Histopathologic Response in the Fathead Minnow (Pimephales promelas) Exposed to 2,4-Dinitrotoluene in an Early Life Stage Toxicity Test.

Abstract

The histopathologic examination of fathead minnows (Pimephales promelas) exposed to 2,4-dinitrotoluene (2,4-DNT) in an early life stage (ELS) toxicity test was compared with a chronic life cycle test performed by Liu and Bailey (1981) at SRI International (SRI). Pathologic conditions associated with 2,4-DNT exposure were found in the gill, liver, spleen and trunk kidney . in all concentrations tested (ranging from 0.27 - 3.58 mg/L). Edematous "ballooning" and fused "blanketing" of secondary lamellae characterized gill damage. Lipid accumulation and limited focal fatty necrosis were observed in the liver. Abnormal accumulations of hemosiderin in the spleen and atypical renal tubules and corpuscles in the trunk kidney were evident. A weighting scheme was applied based on biological significance of the lesions observed to determine a no-effect level. No threshold level was attained below which histologic effects would be expected to be absent. The SRI chronic maximum allowable toxicant concentration (MATC) was less than 0.44 mg/L 2,4-DNT. In the ELS test, the MATC was less than 0.27 mg/L 2,4-DNT. Thirty day survival effects in the ELS test compared favorably. Thirty day SRI F0 growth effects were found at concentrations of 1.75 mg/L and above. No growth effects were observed in the ELS test at concentrations up to 3.58 mg/L. Based on these comparisons, the usefulness and sensitivity of ELS toxicity testing is increased with the addition of histopathologic evaluation, thereby helping to formulate more appropriate water quality criteria.