when was it discovered that lead was poisonous
Lead poisoning In 2013 lead is believed to have resulted in 853,000 deaths.[2] It occurs most commonly in the developing world.[2] Those who are poor are at greater risk.[2] Lead is believed to result in 0.6% of the world's disease burden.[5] People have been mining and using lead for thousands of years.[4] Descriptions of lead poisoning date to at least 2000 BC,[4] while efforts to limit lead's use date back to at least the 1500s.[5] Concerns for low levels of exposure begin in the 1970s with there being no safe threshold for lead exposure.[2][4]
Graphite From the 16th century, all pencils were made with leads of English natural graphite, but modern pencil lead is most commonly a mix of powdered graphite and clay; it was invented by Nicolas-Jacques Conté in 1795.[39][40] It is chemically unrelated to the metal lead, whose ores had a similar appearance, hence the continuation of the name. Plumbago is another older term for natural graphite used for drawing, typically as a lump of the mineral without a wood casing. The term plumbago drawing is normally restricted to 17th and 18th century works, mostly portraits.