considered, resulting in pneumoconiosis in general, or the more sever silicosis and asbestosis.
Sources of dust include rock cutting, lifting from the invert by ventilation of people/vehicle movement, concrete spraying and mixing materials.
Dust can be categorised into inhalable dust (maximum UK exposure – TWA limit of 10 mg per m3 over 8 hours), respirable dust into gas exchange regions of lungs (4 mg per m3 TWA) or the more serious respirable crystalline dust at 0.1 mg per m3 limit. Workplace Exposure Limits (WELs) have replaced the old OELs and MELS with values as 15-minute or 8-hour time weighted average in dust sampling.
Excessive exposure can lead to lung damage with severe respirator and consequent heart problems, with loss of quality of life, incapacity for work and early death.
Actions to be taken on dust control can start with monitoring through air sampling general or personal) and dust lamps to indicate its presence in the air. Dust caused by rock cutting should be suppressed at source by water sprays and or removed by extraction fans.
Roadheaders complying with the new EN 12111 standard are equipped to deal with dust in such ways. Dust from sprayed concrete can be minimised by using wet-process rather than dry-process equipment.
If dust cannot be eliminated at source, adequate ventilation is required to remove it, preferably by a forced and extraction dual duct system with dust filters and scrubbers in the ventilation stream. As a last resort, or additional precaution, specially designed dust masks can be used.
The health of those that might be affected by dust should be checked using a lung function spirometry test, and periodic X-ray or RMI scanning.
Welfare facilities
Provisions of facilities to improve the welfare of employees during and after work can produce benefits in hygiene, wellbeing, and employee satisfaction through respect and less stress, resulting in improved performance.
Facilities listed by Lamont that should, or must, be available include basic toilets, washing facilities, mess/eating areas and first aid provision.
Other considerations relate to the normal lifestyle of the workforce. As peripatetic groups they often lack basic access to national health service facilities. Lamont says consideration should be given to providing general practitioner services in remote locations, plus dentistry and chiropody services.
Internationally
Although this article is based mainly on UK experience, good practice around the world is similar. “Noise, vibration and manual handling are all covered by European directive so standards should in theory be similar throughout Europe,” says Lamont. “The USA, Canada and Australia tend to be on a par with Europe. The Far East adopts UK practice where there is a history of UK involvement, such as in Singapore and Hong Kong. Elsewhere things may not be so good.”
Conclusions
The occupational hazards to health dealt with in this article may only be a small part of those that could be encountered in any one tunnelling project. The risks arising from them can be mitigated in the design and construction of tunnelling projects, but preferably eliminated when found if possible.
Lamont says that, apart from (the use of) compressed air, none of the hazards discussed are unique to tunnelling, but what is unique is the complexity of the combinations in which they are found.
Acknowledgement
This article is based on information drawn from a presentation made by Dr Donald Lamont, director of Hyperbaric & Tunnel Safety Ltd, and formerly HM Principal Specialist Inspector and Head of Tunnel and Ground Engineering in UK Health & Safety Executive’s Civil Engineering specialist team, to the Young Members Section of the British Tunnelling Society, for which Tunnels & Tunnelling International is grateful to Dr Lamont.
Full personal protective equipment including a respiratory helmet is necessary in dealing with contaminated ground, as here at West Ham, east London Tunnellers should undergo a health check before beginning work HVLab Diagnostic Equipment helps diagnose the vascular and neurological effects of hand-arm vibration syndrome