i googled for this issue and found this

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Kidsafe Victoria has prompted an investigation into the safety of Chinese-made children's foam play mats after they were banned in France and Belgium.
The popular interlocking foam mats, with alphabets and other designs, have been found to contain formamides which have been linked to cancer.
Formamide is also toxic to the reproductive system and can pose harm to fetuses and infants and exposure can cause eye, nose, throat and skin irritation.
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Kidsafe Victoria president Dr Mark Stokes says the ACCC will begin testing the mats to see if they are safe for children.
"Children should not be exposed to high level toxic products," Dr Stokes said.
"Young children are potentially at most risk as they have a tendency to place everything in their mouths.
"Tests need to be conducted to see if these toxins are present in products available in Australia, and if so, in what levels."