Lead is a hazard in nonferrous foundries making leaded bronzes and brasses. The scrap metals used in ferrous foundries may be contaminated with lead. Exposure to chromium, nickel, manganese, and fumes of other alloyed metals may occur in steel alloy foundries. Crystalline silica, carbon monoxide (especially if sea coal is used), PAHs (formed by the pyrolysis of organic material in green sand), MDI, formaldehyde, acrolein, and benzene are also released during melting and pouring. Beryllium fume is produced in foundries making copper-beryllium alloy. [Burgess, p. 127-35] "In the foundry environment, CO is mainly produced by cupola melting and casting operations." [IARC 2012: Iron and steel founding] See the agent "Iron and steel founding."