Northern Iron is the largest stationary emitter of small particulates (PM10 or PM2.5) in Ramsey County. Fine particulates are tiny bits of dust that can penetrate human lungs and cause irritation. Studies from other foundries show that particulates can also carry lead and other hazardous metals from foundry processes. These can include manganese, arsenic, mercury, beryllium, cadmium, chromium, cobalt, nickel, and selenium.