Md. Cohen et al., IMMUNOTOXICOLOGIC EFFECTS OF INHALED CHROMIUM - ROLE OF PARTICLE SOLUBILITY AND COEXPOSURE TO OZONE, Toxicology and applied pharmacology, 152(1), 1998, pp. 30-40
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.