PULMONARY RETENTION AND DISTRIBUTION OF INHALED CHROMIUM - EFFECTS OFPARTICLE SOLUBILITY AND COEXPOSURE TO OZONE

Soluble and insoluble chromium (Cr) agents are concomitantly released with ozone (O-3) during welding. Although pulmonary implications from exposure to each agent individually have been investigated, the effect s from simultaneous exposure, as occurs under actual working condition s, are unclear. To investigate the retention/distribution of inhaled C r, male F-344 rats were exposed nose-only to atmospheres containing so luble potassium chromate (K2CrO4) or O-3, either alone or in combinati on, at 360 mu g Cr/m(3) and 0.3 ppm O-3. In a second phase of the stud y, insoluble barium chromate (BaCrO4) was used in place of K2CrO4. Rat s 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 i ntact or lavaged for quantitation of tissue-, lavaged cell-, and acell ular lavage fluid-associated Cr. In general, rats inhaling insoluble C r had greater total lung Cr burdens than did rats exposed to soluble C r. Simultaneous inhalation of O-3 and K2CrO4 led to reduced lung Cr le vels compared to those in rats receiving K2CrO4 only; with BaCrO4 coex posure to O-3 resulted in increased lung BaCrO, levels compared to BaC rO3 alone. Particle solubility also affected Cr levels in lavageable c ells, with those from rats inhaling BaCrO, alone or BaCrO4 + O-3 consi stently having greater burdens than their K2CrO4 counterparts; the pre sence of O-3 itself had no effect upon cell Cr levels when either comp ound was used. Solubility-dependent differences were also apparent in acellular lavage fluid, with Cr levels initially being greater in flui ds from rats inhaling K2CrO4 alone; as exposures continued, these burd ens became greater in the rats inhaling BaCrO4 alone. Although inhalat ion of either Cr/O-3 mixture yielded significant differences in fluid Cr levels, the presence of 4 did lead to reductions in levels compared to those in rats inhaling either Cr agent alone. In postlavage lung t issue, there were time-dependent increases in Cr levels in rats from a ll exposure groups; however, the most dramatic increase occurred with rats exposed to BaCrO4 + O-3. Lastly, while significant solubility-dep endent differences in the relative distribution of Cr among the three pulmonary compartments were discerned, a specific effect attributable to O-3 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 O-3, are modulated by the solubility of the inhale d Cr particles.