IMMUNOTOXICOLOGIC EFFECTS OF INHALED CHROMIUM - ROLE OF PARTICLE SOLUBILITY AND COEXPOSURE TO OZONE

Soluble and insoluble hexavalent chromium (Cr6+) agents are concomitan tly released with ozone (O-3) during welding. Although pulmonary/immun ologic implications from exposure to each agent individually have been investigated, the effects from simultaneous exposure, as occurs under actual working conditions, are unclear. To investigate immunomodulato ry effects of inhaled Cr6+, F-344 rats were exposed for 5 h/day, 5 day s/week for 2 or 4 weeks to atmospheres containing soluble potassium ch romate (K2CrO4) or insoluble barium chromate (BaCrO4), each alone at 3 60 mu g Cr/m(3) or in combination with 0.3 ppm O-3. One day after the final exposure, rats were euthanized, their lungs were lavaged, and pu lmonary macrophages (PAM) were recovered for assessment of basal and i nducible functions. Rats inhaling K2CrO4-containing atmospheres had gr eater levels of total recoverable cells, neutrophils, and monocytes in bronchopulmonary lavage compared to rats exposed to insoluble Cr6+ at mospheres, O-3 alone, or air; these rats also had a reduced percentage of PAM, although total PAM levels remained unaffected. Although Cr ex posure-related changes in PAM functionality were evident, any dependen ce upon Cr solubility was variable. K2CrO4-containing atmospheres modu lated PAM-inducible interleukins-1 and -6, and tumor necrosis factor-c y production to a greater degree than those containing BaCrO4. Convers ely, BaCrO4-containing atmospheres affected PAM, basal nitric oxide pr oduction and interferon-gamma-primed/zymosan-stimulated reactive oxyge n intermediate production to a greater extent than did those containin g K2CrO4. In none of the PAM assays did co-inhalation of O-3 result in a modulation of the effects obtained with either Cr6+ compound itself . The results indicate that, while immunomodulatory effects of inhaled Cr6+ upon PAM are related to particle solubility, the co-inhalation o f O-3 apparently does not cause further modifications of the metal-ind uced effects. (C) 1998 Academic Press.