I saw this shocking news from Sydney Morning Herald "parents search for answers" headline. Which talks about a medical supplies company called "Unomedical" in Mona Vale area:
"FOURTEEN children on the northern beaches have developed cancer in the 10 years since a medical supplies company there began discharging a gas associated with the disease."
"Two of the children live less than a kilometre from the factory."
"Pittwater Council shut Unomedical's medical equipment sterilisation unit after it was revealed last month that untreated ethylene oxide had escaped from the plant, which had not been fitted with a filter."
You can also get the PDF version of their front page from this link.
Looks like it's going to have huge impact to the house price in that area...