One of the largest recreational areas in Sydney's inner suburbs has been declared to be "significantly contaminated land" while the environmental watchdog assesses the extent of the pollution.

Details of the declaration by the Environment Protection Authority were buried in the final NSW Government Gazette, released on Friday before the start of pre-election caretaker period.

Sydney Park has been declared to be "significantly contaminated land". Credit:Janie Barrett

A spokeswoman for the EPA said Sydney Park in St Peters was "safe for use" even though the Gazette noted "more accurate calculations of flow rates and ongoing management is required to better define and manage any risks".

Staff from the City of Sydney were handing out flyers to park users on Wednesday that stated recent testing had revealed "elevated concentrations of methane and carbon dioxide at the park's perimeter", but adding "there are no identified health risks".