Acute aquatic toxicity studies were performed with 14 commercial phthalate esters and representative freshwater and marine species. The 14 esters were dimethyl phthalate; diethyl phthalate; di‐n‐butyl phthalate; butyl benzyl phthalate; dihexyl phthalate; butyl 2‐ethylhexyl phthalate; di‐(n‐hexyl, n‐octyl, n‐decyl) phthalate; di‐(2‐ethylhexyl) phthalate; diisooctyl phthalate; diisononyl phthalate; di‐(heptyl, nonyl, undecyl) phthalate; diisodecyl phthalate; diundecyl phthalate; and ditridecyl phthalate. Phthalate esters with alkyl chain lengths of four carbon atoms or fewer were determined to be acutely toxic at concentrations ranging from 0.21 to 377 mg/L depending on the ester and the solubility of the test chemical in water. There was a general trend for the lower‐molecular‐weight phthalate esters (C1 to C4 alkyl chain lengths: dimethyl phthalate; diethyl phthalate; di‐n‐butyl phthalate; and butyl benzyl phthalate) to become more toxic with decreasing water solubility for all species tested. There were only minor differences in species sensitivity to each of the phthalate esters. Phthalate esters with alkyl chain lengths of six carbon atoms or more were not acutely toxic at concentrations approaching their respective aqueous solubilities. Insufficient mortality occurred to calculate either LC50 or EC50 values or acute no‐observed‐effect concentrations for these higher‐molecular‐weight phthalate esters. The lack of toxicity observed for the higher‐molecular‐weight phthalate esters resulted from their limited water solubility (≤1.1 mg/L).

Abstract-The extensive database of acute and chronic aquatic toxicity data for 18 phthalate esters was reviewed and summarized for freshwater and saltwater aquatic microorganisms, algae, invertebrates, and fish. Phthalate esters have been tested with six species of microorganisms, including bacteria and protozoans. Fifteen algal species have been tested, including green and bluegreen algae in both freshwater and saltwater. Nineteen freshwater and saltwater invertebrate species inhabiting surface waters and sediments and 21 freshwater and saltwater fish inhabiting cold and warm water bodies have been tested. The results of most studies indicate that acute and chronic toxicity to microorganisms, algae, aquatic invertebrates, and fish are limited to the lower molecular weight phthalate esters (i.e., dimethyl-, diethyl-, diallyl-, dipropyl-, dibutyl-, diisobutyl-, and butylbenzylphthalate). In contrast, higher molecular weight phthalate esters are not acutely or chronically toxic to aquatic organisms. Although conflicting data on chronic effects for high molecular weight phthalate esters have been reported for daphnids, these inconsistencies are attributed to physical effects imposed on daphnids when exposed to test concentrations in excess of true water solubilities. Altogether, nearly 400 test results covering more than 60 species of microorganisms, algae, invertebrates, and fish are reported for both freshwater and saltwater aquatic species. While most investigators used several common species and standard protocols to assay conventional endpoints, many nontraditional species and toxicological endpoints were also used. This has created a toxicological database of both sufficient depth to compare many similar tests and sufficient breadth to encompass virtually all important types of aquatic habitats and classes of aquatic species.

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Chronic toxicity studies were performed with commercial phthalate esters and Duphniu mugnu (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. mugnu ranged from 0.63 to 34.8 mg/L. For the higher-molecular-weight phthalate esters-dihexyl phthalate (DHP), butyl2-ethylhexyl phthalate (BOP), di-(n-hexyl, n-octyl, n-decyl) phthalate (610P), di-(Zethylhexyl) phthalate (DEHP), diisooctyl phthalate (DIOP), diisononyl phthalate (DINP), di-(heptyl, nonyl, undecyl) phthalate (71 lP), 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 mgiL, 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.