THE NSW Health Commission tried to cover up the dangers of a radioactive waste site in Hunters Hill in the 1970s, warning staff not to tell families who lived on blocks that were known to emit gamma rays at well above the safe level.

An internal memo dated February 9, 1977, told staff to "please stall and be non-committal" when responding to queries, and residents were told there was "no logical reason" to carry out radiation or health tests, even though the organisation already knew of the radiation threat.

The state government had started feeling the heat in 1977 because one of the most radioactive plots on Nelson Parade, No. 11, had been bought and developed by Justice Mary Gaudron, later Australia's first female High Court judge.