BILLINGS, Mont. — The levels of air and noise pollution that Yellowstone National Park workers were exposed to declined after new limits on the number and type of snowmobiles allowed in the park went into effect, a new study shows.
But researchers say further study is needed before any direct correlation can be made between the declines and the new snowmobile rules.
"We'll see if (the results) change this winter," said Terry Spear, the study's lead author and head of the Safety, Health and Industrial Hygiene Department at Montana Tech in Butte.
The study, commissioned by the National Park Service, is one of several that park officials say they will take into account as they develop a long-range plan for winter use in Yellowstone and Grand Teton national parks. This study focused on employee exposure to certain air contaminants and noise related to snowmobile use. Other studies are looking at such things as the effects on wildlife and ambient air quality, said Kevin Schneider, a planner at Yellowstone.
The study focused on the west entrance, typically the park's busiest for snowmobile traffic, and the warming hut near the headwaters of the Madison River. Evaluations were done over the extended Martin Luther King Jr. and Presidents Day holiday weekends.
Exposure was also measured at a Mammoth Hot Springs maintenance shop in February.
The study found that worker exposure to a range of air contaminants and noise were well below Occupational Safety and Health Administration exposure limits. The only area of concern was noise exposure among those who rode snowmobiles for much of their shifts, the study said.
Spear said researchers this winter want to try to focus on the sources of noise.
The current snowmobile rules, expected to be in place through the winter of 2006-07, allow for up to 720 snowmobiles to enter Yellowstone every day.
Schneider said the findings show that restrictions on snowmobiles, including requiring the use of cleaner, quieter machines, are having an effect. However, the limit of 720 snowmobiles per day was never reached last season, and the study's authors said exposure to pollution among workers could increase if the daily snowmobile limits are reached.
A draft environmental study of a long-range winter use plan is expected some time next spring, Schneider said.