Dr Prassana Krishnan is a specialist in occupational medicine. Last month he reviewed silicosis resulting from exposure to dust. This month he examines another main occupational concern of stonemasons – hand arm vibration syndrome (HAVS)
About 5million people are exposed to hand-arm vibration in the UK (MRC Study 1999). Stone working is one of the most commonly effected occupations with one of the highest levels of exposure. Most people in the industry will know at least one person who suffers from ‘white finger’, if they do not suffer from it themselves.
The Control of Vibration at Work Regulations (COVWR) 2005 place legal duties on employers and others to control and manage the risks from vibration (hand arm and whole body, although for masons the main risk is from hand arm vibration resulting from the use of stone working tools).
Hand arm vibration syndrome (HAVS) is an all-encompassing term describing the signs and symptoms of a disorder caused by vibration exposure.
It is important to remember that HAVS does not result just from the use of power tools. It can also arise from exposure to hand-held, hand guided or hand-fed machines.
Vibration exposure can lead to damage of the blood vessels (vascular component), nerves (neurological component) and muscles & joints (musculo-skeletal component). Each component may occur independently.
For vascular symptoms, individuals describe well-defined episodes of blanching or whiteness in one or more of their fingers, which usually lasts between 15minutes and an hour.
Historically, various terms were used to describe the vascular symptoms – vibration white finger, grinder’s cramp, dead man’s fingers.
Neurological symptoms initially present with tingling and/or numbness, then reduced sensation in the hands and later reduced manual dexterity.
The musculo-skeletal component can present with muscle and joint pains and reduced grip strength.
Health effects can be seen after six months of exposure to vibration but the average latency (ie time from first exposure to vibration to the development of disease) is 16 years.
HAVS can lead to significant impairment and disability.
Advanced cases generally show little reversibility of symptoms when vibration exposure is reduced or stopped. To date, there are only limited treatments available and they are mainly aimed at helping to control symptoms only.
The COVWR came into force in July 2005, which was implementing the European Physical Agents Directive. To comply with the regulations employers should: Assess vibration risks to health and safety or workers; Eliminate vibration risk at source or reduce to lowest level reasonably practicable; Provide information and training for employees on vibration risks and measures for controlling those risks.
The Exposure Action Value (EAV) is 2.5m/s2 A(8) (ie over an eight-hour period), which is lower than the old HSE recommended action value but still not a safe level of exposure as harm can occur to the operator at or below the EAV.
If the EAV is likely to be exceeded, a programme of organisational and technical measures should be put in place to reduce vibration exposure to the lowest level reasonably practicable.
The Exposure Limit Value (ELV) – the maximum legal limit of daily exposure – is 5m/s2 A(8). There is a transitional period until July 2010 for companies to achieve the ELV if their equipment has been in use since before 6 July 2007 and it is not yet reasonably practicable to comply with the ELV.
However, it is important to ensure employees are not exposed to vibration above the ELV. If they are, you should take immediate action to prevent a recurrence.
Health surveillance is required for individuals exposed to vibration levels above the EAV. It is also a requirement for people who have been diagnosed with HAVS, even if their current exposure level is below the EAV.
The purpose of health surveillance is to: identify anyone exposed or about to be exposed to hand-arm vibration who may be at particular risk; identify any vibration-relation disease at an early stage in employees regularly exposed to hand-arm vibration; prevent disease progression and eventual disability; help people stay in work; check the effectiveness of vibration control measures.
Health surveillance consists of five tiers: Level 1 – Pre-employment assessment (role for occupational health provider); Level 2 – Routine annual screening (role for responsible person); Level 3 – Clinical assessment (role for occupational health nurse); Level 4 – Diagnosis (role for occupational health physician); Level 5 – Optional standardised tests.
The ‘responsible person’, who is somebody nominated by the company, does not need to be medically qualified but should have received some general training on HAVS. They should be carefully selected, accepted by the employees and understand the importance of medical confidentiality.
They should never diagnose and must refer for clinical assessment any individual with symptoms.
The ‘responsible person’ should refer for clinical assessment any employee with three consecutive years of negative responses on the self-completed questionnaire.
The Occupational Health Physician is responsible for diagnosis and fitness for work decisions.
Standardised tests are only available at specialist centres. They were developed to assess dysfunction associated with vibration exposure and can be helpful in assessing the progression of disease.
Health surveillance is, of course, only one measure in the hierarchy of control measures. The primary aim should always be to eliminate exposure to harmful vibration.
Where that cannot be practically achieved, other measures to be taken include tool selection and maintenance, engineering controls, management of exposure and personal protective equipment (PPE).
Anti-vibration gloves are available but it is very difficult to assess their performance and they are unlikely to reduce frequency-weighted vibration exposure very much.
You should remember that HAVS is a reportable condition under the Reporting of Injuries, Diseases & Dangerous Occurrences Regulations (RIDDOR) 1995. You must report any incidences to the Health & Safety Executive.
And you should be aware that employees who have been formally diagnosed with HAVS are entitled to statutory compensation through the Industrial Injuries Disablement Benefit Scheme.
Footnote on RCS: Some readers have pointed out an error in the previous article relating to exposure limits to respirable crystalline silica (RCS). I apologise for the error. The current workplace exposure limit (WEL) for RCS is 0.1mg per cubic metre of air (0.1mg/m3) averaged over an eight-hour period. It is important to remember that silicosis can still occur at exposures at or below the WEL and that this should not be considered a ‘safe’ level of exposure.
Dr Prassana Krishnan is a specialist in occupational medicine accredited with the Faculty of Occupational Medicine of the Royal College of Physicians of London who recently set up his own occupational health business. He has a special interest in the occupational hazards to stonemansons. Previously he was the Lead Physician to the Greater London Authority and British Transport Police. He is currently an occupational health advisor at Ford Motor Company and Coryton Petroplus Oil Refinery.