Is my hot water bottle still safe to use?

[Elaine_C]

With the clocks having gone back last weekend and the cooler nights approaching, I brought my hot water bottle back into use last night after being stored away for the summer. When I emptied it this morning it left behind little bits of blue rubber in the sink. I’ve had the bottle for about 4 years, so why has this just started to happen now? Is my bottle still safe to use or should I throw it away? What should I do with it?