The uptake, disposition, biotransformation, and elimination of ¹⁴C-2-methylnaphthalene and ¹⁴C-naphthalene have been studied in several species of fish. The half-lives of elimination of ¹⁴C from several tissues, following the exposure of rainbow trout fingerlings to both compounds for 8 h, were less than 24 h. After exposure of the trout to ¹⁴C-naphthalene for four weeks, the half-life of elimination was hundreds of hours. After exposure to ¹⁴C-2-methylnaphthalene for four weeks, the elimination of ¹⁴C was biphasic; the rapid phase of elimination had a half-life of less than 24 h while the half-life of the slow phase was hundreds of hours. Examination of the muscle ¹⁴C by thin-layer chromatography (TLC) suggested that differential elimination of the parent compound and its metabolites may be involved in these differences. The elimination of ¹⁴C from fingerling carp after four weeks of exposure to ¹⁴C-2-methylnaphthalene, was also biphasic.

Bile ¹⁴C from rainbow trout, carp, and sheepshead which had been exposed to ¹⁴C-2-methylnaphthalene was present mainly as metabolites. Most of the metabolites appeared to be conjugated when examined by TLC.

Greater bile ¹⁴C to water ¹⁴C ratios resulted from exposure of the fish to ¹⁴C-2-methylnaphthalene than from exposure to ¹⁴C-naphthalene and were probably related to the greater uptake of ¹⁴C-2-methylnaphthalene. This ratio was also affected by the water level of the chemical, the exposure duration, and the species of the fish.

The disposition and biotransformation of ¹⁴C-naphthalene, ¹⁴C-2-methylnaphthalene, and ¹⁴C-1,2,4-trichlorobenzene in rainbow trout were affected by pretreatment of the trout with an inducer of microsomal enzymes, β-naphthoflavone. Biliary ¹⁴C levels were much higher in the induced trout, and the tissues contained a greater proportion of ¹⁴C as metabolites in the induced trout than in the controls.