Nickel (Ni)

Nickel (Ni) is a silvery heavy metal that, in its airborne compounds, is a respiratory carcinogen and a cause of contact dermatitis and lung disease. Certain nickel compounds are classified as Group 1 human carcinogens. Because of its toxicity at trace levels, it is included in the NAAQS with a very low annual ambient limit of 20 ng/m³ (nanograms per cubic metre).

Nickel enters the air as fine particulate from smelting and metal refining, electroplating, alloy and stainless-steel manufacture, battery production, and the incineration of nickel-bearing waste. In recycling, nickel is most relevant to two sectors: lithium-ion battery recycling (NMC and NCA cathodes are nickel-rich, so dust from crushing, the black mass, and any pyrometallurgical step carry nickel), and e-waste recycling (nickel plating, connectors and Ni-bearing alloys release it during shredding and thermal treatment).

The exposure pathway is inhalation of nickel-bearing dust and fume, plus skin contact. Battery and e-waste workers handling black mass, plated components or smelter fume are the most exposed, and chronic inhalation is the carcinogenic concern. Nickel is measured at trace levels in ambient air by AAS or ED-XRF on collected filters.

Control combines dust capture and worker protection: enclose and ventilate crushing and shredding, run a baghouse to capture metal-bearing PM (which doubles as material recovery for valuable nickel), keep black-mass handling under local exhaust, and provide respirators and skin protection. For battery recyclers, capturing nickel-bearing dust is both an emission-control and a value-recovery measure, since nickel is one of the most valuable elements in the black mass.