Here's an article, one of many I'm sure
Lead poisoning
While I understand that lead occurs naturally in the earth and was common in paint years ago, articles have warned about eating off of ceramic items painted or glazed as the lead can leach into the body and is toxic. Unfortunately most of the warnings of the past few years pertain to items from China.
I understand that I probably have items (though no coffee cups) like plates and such that get used rarely, I would be very hesitant to use a drip tip made of this, both from it touching my lips as well as inhaling vaper through this type of tip. JMTC & HTH