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Course 711 - Introduction to Ergonomics

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Risk Factors in the Environment

Heat Stress


Externally generated heat in the workplace can cause an excessive total heat load on the body, which can result in heat stroke, a potentially life-threatening condition. Heat exhaustion, heat cramps, dehydration, electrolyte imbalance, and loss of physical/mental work capacity can also result from heat stress. Heat stress is made even more dangerous in the presence of high humidity due to the reduced ability of the body to cool itself.

High temperature conditions at work may be brought on by:

  • Summer heat;
  • Tropical heat;
  • Heat from engines;
  • Heat from chemical processes and reactions;
  • Body heat;
  • Welding; and/or
  • Friction.

Cold Stress


If the worker is exposed to an environment so cold that the body cannot maintain adequate deep core temperature, hypothermia, which can also be life-threatening, may result. Symptoms brought on by cold stress include:

  • Shivering;
  • Clouded consciousness;
  • Pain in the extremities;
  • Dilated pupils;
  • Reduced grip strength and coordination; and/or
  • Possibly ventricular fibrillation.
Low temperature conditions may be caused by:
  • Winter cold;
  • High altitudes;
  • Refrigerated surfaces; or
  • Cryogenic lines and equipment.

These can result in muscle strain as well as cold "burns," frostbite, and hypothermia.

For more detailed information about staying safe in extreme temperatures, please click here to go to our 602: Heat and Cold Stress Safety.


Lighting in one workstation may be appropriate, but for another workstation, that same lighting may be potentially harmful. Illumination may be too high, too low, or cause glare. Illumination levels above 1000 lux present problems in the office environment.

Outside lighting is an important factor to consider. Light for outside work should aid production and, at the same time, be high enough to be safe.


Adequate general and local lighting must be provided for rooms, building, and work areas during the time of use. Below is a list of factors influencing the adequacy and effectiveness of illumination.

  • The quantity of light as specified in American National Standard ANSI All.1-1965, "American Standard Practice for Industrial Lighting".
  • The quality of light in terms of freedom from glare, correct direction, diffusion, and distribution.
  • Freedom from shadows and extreme contrasts.
  • All skylights, side windows, lamps, and other accessories which are necessary for illumination must be kept clean and in working order.

It's interesting to note that lighting has been used to treat depression associated with light deprivation, and may also affect biological clocks and sleep patterns in humans. Although controversial, light has been used to maintain alertness and to increase productivity in shift workers.



Noise is any sound that is unwanted. It can be so powerful as to cause pain in the ears, or it may represent only a nuisance. Its pitch may be quite high or very low; its duration, continuous or intermittent; and its onset, sudden or gradual.

Exposure may lead to:

  • Serious, temporary, or permanent deafness;
  • Tinnitus;
  • Paracusis; or
  • Other hearing disorders.

The louder the noise and the longer the duration, the greater the risk of injury. Nuisance noise may interfere with a worker's ability to focus or concentrate on the work at hand, and may therefore, actually be the indirect cause of an accident.

Oregon OSHA conducted measurements and found sound levels produced by computer workstations and associated equipment to be consistently below those that damage hearing. However, equipment noise can still be disruptive, annoying, or distracting, and many people are sensitive to the low-level, high-frequency noise that the Central Processing Unit (CPU) may emit. As a result, ambient sound levels should be kept below 55 decibels on the A-scale (dBA). Also, narrow-band tones above ambient sound levels should be reduced. It is good practice to isolate main CPUs and disk drives and provide noise-control covers on high-speed printers.

Psychosocial Risk Factors


A healthy ergonomic work environment depends a great deal on the attitudes of those involved. How management handles or responds to problems or concerns relating to ergonomics may determine the development and the severity of many problems in the workplace. To create a healthy work environment:

  • All parties should understand their roles in the overall work process;
  • End users should participate in the selection of equipment, software, tools and accessories; and
  • Employers should provide adequate operator training on the setup, adjustments, and risks associated with performing the job.

Psychosocial Factors and MSDs

In general, four plausible types of explanations have been suggested to account for associations between work-related psychosocial factors and MSDs.

  • Psychosocial demands may produce increased muscle tension and exacerbate task-related biomechanical strain.
  • Psychosocial demands may affect awareness and reporting of musculoskeletal symptoms, and/or perceptions of their cause. Within this second explanation may fall in the "perverse incentive" view, in which societies may provide workers with systems (such as workers' compensation) that may lead to over-reporting of MSD symptoms.
  • Initial episodes of pain based on a physical insult may trigger a chronic nervous system dysfunction, physiological as well as psychological, which perpetuates a chronic pain process.
  • In some work situations, changes in psychosocial demands may be associated with changes in physical demands and biomechanical stresses, and thus associations between psychosocial demands and MSDs occur through either a causal or effect-modifying relationship.

Though the findings of the studies reviewed are not entirely consistent, they suggest that perceptions of intensified workload, monotonous work, limited job control, low job clarity, and low social support are associated with various work-related MSDs. As some of these factors are seemingly unrelated to physical demands and a number of studies have found associations even after adjusting for physical demands, the effects of these factors on MSDs may be, in part or entirely, independent of physical factors.

Epidemiologic studies of upper extremity disorders suggest that certain psychosocial factors (including intensified workload, monotonous work, and low levels of social support) have a positive association with these disorders. Lack of control over the job and job dissatisfaction also appear to be positively associated with upper extremity MSDs, although the data is not as supportive.

There is also increasing evidence that psychosocial factors related to the job and work environment play a role in the development of work-related MSDs of the upper extremity and back.

Manual Handling


Before beginning this quiz, we highly recommend you review the module material. This quiz is designed to allow you to self-check your comprehension of the module content, but only focuses on key concepts and ideas.

Read each question carefully. Select the best answer, even if more than one answer seems possible. When done, click on the "Get Quiz Answers" button. If you do not answer all the questions, you will receive an error message.

Good luck!

1. Heat stress can result in _____.

2. Heat stress is made even more dangerous in the presence of _____ due to the reduced ability of the body to cool itself.

3. This condition may result if the worker is exposed to an environment so cold that the body cannot maintain adequate deep core temperature.

4. Which of the following is not mentioned as one of the symptoms brought on by cold stress?

5. Which of the following is not a high temperature work condition?

6. The _____ the noise and the _____ the duration, the greater the risk of injury.

7. Factors influencing the adequacy and effectiveness of illumination include the following, except _____.

8. Nuisance noise is not considered an environmental risk factor that may interfere with a worker's ability to focus or concentrate on the work.

9. To create a healthy work environment that reduces the risk of ergonomics injuries, management should do all of the following, except _____.

10. Which of the following are not mentioned as employee perceptions associated with various work-related MSDs?

Have a great day!

Important! You will receive an "error" message unless all questions are answered.