I had to look up the cause, and it was because it used a high Nickel alloy for the tool steel.
I had not associated Nickel as particularly harmful, but... it's relatively nasty in regards to human health (particularly when inhaled in even small amounts).
So I was curious and scrolled down to page 81 in the linked document on this post - they do a fairly thorough walk through of the potential harms, and it's worth reading for the folks who do this at home.
I've copied the relevant regulatory warnings from the document here:
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¹Nickel salts (e.g., Ni sulphate, Ni sulphamate) carry the following human health hazard classifications under GHS: (Global Harmonized System): Acute Tox. 4 (H302: Harmful if swallowed and H332: Harmful if inhaled), Skin Irrit. 2 (H315: Causes skin irritation), Resp. Sens. 1 (H334: May cause allergy or asthma symptoms or breathing difficulties if inhaled), Skin Sens. 1 (H317: May cause an allergic skin reaction), Repr. 1B (H360: May damage fertility or the unborn child, developmental effects), Muta. 2 (H341: Suspected of causing genetic defects), Carc. 1A (H350: May cause cancer by inhalation route only), and STOT Rep. Exp. 1 (H372: Causes damage to respiratory tract through prolonged or repeated inhalation exposure). Nickel metal carries the following human health hazard classifications under GHS: Skin Sens. 1 (H317: May cause an allergic skin reaction), Carc. 2 (H350: May cause cancer by inhalation route only), and STOT Rep. Exp. 1 (H372: Causes damage to respiratory tract through prolonged or repeated inhalation exposure).
What is specific to nickel is that much more people, especially women, are allergic to it, in comparison with other common metals. Therefore surfaces covered with nickel or nickel alloys with high nickel content are not recommended for contact with skin.