Kansas City, Mo. ? Air-quality experts in Kansas City have joined other groups raising concerns about a BNSF Railway proposal to build a freight center in Johnson County.

An area newspaper reports that experts with the Mid-America Regional Council say diesel emissions from the rail project near Gardner would increase air pollution in the area, where it already exceeds federal air standards.

MARC has submitted its concerns about the air-quality issues in public comments to the U.S. Army Corps of Engineers. The corps is deciding whether to allow the Burlington Northern Santa Fe Railway to build a $750 million freight hub.

MARC is challenging an initial conclusion from the corps that the only serious pollution issue from the freight hub would be dust from vehicles using the site.

MARC officials contend diesel emissions from the rail yard would increase the level of fine particles of pollution, which are considered more hazardous than dust and other larger particles of pollution because they can enter the body more easily and cause respiratory problems.

BNSF Railway has said the initial report from the corps shows that ozone-threatening emissions from the rail yard would decrease substantially in the hub’s first two decades of operation.

The project won’t result in “significant changes to ozone-causing emissions in the greater Kansas City area,” the railroad said in a statement.