L-Aspartic acid, N,N'-1,2-ethanediylbis-

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

PNEC aqua (freshwater)

PNEC value:

0.52 mg/L

Assessment factor:

50

Extrapolation method:

assessment factor

Marine water

Hazard assessment conclusion:

PNEC aqua (marine water)

PNEC value:

0.052 mg/L

Assessment factor:

500

Extrapolation method:

assessment factor

STP

Hazard assessment conclusion:

PNEC STP

PNEC value:

16.7 mg/L

Assessment factor:

30

Extrapolation method:

assessment factor

Sediment (freshwater)

Hazard assessment conclusion:

PNEC sediment (freshwater)

PNEC value:

12.3 mg/kg sediment dw

Extrapolation method:

equilibrium partitioning method

Sediment (marine water)

Hazard assessment conclusion:

PNEC sediment (marine water)

PNEC value:

1.23 mg/kg sediment dw

Extrapolation method:

equilibrium partitioning method

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:

PNEC soil

PNEC value:

0.26 mg/kg soil dw

Assessment factor:

100

Extrapolation method:

assessment factor

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

PNEC oral

PNEC value:

54.4 mg/kg food

Assessment factor:

90

Additional information

PNEC aqua (freshwater)

For trisodium EDDS, there are reliable short-and long-term toxicity tests with freshwater fish and invertebrates, and for EDDS acid and its trisodium salt there are reliable algae studies, covering three trophic levels (predators, plant-eating animals, and primary producers). NOECs have been reported for each trophic level.

The most sensitive NOEC (0.125 mg/L) was from the freshwater algae, Chlorella vulgaris, following exposure to trisodium EDDS (Neven and Henderix, 1990). However, for chelating agents, the findings from this test are not considered as measures of direct toxicity to algae, but rather an indirect effect of complexing the trace metals in the medium, resulting in limited availability of essential nutrients (Schowanek et al. 1996). If algal laboratory data are extrapolated to the field in this way an unrealistically low PNEC value will be obtained (Jaworska et al. 1999). According to the EU RARs on EDTA and tetrasodium EDTA, the apparent toxicity of complexing agents to algae in standard tests is related to essential trace metal bioavailability. Trace metal levels tend to be more important in algal growth tests than in other short-term tests (e.g. on fish or daphnia); the main reason is the rapid increase of biomass during the test. In standard tests using uncomplexed agents, the concentrations of free essential metal ions decrease drastically, leading to nutrient deficiency and relatively low effect concentrations. Addition of stoichiometric amounts of nutrients results in detoxification of the agent. Therefore direct effects caused by intrinsic toxicity are not expected in surface waters, where in nearly every case a stoichiometric surplus of metal ions is present (EU 2004a,b). Consequently, it is expected that such toxicity to algae would not be seen in the environment, and therefore this is not a realistic and relevant NOEC to use as the basis for deriving a PNEC aqua (freshwater).

 

Therefore, we turn our attention to plant-eating animals and predators. In this instance, we have good quality and reliable studies for fish and invertebrates. For freshwater zebra fish a 96-h NOEC of 1000 mg/L and a 30-day NOEC of 61 mg/L were identified for trisodium EDDS (Hooftman and van Drongelen-Sevenhuijsen, 1993, 1997). For the freshwater crustacean, Daphnia magna, a 48-h NOEC of 1000 mg/L (Hooftman and van Drongelen-Sevenhuijsen, 1993) and a 21-day NOEC of 32 mg/L (Hooftman and Kauffmanvan Bommel, 1994) were identified for trisodium EDDS. Therefore, the most sensitive species and relevant study appears to be the long-term study on D. magna.

 

In a GLP study (similar to OECD Guideline 211 and EU Method C.20) the 21-d NOEC for trisodium EDDS for effects on reproduction, survival, condition and size of D. magna in freshwater was 32 mg/L (Hooftman and Kauffmanvan Bommel, 1994). As this study was conducted on the trisodium salt of EDDS, a correction for the difference in molecular weights is necessary. Trisodium EDDS has a molecular weight (MW) of 358 and EDDS acid has a MW of 292. Thus, a NOEC of 32 mg/L for trisodium EDDS is equivalent to a NOEC of 26.1 mg/L for the free acid [32 x 292/358 = 26.1 mg/L].

 

An assessment factor (AF) of 10 would usually be sufficient as long-term toxicity results are available from three species across three trophic levels (e.g. fish, Daphnia, and algae), and is considered to be protective of other aquatic freshwater species. However, as we are discounting the algae tests as unrealistic, it is conservative and precautionary to include an AF of 50 as we essentially have long-term results from two species representing two trophic levels (fish and Daphnia).

PNEC_{aqua (freshwater)} = 26.1 mg/L / 50 = 0.52 mg/L

PNEC aqua (saltwater)

For EDDS acid and its simple salts, no relevant data with marine/estuarine predators, plant-eating animals or primary producers were identified. The most relevant study to determine the PNEC aqua (saltwater) is to extrapolate from the well-conducted and reliable D. magna study [described above in more detail] (Hooftman and Kauffmanvan Bommel, 1994), in which a 21-d NOEC of 32 mg trisodium EDDS/L [equivalent to 26.1 mg/L as the free acid] was determined. It is assumed that the greater species diversity in the marine environment, compared to freshwaters, including the presence of a number of taxa that occur only in the marine environment, implies a broader distribution of sensitivities of species and a higher uncertainty in extrapolation. Therefore, REACH technical guidance (Chapter R.10) states that an AF of 100 will be applied when longer-term toxicity results are available from three freshwater or saltwater species (algae, crustaceans and fish) across three trophic levels. However, as we are discounting the algae tests as unrealistic, it is conservative and precautionary to include an AF of 500 as we essentially have long-term results from two species representing two trophic levels (fish and Daphnia).

PNEC_{aqua (saltwater)} = 26.1 mg/L / 500 = 0.052 mg/L

 

PNEC aqua (intermittent releases)

REACH guidance (Chapter R.16) states that “Intermittent releases are defined as occurring infrequently, i.e. less than once per month and for no more than 24 hours”. It is not anticipated that such releases will occur, therefore, a PNEC aqua for intermittent release has not been derived. If, however, such releases do occur in the future, the PNECs derived for continuous exposure (0.52 and 0.052 mg/L, in the freshwater and saltwater compartments, respectively) are considered protective of intermittent releases, and can therefore be used.

PNEC microorganisms (STP; sewage treatment plant)

No activated sludge respiration tests were identified for EDDS acid or its simple salts. However, in a test for biodegradability in sludge, 85% of trisodium EDDS was degraded after 28 days, demonstrating that the test substance did not significantly inhibit the activity of the sludge microflora (Geukens, 1993a). In addition, due to its good biodegradability, adverse effects on the sewage treatment plant are not anticipated (Jaworska et al. 1999).

A 22-h NOEC and EC50 of 0.125 and 0.23 mg/L, respectively, were calculated for EDDS acid in the Microtox test (which measures the ability of a substance to inhibit the metabolic conversion of chemical energy to bioluminescence) in the marine bacterium Vibrio fischeri (Radix et al. 1999). [The bacterium used requires a saline environment, and therefore the results are only of limited relevance for assessing the potential toxicity to microorganisms residing in sewage treatment plants.]

In a test conducted according to OECD Guideline 209, no significant inhibition of the respiration rate was detected in an activated domestic sewage sludge treated with disodium EDTA at up to 500 mg/L ("referred as H4EDTA") after 30 minutes. Equimolar amounts of CaCl2 were added, thus calcium EDTA was formed in the stock solutions. Both the EC10 and NOEC values were concluded to be above 500 mg/L (van Ginkel and Stroo, 2000). The EU RAR (2004a,b) on EDTA and tetrasodium EDTA considers the EC10 of 500 mg/L determined in this study as the most relevant to use for deriving a PNEC STP. Due to their structural similarity, data on EDTA (and its simple salts) are considered relevant to use for understanding the effects of EDDS acid (and its trisodium salt) on the inhibition of microbial respiration rate, and are acceptable for using as read-across information.[No correction for differences in molecular weights is required, as both EDTA and EDDS acid have a MW of 292.]

REACH guidance suggests that an AF of 10 can be applied to the NOEC or EC10 from a respiration inhibition test using mixed bacterial populations. An additional AF of 3 will be included due to the increased uncertainty in using data on a closely-related material (i.e. read-across information).

PNEC_{microorganisms} = 500 mg/L / 30 = 16.7 mg/L

PNEC sediment (freshwater)

There are no studies currently available on the effects of exposure of sediment-dwelling organisms to EDDS acid or its simple salts. Therefore, the PNEC sediment (freshwater) may be provisionally calculated using the equilibrium partitioning method (EPM).

The following formula, which is based on equilibrium partitioning theory, is applied:

 

PNEC_sediment = K_susp-water  x  PNEC_freshwater  x  1000

                        RHO_susp

 

Therefore:

 

PNEC_sediment = 124.7  x  0.52  x  1000 = 56.4 mg/kg of wet sediment

                        1150

Where:

PNEC_aqua(freshwater) [mg EDDS acid/L]

RHO_susp(bulk density of wet suspended matter) [kg/m³] = 1150, using standard environmental characteristics

K_susp-water(partition coefficient suspended matter-water) = [m³/m³]

PNEC_sediment(freshwater) [mg/kg of wet sediment]

 

Where Ksusp-water can be calculated as follows:

 

Kp_susp-water = F_water-susp  +  F_solid-susp  x  Kp_susp  x  RHOsolid = 0.9 + 0.1  x  Kp_surp  x  2500

                                                              1000                                                  1000

 

Where F_water-susp = volume fraction water in susp. matter = 0.9; F_solid-susp =volume fraction solids in susp. matter = 0.1, and RHOsolid = 2500, using standard environmental characteristics.

 

and where for the geometric mean Koc (4.95 x 10³):

 

Kp_susp = Foc_susp  x  Koc = 0.1  x  4.95E3 = 495

 

Where Foc_susp =weight fraction of organic carbon insuspended matter = 0.1, using standard environmental characteristics

 

Therefore:

 

K_susp-water = 0.9 + 0.1  x  495  x  2500 = 124.7

                                       1000

 

As the log Kow for EDDS acid is low (<-1.4 at 23°C) (Gair et al. 2002), uptake via other pathways (ingestion of sediment and indirect contact with sediment) are not considered important exposure routes.

 

It has to be considered that the equilibrium partitioning method may result both in an overestimation or underestimation of the toxicity to benthic organisms. Therefore this method can only be used as rough screening to decide whether sediment toxicity tests with benthic organisms are required.

 

To convert the PNEC_sediment to a dry weight basis from a wet weight basis, 56.4 mg/kg wet sediment is divided by 4.6. This results in a PNEC_sediment  (freshwater) of 12.3 mg/kg dry sediment

 

PNEC sediment (saltwater)

There are no studies currently available on the effects of exposure of sediment-dwelling organisms to EDDS acid or its simple salts. Therefore, the PNEC sediment (saltwater) may be provisionally calculated using the EPM. The following formula, which is based on equilibrium partitioning theory, is applied:

 

PNEC_sediment = K_susp-water  x  PNEC_saltwater  x  1000

                        RHO_susp

 

Therefore:

 

PNEC_sediment = 124.7  x  0.052  x 1000 = 5.64 mg/kg of wet sediment.

                        1150

 

Where:

PNEC_aqua (saltwater) [mg/L]

RHO_susp (bulk density of wet suspended matter) [kg/m³]

K_{susp water} (partition coefficient suspended matter-water) = [m³/m³]

PNEC_sediment (saltwater) [mg/kg of wet sediment]

 

 

Where Ksusp-water can be calculated as follows:

 

K_susp-water = F_water-susp  +  F_solid-susp  x  Kp_susp  x  RHOsolid = 0.9 + 0.1  x  Kp_susp  x  2500

                                                            1000                                                   1000

 

Where for the geometric mean Koc (4.95 x 10³):

 

Kp_susp = Foc_susp  x  Koc = 0.1  x  4.95E3 = 495

 

Therefore:

 

K_susp-water = 0.9 + 0.1  x  495  x  2500 = 124.7

                                        1000

As the log Kow for EDDS acid is low (<-1.4 at 23°C) (Gair et al. 2002), uptake via other pathways (ingestion of sediment and indirect contact with sediment) are not considered important exposure routes.

It has to be considered that the equilibrium partitioning method may result both in an overestimation or underestimation of the toxicity to benthic organisms. Therefore, this method can only be used as rough screening to decide whether sediment toxicity tests with benthic organisms are required.

 

To convert the PNEC_sediment to a dry weight basis from a wet weight basis, 5.64 mg/kg wet sediment is divided by 4.6. This results in a PNEC_sediment (saltwater) of 1.23 mg/kg dry sediment

PNEC soil (terrestrial)

There is a prolonged toxicity test with plants [see note below] and a short-term test with earthworms with trisodium EDDS (covering primary producers and consumers, respectively) and a short-term microorganism toxicity test with EDDS acid (covering decomposers).

In a GLP study conducted according to OECD Guideline 208, the 18-d NOEC values for the growth of Avena sativa (oat), Lactuca sativa (lettuce) and Lycopersicon esculentum (tomato) were 1000, 100 and 320 mg trisodium EDDS/kg of dry soil, respectively. The corresponding 18-d NOECs for their condition (visual appearance) were 1000, 32 and 100 mg/kg of dry soil, respectively, and for their emergence and survival were 1000, 320, 1000 mg/kg of dry soil, respectively (Henzen, 1999b). [Please note: studies conducted according to the updated OECD Guideline 208 are designed to assess the potential effects of substances on seedling emergence and growth. Therefore, it is specific to a part of the plant's life-cycle and does not cover chronic effects or effects on reproduction. However, it is assumed to cover a sensitive stage in the life-cycle of a plant and therefore data obtained from this study can be used to estimate chronic toxicity.]

In a GLP study conducted according to OECD Guideline 207, the 14-d LC50 (survival) of trisodium EDDS to the earthworm, Eisenia fetida, was calculated to be 115 mg/kg dry soil. Further, the 14-d NOEC for survival, appearance, behaviour and weight loss was 32 mg/kg dry soil.

In a study using several endpoints to measure toxicity to soil microorganisms, EDDS acid at 1000 mg/kg dry weight soil for 3 days (considered the study NOEC) did not affect substrate-induced respiration (used as an indicator of potential biomass activity) or the activity of four enzymes (considered important for the breakdown of organic matter), although it did cause a significant inhibition of soil basal respiration (Epelde et al. 2008).

Therefore, the most sensitive species appear to be L. sativa and E. fetida. As the plant study can be used to estimate chronic toxicity, REACH guidance (Chapter R.10) recommends applying a default AF of 100 to the NOEC for one long-term toxicity test (i.e. the 18-d NOEC of 32 mg/kg dry wt soil [equivalent to 26.1 mg EDDS acid/kg dry wt soil] for effects on plant condition).

 

Therefore, 

 

PNEC_soil: 26.1 mg/kg dry wt / 100 = 0.26 mg/kg dry wt

PNEC oral (secondary poisoning; birds/mammals)

No avian toxicity studies on EDDS acid or its simple salts were identified.

 

In a GLP study conducted according to OECD Guideline 408 (available at the time), a 90-day NOAEL of 300 mg/kg bw/day was established for trisodium EDDS based on a reduction in body weight gain and effects on the pancreas seen in rats at 700 mg/kg bw/day and above following repeated dietary administration (Dotti et al. 1995). Using a conversion factor of 20 (for rats over 6 weeks of age) from a NOAEL of 300 mg/kg bw/day corresponds to a NOEC of 6000 mg/kg food [equivalent to 4894 mg/kg food for the acid]. According to REACH guidance, an AF of 90 is appropriate for extrapolation from a 90-day study in mammals, which takes into account both interspecies variation and lab-to-field extrapolation.

 

PNEC_{oral (mammal)}; 4894 mg/kg diet / 90 = 54.4 mg/kg food

 

Atmospheric compartment

No data are available on possible effects of EDDS acid (or its simple salts) on the atmospheric compartment. However, given its low volatility, neither biotic nor abiotic effects (e.g. global warming, ozone depletion/formation, acidification) are considered likely.

Conclusion on classification

According to the available data, EDDS acid would not be classified as dangerous to the environment (according to the EU DSD) or hazardous to the environment (according to the EU CLP). In addition, EDDS acid does not meet the critieria as a PBT or vPvB substance (see CSR for details).