Carcinogenic risk assessment criteria associated with inhalation of airborne particulates containing chromium (VI/III).

Contaminated land sites and unused chromate production facilities raise the possibility that remediation operations could involve generation of airborne particles of respirable size containing both Cr(VI) and Cr(III) in soluble and insoluble forms. These airborne particles reaching human populations in the neighborhoods involved, can pose carcinogenic risks via Cr(VI)-containing material retained in the lungs. It is proposed that the risk assessment process for this inhalation exposure be governed by the following considerations. (i) Only the respirable fraction (0.2-10.0 microns diameters) of the inhaled particulates should be considered as contributing to delivered dosage of Cr(VI) to the lung. (ii) In accordance with the ICRP analysis of particulate retention in the lung for extended intervals, the airborne respirable particle intake should be multiplied by the factor 0.125 to generate an estimate of dosage of particles retained in the lung for extended intervals, leading to possible carcinogenesis from the Cr(VI) content. And (iii), the inhalation carcinogenic risk for Cr(VI) should only be modelled in increments above a daily total chromium intake of 100 micrograms per day, a current estimate of the required daily intake of this essential mineral.