PULMONARY RETENTION AND DISTRIBUTION OF INHALED CHROMIUM: EFFECTS OF PARTICLE SOLUBILITY AND COEXPOSURE TO OZONE

Abstract

Soluble and insoluble chromium Cr agents are concomitantly released with ozone O3 during welding. Although pulmonary 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 the retention distribution of inhaled Cr, male F-344 rats were exposed nose-only to atmospheres containing soluble potassium chromate K2CrO4 or O3, either alone or in combination, at 360 mug Cr m3 and 0.3 ppm O3. In a second phase of the study, insoluble barium chromate BaCrO was used in place of K2CrO4. Rats were exposed for 5 h day, 5 days wk for 2 or 4 wk. One day after the final exposure, rats were euthanized and their lungs either removed intact or lavaged for quantitation of tissue-, lavaged cell-, and acellular lavage fluid-associated Cr. In general, rats inhaling insoluble Cr had greater total lung Cr burdens than did rats exposed to soluble Cr. Simultaneous inhalation of O3 and K2CrO4 led to reduced lung Cr levels compared to those in rats receiving K2CrO4 only; with BaCrO4, coexposure to O3 resulted in increased lung BaCrO4 levels compared to BaCrO4 alone. Particle solubility also affected Cr levels in lavageable cells, with those from rats inhaling BaCrO4 alone or BaCrO4 + O3 consistently having greater burdens than their K2CrO4 counterparts; the presence of O3 itself had no effect upon cell Cr levels when either compound was used. Solubility-dependent differences were also apparent in acellular lavage fluid, with Cr levels initially being greater in fluids from rats inhaling K2CrO4 alone; as exposures continued, these burdens became greater in the rats inhaling BaCrO4 alone. Although inhalation of either Cr O3 mixture yielded significant differences in fluid Cr levels, the presence of O3 did lead to reductions in levels compared to those in rats inhaling either Cr agent alone. In postlavage lung tissue, there were time-dependent increases in Cr levels in rats from all exposure groups; however, the most dramatic increase occurred with rats exposed to BaCrO4 O3. Lastly, while significant solubility-dependent differences in the relative distribution of Cr among the three pulmonary compartments were discerned, a specific effect attributable to O3 itself was not evident. The results of this study indicate that Cr retention and distribution within the lungs, as well as any effect from coexposure to O3, are modulated by the solubility of the inhaled Cr particles.