SEATTLE - While authorities are checking the safety of school buses, researchers in Seattle are monitoring the health hazards of school bus emissions. A new study has found children are exposed to a substantial amount of air pollution when riding school buses. Seattle and Maple Valley schools are taking steps to change that.

This time last year, KING 5 followed a team of diesel study technicians as they took readings of air quality in and around Seattle school buses. What they found was surprising.

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Children are exposed to a substantial amount of air pollution when riding school buses.

“If you want to protect children’s health, then what you want to do is cut down the pollution from the crankcase emissions,” said associate professor Sally Liu at the University of Washington, who presented this year's crankcase findings to a team of school officials from the transportation department

Contrary to previous studies, the UW researchers found tailpipe pollution accounted for a very small portion of emissions from school buses. According to the study, the crankcase is responsible for most of it.

Students who were part of the study carried a personal monitoring kit with a series of air pollution monitors to measure their personal exposure.

The study, now entering its third year, will continue to monitor air pollution and work with the school district to make improvements.The Seattle school district has already taken the first step. This year each school bus will be fueled with biodiesel and next year, the district will begin retrofitting the crankcases.

The legislature has allocated $20 million over five years to fund the improvements. One major crankcase manufacturer has also pledged to re-engineer its assembly to make certain its crankcases achieve near zero emissions.