A mothballed brownfield is a property where the property owner is unwilling or unable to transfer the brownfield or put it into productive reuse. Mothballed brownfields, like most brownfields, cause blight to neighborhoods, inhibit economic development, threaten public health and the environment, discourage productive reuse of infill areas, and encourage urban sprawl. Mothballed properties may pose particular problems to communities when these stagnant properties inhibit broader redevelopment or revitalization initiatives that cannot be successfully completed without addressing holdout brownfield properties. The United States Conference of Mayors reports that mothballed brownfields remain the toughest brownfields barrier to local leaders. The National Brownfield Association issued a study, Bringing Corporate Brownfield Properties to Market, that concludes that property owners need additional comfort, and a redevelopment partnership approach to brownfields, before many will transfer these properties.