The Alliance for California Business, a group that represents California trucking and farming businesses, recently won a small battle in the fight against the California Air Resources Board (CARB).

Since 2013, the group has tried to get lawmakers to roll back CARB’s Diesel Particular Filter (DPF) mandate by proving that the filters are neither safe nor mechanically reliable.

In a recent public notice, CARB has acknowledged that trapped soot in DPFs may indeed cause engine damage. The staff report, published in March 2016, states the following:

“… trapped soot in the wall-flow DPF builds up over time, increasing the backpressure on the engine as it continues to operate. Operating the engine at excessive backpressure for extended periods will impact engine performance and eventually cause engine damage.”

This information was not publicly available in 2015, when a Glenn County Superior Court judge denied a preliminary injunction against the DPF Mandate. The group hopes to use the new information to convince lawmakers to take their side in the fight against CARB.

“It is time for CARB to do the right thing: issue a recall on all DPFs until they are proven safe and mechanically reliable,” the Alliance for California Business said.

You can read the full press release here.