The report says Texas has made real progress in cleaning up dirty diesel engines on school buses, and that Houston has led that effort. Elena Craft is a health scientist at the Environmental Defense Fund.
"Houston's program has actually accounted for the lion's share of replacement of all buses across the state, so about 70 percent of the new buses in Texas are in the Houston region. That's great for Houston and that's great for the kids who are riding to school in buses in Houston. There are still though buses that could be replaced or retro-fitted."
The Houston School District has a fleet of almost 1,000 buses.
Last year, the district bought 27 propane buses. Another 58 are on order this year, with 40 more likely to be purchased in the next year or so.
The district has replaced many of the old diesel engines with so-called "green" diesel engines that are much more environmentally friendly. Mark Swackhammer manages HISD's fleet operations.
"It's a major priority for HISD. We are not just a large school district, but we're a governmental agency and we have a large fleet, so we very, very strongly feel that it's our duty to help clean the air in any way possible."
Swackhammer says about half of HISD's buses have been retrofitted with devices that help clean diesel emissions, and it's all been done with grant money.
"We have a couple of hundred buses that have been retrofitted with particulate traps and they're using grant money — no cost to the district — that's reduced our particulate matter out of our exhausts by over 90-percent. We have over 300 buses that we've added closed crank case ventilation systems, so all that's been done, no cost to the district. It's all just strictly been grant money that this happened."
He says although they're too expensive right now, the district is also considering compressed natural gas buses as a way to reduce fleet emissions.
The Environmental Defense Fund report says there are still 17,000 of the older diesel school buses on the road in Texas.