Occupational disease
Occupational disease due to local vibration
Apr
Vibration is a mechanical oscillation phenomenon generated by engines and tools when their center of mass or axis of symmetry moves periodically in space. Vibration can occur vertically, horizontally, or in multiple directions.
Occupational diseases caused by local vibration affect only specific parts of the body. Local vibration effects are most commonly observed in jobs using pneumatic or handheld electric devices such as rock drills, chisels, riveting hammers, mold tamping machines in foundries, and more.
Localized occupational disease is a pathological condition caused by exposure to vibration, primarily affecting bones, joints, and vascular disorders, and may also involve tendons, muscles, and nerves.
1. What is localized occupational vibration disease?
Localized vibration (also called local vibration) occurs at high frequencies above 20Hz. Local vibration is mainly transmitted through the hands in people using handheld tools.
Workers exposed to local vibration for long periods may experience pain, muscle fatigue in the hands and arms, and reduced muscle strength. Vibration exposure can reduce hand grip strength, and in some cases, muscle fatigue can lead to disability.
2. Occupations at risk of localized vibration disease
Localized vibration occupational disease is common among workers exposed to continuous vibration on the body, especially joints, muscles, and ligaments. Typical occupations and sources of exposure include:
- Operating pneumatic hand tools such as hammers, chisels, riveting hammers, mold chisels, mold casting tools, rock drills, etc.
- Using handheld motorized machines such as saws, grinders, drills; oilfield drilling machines; metal polishing machines; and rotating grinding tools.
- Other jobs that require exposure to local vibration.
Any occupation involving machinery and equipment that generates local vibration carries a risk of occupational vibration disease.
3. Mechanism and causes of localized occupational vibration disease
When operating handheld machines, the left hand often holds and stabilizes the tool, while the elbow, shoulder, or thigh acts as support points, and the right hand applies force. With average machine weights of 20–35kg, the machine generates strong and continuous vibrations that are transmitted directly to the worker’s body, causing localized vibration disease.
Workers using high-vibration handheld machines must exert significant effort to maintain the correct posture, which requires frequent and strong muscle contractions. This strain facilitates the spread of vibrations throughout the upper limb and shoulder, leading to muscle contraction, cramps, and, in severe cases, muscle atrophy.
According to H. Desoille, muscle atrophy is often observed in the little finger and thumb, with interosseous and arm muscles also affected, but to a lesser extent.
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4. Symptoms and effects of localized occupational vibration disease
Bone and joint symptoms:
- Joint pain: dull pain appearing after work or at the beginning, relieved after rest.
- Joints: no deformity, no swelling, but slight muscle atrophy around the joints.
- Limited joint movement when bending, slight changes when extending.
Vascular disorders (occupational Raynaud’s disease):
- Includes circulatory disorders of the extremities and sensory disorders in the hands. The disease progresses in two stages:
- Stage 1: occasional blanching of one or more fingertips, followed by paleness and numbness in cold environments.
- Stage 2: intermittent pain, sometimes severe, with warmth sensation, occasional redness turning to purple in the fingers.
- Most severe in the middle and ring fingers. The thumb is usually unaffected. Muscle atrophy may occur in the hypothenar and interosseous regions.
Tendon, muscle, and nerve damage:
- May include atrophy of the thenar or hypothenar muscles, loss of reflexes, without sensory disturbance.
- Pain may occur in the hands, forearms, upper arms, and shoulders.
- Cramping may occur, particularly in the deltoid muscles.
X-ray images may show small bone defects, bone spurs, joint debris, osteoporosis, demineralization, and periosteal reactions.
Microvascular changes may include constriction or dilation, slowed circulation, deformed capillaries, and reduced capillary density.
5. Protective equipment to prevent localized occupational vibration disease
Workers in high-risk industries must be equipped with the following protective equipment:
- Protective gloves to shield hands and wrists from impact while reducing vibration and friction.
- Safety shoes to protect feet from impact while minimizing vibration and friction.
- Protective clothing to protect the entire body from strong impacts.
Proper training in using and maintaining protective equipment is crucial to ensure effectiveness.
6. Compensation for workers with localized occupational vibration disease
According to Vietnamese social insurance law, workers affected by localized vibration occupational disease are entitled to:
- Health loss compensation based on severity and work capacity.
- Healthcare and treatment to reduce symptoms.
- Support for retraining or learning new skills if unable to continue in the current job.
- Other benefits such as medical insurance, social insurance, family allowances, and leave entitlements.
Workers must provide complete documentation to prove the occupational disease and treatment process.
7. Treatment of localized occupational vibration disease
Treatment for bone and joint damage is often ineffective. Vascular, nerve, and muscle-tendon disorders may be treated using vasodilators, physiotherapy, vitamins, warming stimuli, and vasodilator medications.
Treatment should be diagnosed and monitored by experienced medical professionals.
8. Prevention of localized occupational vibration disease
- Do not recruit workers with pre-existing musculoskeletal, neurological, or vascular disorders for vibration-related jobs.
- Regular health checks, including X-rays of upper limbs every 2–3 years.
- Cold tests to monitor for white fingertips and occupational Raynaud’s disease.
- Provide protective gear such as rubber-lined gloves, earplugs, hand soaking, massage after work, and limit vibration exposure to 3–5 hours/day.
- Reduce noise and vibration from equipment.
Training programs are also effective for raising awareness about vibration hazards and proper tool usage.
9. Employer responsibilities in preventing localized occupational vibration disease
- Train employees on risks and preventive measures.
- Provide protective equipment such as anti-vibration pads, gloves, ear protectors, and anti-vibration helmets.
- Adjust high-frequency vibration equipment to minimize impact.
- Implement safety measures to reduce injury and vibration-related disorders.
- Conduct regular health checks for early detection.
- Carry out occupational environment monitoring and report results regularly to improve the workplace environment.
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