Chronic toxicity of 14 phthalate esters to Daphnia magna and rainbow trout (Oncorhynchus mykiss)

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Abstract
Chronic toxicity studies were performed with commercial phthalate esters and Daphnia magna (14 phthalates) and rainbow trout (Oncorhynchus mykiss) (six phthalates). For the lower‐molecular‐weight phthalate esters–dimethyl phthalate (DMP), diethyl phthalate (DEP), di‐n‐butyl phthalate (DBP), and butylbenzyl phthalate (BBP)–the results of the studies indicated a general trend in which toxicity for both species increased as water solubility decreased. The geometric mean maximum acceptable toxicant concentration (GM‐MATC) for D. magna ranged from 0.63 to 34.8 mg/L. For the higher‐molecular‐weight phthalate esters–dihexyl phthalate (DHP), butyl 2‐ethylhexyl phthalate (BOP), di‐(n‐hexyl, n‐octyl, n‐decyl) phthalate (610P), di‐(2‐ethylhexyl) phthalate (DEHP), diisooctyl phthalate (DIOP), diisononyl phthalate (DINP), di‐(heptyl, nonyl, undecyl) phthalate (711P), diisodecyl phthalate (DIDP), diundecyl phthalate (DUP), and ditridecyl phthalate (DTDP)‐the GM‐MATC values ranged from 0.042 to 0.15 mg/L. Survival was equally sensitive and sometimes more sensitive than reproduction. The observed toxicity to daphnids with most of the higher‐molecular‐weight phthalate esters appeared to be due to surface entrapment or a mode of toxicity that is not due to exposure to dissolved aqueous‐phase chemical. Early life‐stage toxicity studies with rainbow trout indicated that survival (DMP) and growth (DBP) were affected at 24 and 0.19 mg/L, respectively. This pattern of observed toxicity with the lower‐molecular‐weight phthalate esters and not the higher‐molecular‐weight phthalate esters is consistent with previously reported acute toxicity studies for several aquatic species.