Snowmobile Noise Exposure Monitoring of Yellowstone National Park Employees

In Yellowstone National Park (YNP) the use of snow machines has steadily increased since 1949. Paralleling the rise in snow machine travel were concerns over increases in noise emissions. The concerns resulted in the establishment of winter-use plans for YNP. As periodic iterations of winter-use plans began to appear, input was needed concerning noise exposures received by YNP employees regulating snow machine traffic entering the Park. This study provides noise monitoring results of worker exposure from snow machine traffic at the west entrance to YNP. The study objectives were to characterize noise exposures received by YNP employees and to evaluate these exposures relative to Occupational Safety and Health Administration (OSHA) standards. Concerning area and personal monitoring of YNP employees supervising snow machine traffic, study results suggest compliance with OSHA regulations. This is also true when applying a more conservative approach to estimate daily noise exposure. In contrast, monitoring results estimating noise exposures received by YNP employees operating snowmobiles revealed that 1 of 10 (10%) were not compliant with the OSHA noise standard and 5 of 10 (50%) equaled or exceeded its action level. While the findings associated with snowmobile operators serve to provide awareness of the potential for adverse exposures, limitations concerning these exposure estimates are discussed and point to the need for additional monitoring using more precise methods. Given that winter-use plans for YNP will continue to evolve, it is anticipated that the results of this study will provide information that can better manage occupational noise exposure and the protection of employee health