Health And Safety Of Workers Exposed To Vibrations

Health and safety of workers exposed to vibrations

The increase in industrialization and mechanization of work processes has resulted in greater exposure to risks produced by physical agents, among which are vibrations.

From an perspective of safety and health at work, it has been shown that exposure to critical vibrations in the body bodily segment, combined with other factors, such as uncomfortable positions, exposure time, among others;The health and well -being of workers can significant. From an perspective of safety and health at work, it has been shown that exposure to critical vibrations in full body, combined with other factors, such as uncomfortable postural demands, can significantly affect the health and well -being of workers.

Characteristics of vibrations

Vibrations are understood as any oscillating movement that makes a particle around a fixed point. This movement can be regular or random in direction, frequency and/or intensity. Those random vibrations are more common. The vibration to which a person is subjected can be unidirectional and in a single frequency or, what is usually more common, in several directions and frequencies. 

Classification of vibrations

Vibrations transmitted to the hand-jack system

These vibrations are those that transmit their energy to the human body through the hand-jack system.

Exposure to this type of vibrations occurs in working conditions where the intensity of the vibration is transmitted to the worker’s hands and arms as a consequence of work with machines and manual equipment, the manipulation of parts that are being mechanized, orManagement of control elements subjected to vibration.

In these cases, the human body may be exposed to vibrational levels that can cause damage to diverse nature in the medium and long term.

When the point of contact is the hand, the vibration is cushioned by the hand-jombre set, so that it can be considered approximately, as an independent and isolated system from the rest of the body. This should not be generalized and assumed that all the effects of hand-jack vibrations are always limited to the upper members.

Some biomechanical checks have determined that vibrations below 50 Hz are transmitted with little attenuation along the hand and forearm. The attenuation in the elbow will depend on the flexion angle of the same, so that, at greater angle, the transmission decreases.

Vibration transmitted to the entire body

The vibrations of the full body are those that the body receives when much of its weight rests on a vibrant surface (seat or backing of the driving position of a mobile machine, vibrant platform, etc.).

“Mechanical vibration that when it is transmitted to the entire body, entails risks to the health and safety of workers, particularly low back pain and spine injuries."

The transmission of vibrations to the body and its effects depend largely on the posture, and the individual’s own sensitivity itself. In this way, exposure to vibrations may not have the same consequences and effects on all situations. The frequency range of interest to evaluate the health effects derived from exposure to entire body vibrations, is between 0.5 Hz to 100 Hz, except in the maritime navigation sector that would be above 1 Hz. Below the 0.5 Hz are the vibrations that cause effects such as dizziness such as dizziness.

Vibrations are understood as any oscillating movement that makes a particle around a fixed point. This movement can be regular or random in direction, frequency and/or intensity. Those random vibrations are more common.

Vibrations measurement

The vibrations are defined, as seen above and simplified, for its intensity and for their frequency. The instrument to measure vibrations is the vibrometer (Figure 5). As with noise, a series of weighting filters are necessary capable of measuring complex accelerations and transforming them into a value, taking into account the most harmful to the human organism.

The accelerometer is what in noise would be equivalent to a microphone. It must be placed in the organism area with the element that transmits the vibrations;For example: in a vehicle it would be placed in the seat, in the back and on the feet;in activities that stand up, on the ground under the feet;In the case of handling tools, in the hand – tool interface (Figure 6).

There are vibrometers that make measurements in the three orthogonal axes;Those who do not have this option must take three consecutive measures on each axis.

Evaluation criteria for comfort vibrations

ISO 2631: 1-1997 studies the effect of vibrations on comfort and perception of healthy people who are exposed to periodic, random or passenger vibrations traveling, at work or carrying out leisure activities. The frequency range analyzed is 0.5 Hz at 80 Hz.

It is known that the degree of discomfort is related to the frequency of vibration and that it is proportional to the intensity of the same. At low frequencies 1-2 Hz the same movement is transmitted along the body, at a bit higher frequencies resonances appear in various parts of body and increases the discomfort and if the frequencies are higher, the body attenuates the vibrations and decreases thediscomfort. For example, monotonous vibrations of low frequencies seem to produce fatigue while transient vibrations activate the individual and can produce stress, etc.

Regarding the intensity of vibrations, those that exceed the limit of perception activate the senses (for example, vision and balance receptors), and the brain receives additional information that needs to interpret and manage.

Psychophysiological effects

Hand-jack vibrations

The transmission of vibrations depends on their physical characteristics (intensity and frequency), the direction and the dynamic response of the hand. The adverse effects will also depend among other factors of the grip pressure, on the applied static force, on the upper limb posture, as well as the exposure and recovery time.

Disorders may be:

• Vascular disorders: the best known is the so -called Raynaud phenomenon (or white -induced white finger). It consists of a temporary occlusion of blood circulation to the fingers, causing a feeling of paleness or white finger. While it occurs, the worker perceives a loss of sensitivity and skill in the fingers, which can increase accident risks. In the most serious cases they can even produce ulceration and gangrene.
• Neurological disorders: Another effect is the sensation of tingling and numbness in the fingers and in hand. If it extends over time, it ends up impacting the ability to work and normal life activities. Mano-jug vibrations are a factor that can increase the risk of the appearance of the carpal tunnel syndrome (disorder due to the compression of the medium nerve in its passage through the dolls).
• Osteoarticular disorders: there is an increase in bone lesions and joints in workers who use percussion tools. Specifically, a higher prevalence of wrist and elbow osteoarthritis has been described in those workers exposed to low frequency vibrations.
• Muscle disorders: can produce muscle weakness and hand and arms pain, as well as a decrease in grip force. Disorders such as tendonitis and tenosinovitis in the upper extremities may also appear.
• Other disorders: they have been related to hearing loss, although it is not well known if it is due to the noise association that vibrations usually entail or directly to the vibrations themselves.

Whole body vibrations

You have to distinguish between acute effects and long -term effects

Regarding the acute effects:

• Respiratory disorders: They can cause hyperventilation, probably caused by the mechanical influence of vibrations on the diaphragm and chest.
• Musculoskeletal disorders: in some studies it has been observed that vibrations activate some muscles. This activation produces passive and involuntary muscle movements.
• Sensory disorders and central nervous system: great amplitude vibrations cause what is known as "evil of movement" or "dizziness induced by movement".
• Other effects: problems such as increased heart rate, blood pressure and oxygen consumption may appear. Changes in some hormones have also been observed, such as catecholamines and adrenocortopicotropic.

• Regarding the long -term effects:

• Effects on the musculoskeletal system: When vibrations continue over time, changes in the spine can be pathological. They can produce a high incidence of degenerative changes and deviations from curvature, mainly in the lumbar part. It is a factor that increases the possibility of disorders in the thoracic region, even arthrosis in the joints. As the intensity and duration of vibrations increase, it increases the risk of these types of disorders. This type of effects have been described even in exhibitions at low intensities.
• Effects on the nervous system: the main alterations are produced in exhibitions above 8 pm. These are usually nonspecific, such as headaches, irritability, etc. Sometimes they can produce alterations in cortical and subcortical structures, altering blood supply to the brain.
• Effects on the cochlear-vestibular system: It can cause a greater incidence of vestibular disturbances, as is the case with vertigo. It is possible to enhance the loss of noise induced hearing.
• Effects on the circulatory system: there is a diversity of circulatory disorders related to vibrations. They are divided into four main groups: peripheral disorders;varicose veins in lower extremities, hemorrhoids and varicocele;ischemic alterations and hypertension;and neurovascular changes.
• Effects on the digestive system: exposure to vibrations can cause a greater incidence of disorders of the digestive system: gastric and duodenum ulcers, gastritis, appendicitis, colitis … This type of alterations may appear in low intensity exhibitions.
• Effects on female reproductive organs, gestation and male genitourinary apparatus: in women there is a higher risk of alterations: menstrual, abortion threats and other complications in pregnancy;In men a greater incidence of prostatitis has been detected.

Factors such as work postures, anthropometric characteristics, muscle tone, physical overload situations and individual susceptibility will be decisive for the appearance of these effects, especially of musculoskeletal disorders.

Preventive measures

Preventive measures can be classified as follows:

Technical action on the focus and on the medium

• Technical actions consist of minimizing the intensity of vibrations before they are transmitted to the individual. Example of this type of action are the preventive maintenance of facilities and equipment.
• Sometimes the modification of resonance frequencies to discourage vibrations may interest. The use of suspension mechanisms, for example, in transport vehicles, is another technical measure.
• The tools must be ergonomically designed. When selecting a tool, its design must be taken into account: stability, ease of grip, adapt to the task and position that the worker needs to adopt.
• Vibrations, sometimes, are usually accompanied by noise. If the intensity of the vibrations are reduced, the acoustic pressure level will be reduced.

Technical action on the receiver

• The use of EPI as gloves or footwear, even those who are not expressly designed for vibration absorption, can reduce the transmission of vibrations intensity.
• An aspect that must be contemplated when selecting a glove is its adaptation to the user’s hand. The more he adjusts to the hand, the better the grip to the tool or machine will be and, therefore, the lower the transmission of vibrations.

Organizational action

• It is based on organizing the work in such a way that the exposure time is reduced: rotation of jobs, establishment of pauses and adaptation of tasks to the different individual characteristics.
• Adequate training and information is fundamental and sometimes it can be convenient to contemplate this risk in health surveillance.

Bibliography

1. Alfaro, m. G.-C. (2007). INSHT.
2. Garcia, f. G. (December 2006). Autonomous Community of the Region of Murcia.
3. Work, i. N. (November 2014). INSHT.