The Environmental Protection Agency defines a brownfield as land or buildings, typically in urban areas, the further use of which may be hampered by the presence of pollution or contaminants. Greenfields are areas available for development on the edges of urban areas or in suburban locations.
For legal purposes, some properties that might be designated as brownfields are excluded because they are covered under their own legal terminology, including sites contaminated with polychlorinated biphenyls and closed solid waste facilities. Brownfields are generally located closer to city centers than greenfields. Cleaning up and redeveloping these sites stimulates the inner city economy, is more likely to generate use of mass transit and improves community connectedness.