How does vibration affect workers’ health?

Vibration is a mechanical oscillation, generated by the regular periodic or changing displacement of an object around its position. Machines, equipment, and tools using various power sources all generate mechanical oscillations in the form of vibration when operating.

Vibration is a leading cause of occupational diseases in workers in the fields of mechanical engineering, construction, transportation, mining, etc.

1. What is Vibration?

Vibration/Jerk (Shock): refers to mechanical oscillations generated by engines and production equipment. These oscillations can be harmonic or non-harmonic. In harmonic oscillation or sine wave oscillation, an object moves from its starting position (equilibrium position) to one side or the other, then returns to the starting position within a specific time period.

Vibration is a type of oscillation with high frequency and small amplitude . In practice, machines and tools often generate complex oscillations, which are a composite of many simple oscillations.

Jerk (Shock) is often encountered in various transportation sectors; these are non-harmonic oscillations, typically with low frequency and large amplitude .

Vibration is a mechanical phenomenon of oscillation generated by engines and production equipment when their center of gravity or axis of symmetry periodically shifts in space. Vibration can occur in vertical, horizontal, or multiple directions.

There are two types of vibration:

• Whole-body vibration (or general vibration ), primarily low-frequency from 2 – 20Hz , which at this frequency is also called jerk (or shock ), and very low frequency below 2Hz. Whole-body vibration can also occur at higher frequencies.
• Local vibration (or segmental vibration ), a type of high frequency above 20Hz . Local vibration primarily affects the hand-arm system, in people who use handheld tools.

The permissible values are regulated according to the 3 axes of the orthogonal coordinate system attached to the human body, conventionally defined as follows:

• z – the vertical axis, perpendicular to the ground and directed from the feet up to the head.
• x – the horizontal axis, directed from the back to the chest.
• y – the horizontal axis, directed from the right shoulder to the left shoulder.

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2. Where does Vibration originate within a Manufacturing Plant?

Vibration in a manufacturing plant can originate from various sources. Below are some common causes of vibration in a production environment:

• Production processes such as machining, cutting, drilling, pressing, grinding, material handling,… can also generate vibration.
• Electronic equipment like motors, variable frequency drives, industrial electrical systems, or automatic control systems can generate vibration. If not properly installed or configured, electronic components can cause vibration or generate unwanted oscillations.
• The factory structure and materials used in the production process can generate vibration. If the structure is not designed to be robust or is not installed correctly, it can vibrate and create sound. Vibration can also arise from materials when they are impacted or subjected to deformation.
• Machinery and equipment in the plant can generate vibration when operating. This can be due to imbalance, dropping, swaying, or the system not being properly maintained.

To minimize vibration in a manufacturing plant, the following measures can be applied: regular inspection and maintenance of machinery and equipment, proper balancing and configuration of electronic systems, improvement of structure and materials, use of soundproofing and vibration-damping measures, and adherence to occupational safety regulations.

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3. Occupations with Vibration Factors that Pose a Risk to Workers

Several occupations with high vibration exposure can pose a risk to workers. These occupations often involve the use of tools, machinery, or equipment that generate strong and continuous vibration. Below are some examples of such occupations:

• Construction workers often work with heavy tools and machinery such as drills, cutters, jackhammers, compressors,… These tools can generate strong and prolonged vibration during use, posing a danger to the skeletal, muscular, nervous, and other bodily systems.
• In the mining industry , workers often operate heavy equipment such as drills, crushers, transportation equipment,… which have significant vibration.
• Metal processing industries such as welding, casting, machining, mold making,… also frequently involve high vibration factors.
• In the aerospace industry , workers are exposed to aircraft, aircraft engines, and other equipment that generate vibration. Aviation technicians and engineers are at risk of prolonged vibration effects.
• Some other sectors, occupations, and jobs involve exposure to vibration.

It is important to note that in these occupations, prolonged and uncontrolled exposure to vibration can cause serious health problems. Therefore, safety and occupational protection measures must be implemented to minimize the impact of vibration on workers.

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4. How Does Vibration Affect Worker Comfort?

Vibration can negatively impact the comfort and health of workers. Below are some main effects of vibration on worker comfort:

• Continuous exposure to vibration can cause fatigue and stress for workers, such as feelings of discomfort and psychological stress.
• Vibration can cause health problems such as back pain, neck pain, shoulder pain, and issues with the skeletal, muscular, nervous, and vascular systems,… If uncontrolled, prolonged vibration can cause serious health problems leading to occupational diseases in workers.
• When workers have to operate in an environment with harmful vibration factors, their ability to concentrate , work ethic , and accuracy can be affected. This can lead to lack of focus, errors, and reduced labor productivity.
• Vibration can create an uncomfortable working environment and affect the psychological health of workers. Feelings of instability, tension, and pressure can increase, making it difficult to create a positive and comfortable work environment.

To ensure worker comfort, preventative measures and steps to reduce vibration in the working environment should be implemented.

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5. Permissible Vibration Exposure Levels in the Workplace

According to QCVN 27:2016/BYT National Technical Regulation on Vibration – Permissible Values in the Workplace:

• Local Vibration
  • The permissible levels for vibration acceleration and velocity across octave frequency bands are regulated in Table 1.

Table 1. Average values of vibration acceleration and velocity in octave frequency bands not to exceed the following values:

Frequency Band (Hz)	Permissible Level
	Vibration Acceleration (m/s2)	Vibration Velocity (m/s) $\times 10^{-2}$
8 (5.6-11.2)	1.4	2.8
16 (11.2-22.4)	1.4	1.4
31.5 (22.4-45)	2.7	1.4
63 (45-90)	5.4	1.4
125 (90-180)	10.7	1.4
250 (180-355)	21.3	1.4
500 (355-700)	42.5	1.4
1000 (700-1400)	85.0	1.4

• • The permissible levels for weighted acceleration and velocity in each octave frequency band depend on the exposure time, regulated in Table 2.

Table 2. Average values of weighted acceleration and velocity in each frequency band according to exposure time

Exposure Time, minutes	Permissible Level
	Vibration Acceleration (m/s2)	Vibration Velocity (m/s)
480	1.4	$1.4 \times 10^{-2}$
240	2.0	$2.0 \times 10^{-2}$
120	2.8	$2.8 \times 10^{-2}$
60	3.9	$3.9 \times 10^{-2}$
30	5.6	$5.6 \times 10^{-2}$

*Note:* The maximum permissible vibration value shall not exceed the permissible value corresponding to 30 minutes of exposure time (according to Table 2).

• • Permissible levels for weighted acceleration and velocity: for vibration at other frequencies, when the exposure time is within 8 hours (480 minutes), the weighted acceleration shall not exceed $4 \text{ m/s}^2$, and the weighted velocity shall not exceed $4 \text{ cm/s}$.
  • Permissible levels for weighted acceleration and velocity according to exposure time: if the exposure time is less than 8 hours per day, the permissible weighted acceleration and weighted velocity are calculated using the following formula: [ *The formula is missing in the original Vietnamese text *].

• Whole-body Vibration
  • The permissible levels for vibration acceleration and velocity across octave frequency bands are regulated in Table 3.

Table 3. Permissible levels for vibration acceleration and velocity in octave frequency bands not to exceed the following values:

Frequency Band (Hz)	Vibration Acceleration (m/s2)		Vibration Velocity (m/s)
	Vertical Vibration	Horizontal Vibration	Vertical Vibration	Horizontal Vibration
1 (0.08-1.4)	1.10	0.39	$20.0 \times 10^{-2}$	$6.3 \times 10^{-2}$
2 (1.4-2.8)	0.79	0.42	$7.1 \times 10^{-2}$	$3.6 \times 10^{-2}$
4 (2.8-5.6)	0.57	0.80	$2.5 \times 10^{-2}$	$3.2 \times 10^{-2}$
8 (5.6-11.2)	0.60	1.62	$1.3 \times 10^{-2}$	$3.2 \times 10^{-2}$
16 (11.2-22.4)	1.14	3.20	$1.1 \times 10^{-2}$	$3.2 \times 10^{-2}$
31.5 (22.4-45)	2.26	6.38	$1.1 \times 10^{-2}$	$3.2 \times 10^{-2}$
63 (45-90)	4.49	12.76	$1.1 \times 10^{-2}$	$3.2 \times 10^{-2}$

*Note: When studying vibration, usually only one of the two quantities (vibration acceleration or vibration velocity) is measured.*

• • Permissible levels for weighted acceleration for vertical vibration shall not exceed $0.54 \text{ m/s}^2$ (along the z-axis), and for horizontal vibration shall not exceed $0.38 \text{ m/s}^2$ (along the x,y-axes).
  • Permissible levels for weighted acceleration according to exposure time: different types of vehicles and working positions have different correction factors:
    • Type 1: Transportation Vibration, vibration in traffic affecting the workplace of mobile machines and transportation vehicles while operating. Example: Driving trucks, operating agricultural tractors, road construction machines… The permissible weighted acceleration according to exposure time is the weighted acceleration multiplied by a factor of 1. For vertical vibration, it shall not exceed $0.54 \text{ m/s}^2$ (along the z-axis), and for horizontal vibration, it shall not exceed $0.38 \text{ m/s}^2$ (along the x,y-axes).
    • Type 2: Transportation – Technological Vibration, affecting the workplace of mobile machines and vehicles restricted to certain areas of the production floor or mining area. Example: Operating excavators, various types of cranes, various types of mining machines (combined mining machines). The permissible weighted acceleration according to exposure time is the weighted acceleration multiplied by a factor of 0.5. For vertical vibration, it shall not exceed $0.27 \text{ m/s}^2$ (along the z-axis), and for horizontal vibration, it shall not exceed $0.19 \text{ m/s}^2$ (along the x,y-axes).
    • Type 3: Production Technology Vibration, affecting the workplace of stationary machines or transmitted to workplaces without a vibration source. Example: Operating machine tools, the foundation of stationary machines in production. The permissible weighted acceleration according to exposure time is the weighted acceleration multiplied by a factor of 0.16. For vertical vibration, it shall not exceed $0.086 \text{ m/s}^2$ (along the z-axis), and for horizontal vibration, it shall not exceed $0.06 \text{ m/s}^2$ (along the x,y-axes).

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6. What Occupational Diseases Result from Prolonged Exposure to Harmful Vibration?

When exposed to harmful vibration for a long period, workers can suffer from a number of vibration-related occupational diseases, collectively known as whole-body vibration occupational disease and local vibration occupational disease. Below are some diseases associated with vibration:

• Continuous and prolonged vibration exposure can cause damage and imbalance in the skeletal, joint, and muscular systems , leading to problems such as back pain, arthritis, spinal inflammation, and muscle diseases,…
• It can cause damage to the nervous system , leading to issues such as pain and numbness, nerve damage, loss of sensation, and inappropriate sensation regulation.
• Vibration can affect the vascular system , causing problems such as reduced blood circulation, swelling, and loss of sensation in the fingers and toes.
• Vibration can damage the motor nervous system , leading to reduced control and grip strength.
• Some jobs with vibration exposure can cause damage to vision , leading to problems such as decreased visual acuity,…

These pathologies can affect the quality of life, health, and work efficiency of workers. Therefore, ensuring a safe working environment and implementing occupational protection measures are very important to minimize this impact.

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7. Measures to Mitigate the Effects of Vibration on Worker Health

To minimize the effects of vibration on worker health, the following measures can be applied:

• Ensure that the job design and working environment are suitable to reduce vibration exposure . This includes using work equipment with vibration reduction features, arranging the workplace for convenience and comfort, and reducing noise and vibration in the working environment.
• Use anti-vibration equipment such as gloves, anti-vibration shoes, anti-vibration mats,… to reduce direct contact with vibration.
• Limit exposure time to vibration and ensure rest periods for the body to recover after exposure.
• Conduct periodic health checks to detect vibration-related health problems early and provide timely treatment.
• Ensure adherence to industry vibration safety regulations and standards and implement preventative measures.
• Worker Training : Workers need to be trained on health protection measures while working, so they can self-protect their health when operating in such an environment.
• Periodically organize work environment monitoring in factories and enterprises, collecting and analyzing harmful factors for workers, thereby adjusting to reduce the hazard level to prevent occupational diseases for them.

These measures will help minimize the impact of vibration on worker health and enhance their work efficiency.

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