OSA Magazine Logo

Hand Arm Vibration

Published: 10th Dec 2010 in OSA Magazine

Hand arm vibration syndrome (HAVS), previously known as ‘vibration white finger’ (VWF), is caused by repeated and frequent use of hand-held or hand guided vibrating tools or machinery. It is not certain how vibration causes the condition, but it is believed that repetitive small injuries to the peripheral nervous and vascular system in the fingers and arms causes the resultant loss of function in those areas of the body. It is key to realise that exposure to cold temperature while using hand tools increases the likelihood of the condition occurring and accentuates its symptoms.

The effects of vibrating hand tools on the body are far wider than VWF, hence the phrase has been superseded by HAVS. The difference is that VWF
is limited to the vascular symptom, whereas HAVS also includes nerve-related symptoms.

Examples of HAVS are as follows:

• Numbness and tingling in the fingers
• A reduced sense of touch and temperature due to damage to nerves in the hand; this damage can make it difficult to feel and to work with small objects
• ‘White finger’ or blanching - periodic attacks during which the blood circulation in the fingers is impaired and parts of the fingers become white and feel numb, known as ‘vasospasm’, which can occur for 20-60 minutes
• As blood circulation returns to normal either by itself or after re-warming, the fingers typically throb, are red and painful, known as ‘reactive hyperaemia’; in very advanced cases, blood circulation may be permanently impaired
• Joint pain and stiffness in the hand and arm
• Grip strength can be reduced due to nerve and soft tissue damage
• Carpal tunnel syndrome can also be caused by exposure to vibration

An individual with HAVS may not experience the complete range of symptoms; there may be symptoms of vascular problems but no neurological symptoms and vice-versa. The symptoms of HAVS are usually progressive as exposure to vibration continues, with effects seen initially in the tips of the fingers. As exposure continues over time the symptoms spread up the finger. Typically, neurological symptoms become apparent before ‘white finger’ occurs.

Employees suffering from HAVS can experience difficulty in carrying out tasks in the workplace involving fine work or manipulative work and are less able to work in cold conditions. It’s important to consider that the disease may have an impact on earnings and on social and family life. Attacks of ‘white finger’ will take place not only at work, but during other activities, especially if people get cold. If vibration exposure continues unabated the damage to the hands and arms may become irreversible.

The rate of degeneration varies greatly from individual to individual. What is known is that once nerve damage has occurred the symptoms will not improve. In the case of vascular damage, some improvement will be seen over time if identified early enough, and control measures put in place to manage the condition and the cause of the problem. However, recovery tends to be age dependant and the level of success depends on the how long the condition has gone unnoticed, and how extreme the exposure to vibration was.

Once an individual has the condition a number of other factors can exacerbate the problem, generally relating to factors that lead to vasoconstriction:

• Smoking will make symptoms worse as nicotine is a vasoconstrictor; this causes blood vessels to narrow, increasing the potential for pain and blanching, especially in cold weather. Stopping smoking can reduce the impact of an attack
• Medicines that are used to treat other conditions sometimes trigger symptoms or make them worse. Such medicines include beta-blockers, some anti-migraine medicines and pseudoephedrine
• Caffeine triggers symptoms in some people, again due to it being a vasoconstrictor
• Recreational drugs and stimulants - amphetamines, cannabis and cocaine may be a trigger
• Stress is well a known cause of vasoconstriction
• Workplace chemicals including arsenic, mercury compounds, antimony, methylbutyl ketone, acrylamide, n-hexane, carbon disulphide, some organophosphates diethyl thiocarbamate, thallium, inorganic lead and tri-ortho cresyl phosphate (TOCP)
• Pre existing medical conditions such as diabetes and primary Raynaud’s syndrome

The law in Europe

In Europe EU Directive 2002/44/EC (part of the Physical Agents Directive) sets an exposure action value (EAV) of 2.5m/s2 and an exposure limit value (ELV) of 5.0m/s2 which implemented EU Directive 2002/44/EC.

The EAV is the measured vibration level at which employers should manage exposure and reduce as possible, the ELV being the level that must not be exceeded at any time.

HAVS detection and health surveillance

Obtaining the help of an Occupational Health Professional is crucial in determining whether employees are at risk of, or show early symptoms of HAVS. A competent Occupational Health nurse will be able to detect the symptoms through completing a clinical examination; however, a doctor is responsible for formal diagnosis and fitness for work decisions where HAVS has been detected.

Where a risk assessment or actual vibration measurements show that the daily EAV of 2.5 m/s2 may be exceeded, a Health Surveillance programme must be put into action. Details regarding vibration measurement are given later.

The health surveillance programme should contain four main tiers:

Tier 1: Initial or Baseline Assessment

Tier 1 is a short questionnaire, an example of which can be downloaded from UK Health and Safety Executive’s (HSE’s) vibration website. It is used as a first check for people moving into jobs involving exposure to vibration. The replies to the questionnaire will indicate whether they need to be referred to Tier 3 for a HAVS’ health assessment.

It is recommended that individuals who suffer from certain relevant vascular or neurological disorders affecting the hand or arm (such as Raynaud’s disease and carpal tunnel syndrome) are not exposed to vibration at work.

Tier 2: Annual Questionnaire

Tier 2 is a short questionnaire that an employer can issue once a year to employees exposed to vibration risks to check whether they need to be referred to Tier 3 for a HAVS’ health assessment. Again, an example of a Tier 2 questionnaire is available on the UK HSE’s website.

Tier 3: Assessment by a Qualified Person

This tier involves a HAVS’ health assessment by a qualified person such as an Occupational Health nurse. If the assessment shows that the employee has HAVS, the employee will require a Tier 4 assessment to have a formal diagnosis.

Tier 4: Formal Diagnosis

Formal diagnosis is made by the doctor and ‘fitness for work’ will be determined. Additional standardised tests described in Tier 5 are an option. If these tests are conducted, the results will be considered by the doctor when arriving at a diagnosis of HAVS.

Tier 5: Use of Standardised Tests (Optional)

In addition to clinical findings from Tiers 3 and 4, standardised tests can be conducted at some sites or referral centres for a worker who has signs or symptoms of HAVS. This testing is aimed at providing a quantitative assessment. Various tests are completed including vibrotactile perception threshold and thermal perception threshold tests.

This tier is not ‘required’ as part of routine health surveillance provision for a workforce exposed to HAV. It is considered to be potentially useful for studying the progression of the disease.

Risk assessment

When managing any potential hazard in the workplace the first stage of management is to complete a risk assessment to determine whether those hazards need to be accurately measured and controlled.

To carry out a risk assessment the employer will first need to identify whether there is likely to be a significant risk from hand-arm vibration. In order to complete a risk assessment the employer will need to:

• Find out from employees and supervisors which processes involve regular exposure to vibration
• See whether there are any warnings of vibration risks in equipment handbooks
• Ask employees if they have any of the HAVS symptoms described previously and whether the equipment being used produces uncomfortable strains on hands and arms

If there is likely to be a risk the employer needs to assess who is at risk and to what degree. The risk assessment should enable an employer to decide whether employees’ exposures are likely to be above the EAV or ELV and to identify which work activities need to be controlled.

A risk assessment should include the following information:

• A list of equipment that may cause vibration, and what sort of work it is used for
• Information about the equipment from equipment handbooks (make, model, power, vibration risks or vibration information)
• Make a list of employees who use the vibrating equipment and which jobs they do
• Accurate details of how long employees’ hands are actually in contact with the equipment while it is vibrating - in some cases this ‘trigger time’ may only be a few minutes in several hours of work with the equipment

The next stage is to group the work activities according to whether they are high, medium or low risk. For example:

High risk (above the ELV)

Employees who regularly operate:

• Hammer action tools for more than about one hour per day
• Some rotary and other action tools for more than about four hours per day

Employees in this group are likely to be above the ELV. The limit value could be exceeded in a much shorter time in some cases, especially where the tools are not the most suitable for the job.

Medium risk (above the EAV)

Employees who regularly operate:

• Hammer action tools for more than about 15 minutes per day
• Some rotary and other action tools for more than about one hour per day

Employees in this group are likely to be exposed above the EAV.

The groupings described above should be enough to enable a basic risk assessment to be completed, allowing the employer to decide whether exposures are likely to exceed the EAV and ELV, and allow plans and priorities to be put in place to control exposure.

Alternatively, you may choose either to use available vibration data or to have measurements made to estimate exposures if you want to be more certain of whether the risk is high, medium or low. A more detailed exposure assessment will help you:

• Decide which control actions might be most effective and practicable in reducing vibration exposure
• Be more certain whether exposures are likely to exceed the action or limit values
• Check whether your controls are effective

Estimating exposure

It is possible to get vibration data from the equipment handbook or from the equipment supplier. See Table 1 for examples of vibration levels the UK’s HSE has measured on equipment in use. There are also some databases on the internet which may have suitable vibration data:

• www.operc.com/pages/havteclogin.asp
• www.las-bb.de/karla/index.htm

Where manufacturer’s vibration data is used needs to represent the way the equipment is actually used, since some data may underestimate workplace vibration levels substantially; some materials being drilled or cut generates more feedback that others, causing higher vibration exposure.

Through careful observation it is crucial to know how long employees are actually exposed to the vibration. This is the total daily ‘trigger time’ with the equipment operating and in contact with the employee’s hand. It is possible to observe and measure the trigger time over half an hour and then use the result to estimate the trigger time for the full shift. Where an employee is exposed to vibration from more than one tool it will be necessary to collect information on likely vibration level and trigger time for each one used.

Once the vibration data and exposure times have been collated it is necessary to use an exposure calculator to assess each employee’s daily exposure, or use a simple ‘exposure points’ system in Table 2 to estimate the daily exposure.

It is necessary to multiply the points assigned to the tool vibration by the number of hours of daily trigger time for the tools, and then compare the total with the exposure action value (EAV) and exposure limit value (ELV) points.

100 points per day = exposure action value (EAV)
400 points per day = exposure limit value (ELV)

Workplace vibration measurements

Where a risk assessment or estimation of exposure suggests there may be a problem, it will be necessary and sensible to obtain accurate quantitative data.

This can only be attained by way of direct equipment monitoring.

This needs a competent person to carry out measurements using specialised equipment. Measurement results can be highly variable, depending on many factors, including the operator’s technique, the condition of the work equipment, the material being processed and the measurement method. The competence and experience of the person who makes the measurements is important so that they can recognise and take account of these uncertainties in producing representative vibration data. In the UK, ‘competency’ is deemed as someone who holds either the correct British Occupational Hygiene Society module on Noise and Vibration or the Institute of Acoustics certificate in the Management of Occupational Exposure to Hand Arm Vibration.

Generally speaking, an Occupational Hygienist is the title given to someone competent in investigating workplace exposure issues such as vibration.

Close detail should be paid to the equipment used by the Occupational Hygienist. They should use a calibrated hand arm meter with a tri-axial accelerometer.

Measurement should be completed by creating ‘exposure groups’ whereby vibrating hand tool types and use patterns are grouped together. A number of tools in each exposure group should undergo measurement, not necessarily all the tools, as this is generally unnecessary; one third of the tools in each exposure group is a reasonable proportion that will generate robust data. It is sensible to meet with the hygienist before completing any work, creating a spreadsheet of all tool types and getting their input into the creation of exposure groups. It is important to ensure that the hygienist has estimated sufficient time to complete the necessary measurements. Each measurement can take between 5 and 15 minutes to complete depending on how well the accelerometer attaches to the tool. Triplicate measurement may be needed to meet the requirements of the relevant British Standards.

Once measurements have been taken, the daily vibration exposure is calculated.

The distance that a vibrating surface moves is called the displacement, the time taken to cover this distance is the velocity, and the rate of change of velocity is the acceleration. Acceleration is used to assess vibration using root mean square values which are proportional to the amount of energy. The frequency of the vibration must also be taken into account and frequency weightings are applied to hand-arm vibration measurements in order to take account of the effect of different frequencies. Measurements of vibration are taken simultaneously in three axes and combined by the meter as a vector sum.

Management and control

Once the employer has good information and data on the levels of vibration exposure in the workplace it is necessary to manage this and put controls in place to ensure employees do not exceed the ELV and EAV. Management and control can be split into the following categories:

Work processes

Consideration should always be given to eliminating exposure to vibration by the use of alternative work methods.

Tool Purchasing Policy

The purchase of new tools should always take into account the vibration levels likely to be encountered and supplier’s data should be consulted.

Although the levels given by the suppliers are not always ‘in use’ levels they can be used as a guide. The handles and weight of tools may also play a part in the transmission of vibration to the hand and its effect. Tools which are easier to hold do not require such a firm grip and less vibration is transmitted. Also, air powered tools with a metal handle become cold and cold hands with poorer circulation are more likely to be susceptible to the effects of vibration. The air exhaust route from the tool should also be taken into account for the same reason.

Ongoing Maintenance

The importance of regular tool maintenance must be stressed in order to keep vibration levels to a minimum.

Reduction of Exposure Time

Where it is not possible to eliminate or reduce exposure to vibration by other means it may be reduced by limiting the exposure time.

Protective Equipment

PPE should always be seen as the last resort in managing any exposure issue, but a range of gloves is available to reduce vibration. These typically have a gel filled pad in the palm and fingers, but also have the effect of keeping the fingers warm, which helps reduce the impact and likelihood of vibration ‘white finger’ and hand arm vibration syndrome.

Information, Instruction and Training

All employees who work with hand held vibratory tools should be given information on the hazards from the use of these, and the symptoms to be aware of. Guidance should also be given on contributory factors which increase the risks of vibration exposure, such as poor blood circulation due to cold or smoking. The importance of reporting and replacing damaged tools and the best way to hold and use tools should also be part of this instruction process. Using information such as that given in the UK HSE’s Guidance Note for Employees INDG 296 is a useful tool in imparting some of this information.

Ongoing Health Surveillance

As detailed earlier, the employer is required to provide suitable health surveillance when an assessment indicates a risk to the health of employees or an Action value is exceeded, and shall take specified steps if the health surveillance indicates that an employee has a disease or adverse health effect as a result of exposure to vibration.

Those employees who have been identified, either in a vibration monitoring exercise or a risk assessment, as being exposed to high levels of vibration, should be assessed as to their fitness to work with hand held vibratory tools. This must then be repeated annually or as deemed necessary by the person carrying out the medical surveillance.

Author Details:

Simon Skentelbery, ALcontrol Laboratories






www.osedirectory.com/health-and-safety.php

Published: 10th Dec 2010 in OSA Magazine

Author


Simon Skentelbery BSc (Hons) MSc


General Manager (Occupational Hygiene), ALcontrol On-Site Services


Simon Skentelbery BSc (Hons) MSc

Website:
http://www.alcontrol.co.uk

Email:
simon.skentelbery@alcontrol.co.uk

Phone:
+ 44 (0) 1782 576590

simon.skentelbery@alcontrol.co.uk
http://www.alcontrol.co.uk
+ 44 (0) 1782 576590

Contact Us Events List Terms and Conditions Privacy Policy Sitemap Maintenance