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Long-term toxicity to aquatic invertebrates

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Description of key information

From no effects at low and even at higher concentrations far above water solubility it may be deduced with high confidence that DEHP will not exert any toxicity to invertebrates in water ecosystems. Thus, no meaningful NOEC or EC10 could be derived.

Key value for chemical safety assessment

Additional information

As raised in the RAR, 2008, the toxicity to aquatic invertebrates exposed via water in terms of specifying a NOEC-value for use in the risk assessment is bound up with problems. Most of the studies were performed at concentrations much higher than the water solubility of DEHP which have no relevance in the environment. In these studies some effects observed on Daphnia may be caused by physical effects (entrapments). Therefore these studies are considered as not reliable for assessment.

Today, updating and analysing the literature, the study from Knowles et al. 1987, appeared to be the most relevant from all studies available.

Authors reported a 21-day D. magna reproduction test in a flow through system. Survival and reproduction was not affected in this test at measured concentrations up to 0.158 mg/l (NOEC). LOEC were identified at 0.811 mg/l, (based on survival and mean number of young per surviving adult, which were reduced after both, 7 and 21 days). Floaters were observed and were evidence of test concentrations above water solubility. They appeared, however feeding and healthy. The lowest concentration where the number of floaters significantly differed from the control was 0.158 mg/l at day 0. By day 21, floaters were observed only at 0.811 mg/l. Even if carried out above highest soluble concentration, the associated issues have been taken into account and reproduction endpoint shows clearly no impact even at high concentrations. Therefore this study has been selected as the key study.

This study is supported by two studies from Brown et al. The study from 1982 determined a NOEC-21d (reproduction and mortality) of 0.1mg/L (with acetone as solubilizer). As other studies (e.g. Rhodes et al., 1995) pointed to the possibility that surface effects (surface films observed at higher concentrations above water solubility) may be crucial for observed effects (entrapment of daphnids) also in reproduction studies, in the more recent study from Brown et al. (1998) a 21-day reproduction tests with daphnia magna was performed at very high phthalate ester concentrations (1 mg/L nominal, including DEHP) with dispersant (Tween 20 and Marlowet R40, separate studies). Thus, test items were kept in solution and surface tension in the test vessels was reduced, avoiding entrapment of daphnids by surface films. Indeed, with this test setup, no significant effects on survival and reproduction within 21 days were observed at the concentration of 1.0 mg/L (NOEC 21 d, reproduction and survival, analytically confirmed). Both studies confirm that even at high concentrations no adverse effects of DEHP on Daphnia magna survival and reproduction are observed and effects reported in other studies may be due to physical entrapment caused by surface films of floating test material.

Finally the most recent study, Forget-Leray et al. (2005) examines 28 -days chronic toxicity of DEHP in marine environment. Authors exposed Eurytemora affinis under semi static conditions at the level of the NOEC (10d) concentration of 109 µg/L previously determined in an acute test. Under the test conditions of the chronic test, larval development of the nauplii was inhibited after 12 days at 109 µg/L (LOEC). In consequence, after 12 days the larvae did not reach the copepodid stage and subsequently died. Thus, the concentration tested was too high to determine a NOEC for marine invertebrates (NOEC (28d) << 109 µg/L) and hence cannot be used for risk assessment. As the tested concentration was far above water solubility (DMSO was used as solubilizer) and thus physicochemical effects cannot be excluded, it is difficult to draw firm conclusions from this study.

As conclusion, considering all available data no adverse effects could be reliably attributed to DEHP. Determined NOEC values were determined at concentrations high above the true water solubility of DEHP and are at least in part unbounded (no effects observed at highest concentration). At high concentrations of DEHP colloidal dispersions in water are formed as a first step and at even higher concentrations, surface layers may develop. Data point to a reduced bioavailability even for colloidal DEHP (EU-RAR, 2008). Very high concentrations of DEHP could exert their effects by nonspecific means, e.g. reduced oxygen concentration in the water or reduced oxygen transfer to organisms due to precipitation at the gill surface. Thus, extrapolation from available NOEC for PNEC derivation would yield no reasonable result. Rather, from no effects at low and even at high concentrations far above water solubility it may be deduced with high confidence that DEHP will not exert any toxicity to invertebrates in water ecosystems.