For roughly a decade, Yellowstone National Park officials have known that the snowmobiles buzzing around the park can impair human hearing. In the mid-1990s they became so concerned about the threat that they started schooling their employees on how to protect their hearing while working on or around snowmobiles and snowcoaches.
    Yet, despite several studies pointing to the problem, park officials evidently have not been sharing their concerns with winter visitors. Why not? The best answer I could get from Yellowstone on Wednesday is that they are planning more studies into the noise issue. 

   Noisy Snowmobiles Are Not A New Development

     Noise and snowmobiles long have been a given. You can hear their high-pitched whining from a good distance away, no matter if they're two-stroke or four-stroke models. In Yellowstone, that noise is one of the issues that proponents of a snowmobile ban like to cite.
    Yellowstone officials are well familiar with the noise issue. Bob Seibert, who spent 14 years as the park's West Yellowstone District Ranger, says the issue prompted federal Occupational Safety and Health Administration researchers to visit the park in the mid-to-late 1990s to evaluate Yellowstone employees who worked around snowmobiles. Their visit resulted in the expansion of a hearing conservation program that had been just  for heavy-equipment operators to include employees who worked on or around snowmobiles and snowcoaches.
    "It was quickly realized, by OSHA, that many of the employees were being exposed to sounds, levels of noise, that could end up resulting in loss of hearing," Seibert told reporters listening in on a conference call.  "As they started testing for hearing, they found out that a number of the rangers that had not been testing for hearing loss in the past were showing up with high-range, high-frequency hearing loss, and I happened to be one of them."
    Those findings were made roughly a decade ago, according to Seibert, who told me that while park employees at the time were astounded by some of the noise generated by customized snowmobiles, there was never an effort to warn those riders about the impacts to their hearing.
    "We a number of times spoke with the OSHA guys and among ourselves about how these guys could stand this and not be doing damage to themselves," he said. "The OSHA guys all agreed that they probably can't."

    Yellowstone Employees Cautioned About Hearing Losses

    Move forward to 2004, and again Yellowstone officials were reminded of the health concerns snowmobiles posed to human hearings. The park's safety officer, Brandon Gauthier, suggested in a January 2004 staff meeting that Yellowstone employees "who drive the 2003 Arctic Cat 660 four-stroke machines wear earplugs."
    Most recently, on page 100 of the Environmental Assessment that was prepared in August 2004 for the current Temporary Winter Use Plan, researchers noted that noise levels from "best available technology" snowmobiles -- today's four-strokes -- would generate "adverse to moderate" effects on employee hearing. They added that "employees and visitors may choose to wear hearing protection to mitigate these impacts."
    And yet, despite the OSHA studies, despite the warning from the park's own safety officer, and despite research conducted for the current winter use plan, Yellowstone officials have not decided they need to caution park visitors about taking precautions to protect their hearing.
    "All snowmobile activity in the park now is guided trips, and I don't know the details of the safety briefings that the different outfitters may provide their clients," Yellowstone spokesman Al Nash told me when I asked whether the park requires a hearing safety warning.

   Yale Professor Expresses Concerns to Supt. Lewis

    The issue was brought to the attention of Yellowstone Superintendent Suzanne Lewis in December, when a Yale University professor who specializes in analyzing environmental noise levels wrote her about his concerns. Dr. Peter Rabinowitz became concerned after he reviewed a Yellowstone monitoring study that examined how snowmobile noise levels and exhaust emissions impact park employees.
    Dr. Rabinowitz, an associate professor in Yale's Occupational and Environmental Medicine Program, told Superintendent Lewis in his letter that the park's own study reported average exposure noise levels from four-stroke snowmobiles between 85 and 91 decibels.
    "These levels are sufficient, based on a large body of epidemiological and clinical evidence, of causing permanent noise-induced hearing loss if the exposure is repeated on a chronic basis," the professor wrote. "Furthermore, peak exposure levels even higher, which almost certainly occurred during the rides, could pose a risk of damage to the inner ear in a shorter amount of time."
    He added that, "If members of the public are riding similar types of machines, it appears that they are also at risk for permanent hearing loss from four-stroke snowmobile noise exposure such as has been documented for the Polaris Frontier model. It is important to emphasize this fact, since the public may have been led to believe that 'Best Available Technology' is synonymous for 'safe,' and consequently may not be aware of the risks to their hearing from snowmobile use."
    What the doctor did not note to Superintendent Lewis is that the results of the noise monitoring were based on a daily average of 236 snowmobiles in the park, far fewer than the 720 that could be allowed daily under the temporary winter use plan.
   In discussing the matter with reporters, Dr. Rabinowitz said 85 decibels is the official "action level" at which OSHA requires employers to provide ear protection to their employees. He did not know, though, what responsibility a federal agency, in this case the Park Service, had to protect visitors from hearing impacts, although he pointed out that businesses face fines for not acting.
    "If people are being exposed above 85 decibels and they (businesses) don't have a program in place for hearing conservation that includes things like providing hearing protection and training and annual hearing testing, that workplace is fined by OSHA," he said.
    As to how rapidly hearing loss could occur under the current snowmobile noise levels in Yellowstone, the doctor said it could vary greatly, depending on how much exposure a person has to snowmobiles.
    "At 85 decibels it would be a gradual process of losing some hearing over time, over years even, (if exposed) five days a week, for eight hours a day," he said. Beyond 85 decibels, the doctor said there's a doubling of effect for every 3-5 decibels.
    "If the noise is loud enough, you can get to damaging levels in much less time," said Dr. Rabinowitz. "We also know that whereas the standards were set for constant noise at a constant level, if there are intermittent exposures that are pretty high, you probably can lose your hearing in a much shorter amount of time."
    An unknown, he said, is whether Yellowstone's high altitude exacerbates the impacts.

    Are Politics Driving Yellowstone's Handling of the Threat?

    The cynic might say that Park Service officials don't want to make a big deal about the threats to hearing because they have gotten somewhat behind "best available technology" snowmobiles in discussing Yellowstone's winter-use plan. If they came out and urged riders to use hearing protection while riding these snowmobiles, well, that could cast into question how good that technology truly is.
    In Yellowstone, spokesman Nash said that while Superintendent Lewis did not respond to the Dr. Rabinowitz's letter, it would be "added to our list of substantive comments on issues relating to winter use." He also said studies were continuing this winter into how much hearing protection snowmobile helmets provide riders.
    At the Coalition of National Park Service Retirees, which arranged the conference call, Bill Wade speculated that Yellowstone officials have not taken active steps to alert snowmobile visitors because that would go against the political pressure coming from Washington to see that snowmobile recreation is made permanent for Yellowstone and neighboring Grand Teton National Park.
    "The career professionals in Yellowstone National Park would prefer to do everything they could to make sure that the public understands all of the impacts of snowmobiles, and every other kind of use, whether it be to themselves in terms of public health and safety or to the resources," said Wade, a former superintendent at Shenandoah National Park.
    "But they're up against the political policy...and it makes it very difficult for the career professional managers to operate within that kind of a situation and do, No. 1, what they think is right and, No. 2, what even they might be legally obligated to do in terms of keeping the public informed."