Put simply, contaminated land is land containing substances at levels that would not normally be
present. These substances may be trace elements, organic compounds, gases such as carbon dioxide
or methane, or even plant nutrients like nitrogen or phosphorous. The presence of these substances
at elevated levels may, or may not, be harmful. However, contaminated land is most often used to describe
land where there is at least a suspicion that the contamination could be harmful to humans, water,
buildings, or ecosystems. Countries may have specific legal definitions of contaminated land.