An expert health panel has found no evidence that Helensburgh residents are at increased risk of blood cancers due to environmental exposure.
The panel, formed to look into childhood leukaemia and lymphoma, found that a higher rate of leukaemia between 2005 and 2008 most likely arose "by chance". Rates of lymphoma were within the normal range.
The findings angered Di Young, the mother of nine-year-old Matthew, who became the sixth Helensburgh child in five years to be diagnosed with blood cancer.
"If that's the best they can do - investigate that quickly without contacting me or anyone else, and another kid gets cancer - they can deal with it, not me," Mrs Young said.
"All of Helensburgh will know. It will be case No 7."
The expert panel was set up in October after Mrs Young went public with her concerns about the six cases in the "top end of town".
"I've done everything I can. I guess I can rest easy - I can do no more," Mrs Young said.
"What do they need? Another kid to get cancer? They've done nothing, they haven't spoken to anybody."
Mrs Young said she planned to relocate her family.
"I cannot stay in Helensburgh knowing Matthew is higher risk - not when I'm not 100 per cent sure. How do I know? The soil and water hasn't been tested."
The panel looked into the frequency of cases of leukaemia and lymphoma in Helensburgh from 1996 to 2011.
It noted more cases of leukaemia than expected between 2005 and 2008, but none from 1996 to 2004.
Rates of lymphoma were within the expected range.
The panel also considered the findings of an environmental investigation by the Illawarra Public Health Unit that reviewed past and existing land use in the area and past pollution incidents.
The panel found no evidence that the Helensburgh community was at increased risk due to environmental exposure.
Based on the panel's findings and the results of an environmental investigation by the public health unit, the panel advised that environmental testing was not recommended.
Panel member Professor Bernard Stewart, head of the Cancer Control Program at the South East Sydney Local Health District, said the rate of relatively uncommon diseases such as leukaemia and lymphoma inevitably varied by chance from very high to very low when researchers looked at one age group in a single postcode area.
"The number of cases of childhood leukaemia and lymphoma which has arisen in Helensburgh is most likely due to chance," he said.