Industrial Exposure?

[Cotie, Steve SD]

A laborer at a primary metal smelter has developed a discolored (black)
line on his teeth at the gum line. Additionally, the teeth are pitting.

Please note that the discoloration is on the teeth and not on the gums.

Could this be indicative of heavy metal poisoning, or is the casual
agent unlikely to be industrial in origin?

Please e-mail suggestions to:
sdcotie at theriver.com