Hand-Arm Vibration Syndrome (HAVS)

Work-Related Risk Factors

Hand-Arm Vibration Syndrome is caused by the frequent use of vibrating hand tools that have a frequency range between 8 Hz and 1500 Hz. The most hazardous frequencies are from 100 to 150 Hz. Examples of vibrating hand tools include grinders, chipping hammers, sanders, chain saws, and jackhammers.

Development and Progression

Initially, the nerves are irritated by the vibration, causing tingling and numbness in the hand and fingers. Blood vessels may be irritated and spasm, causing the fingers (especially the tips) to feel cold and possibly painful. Eventually, the finger tips may intermittently turn white (blanch). Blanching is often brought on by use of vibrating tools in cold environments. The blanching may last until the fingers are rewarmed. Attacks of blanching, pain, or numbness generally increase in frequency over time, and they may involve several fingers.At first, the attacks are caused by cold temperatures, but over time they may occur during milder temperatures as well. In cooler climates, improvement in the condition is frequently seen during the summer. For milder cases, when exposure is decreased or eliminated, nearly 50% of patients improve to near their baseline within about five years post-exposure. Improvement is not as good when HAVS is well-established, and some nerve damage may be irreversible.

Common Symptoms

Individuals with HAVS complain of tingling, numbness, loss of feeling, and/or pain in the hands and fingers.They may experience a gradual decrease in hand strength, reduced dexterity, and hand and arm muscles that tire easily.Also, they may have a cold feeling of the fingers and blanching of the finger tips.In more severe cases, shrinking of the hand muscles (atrophy) is possible.

Common Treatment

Most treatment for HAVS focuses on reducing work exposure to vibration. Quitting smoking reduces the frequency and intensity of attacks. In cases where extensive blanching occurs in all fingers, it may be necessary to change occupations.

A comprehensive review by NIOSH concluded there is strong evidence from epidemiology and biological studies that exposure to hand-arm vibration causes hand-arm vibration syndrome (HAVS).The risk increases as the magnitude and duration of exposure to vibrating tools increases.There is also a link between exposure to hand-arm vibration and carpal tunnel syndrome.

The precise level of vibration that is harmful is not fully understood. There are, however, U.S. and international standards that describe doses currently regarded as "acceptable." These standards include the International Standard (ISO) 5349 (1986), American National Standard (ANSI) S3.34 (1986), and the American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit value (TLV) for Hand-Arm Vibration.In general, the higher the acceleration level, the shorted the exposure time should be.

When operating a conventional vibrating tool, the tissues of the fingers and palm absorb more than 90% of the transmitted energy from the tool. This energy absorption causes injuries to the nerves, resulting in deficits in touch and temperature sensation. The small fiber nerve damage appears to be largely irreversible. Large impact tools, such as jackhammers, produce low-frequency tissue waves that can also affect the shoulder and neck.