Pollution Levels Inside School Buses Pose Health Risk

Studies show that air pollutant levels from school bus diesel exhaust can be greater inside the bus than outside. And diesel exhaust is bad for children’s health.
A study by the New Brunswick Lung Association found that average exposures to tiny particles from diesel exhaust were 5-6 times greater than levels outside the bus. Exposures to fine particulate matter and black carbon were about three times higher during bus rides than during the average walking commute.
Diesel exhaust contains carcinogens and tiny particles that can cause or worsen breathing problems, according to the Natural Resources Defense Council. It has been associated with asthma hospitalizations, lower respiratory symptoms and even cancer. Children who ride buses to school every day for many years have a greater risk of getting cancer later in life.
Emissions from school buses come from two sources, according to Environmental Defense: the engine crankcase and the tailpipe. A number of factors affect the amount of emissions that enter the bus, including wind speed and direction, whether the windows are open or closed and the age and condition of the bus. Older buses that are not well maintained will emit a greater amount than more recent models.
Older buses can be modified to make them less polluting. Devices that trap particulates can be installed on buses that run on low-sulfur diesel fuel. Crankcase filtration systems can reduce particulate emissions by more than 90 percent, according to Environmental Defense. Diesel particulate filters can reduce tailpipe particulate emissions by 85 percent or more, but diesel oxidation catalysts reduce the emissions by only about 25 percent.
School systems can reduce children’s exposure to diesel exhaust. The best option, says the Natural Resources Defense Council, is to replace diesel buses with alternative-fuel ones. Installing filters in older buses can also greatly reduce the particulate emissions. Opening the windows when the weather allows will also help reduce levels inside the bus. Finally, since exhaust accumulates in the back of the bus, directing children who must be on the bus the longest to sit near the front will reduce their exposure.