This material is for training purposes only. Its purpose is to inform Oregon employers of best practices in occupational safety and health and general Oregon OSHA compliance requirements. This material is not a substitute for any provision of the Oregon Safety Employment Act or any standards issued by Oregon OSHA. For more information on this online course and other OR-OSHA online training, visit the Online Course Catalog.

MODULE FOUR: ENVIRONMENTAL RISK FACTORS

What are risk factors the environment brings to the job?

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 may be brought on by:

Summer heat
Tropical heat
Heat from engines
Heat from chemical processes and reactions
Body heat
Welding
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 possibly ventricular fibrillation.

Low temperature conditions may be caused by winter cold, high altitudes, refrigerated surfaces and/or cryogenic lines and equipment. These can result in muscle strain as well as cold "burns," frostbite, and hypothermia.

Whole body vibration

When the whole body is subjected to vibration, as most commonly experienced by truck drivers, there is an enhanced risk of injury, especially to the lower back.

Whole-Body Vibration usually results from two types of forces acting on the worker.

A non-cyclical force over a very short period of time (instantaneous shock load). A vehicle striking an obstacle or a sudden drop into a hole may produce these shock loads. If these shock loads are sufficiently great, the operator may be thrown from his seat or struck by objects flying around in the cab.
The most common whole-body vibration forces are not sudden, but rather occur over a period of time. For example, this type of vibration is usually created by large vehicles as they travel over highways and especially terrain.

Duration of exposure plays a large role in the effects of vibration forces. Vibration forces delivered over time are more difficult to define than the instantaneous damage caused by high shock loads. The body will respond significantly to vibrations in the range of .5 to 80 Hz (Hertz, cycles/second). Certain parts of the body are resonant at various frequencies in this range. The body's response to vertical vibration will be greatest between 4 and 8 Hz, while vibrations between 2.5 and 5 Hz generate strong resonance in the vertebra of the neck and lumbar region. Vibrations between 20 and 30 Hz set up the strongest resonance between the head and shoulders. Prolonged exposure to these vibration forces in these frequency ranges may create chronic stresses and sometimes even permanent damage to the affected organs or body parts.

Lighting

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 such 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. Factors influencing the adequacy and effectiveness of illumination include the following:

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, and 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 maintain alertness and to increase productivity in shift workers.

Noise

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, and 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.

OR-OSHA staff has measured and found sound levels produced by VDT 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.

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 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 are 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.

Last Words

There you have it! I hope you have a better understanding of the environmental risk factors impacting MSDs and that you'll be able to apply that knowledge in your workplace. We'll find out, because now it's time complete the quiz below.

MODULE Quiz

31. Heat stress can result in:

a. Heat exhaustion
b. Heat cramps
c. Dehydration
d. All of the above

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

a. low humidity
b. high humidity
c. greater exertion
d. higher force

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

a. hyperthermia
b. hypothermia
c. hyperthermitis
d. hypothermitis

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

a. pulmonary pain
b. dilated pupils
c. ventricular fibrillation
d. shivering

35. The most common whole-body vibration forces are sudden, rather than that occurring over a period of time.

a. True
b. False

36. The body's response to vertical vibration will be greatest between ____ Hz:

a. 2 and 4
b. 4 and 8
c. 8 and 10
d. 10 and 12

37. Factors influencing the adequacy and effectiveness of illumination include the following, except:

a. freedom from concentration
b. freedom from diffusion
c. freedom from glare
d. freedom from shadows

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

a. True
b. False

39. According to the text, to create a healthy work environment that reduces the risk of ergonomics injuries, management should do all of the following, except:

a. understand roles
b. allow participation
c. secure compliance
d. conduct adequate training

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

a. intensified workload
b. limited job control
c. monotonous work
d. poor labor-management relations

Great job! If you're ready, head on over to the next module. You'll be learning more about the various control strategies to help improve the design of your workplace.

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