Bis(2-ethylhexyl) phthalate

Short-term toxicity to aquatic invertebrates

Description of key information

From the short-term toxicity studies available it can be concluded that DEHP has no acute effects on invertebrates at concentrations considerably exceeding its water solubility. Therefore, no EC50 can be derived.

Additional information

Lots of data are available for acute toxicity on aquatic invertebrates. However, as discussed in the RAR, 2008, these data are difficult to interpret in terms of possible adverse effects on aquatic invertebrates due to DEHP exposure. Therefore a weight of evidence approach encompassing four studies has been preferred. Since the previous RAR (2008), two new studies became available (Jonsson and Baun, 2003 and Forget-Leray et al., 2005).

Jonsson and Baun (2003) tested the acute toxicity of DEHP (and other phthalic acid esters) on Daphnia magna according to the ISO 6341 standard. Five to eight concentrations were tested (depending on the compound) with a maximum of 0.003 mg/L for DEHP corresponding to the water solubility limit as reported by Staples et al. (1997). Under the test conditions applied, EC10 (48h) and an EC50 (48h) were above 0.003 mg/L estimated by probit analysis. However, the authors mention problems with surface entrapment of daphnids at the highest tested concentrations of some phthalic acid esters including DEHP. Those concentrations causing physical entrapment were excluded from the data set used to calculate EC-values..

As also 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), Brown et al. (1998) performed acute and 21-day reproduction tests with daphnia magna at very high phthalate ester concentrations (1 mg/L nominal, including DEHP) with dispersant (Tween 20). 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 toxicity was observed for DEHP (NOEC (48 h): 1.0 mg/L, EC50 (48 h): > 1.0 mg/L, analytically confirmed). This study shows that even at high concentrations no adverse effects of DEHP on Daphnia magna are observed and effects reported in other studies may be due to physical entrapment caused by surface films of floating test material. .

For the marine environment, Adams et al. (1995) performed a 96 h US EPA test on Mysidposis bahia and a midge (Paratanytarsus parthogenetica) without using solvent and avoiding formation of a surface film. They showed that DEHP induced no adverse effect to both of these organsims at 0.37 mg/L (near the limit of water solubility).

In their recent study, Forget-Leray et al. (2005) studied the 96 hr-acute toxicity of DEHP to the marine copepod Eurytemora affinis under static conditions according to the ISO standard 14669. The 96– hour LC50 was 511 µg/L based on mortality (NOEC 10 d: 109 µg/L). Although according to the ISO standard, as concentrations were obtained with solubiliser (DMSO) and were above water solubility, this data cannot be considered as reliable for assessment or classification but demonstrate, that hazardous effects are not expected at environmentally relevant concentrations (below or slightly above the true water solubility).

These data are supported by studies on Daphnia magna from Buchen et al. (1995) where no effect was observed between 100 and 165 µg/L (measured) and from Springborn Bionomics laboratory (1984) where the NOEC (immobility) was determined at 0.16 mg/L (measured) but with entrapment observed.

In conclusion, following the weight of evidence approach, from previous studies discussed in the RAR (2008) and from the present discussion, no obvious response is observed.

DEHP has shown no genuine toxic effect in concentrations up to and markedly exceeding the water solubility.