Exposure to Vibration Health Effects of Vibration

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14.1.1 Frequency

A vibrating object moves back and forth from its normal stationary position. A complete cycle of vibration occurs when the object moves from one extreme position to the other extreme and back again. The number of cycles that a vibrating object completes in one second is called frequency. The unit of frequency is hertz Hz. One hertz equals one cycle per second.

14.1.2 Amplitude

A vibrating object moves to a certain maximum distance on either side of its stationary position. Amplitude is the distance from the stationary position to the extreme position on either side and is measured in metres m. The intensity of vibration depends on amplitude.

14.1.3 Acceleration measure of vibration intensity

The speed of a vibrating object varies from zero to a maximum during each cycle of vibration. It moves fastest as it passes through its natural stationary position to an extreme position. The vibrating object slows down as it approaches the extreme, where it stops and then moves in the opposite direction through the stationary position toward the other extreme. Speed of vibration is expressed in units of metres per second ms. Acceleration is a measure of how quickly speed changes with time. The measure of acceleration is expressed in units of metres per second per second, or metres per second squared ms 2 . The magnitude of acceleration changes from zero to a maximum during each cycle of vibration. It increases as the vibrating object moves further from its normal stationary position.

14.2 Exposure to Vibration

Exposure to vibration normally occurs during the operation of powered machinery such as hand tools or whilst travelling on vehicles. Some examples of exposure are given below. Vibration tends to be classified into the following types depending upon the nature of the exposure. 137 Hand-arm vibration is mechanical vibration, which when transmitted to the human hand-arm system, can result in vascular, bone or joint, neurological or muscular disorders. Whole-body vibration is the mechanical vibration that when transmitted to the whole body can result in low-back morbidity and trauma of the spine. Examples of occupational vibration exposure Industry Type of Vibration Common Source of Vibration Agriculture Whole body Tractors Boiler making Hand-arm Pneumatic tools Construction Whole body Hand-arm Heavy equipment vehicles Pneumatic tools, Jackhammers Diamond cutting Hand-arm Vibrating hand tools Forestry Whole body Hand-arm Tractors Chain saws Foundries Hand-arm Vibrating cleavers Furniture manufacture Hand-arm Pneumatic chisels Iron and steel Hand-arm Vibrating hand tools Lumber Hand-arm Chain saws Machine tools Hand-arm Vibrating hand tools Mining Whole body Hand-arm Vehicle operation Rock drills Rivetting Hand-arm Hand tools Rubber Hand-arm Pneumatic stripping tools Sheet Metal Hand-arm Stamping Equipment Shipyards Hand-arm Pneumatic hand tools Shoe-making Hand-arm Pounding machine Stone dressing Hand-arm Pneumatic hand tools Textile Hand-arm Sewing machines, Looms Transportation Whole body Vehicles

14.3 Health Effects of Vibration

Vibration induced health conditions progress slowly. In the beginning it starts as a pain. As the vibration exposure continues, the pain may develop into an injury or disease. Pain is the first health condition that is noticed and should be addressed in order to stop the injury. Vibration-induced white finger VWF is the most common condition among the operators of hand-held vibrating tools. Vibration can cause changes in tendons, muscles, bones and joints, and can affect the nervous system. 138 Collectively, these effects are known as Hand-Arm Vibration Syndrome HAVS. The symptoms of VWF are aggravated when the hands are exposed to cold. Workers affected by HAVS commonly report:  Attacks of whitening blanching of one or more fingers when exposed to cold.  Tingling and loss of sensation in the fingers.  Loss of light touch.  Pain and cold sensations between periodic white finger attacks.  Loss of grip strength.  Bone cysts in fingers and wrists. The development of HAVS is gradual and increases in severity over time. It may take a few months to several years for the symptoms of HAVS to become clinically noticeable. HAVS is a disorder, which affects the blood vessels, nerves, muscles and joints of the hand, wrist and arm and it can become severely disabling if it is ignored. Vibration white finger VWF is a common complaint for workers who regularly use power tools andor drills, which can be triggered by cold or wet weather and result in severe pain in the affected fingers.

14.4 Measurement of Vibration