 The rear glass tube of modern CRTs may be made from leaded glass, which represent an environmental hazard if disposed of improperly.By the time personal computers were produced, glass in the front panel (the viewable portion of the CRT) used barium rather than lead, though the rear of the CRT was still produced from leaded glass.Monochrome CRTs typically do not contain enough leaded glass to fail EPA TCLP tests.