Fifteen new cases have emerged following the publication of a Newcastle Herald special investigation last weekend.

It revealed 24 cases of cancer along the road in the past 15 years, a number that was at the time described as seeming high by two epidemiologists who specialise in cancer cluster investigations.

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All the cases have occurred among people who have lived within a sparsely populated five-kilometre stretch of acreages and hobby farms, immediately south of the Williamtown RAAF base. A network of drains carry water polluted with toxic chemicals off the base and through the properties, which have returned some of the highest pollution readings of anywhere in the red zone.

The poly- and per-fluoroalkyl chemicals, also known as PFAS, are suspected carcinogens that have been linked to a number of health conditions, including impaired immune function.

Kim-Leanne King is stranded on a Cabbage Tree Road property with levels of contaminants in her bore water more than 500 times accepted health risk limits.

She was shocked to hear the chemicals could suppress immunity, after a case of the flu saw her hospitalised last year. Tests showed her white blood cell count was very low.

"They asked me the question, have you ever used IV drugs, because your immune system is like that of an AIDS patient," Ms King, who lost her father to bowel cancer, said. "I burst into tears. I was so upset that someone would think that. And that my immune system was not fighting for me."

Raeleen and Brian Russell were alarmed to hear of the number of cases on the road where they lived until 2007, before relocating to New Lambton.

Ms Russell, 62, was diagnosed with breast cancer last year and has undergone a mastectomy, chemotherapy and radiotherapy.

Our main concern is that I had my two sons and a grandchild living with us as well, Mr Russell said.

The couple were aware of the Williamtown contamination at the time of Ms Russells treatment, and asked a doctor if it could have a connection to her illness.

He told us: I cant tell you if it does or not. The only thing I can tell you is youve got to join a class action to stop these people from doing these things, Mr Russell recalls.

There have been calls for investigation into a gaping discrepancy between the results, after both Defence and the Newcastle Herald sampled water in a drain at the centre of cancer cluster fears in Williamtown.

The Heralds test showed up a staggering level of the PFAS chemicals, up to 23 times higher than levels reported by Defence contractors. Defence stood by its results, saying it had tested the drain around 60 times in three years and was confident its figures were representative. A spokesperson said the differences could have been related to sampling techniques, laboratory analysis methods, cross contamination or rainfall at the time of testing.

But Dr Steven Lucas from the University of Newcastles school of environmental sciences, who took the samples on behalf of Fairfax Media, said the latest readings warranted further investigation.

We did it by standard sampling protocol, he said. The fact we're getting a reading that high is of concern.