The frequency-weighted accelerations in this study were found to be substantial, especially those for the non-dominant hand. It should be noted that all of the measurements were collected with the fork motors operating at maximum speed. In actual beach cleaning operations during the BP Deepwater Horizon oil spill cleanup, these tools were not always operated at full speed. Furthermore, the forks were seldom operated without a load. Thus, actual hand-arm vibration exposures in the field may be lower than the values reported here. The dominant frequency of these tools is about 20 Hz. There is little to no epidemiological evidence to indicate that tools with dominant frequencies below 25 Hz can be associated with vibration-induced white finger (Griffin, 1990). And while low-frequency percussive tools have been linked to bone and joint disorders (Genme and Saraste, 1987), non-percussive tools have not been implicated in the causation of such disorders. These observations have led to much debate about the appropriateness of the frequency weighting presented in the ISO standard, especially at lower frequencies (Bovenzi, 1998). Therefore, it remains debatable whether or not the ANSI DEAV and DELV limits are applicable to low-frequency, non-percussive tools, such as the vibrating forks evaluated in the present study. Even if the ANSI action and limit values are too conservative for this tool type, the high levels of vibration observed could cause considerable discomfort in the anus, shoulders, neck, and head, because low-frequency vibration can be effectively transmitted to these substructures. Recommendations based on this study are as follows: 1.) Limit run time - Operators of these forks should reduce the amount of "trigger time" to short bursts that are just sufficient to separate the debris from the beach sand. 2.) Operate the forks at the lowest possible speed - The forks are equipped with variable-speed motors. Faster operating speeds results in higher vibration exposures. These forks should be operated with just enough speed to get the job done; it is usually not necessary to fully depress the trigger. 3.) Do not operate the forks unloaded - The loaded basket helps to dampen the vibration. These forks should not be operated in the unloaded condition. 4.) Do not use anti-vibration gloves with these tools - Anti-vibration gloves are not effective at attenuating low frequency vibrations, and may even amplify certain frequencies below 150 Hz (ISO 10819; 1996). The dominant frequency for these vibrating forks is around 20 Hz. therefore use of anti-vibration gloves is not appropriate.
Biodynamics; Biological-effects; Biological-factors; Biological-monitoring; Biomechanical-modeling; Biomechanics; Exposure-assessment; Exposure-levels; Gloves; Standards; Hand-tools; Injury-prevention; Mathematical-models; Measurement-equipment; Physiological-effects; Physiological-response; Quantitative-analysis; Statistical-analysis; Tools; Vibration; Vibration-effects; Vibration-exposure
Engineering and Engineering & Control Technology Branch, Health Effects Laboratory Division, National Institute for Occupational Safety and Health, 1095 Willowdale Road, Morgantown, West Virginia, USA