Posssibly not good to overdo camphor in your life, and if you are using the blocks or balls, keep them away from access to children.
"In larger quantities, it is poisonous when ingested and can cause seizures, confusion, irritability, and neuromuscular hyperactivity. In extreme cases, even topical application of camphor may lead to hepatotoxicity.  Lethal doses in adults are in the range 50-500 mg/kg (orally). Generally, two grams cause serious toxicity and four grams are potentially lethal."
It's been pretty much removed from the market here.