ISHN

Winter wear for safety's sake

December 1, 2006


With winter fast approaching, it’s time to prepare your workers for cold weather. Hand safety in particular is affected by cold conditions and requires careful consideration when assessing hazards and specifying control measures.

Low temperatures affect hands and safety in several ways. Actual direct contact with very cold surfaces or materials can result in injury. Exposure to cold air for extended time periods poses a risk for frostbite as temperatures below 5ËšF and moderate wind can result in frostbite within minutes. Decreased temperatures also affect hand safety by affecting blood flow to the hands, reducing grip strength (due to temperature and glove use) and increasing the potential for cumulative trauma-related injuries. Lastly, the combination of colder temperatures, reduced grip strength and changes in material properties (i.e. friction) can lead to accidents through dropping and/or losing control of vehicles or equipment.

Vibration concerns

Cold temperature combined with the use of vibrating tools and equipment is of particular concern as conditions such as Hand-Arm Vibration Syndrome (HAVS), Raynaud’s Syndrome or “White Finger” can develop more easily. With advances in the design of power tools and hand tools, along with better glove materials, such injuries can be significantly reduced. However, the risk of injury still remains, and understanding how injury occurs and recognizing how to avoid injury is important for safety professionals, workers and managers.

In “normal” temperatures, there is a risk for vibration-related hand or upper extremity injury whenever using pneumatic or vibrating tools. Any extended use of a vibrating tool may result in tingling and numbness of the hands and/or fingers. These sensations may appear after a relatively short duration and should be considered a warning for a future injury. They often fade after cessation of the activity, but workers should be aware that they are an indicator of the potential for serious permanent damage. Repeated exposures cause permanent injury by damaging blood vessels that supply the nerves and muscle tissue of the hand. This deprives the nerves and muscle of oxygen and can lead to a “whiteness” that is characteristic of these disorders.


Protecting the hands

Working in cold conditions exacerbates this risk in several ways. Vasoconstriction of blood vessels is a normal response to cold as the body attempts to limit heat loss by restricting blood flow to the extremities. Colder temperatures also result in a certain level of perceived “normal” numbness, and workers can continue working without realizing the damage they are causing.

In order to keep the hands warm, gloves are used. Unfortunately, the wrong type of glove can reduce grip strength, and workers may use even more force to compensate for the glove’s effect. In general, the following principle applies:

“When temperatures drop, the likelihood that a previously acceptable level of powered tool use now becomes dangerous increases.”

Safety and industrial hygiene professionals should consider a variety of measures to address these risks. These include education of workers, medical monitoring, limiting duration of exposures, use of better gloves with improved grip or anti-vibration characteristics, and replacement of older tools with those having improved, lower vibration designs.
  • Education of workers should emphasize the mechanism of injury, the permanent nature of this type of injury, and how it can and often does negatively impact a person’s life and ability to earn a living. Early reporting and recognition by each individual is critical to avoiding the repetitive trauma injuries that can occur when using vibrating or powered hand tools. Highlight the fact that numbness and/or tissue damage is more difficult to recognize and more important to address in colder conditions.
  • Medical monitoring has been shown to be one of the most effective measures. Some elements of an effective program include the use of questionnaires to compile detailed work and symptom histories, clinical evaluation, screening and placement of individuals into risk categories, and follow-up examination (and, potentially, treatment) established at frequencies appropriate to the risk category. The clinical tests used should be established by a physician that is board certified in occupational medicine. Occupational health nurses can perform the clinical examinations.
  • Choosing the most effective glove involves matching the attenuation characteristics of the glove to the type of vibration hazard the task involves. The use of ISO 10,819 anti-vibration gloves has been shown to decrease the damaging effects of HAVS (particularly when combined with interventions to replace older tools with newer, low-vibration tools); however, some studies have shown that the attenuation characteristics of this type of glove will not be effective for certain frequencies of tool/task vibration. Other gloves (not necessarily meeting ISO 10,819 criteria) may provide more effective attenuation.

The bottom line: Good analysis of the hazard and appropriate matching of the glove is warranted. If needed, obtain the services of a certified ergonomist or suitably trained and credentialed professional.



Combined best solution

When specifying gloves in cold conditions, consider each hazard separately and rank them in importance so that a combined best solution can be found. Despite the perception that one must compromise one feature to address another (i.e. dexterity for thermal protection) the myriad of gloves available today offer materials, features and performance combinations that can be tailored to individual needs.