Off-Road Vehicle Emissions and Their Effects on Human Health

In this paper I review off-road vehicle emissions and their deleterious effects on human health. With 36 million registered all-terrain vehicles and 12 million registered snowmobiles in the U.S. alone, these machines are a significant source of pollutants. They run on inefficient two and four-stroke engines that emit several dangerous gasses and chemicals including carbon monoxide (CO), hydrocarbons (HC), nitrogen oxide (NOx), and particulate matter (PM) (US DOT 2001). These emissions have all been shown to affect human health. Despite this fact, the U.S. Environmental Protection Agency (EPA) has yet to establish emission standards for off-road vehicles.

How Emissions Threaten Health
Carbon monoxide binds to the hemoglobin molecule in blood and inhibits the transportation of oxygen in the body. High levels of carbon monoxide exposure have been shown to lead to visual impairment, reduced work capacity and mental dexterity, poor learning ability, nausea, headaches, dizziness, and even death (USEPA 1991). Carbon monoxide is especially dangerous to the elderly, people with cardiovascular disease or other circulation disorders, anemic individuals, young infants, and pregnant women (USEPA 1991). Hydrocarbons are volatile organic compounds that include benzene, toluene, ethylbenzene, and xylenes. While these compounds can cause dizziness, headaches, and loss of consciousness, the EPA has also identified benzene as a carcinogen and those exposed to benzene have an increased incidence of leukemia. Nitrogen oxides can cause shortness of breath and chest pains and increase a person’s susceptibility to respiratory infections and asthma. Long-term exposure can cause chronic lung disease.

Particulate matter, also found in off-road vehicle emissions, is detrimental in fine and coarse forms as it accumulates in the respiratory system, and can lead to decreased lung function, respiratory disease and even death (Janssen and Schettler 2003). Of the pollutants emitted by ORVs, particulates are of special concern because their small size makes them easily respirable and thus deliverable directly into the lungs, causing any number of the aforementioned maladies (NPS 2000).

Snowmobiles
While ATV sales outnumber those of other off-road vehicles, two-stroke snowmobiles are much more polluting and contribute more air pollution per vehicle than any other type of vehicle. Extensive research on snowmobile emissions has been carried out in Yellowstone National Park, and by the Southwest Research Institute, based in Texas. Research conducted in 2000 showed that average carbon monoxide levels sampled over an eight hour period inside the West Yellowstone park entrance exceeded the 9.0 parts per million (ppm) standard of the National Ambient Air Quality Standards (Cain and Coefield 2001). Putting it in sharper perspective, at 25 miles per hour, on-road vehicles (cars, trucks, etc.) emit around 45 gallons/mile of carbon monoxide, while snowmobiles emit 348 gallons/mile. This is an 87 percent difference in emission rates between the two vehicles and the engines that power them (Cain and Coefield 2001). Thus, the 720 snowmobiles that are currently allowed in Yellowstone National Park each day emit more carbon monoxide than 5000 on-road vehicles.

ATVs
The EPA found that ATVs emit more than 381,000 tons of hydrocarbons, 1,860,000 tons of carbon monoxide, and 11,000 tons of nitrogen oxide each year across the country (USEPA 2001). While emissions from on-road vehicles decreased 56 percent over the last 20 years as a result of emission control programs, there was a 42 percent increase in ATV emissions during the same time period (Grambsch 2002). The list of greenhouse gases continues to show the impact of these vehicles. For example, on-road vehicle emissions of nitrogen oxide were virtually unchanged during the same twenty-year span, while emissions from off-road vehicles increased 56 percent (Grambsch 2002). Anthropogenic emissions of nitrogen oxide account for a large majority of all nitrogen inputs in the environment and off-road emissions are a large contributor (Grambsch 2002).

The EPA went even further to research individual ATVs: they showed that a two-stroke ATV or motorcycle could emit as much pollution as more than thirty automobiles operating in the same time frame. Even more shocking is that the ATV took a distant second from two-stroke snowmobiles, which can emit as much as nearly one hundred automobiles in the same time frame (USEPA 1996).

Mitigation Measures
The EPA must establish emission standards for ATVs and snowmobiles and require industry to meet them. Industry standards have already started to show improvement without formal emission standards in place, but this trend must be hastened. Movement toward four-stroke technology should help, as it results in less unburned hydrocarbons, particulate matter, carbon monoxide, and carbon dioxide in comparison with two-stroke engines (MDEQ 2005b). Emissions for two-stroke engines are significantly higher for all compounds in comparison to a four-stroke engine, except for nitrogen oxide emissions, which are slightly higher on four-stroke engines (Sive et al. 2002).

There are other mitigation measures that could be employed, such as using bio-based fuels and biosynthetic lubricants like ethanol-blended fuel. Ethanol fuel has been shown to produce moderate reductions in emissions with both two-stroke and four-stroke technology (MDEQ 2005a, MDEQ 2005c). Fuel injection should take the place of carburetion, simply for its more efficient fuel use, lower emissions, and increased engine power (MDEQ 2005b). Lastly, exhaust systems should be updated and modified with catalytic converters, which change pollutants and combustion by-products during the exhaust process (MDEQ 2005b).

Conclusion
It is well-established that off-road vehicles contribute a large amount of pollution to the air. According to the EPA, if left uncontrolled, off-road vehicles will contribute 33 percent of hydrocarbon emissions, nine percent of carbon monoxide, nine percent of nitrogen oxide, and two percent of particulate emissions nationally by 2020 (USEPA 1996). The Environmental Protection Agency has yet to establish emission standards for off-road vehicles and the engines on which they run. The off-road vehicle industry has been slow to adopt technological changes that could lessen the impact of its machines on air quality at the local and, even the global, level. And while the industry has been sluggish, government regulatory and enforcement agencies have been all-too complacent in allowing continued degradation.

— Jason Brininstool is a graduate student in the University of Montana’s Environmental Studies program.

References

Cain, C.J. and J. Coefield. 2001. Preliminary Air Dispersion Modeling Analysis of Yellowstone National Park West Entrance: Wintertime Carbon Monoxide Emissions. Monitoring and Data Management Bureau, Montana Department of Environmental Quality, Helena, MT.

Grambsch, A. 2002. Climate change and air quality. In: The Potential Impacts of Climate Change on Transportation. Federal Research Partnership Workshop, Department of Transportation Center for Climate Change and Environmental Forecasting.

Jamssem, S., T. Schettler. 2003. Health implications of snowmobile use in Yellowstone National Park. 27p. http://www.womenandenvironment.org/Health_Imp_snow.pdf

Lela, C.C. and J.J. White. 2002. Laboratory Testing of Snowmobile Emissions: Final Report. Southwest Research Institute, SwRI 08.05486, Texas.

Montana Department of Environmental Quality (MDEQ). 2005a. Solutions-Oxygenated Fuels. http://www.deq.mt.gov/cleansnowmobile/solutions/fuels/oxygenated.htm

Montana Department of Environmental Quality (MDEQ). 2005b.Solutions-Two-Stroke Engine Modifications. http://deq.mt.gov/CleanSnowmobile/solutions/engine/modifications.asp

Montana Department of Environmental Quality (MDEQ). 2005c. Emissions from Snowmobile Engines Using Bio-based Fuels and Lubricants. http://deq.mt.gov/Energy/bioenergy/biofuels.asp

National Park Service (NPS). 2000. Air Quality Concerns Related to Snowmobile Usage in National Parks. Washington, D.C.

Sive, B., D. Shively, and B. Pape. 2002. Spatial Variation and Characteristics of Volatile Organic Compounds Associated with Snowmobile Emissions in Yellowstone National Park: A Preliminary Research Report Submitted to the National Park Service, United States Department of the Interior. Central Michigan University, MI, 2002.

United States Department of Transportation (USDOT). 2001. About Transportation and Climate Change. Center for Climate Change and Environmental Forecasting http://climate.volpe.dot.gov/national.html

United States Environmental Protection Agency (USEPA). 1991. Air Quality Criteria for Carbon Monoxide. Washington, D.C. EPA-600/8-90-045A.

United States Environmental Protection Agency (USEPA). 1996. Non-Road Engines and Air Pollution. Office of Mobile Resources, EPA 420-F-94-003, Washington, D.C.

United States Environmental Protection Agency (USEPA). 2001. Environmental Fact Sheet, Frequently Asked Questions: Emission Standards for All-Terrain Vehicles (ATVs). Office of Transportation and Air Quality, EPA 420-F-01-027, Ann Arbor, MI.