A review of world literature finds iron oxides noncarcinogenic

Iron oxide appeared in the first list of 154 Threshold Limit Values adopted by the American Conference of Governmental Industrial Hygienists at its April 1949 annual meeting. It was set to control dust and fume at the recommended value of 15 mg/M3, at the time, the limit for an inert or "nuisance" dust, and was based on studies of welders made earlier by the U.S. Dept. of Labor and by Drinker and Nelson. By 1964, the TLV was tentatively reduced to 10 mg/M3 after a considerable body of literature had accumulated not only on the health experience of welders, but of other occupations involving iron oxides as well. As a group, these studies indicated that 15 mg/M3 permitted too great accumulations of iron pigmentation in the lung whose chronic retention effects were not known with certainty. Also, an occasional report of cancer of the lungs appeared particularly among British hematite miners, although these findings were immediately questioned on statistical grounds. In seeming confirmation of these early reports of cancer, an alarming number of reports of cancer of the lung and respiratory tract among welders and foundrymen began to appear by 1970, reaching a crescendo by the end of that decade. As past chairman of the TLV Committee, I decided to examine the bases of these findings. This review is the result of this examination.