More than 750,000 children across Massachusetts ride buses to and from school every day. School buses are a safe mode of transportation and their diesel engines are both durable and economical.

However, there is growing concern about pollution from diesel engines. Scientific studies indicate that exposure to exhaust from diesel vehicles over time can cause cancer and other serious health problems.

That is why the Department of Environmental Protection (MassDEP) is working with school districts across Massachusetts to promote practical and effective actions for reducing our children's exposure to diesel pollutants.

MassDEP is also working to reduce smoke from buses, trucks and other heavy-duty vehicles by requiring them to undergo emissions testing and by requiring new diesel engines sold in Massachusetts to meet stringent California emission standards in model year 2005 and beyond.

Health Effects of Diesel Pollution

Blue clouds and black soot are the most noticeable forms of exhaust from buses, trucks and other heavy-duty vehicles, but it is the diesel pollution people can't see or smell that poses the greatest risks to their health.

Exhaust from school buses and other diesel-powered vehicles contains particulate matter, including fine particles that can penetrate deep into the lungs and even enter the blood stream, posing serious health problems for children, the elderly, and people with respiratory ailments. Fine particles can cause lung damage, aggravate respiratory conditions such as asthma and bronchitis, increase heart disease, lead to cancer, and even result in premature death.

Children and drivers can be exposed to diesel fumes when getting on and off school buses, and even while on board when the engines are running. Diesel exhaust from idling buses accumulates in and around school yards, and if air intake vents are located near bus stops, even the air inside school buildings can become polluted and pose health risks to children and teachers during the day.

The State Anti-Idling Law

In Massachusetts, state laws (M.G.L. Chapter 90, Section 16A and M.G.L. Chapter 90, Section 16B) and MassDEP regulations (See 310 CMR 7.11(1)(b) in the complete Air Pollution Control Regulations ) limit vehicle idling to no more than five minutes in most cases. A vehicle may idle longer only if absolutely necessary. There are exceptions for vehicles being serviced, vehicles making deliveries that need to keep their engines running (to power refrigerators, for example), and vehicles that need to run their engines to operate accessories (such as power lifts).

Local boards of health, local police, and state and federal officials are authorized to enforce the state anti-idling law. MassDEP enforces its own regulations.

What Schools Can Do

Here are some steps your school district can take to reduce diesel pollution from its school buses and ensure that its bus drivers are complying with the requirements of the state anti-idling law and MassDEP regulations:  

  • Limit school bus idling time during pre-trip safety "circle checks."
  • Direct drivers to turn off their buses as soon as they arrive in the school yard.
  • Provide a space inside the school where drivers who arrive early can wait, particularly during the winter.
  • Post "idling limit" signs wherever school buses linger (see example to the right).
  • Retrofit existing buses with pollution controls, and purchase new buses with cleaner burning engines.

For additional information, see MassDEP's recommended Best Management Practices For Reducing Diesel Pollution at Schools .