The cytopathologic effects of specific aromatic hydrocarbons.

A heterogeneous mixture of the aromatic hydrocarbons benzene, toluene, and xylene is capable of inducing cellular lesions among selected organs of the fat-head minnow at the respective concentrations of 10.7, 7.4, and 2.7 mg/l. The gill, pseudobranch, liver, and nasal mucosa of experimental fish were exposed for a period of 6, 12, 24, or 48 hours to the hydrocarbons, whose source was the water-soluble fraction of jet aviation fuel JP-4. While many of the initial cellular changes appeared reversible, the extent and magnitude of injury increased as the exposure period progressed, with an apparent concomitant development of irreversible lesions. Manifestations of cytotoxicity among cells of the gill included multivesiculated blebs, distended mitochondria, intercellular spaces between surface and underlying epithelial layers, and evaginations of the endothelial lining associated with capillaries of secondary lamellae. Cells comprising the pseudobranch were characterized by a significant increase in lipidlike droplets, proliferation of cytoplasmic vacuoles, and disruption of the normally ordered association of mitochondria and tubules. The nasal mucosa was characterized by a loss of cilia and cellular necrosis within the underlying epithelial layers. Cytotoxicity among hepatocytes was evident in the forms of vesiculated endoplasmic reticulum and both swollen and condensed mitochondria.