Impact on Asthma

Outdoor air pollution can affect the health of students and staff in two ways: 1) people are exposed to air pollutants before they enter the school, and 2) outdoor air pollutants can travel into the building through air intakes, doors, windows, and ventilation shafts. Particulate matter is one source of outdoor air pollution associated with increased respiratory symptoms that has been linked to asthma exacerbation in children. Particulate matter is made up of very small-sized particles that can go deep into the lungs. Once breathed in, particulate matter can irritate the respiratory system which can cause asthma episodes and many other health problems. Air pollution is damaging to lung health, and children are particularly at risk because their lungs are still developing.

Causes of Air Pollution Exposure in Schools

The location of school buildings can be an important determinant for the effects of outdoor air pollutants. Buildings next to high-traffic areas or school buses idling next to school entrances, windows, and air intakes are more likely to have higher levels of outdoor air pollutants drawn indoors. Pollutants such as smoke, road dust, car exhaust, and factory emissions can add up to poor-quality air. Higher concentrations of particulate matter in outdoor air can worsen indoor air quality in buildings with less than adequate ventilation, ineffective or lack of air filtration, or buildings that are located in proximity to roadways or idling school buses and other vehicles. Depending on climate conditions and season, particulate matter concentrations may vary and will need to be considered for children with asthma.

Schools can reduce the exposure of outdoor air pollution by addressing factors such as near-road pollution, idling, and school siting; below is a brief description of each. Implementation of multiple best practices and strategies to reduce overall exposure is recommended.

Near-road Pollution

Pollutants directly emitted from cars, trucks, and other motor vehicles are found in higher concentrations near major roads, and during rush hour. The highest levels of pollutants are generally within 500 feet of a roadway. The time of day and surrounding terrain also impacts the level of pollutants in the air. There are many best practices and resources that schools can explore and implement for near-road pollution. For example, trees planted near roadways can act as a barrier or buffer to reduce impacts of pollutants to buildings in proximity to roadways. It should be noted that trees should be planted near the roadway rather than near buildings; the roots of trees and shrubs can damage a building’s foundation and exterior. Furthermore, idling contributes to near-road pollution and can be a relatively easy starting point for reducing air pollution (see below).


An idling vehicle is one whose engine is turned on while it is parked or not in use, creating smog and pollution. Combustion products discharged by idling vehicles can enter the building through open windows or be drawn into the ventilation system and distributed throughout a classroom or building. Minimizing idling outside of schools has a positive impact on outdoor and indoor air quality.

School Siting

The location of where a school is built plays a significant role in long-term school health. Potential exposures to contaminants in the air, water, and soil can cause adverse health effects for school staff and children who are particularly vulnerable. Examples of air pollutants from near-road traffic include particulate matter, carbon monoxide, and oxides of nitrogen, which can increase respiratory symptoms and exacerbate asthma. Utilizing school siting guidelines to evaluate potential hazards, as well as “green school” building design that can mitigate some hazards, will help communities make health-based decisions for this important investment.

Policy Guidance

There are some laws, regulations and guidelines that help to address outdoor air pollution better. For example, Massachusetts state law (M.G.L. Chapter 90, Section 16B) requires schools to have an anti-idling policy to restrict idling time on school grounds. The law prohibits idling by vehicles that are stopping for more than five minutes by requiring that the engine be turned off. Local boards of health, local police, and state and federal officials are authorized to enforce the state anti-idling law. 

Massachusetts Registry of Motor Vehicles: Regulation of Motor Vehicle Idling on School Grounds

The EPA recommends that all properties or structures proposed for use as a school, as well as surrounding properties, be carefully evaluated for potential environmental hazards before making final decisions to use a site or structure for a school. The Massachusetts School Building Authority provides guidance, financial support, and incentives on school siting, design, and construction to help minimize exposure to outdoor air pollutants.  

Massachusetts School Building Authority: Policies, Forms and Guidelines

Example Policy

Even though it may be hard for one school to affect outdoor air pollution, there are policies that schools can institute to minimize exposure while outdoors, and also improve the indoor environment, to make sure that the air inside the school is as clean as possible. Your school may start off by addressing one factor of outdoor air pollution such as idling, expand an existing policy, and/or choose a more comprehensive approach.

Sample School Policy Managing Student’s Exposure to Outdoor Air Pollution, American Lung Association: Includes guidance on monitoring and disseminating air quality information, and potential solutions to reducing student exposure to air pollution.

Sample Policy Outdoor Air Quality Awareness, Sustainable Jersey Schools: Includes the purpose of the policy, protocol for communicating unhealthy outdoor air quality, and considerations for physical education and recess during poor outdoor air quality days, especially for those with respiratory issues.

All schools in Massachusetts are required to have an anti-idling policy. Strong policies include language regarding types of vehicles and areas where the policy is in effect, a plan for how to reduce emissions, and guidance for addressing violations and enforcing the policy.

School Bus No Idling Policy, Asthma Regional Council: A model policy for any school to adapt, including rationale for the policy and guidance to reduce emissions.

Proper ventilation with outdoor air is a key component for healthy indoor air quality. It is important that school buildings have ventilation systems that provide adequate outdoor ventilation air with proper filtration in compliance with the American Society of Heating, Refrigerating and Air Conditioning Engineers’ standard, (ASHRAE) 62.1-2010, or local codes.

Best Practices 

Educate staff about best ventilation practices such as keeping air vents clear of clutter that may block airflow, and simply keeping HVAC (heating, ventilation, and air conditioning) systems turned on throughout the day.

Have a maintenance plan for the ventilation system that includes a schedule for changing air filters. Assess whether you can increase filtration in your ventilation system for areas of the building that are near heavy road pollution.

Keep windows and doors closed during morning and evening rush hours when levels of pollutants are high. In addition, avoid scheduling strenuous activities such as physical education and sports outside during peak traffic times.

Ensure that air intakes are away from roadways, idling buses, drop-off zones, and other pollutant sources (e.g., designated smoking areas). For example, redesign/move school bus parking zones and drop off/pick up locations to minimize pollutants from exhaust getting into the school.

Encourage active transportation like walking and biking to minimize the number of motor vehicles on the road. Students and their families will not only breathe cleaner air, but also be more physically active.

Institute and reinforce anti-idling policies — a policy is only as good as its implementation. Make sure that the anti-idling policy is clearly communicated to everyone. This can include letters and/or emails to parents, training for bus drivers, and signage near parking lots and drop-off/pick-up zones.

Consider upgrading school bus fleets so that they either have particulate matter filters or are replaced by newer models.

Consider locating new school buildings away from major roads. In addition, consider locating spaces that are often occupied by people (e.g., classrooms, playgrounds, and athletic fields) away from busy roads, and put spaces for maintenance, storage, and parking there instead.

Educate parents, staff, and bus drivers about the harmful impacts of outdoor air pollution, and include them when planning and making decisions around various policies and practices.

Resources & Tools

Near-road pollution

AirNow Air Quality Flag Program, Environmental Protection Agency: Provides alerts to schools and other organizations on the local air-quality forecast, and helps them take actions to protect people’s health, including those with asthma (also available in Spanish).

Best Practices for Reducing Near-Road Pollution Exposure at Schools, Environmental Protection Agency: Publication containing best practices for reducing traffic-related pollution exposure at schools. It includes an outline of building design and operations strategies, and site-related strategies.

Regional Operations & Maintenance Guide for High Performance Schools and Public Buildings in the Northeast and Mid-Atlantic, Northeast Energy Efficiency Partnerships: Guidance on establishing operations and maintenance policies, developing plans for training staff, maintaining ventilation systems, and a checklist of provisions to include in anti-idling policies.


Idling Reduction Toolkit, Massachusetts Department of Environmental Protection: Tools to develop and implement an idling reduction campaign including sample pledge, letter to parents, press release, and outline of community organizing.

Clean Air for Schools: Engines Off!, American Lung Association: Educational, curriculum-based program for schools, and facts about idling and pollution.

Clean Diesel Rebates, Environmental Protection Agency: School bus replacement and retrofit rebates to reduce emissions from older school buses.

Idle-Free Schools Initiative, Pioneer Valley Asthma Coalition (PVAC): The story of PVAC’s Idle-Free Schools Initiative, including artwork for a no-idle zone “ticket” and flyer, and other resources (available in English and Spanish).

Safe Routes to Schools Programs, Boston Public Schools: Safe Routes to School Boston is part of the national Safe Routes to School initiative to increase safety and promote walking and biking to school. Safe routes strategies and examples from Boston Public Schools are available.

Massachusetts Safe Routes to School (SRTS), Massachusetts Department of Transportation: Massachusetts SRTS is a federally-funded initiative of the Massachusetts Department of Transportation. Safe Routes to School works with schools, communities, students, and families to increase biking and walking among elementary and middle school students in the Commonwealth.

School siting

School Siting Guidelines, Environmental Protection Agency: A comprehensive publication on the process for making decisions, environmental factors to consider in the process, and how to conduct an environmental review of prospective school sites. The document covers how to meaningfully engage the community, including how to establish a school-siting committee and how to develop a communication plan.

Policies, Forms, and Guidelines, Massachusetts School Building Authority: Provides guidance, financial support, and incentives on school siting, design, and construction. Guidelines emphasize increased energy efficiencies, efficient transportation costs, lower water consumption, reduced use of materials, and quality indoor environments for educational settings.  

Massachusetts Collaborative for High Performance Schools Criteria 2009: Strategies and tools for creating high performance green schools that save money for school districts through energy savings, and also improve the wellness of building occupants.

Case Study: Community Mobilizes to Minimize Idling at Schools