Brownfield is previously developed land that has been abandoned or left underused, and which may carry pollution or a risk of pollution from previous industrial use. The definition varies and is decided by policy makers and land developers within different countries. The main difference in definitions of whether a piece of land is considered a brownfield or not depends on the presence or absence of pollution. Overall, brownfield land is a site previously developed for industrial or commercial purposes and thus requires further development before reuse.
Examples of post industrial brownfield sites include abandoned factories, ash ponds, landfills, dry cleaning establishments, and gas stations. Typical contaminants include hydrocarbon spillages, solvents and pesticides, asbestos, and heavy metals like lead.