A more thorough explanation:

Definition: A brownfield site is a piece of land that was previously used for industrial or commercial purposes but is now abandoned, idle, or underused due to environmental contamination. These sites are difficult to redevelop or expand because of the presence of hazardous substances.

Example: An old factory that used to produce chemicals is now closed and the land is left unused. The soil and groundwater on the site are contaminated with toxic chemicals, making it difficult to redevelop the land for other purposes.

Explanation: The example illustrates how a brownfield site can be an abandoned industrial or commercial property that is contaminated with hazardous substances. The presence of these substances makes it difficult to redevelop the land for other purposes, such as residential or recreational use. Brownfield sites can pose a risk to human health and the environment if not properly cleaned up and remediated.