Brownfields are...

 

...abandoned, idled, or under-used industrial and commercial facilities where expansion or redevelopment is complicated by real or perceived environmental contamination (U.S. EPA).

...abandoned, unused or underutilized properties, suspected of or being known to be contaminated, that are believed to be potentially reusable (Dr. Charles Powers, State Brownfields Policy and Practice-June,1994).

..."dead zones" and "pockets of disinvestment, neglect and missed opportunities" that exist within American cities (U.S. Conference of Mayors).