IAQ Tools for Schools
IAQ Reference Guide
Appendix I - Emissions from Motor Vehicles and Equipment
"Mobile sources" is a term used to describe a wide variety of motor vehicles, engines, and equipment that generate air pollution and that move, or can be moved, from place to place.
- Mobile sources at School
- Mobile Source Emissions
- Air Quality Issues
- Reducing Emissions
- Transportation Choices
- Other Mobile Sources on School Grounds
Beneficial or Environmentally Friendly Landscaping
- Additional Resources
Mobile Sources at School
Some mobile sources at your school may include:
- School buses
- Delivery trucks
- Portable fuel containers
- Mowers, snow blowers, trimmers, and other equipment used for grounds maintenance
Special situations involving motor vehicles or equipment off school property may also contribute to the deterioration of the overall air quality near schools. These might include, for example, truck loading docks or construction sites.
Mobile Source Emissions
Mobile sources pollute the air through fuel combustion and fuel evaporation. These emissions contribute to air pollution nationwide and are the primary cause of air pollution in many areas. Mobile sources emit several significant air pollutants that affect human health and the environment, including carbon monoxide, hydrocarbons, nitrogen oxides, and particulate matter. See Appendix E: "Typical Indoor Air Pollutants," for more information about these pollutants.
In addition, mobile sources produce air toxins (e.g., acetaldehyde, acrolein, benzene, 1,3-butadiene, diesel exhaust, and formaldehyde), which are pollutants known or suspected to cause cancer or other serious health or environmental effects. Mobile sources are responsible for about half the air toxin emissions and risk nationwide.
Fine particulate matter (PM2.5) in diesel exhaust creates further health concerns. Recent studies suggest that children on or near school buses may be exposed to elevated levels of diesel exhaust. Children are especially susceptible to advance respiratory effects of PM2.5 because it can penetrate children’s narrower airways, reaching deep within the lungs where it is likely to be retained, and because children have higher rates of respiration per unit of their body weight than adults.
Air Quality Issues
Mobile source air pollutants can contribute to air quality issues at schools. With sufficient concentrations and duration, these pollutants may increase the chance of cancer or other serious health effects, such as asthma.
- Studies indicate that students can be exposed to high levels of diesel exhaust when they are inside school buses, near idling school buses, and even inside schools (due to exhaust penetration from idling buses). Queuing of buses for pick-up and drop-off and periods of idling during the bus commute itself may be particular problems. Diesel exhaust can aggravate respiratory and cardiovascular disease and existing asthma. It can also cause acute respiratory symptoms, chronic bronchitis, and decreased lung function.
- Outdoor emissions can infiltrate through windows and air intakes, resulting in student and staff exposure to pollutants and toxics.
- Chemicals and gasoline stored in school buildings can contribute to indoor air quality concerns, and equipment usage can result in exposure to air pollutants and toxics.
- Students, staff, and vehicles sometimes congregate in the same place at the same time, which increases their exposure.
Successful reduction of vehicle and equipment emission involves a variety of approaches, some of which are no- or low-cost options. Those concerned about improving air quality in and around school can choose from options ranging from better vehicle technology and better transit options to cleaner fuels.
Schools can help reduce air pollution from mobile sources in a number of different ways. A comprehensive program might include bus retrofits and replacement, anti-idling policies, reduced power equipment usage, environmentally friendly transportation choices, and equipment replacement. Some other smart actions that reduce emissions include adopting driving practices that save gas and improve mileage, maintaining vehicles on a regular basis, and using cleaner fuels.
Policies to minimize idling offer a smart, effective, and immediate way to reduce emissions at little or no cost. In fact, reduced idling will save money in most cases because idling wastes fuel. The easiest way to reduce vehicle idling emissions is to "Just turn it off!" Today’s bus engines generally require only three to five minutes of warm-up time, even in cold weather. The problem of diesel fuel gelling in cold weather has been resolved by the creation of winter blends of fuel and fuel additives that better withstand colder temperatures.
Contrary to popular belief, idling actually does more damage to an engine than starting and stopping. Idling causes additional wear on an engine’s internal parts and, therefore, can increase maintenance costs and shorten the life of the engine.
Several States and local communities have already implemented anti-idling laws. These programs can reduce pollution, odor, and noise, and save schools money by reducing engine wear and fuel consumption. Finally, anti-idling information is easy to incorporate into existing training and communications opportunities. See Appendix B: "Developing Indoor Air Policies" in the IAQ Coordinator’s Guide for sample anti-idling policies and a sample memo to bus drivers.
Alternative transportation choices can also be beneficial for reducing emissions. For instance, "school-pooling" programs encourage carpools, bike partners, or "walking school buses" that reduce the number of vehicles on school grounds. Public transit buses may also be an appropriate option for some students or staff.
Other Mobile Sources on School Grounds
Since cars and trucks are not the only mobile sources on school grounds, attention should also be paid to lawn and garden equipment for reducing emissions. The two main ways to reduce emissions from such equipment are to replace existing equipment with cleaner options (e.g., manual, electric, or new 4-stroke, gasoline engines) and to reduce usage.
EPA adopted more stringent standards for gasoline-powered equipment, such as lawnmowers and string trimmers, which will lower hydrocarbon and nitrogen oxide emissions. Schools can reduce harmful emissions by ensuring their grounds maintenance equipment meets current standards. Like school bus retrofits and replacements, alternate equipment choices will be specific to your school’s situation. While manual and electric equipment are most beneficial because they do not produce emissions, these options are not always practical for large grounds.
Portable gasoline containers are another source of emissions on school grounds. Due to evaporation of gasoline, these cans pollute even when they are not being used, and especially when they are stored in a warm place. New, low-emission gasoline cans are designed for easy use and have a thicker lining in order to reduce fuel evaporation. They meet specified standards to minimize air pollution, including automatic closure, automatic shut-off, only one opening, and limited permeation. Many portable containers available nationwide meet all but the permeation standard. In addition, they are inexpensive (approximately $10), making them cost-effective solutions for reducing exposure to evaporated fuel.
Finally, proper maintenance and storage help decrease exposure to emissions from lawn and garden equipment. For example, lawn and garden equipment should be maintained regularly according to manufacturer guidelines to prevent problems that decrease efficiency and increase emissions. Keeping equipment tuned and in good condition is inexpensive and beneficial for minimizing emissions. In addition, fuels, chemicals, and equipment should be stored appropriately in a well-ventilated, cool, and dry space. For extended periods of storage (e.g., wintertime), gasoline should be emptied from equipment and containers or a stabilizer should be added to decrease evaporation.
Beneficial or Environmentally Friendly Landscaping
Ways to Reduce Emissions from Mobile Sources
- Diesel vehicle replacement and retrofit.
- Idling policy and training.
- "School-pooling" and transportation choices.
- Environmentally friendly landscaping.
- Low-emission gas cans.
- "Best Practices" for equipment maintenance and storage.
Beneficial landscaping refers to a suite of landscaping practices that yield environmental, economic, and aesthetic benefits. These environmentally friendly practices include planting native species and low-maintenance turf grasses, reducing lawn area, strategic use of trees, integrated pest management (see Appendix K: "Integrated Pest Management"), and optimizing water efficiency. Ultimately, beneficial landscaping produces a healthier environment and reduces air, water, and soil pollution by minimizing emissions from power equipment, chemicals, fertilizer, and water.
In addition, beneficial landscaping is effective on any size of land. Emission reductions from beneficial landscaping alone can result in nearly 100 pounds less of smog-forming hydrocarbons and 10 pounds less of nitrogen oxide emissions per year per acre of lawn converted to natural landscaping due to reduced mowing. Hence, even small converted areas can contribute to notable reductions in emissions.
Grass can be replaced with trees, shrubs, native wildflowers, and other native plants that do not require mowing and are already adapted to local conditions. Trees, shrubs, and native plants absorb water more efficiently than lawns and therefore minimize runoff and erosion. They can also decrease the amount of time you spend on weeding and watering and reduce the need for fertilizers and pesticides.
Beneficial landscaping can result in reduced building heating and cooling costs. For example, planting deciduous trees on the south side of a building provides shade, reducing heat absorbed by the building during the summer. This practice can decrease air conditioning costs by up to 20 percent. In the winter, deciduous trees lose their leaves, allowing the winter sun to warm the building. Planting conifers on the northwest side of a building helps to block northwest winds, reducing heating costs. Finally, planting trellis vines on the bare walls of buildings helps to keep these walls cooler by absorbing the sunlight. Planting trees around parking lots helps shade paved areas and further reduce sun-heating effects.
Finally, schools should use outdoor water efficiently by laying mulch in appropriate areas and installing efficient irrigation systems.
What are good practices to use in areas where maintaining lawns is necessary?
Cleanest Equipment Choices
- Reel mowers, rakes, clippers, shovels
- Walk-behind mowers, shredders, edgers, tilers, hedge trimmers, hand-held leaf blowers
4-stroke gasoline engines:
- Available in almost al new lawn and garden equipment
Where lawns are necessary on school grounds, such as on play areas or sports fields, the following practices are best suited for reducing environmental impacts:
- Plant low-maintenance turf grasses that grow slowly and require less mowing.
- Leave grass clippings on lawns. This practice decreases the need for fertilizers and the amount of municipal solid waste entering landfills.
- Keep grass well maintained. Only one-third of the grass blade should be cut off at one time, and no more than one inch should be cut at one time.
What are the benefits?
Many advantages are associated with beneficial landscaping. Beneficial landscaping can be incorporated into science and environmental education. It creates hands-on learning experiences for students, while encouraging them to learn about natural habitats and take an interest in their surroundings.
Beneficial landscaping helps create a safer environment by reducing student and staff exposure to harmful emissions. It leads to fewer emissions from fossil fuel consumed during mowing, less fertilizer use, and lower landscape maintenance labor and costs. Beneficial landscaping can also help decrease heating and cooling bills, reduce noise pollution (due to less mowing), conserve water, reduce flooding and storm water management costs, and decrease the strain on municipal waste collection and water treatment plants. In addition, it can lead to cleaner water bodies for fishing, swimming, and drinking due to reduced chemical use and erosion.
For more information about mobile sources on school grounds, please visit the EPA Clean School Bus USA Initiative at www.epa.gov/cleanschoolbus. Clean School Bus USA provides information and resources to school districts on how to reduce pollution from school buses through retrofit, replacement, and anti-idling programs.