Bis(2-ethylhexyl) phthalate

Bioaccumulation: aquatic / sediment

Key value for chemical safety assessment

BCF (aquatic species):

614 dimensionless

Additional information

Aquatic bioaccumulation

As reported in the previous EU Risk Assessment Report 2008, most available studies are based on total radioactivity measurements and no distinction is made between parent compound and metabolites. Therefore such data are not reliable for assessment as they will overestimate the DEHP concentrations. No new study is available since the RAR.

Bioaccumulation into fish:

3 studies followed DEHP and its main metabolites separately into organisms and will be used in the present assessment. Mayer and Sanders (1973) exposed Fathead minnows to DEHP during 56 days followed by a depuration phase of more than 28 days to follow the elimination in freshwater. The radioactivity was analysed for DEHP and residues. Authors calculated a BCF of 1380 with a plateau after 28d of exposure. Depuration reached 50% of the accumulated DEHP after 7 days in non spiked freshwater. However, in a later study by Mehrle and Mayer (1976) adult fathead minnows were exposed to DEHP for 56 days at 25°C in a flow-through system, followed by a depuration phase of 28 days. Test concentrations of DEHP were 1.9, 2.5, 4.6, 8.1, 14, 30 and 62μg/l (mean measured). Only the three lower concentrations were considered as relevant as they were around the limit of water solubility of DEHP. At these concentrations the BCF values based on 14C-DEHP were between 582 and 614 and between 737 and 891 when based on total 14C which is much less than in the earlier study of Mayer and Sander (1973). Besides, at the lowest three test concentrations (1.9, 2.5 and 4.6μg/l), BCF values were also calculated using a computer program BIOFAC (U. S. EPA, 1982), resulting in a mean BCF of 842±105 based on total 14C. In conclusion BCF values from Mehrle and Mayer (1976) are regarded to be of higher validity compared to results from the earlier work, especially as different exposure concentrations were tested and metabolites analysed.

As a result from the latter study, the highest BCF for fish based on DEHP alone (not on total radioactivity) is 614.This BCF-value of 614 will be used in the further assessment of DEHP. Would MEHP be included for calculation of BCF-values, these would be between 670 and 827 for the relevant concentration range of DEHP (1.9, 2.5 and 4.6μg/l). As however MEHP is of much higher polarity and not persistent, deviating from EU-RAR for DEHP (2008) this is not included for derivation of the relevant BCF for CSA of DEHP.

In addition, Mackintosh et al. (2004) investigated the distribution of phthalate esters in a marine aquatic food web in order to study their potential for biomagnification. Eighteen species (pelagic and benthic) representing approximately 4 trophic levels assigned both a trophic position model and stable nitrogen isotope analysis were sampled between June and September at three different locations in False creek, Vancouver. Food-web magnification factors (FWMFs) were determined as the antilog of the slope of the log-linear regression between substance concentration and trophic level or "delta"15N (increasing proportion of stable nitrogen isotop with trophic level position). It has been shown that for the high molecular weight phthalates the lipid equivalent concentrations significantly declined with increasing trophic position. The FWMF for DEHP was 0.32 (0.14-0.17, 95% CI) based on delta15N and 0.34 (0.18-0.64, 95% CI) based on trophic position indicating that DEHP does not biomagnify in the aquatic food web studied, rather it undergoes trophic dilution.

These results support the previous BCF values determined in studies on fathead minnows.

Bioaccumulation into invertebrates:

None of the available studies on invetebrates (Chironomus sp., Gammarus sp., Hexagenia sp., Hasellus sp., Daphnia sp. or Mytilus sp....) are clearly reliable for assessment with exposure concentrations much higher than water solubility of DEHP and all on total radioactivity instead of DEHP only.

From all these studies the BCF (even if overestimated) varies from around 2700 in Gammarus and 2500 in Mytilus species (Sanders et al., 1973; Perez et al. 1983) to below 250 in Daphnids or lower with BCF of 14 in the snowbug (Sanders et al., 1973).

On the other hand, from the reliable study on biomagnification in a natural marine ecosystem with measurement of DEHP in 4 trophic levels including various invertebtrates (Mackintosh, 2004), the highest concentration in DEHP occured in green macroalgea and plankton showing that the lipid equivalent concentration of the high molecular phthalate esters including DEHP, significantly declined with increasing trophic position and stable nitrogen isotope in the food web (p<0.05). In fact, with biomagnification factors of 0.32 and 0.34 according to stable nitrogen isotope and trophic position level, DEHP do not biomagnify in the aquatic marine food web studied. It thus indicates a trophic dilution.

Gobas et al. (2003) explored the bioaccumulation behaviour of DEHP and other phthalic acid esters on basis of available literature on laboratory studies, food web biomagnification field studies and the results of bioaccumulation modelling studies. They thus demonstrated that the low bioavailability of DEHP prevents its bioaccumulation into organisms and its biomagnification in food-webs including invertebrates. According to this the assumption of the previous RAR (2008) that DEHP in colloidal form and DEHP adsorbed to particles would be more easily available for filter feeders to assess specific scenarios for bioaccumulation in invertebrates may be an overestimation.

In conclusion, while high BCF-values were determined for mussel (Mytilus edulis) and amphibod (Gammarus), these are deemed not to be relevant: Firstly, actual BCF values may be considerably lower, as these values were based on total radioactivity likely leading to an overestimation as discussed in EU-RAR (2008). In addition, the RAR also states that the elimination half-life for Gammarus was very short (less than 4 days). Secondly, trophic dilution is clearly evident from the studies outlined above and is in line with conclusions drawn within EU-RAR on DEHP. Thus, for CSA and PBT assessment it is scientifically well justified to use the BCF derived from the reliable fish study performed byMehrle and Mayer (1976).

Value used for CSA and PBT-assessment:BCF: 614 dimensionless (L/kg ww or dimensionless)