Oddly the new packaging on the mantles does not have the warning the old ones had... I was furious when a friend of mine knocked the ash of an old mantle onto my coat... the coat I was I was going to have to get through airport security the next day.
I was ready for the anal probe as a result.
It was alarming how ignorant and careless some people can be about these mantles... I was held up at the same time as a 13 year old little girl that had just come from a soccer game in her uniform and the fertilizer for the soccer field tripped off the bomb detector.
Many newer mantles use Yttrium.