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Vermont Legislative Research Shop


Snowmobile Impact on the Natural Environment: An Overview


Recreational two-stroke vehicles including snowmobiles, all terrain vehicles (ATV’s), mini-bikes, and other specialty vehicles, are significantly more polluting than four stroke engines due to their poor combustion. The typical snowmobile produces significantly more Carbon monoxide (CO) and unburned hydrocarbons (UHC) then a modern automobile (National Park Service).

Figures submitted to the California Air Resources Board by the snow machine industry show that one snowmobile emits the same volume of hydrocarbons and nitrous oxides as 1,000 cars, and as much carbon monoxide as 250 to 500 automobiles (Bama 1995). Levels of carbon monoxide (CO) and particulate matter (PM) are a primary concern. CO is noxious to humans and PM is a recently confirmed human carcinogen by the Environmental Protection Agency. There are currently no emission standards required of snowmobiles. In February 1999 the EPA announced plans to write emission standards for two-stroke non-road vehicles. The announcement is based on a 1999 EPA document which lists the emissions of non-road spark ignition engines either rated above 19 kilowatts or found in land-based recreational vehicles. The cause for concern stems from a 1991 EPA report entitled "Non-road Engine and Vehicle Emissions Study," which estimates that in the year 2000 recreational vehicles with 2 stroke engines will contribute 15% of all mobile source hydrocarbon emissions and 9% of all mobile source carbon monoxide emissions. These emission estimates do factor in population growth and the effects of regulatory control programs. The effectiveness of all control programs is offset by the anticipated growth in engine production (U.S. EPA 1999).

The EPA determined that emissions of NOx, HC, and CO from nonroad engines and equipment contribute significantly to Ozone and CO concentration in more than one nonattainment area. The EPA states that air pollution may reasonably be anticipated to endanger public health or welfare. The smoke emissions can be inhaled into the lower lung cavity, posing potential health threat. The EPA also noted that the smoke affects visibility and soiling of urban buildings and other properties (U.S EPA, 1999 ).


Snowmobile noise is known to have a negative aesthetic effect on winter walkers, Nordic skiers, and people seeking quietness and solitude. Noise levels are described in decibels (dBA), which express the relative intensity or loudness of noise. The most commonly used weighting scale for noise levels is the typical A-weighted scale or dBA. According to a 1988 report submitted by the International Snowmobile Industry Association, snowmobiles produced since 1975 and certified by the Snowmobile Safety and Certification Committee’s independent testing company emit up to 78 dBA from a distance of 50 feet while traveling at full throttle (US Dept. of Interior 1991). For point of reference, the sound level of snowmobiles (78 dBA) falls between the sound level of a diesel truck at 50 feet (80 dBA) and passenger car, 65 mph at 50 feet (75 dBH).

Some states describe snowmobile noise laws, that is, the maximum legal decibel (dBA) level at 50 feet. They are as following:

  • Indiana: muffler required
  • Maine: 82 dBA
  • Michigan: 78 dBA
  • Minnesota: 78 dBA
  • Nebraska: muffler required
  • Utah: noise control device required
  • Vermont: 73 dBA
  • Wisconsin: 78 dBA

(for sources see: www.uvm.edu/~vlrs/doc/snowmobile_safety)


Dorance et al. (1973), Moen (1978), Hudson (1973), Harlow et al (1987) all found that energy use by animals is of crucial importance during the winter. As winter progresses, many animals experience a negative energy balance, with more energy being used to survive than is being consumed in the form of forage. Natural (i.e., predators, snow) or, artificial (i.e., snowmobiles, hunting) perturbations to an animal's environment or behavior which affect, either negatively or positively, an animal's energy balance or stress level can have a substantial effect on survival and productivity, and can impair immune function. Furthermore, Dorance et al., (1973), Moen (1976) have suggested that additional human caused stress on wildlife in the winter is undesirable since it may increase energy use and stress resulting in increased mortality, decreased productivity, and changes to behavioral adaptations.


There are two alternatives for improving the current snowmobiles. First, it is possible to make them less polluting by requiring the use of oxygenated fuels. The National Parks Association recently conducted a study that concluded that oxygenated fuels could reduce UHC and CO emissions by 10-20%. This is also beneficial for snowmobilers because oxygenated fuels have higher octane ratings, which would improve engine performance (National Parks Association).

Snowmobiles could also be altered by switching to a small four-stroke engine with conventional pollution control equipment, running a two-stroke engine slightly lean with catalytic after-treatment, or using two stroke engines with fuel injection would also aid the environment. The downfall of these suggestions is that the cost of snowmobiling would increase (National Parks Association).


Bama, Lynne. 1995. "Yellowstone Snowmobile Crowd May Hit Limit," High Country News (Vol. 27, No.4)

Dorance , M.J., P.J. Savage, and D.E. Huff. "Effects of Snowmobiles on White-tailed Deer." Journal of Wildlife Management. 39(3):563-569. 1973.

Fussell, Lori Marie Snook. 1999. " Carbon monoxide Exposure by Snowmobile: Emissions Pose Potential Risk" NPS Park Science. http://www.aqd.nps.gov/parksci/vol17(1)/07carbon.htm

Harlow, H.J., E.T. Thorne, E.S. Williams, E.L. Belden, W.A. Gern. "Adrenal Responsiveness in Domestic Sheep (Ovis ovis) to Acute and Chronic Stressors as Predicted by Remote monitoring of Cardiac Frequency." Canadian Journal of Zoology. 65:2021-2027. 1987.

Haste, Ron. 1999. California Air Resources Board, Mobile Source Control Division. EM: rhaste@arb.ca.gov

Hudson, R.J. "Stress and In Vitro Lymphocyte Stimulation by Phytohemagglutinin in Rocky Mountain Bighorn Sheep." Canadian Journal of Zoology. 51:479-482. 1973.

Moen, A.N. "Seasonal Changes in Heart Rates, Activity, Metabolism, and Forage Intake of White-tailed Deer." Journal of Wildlife Management. 42(4):715-738. 1978.

Scranton, Eric. 1999. Telephone interview. Department of Environmental Conservation, Office of Mobile Sources

United States Department of the Interior National Park Service. 1991. "Revised Draft Environmental Impact Statement for a Wilderness Recommendation." Voyageurs National Park, Minnesota.

United States Environmental Protection Agency. 1999. Office of Mobile Sources L&E:1,3- butadiene (part c). "Control of Emissions from New Nonroad Spark-Ignition Engines Rated above 19 Kilowatts and New Land-Based Recreational Spark-Ignition Engines." http://www.epa.gov/ttnchiel/efdocs/butadn/c.pdf


Completed by Lucinda Newman and Justine Sears, April 29, 1999.

Revised by Sara Davies and Sarah Fisher. February 28, 2000