The Illawarra's Public Health Unit yesterday confirmed it had investigated concerns about the high rate of childhood cancers in Helensburgh.
"These concerns were first raised in 2008 and since that time the Public Health Unit (PHU) has monitored the occurrence of leukaemia both in Helensburgh and the broader Illawarra and Shoalhaven community," acting director Curtis Gregory said.
"To date, no evidence has been found of an increased risk or clustering of leukaemia in the 2508 postcode, which includes the Helensburgh township," Mr Gregory said.
"The PHU has also investigated whether any unusual environmental risk factors might be present in the area and considers that this is unlikely."
Mr Gregory was responding to Helensburgh resident Diane Young's concerns after her son, Matthew, became the sixth child in five years to be diagnosed with blood cancer.
Matthew was told in August that he had the rare Burkitt's lymphoma; another child received the same devastating news three years earlier.
Four more children were diagnosed with leukaemia. Two of them have since died.
Mr Gregory said the PHU had looked at cancer rates over recent years and found "no evidence of an unexpected number of cancer cases in Helensburgh or surrounding areas".
"With any disease that is rare, the number of cases in a local community will typically be quite small, but can vary significantly over time, without any common underlying cause," he said.
"The Public Health Unit treats all reports of possible disease clusters as a priority and acknowledges the concerns of the community about the number of childhood cancers in Helensburgh."
Mr Gregory said leukaemia and non-Hodgkin's lymphoma (Burkitt's) were different types of cancer "unlikely to be caused by a single unusual environmental factor".
"The only known environmental cause of leukaemia is occupational exposure to (the chemical) benzene in adults," he said.
"In light of recent concerns, the PHU is obtaining the most current available Cancer Registry data to include non-Hodgkin's lymphoma and will continue to monitor this information," he said.
Helensburgh mother-of-three Angela Fagerstrom is one of a growing number of residents calling for further investigation.
"Alarm bells have been ringing in this community for some time," Mrs Fagerstrom said.
"In March of this year I wrote to The Cancer Institute, asking them to consider a cluster study. That was well before Matthew Young's diagnosis. I never heard back."
Mrs Fagerstrom said it was a credit to the town that it rallied together when a child was unwell.
"We have a tight community, many of whom have links with the local coalmine. To point the finger without evidence can harm that sense of community - the science needs to be good," she said.
"There could be any number of factors at play, including coincidence. But without comprehensive and transparent studies there can be no way of knowing what is behind the apparently higher rates of blood cancer."