The term “sites suspected of being contaminated” refers to areas where contamination is suspected. Contaminated sites include, for example, decommissioned landfills for municipal or commercial waste (old landfills) or decommissioned facilities, defense sites, and industrial sites where environmentally hazardous substances were handled (historically contaminated sites), provided that this has resulted in harmful soil contamination or other hazards. The Contaminated Sites Registry compiles data on contaminated sites and sites suspected of contamination.

Under the Environmental Information Act (UIG), every person has the right to free access to environmental information held by an agency required to provide such information. In Lower Saxony, the UIG applies in conjunction with the Lower Saxony Environmental Information Act (NUIG). Access may be granted by providing information, allowing access to files, or by other means. Upon request, any person may therefore obtain information from the Contaminated Sites Register. Such information is important, for example, when buying or selling a property, in connection with construction or demolition projects, and when using groundwater in the vicinity of contaminated sites. However, in many cases, information about a contaminated site or a site suspected of contamination may constitute personal data. The competent authority must then determine whether disclosing the information would significantly harm the interests of the affected party; if necessary, it must weigh the interests involved.