2-phenylpropionaldehyde-dimethyl acetal

Toxicity to aquatic algae and cyanobacteria

Description of key information

For Hydratropic Ald DMA, no data on growth inhibition on aquatic plants is available. The toxicity to aquatic plants is derived from the close structural analogue Phenylacetaldehyde Dimethyl Acetal. The summary of the experimental information is presented first and thereafter the read across rationale.

Hydratropic Ald DMA

For the determination of the 72h-EC50 and 72h-EC10 of Hydratropic Ald DMA, the values derived from Phenylacetaldehyde Dimethyl Acetal (68.7 and 81.3 mg/L, respectively) were corrected for molecular weight and log Kow (Log EC50 target (mmol) = Log EC50 source (mmol) x log Kow source/Log Kow target). The converted 72h-EC50 and 72h-EC10 for Hydratropic Ald DMA were calculated to be 69 and 55 mg/L, respectively.

Phenylacetaldehyde Dimethyl Acetal

In a Freshwater Alga and Cyanobacteria, Growth Inhibition Test performed in accordance with OECD 201 and following GLP, Pseudokirchneriella subcapitata was exposed to the test substance in a 72-hour static test. The definitive test was carried out with five concentrations in a geometrical series with a dilution factor of 2.5: 10.24, 25.6, 64.0, 160 and 400 mg/L including a control. The measured concentrations of the test item at test start (0 h) were between 87 and 115% of the nominal values. The measured concentrations at the end of the test (72 h) were in the range of 82 to 100% of the nominal values. Thus, it is justified that the effect concentrations are based on the nominal concentrations. Inhibition of growth was recorded resulting in a 72h-ErC10 of 68.7 mg/L (95 % CI: 44.9 – 130 mg/L) and a 72h-ErC50 of 81.3 mg/L (95 % CI: 64.6 – 135 mg/L).

Hydratropic Ald DMA (Cas no.: 90-87-9) and its algae toxicity using read acrossfrom Phenylacetaldehyde Dimethyl Acetal (CAS no.: 101-48-4) Introduction and hypothesis for the analogue approach

Hydratropic Ald DMA is an ethylbenzene with a methyl-group attached to the first position of the ethyl-group and two methoxy-groups attached to the second position. For this substance, no data on algae toxicity is available. In accordance with Article 13 of REACH,lacking information can be generated by means of applying alternative methods such as in vitro tests, QSARs, grouping and read-across. For assessing the algae toxicity of Hydratropic Ald DMA, the analogue approach is selected because for a related analogue, reliable algae toxicity data are present, which can be used for read-across.

Hypothesis: Hydratropic Ald DMA has the same algae toxicity as Phenylacetaldehyde Dimethyl Acetal.

Available experimental information: For Hydratropic Ald DMA Daphnia toxicity data is available but not for algae. For the structural analogue Phenylacetaldehyde Dimethyl Acetal an OECDTG201 guideline algae study is available rated reliability Klimisch 1, providing a 72h-ErC50 of 81.3 mg/L and a 72h-ErC10 of 68.7 mg/L.

Target chemical and source chemical(s)

Chemical structures of the target chemical and the source chemicals and relevant information on these substances are shown in the data matrix.

Purity / Impurities

Hydratropic Ald DMA is a mono-constituent with a purity of 98.4% and all impurities are < 1%.

Analogue approach justification

According to Annex XI 1.5 read across can be used to replace testing when the similarity can be based on a common backbone and a common functional group. When using read across the result derived should be applicable for C&L and/or risk assessment and it should be presented with adequate and reliable documentation, which is presented below.

Analogue selection: For Hydratropic Ald DMA the structural close analogue Phenylacetaldehyde Dimethyl Acetal is selected for read across because for this substance algae information was available.

Structural similarities and differences: Hydratropic Ald DMA and Phenylacetaldehyde Dimethyl Acetal have the same backbone and functional groups. They are both ethylbenzenes with two methoxy-groups attached. The difference is an additional methyl group attached to the ethyl-group of Hydratropic Ald DMA. This additional -CH3 fragment increases the log Kow with 0.5 using KowWIN for prediction.

Bioavailability: Hydratropic Ald DMA and Phenylacetaldehyde Dimethyl Acetal have similar bioavailability based on the similarity in chemical structure and physico-chemical properties as presented in the data matrix. In view of the higher log Kow of 0.73 for Hydratropic Ald DMA, the aquatic toxicity values for Phenylacetaldehyde Dimethyl Acetal are converted using molecular weight and log Kow.

Mode of Action (MoA): Both Hydratropic Ald DMA and Phenylacetaldehyde Dimethyl Acetal have a neutral MoA according to ECOSAR and OECD Toolbox.

Other acute aquatic toxicity: For both Hydratropic Ald DMA and Phenylacetaldehyde Dimethyl Acetal, the Daphnia 48h-EC50 exceeds 100 mg/L supporting low toxicity for invertebrates.

Algae toxicity: For Phenylacetaldehyde Dimethyl Acetal, the algae 72h-ErC50 and 72h-ErC10 are 81.3 and 68.7 mg/L, respectively. The conversion of the results based on higher MW and Log Kow and therefore some increase in toxicity is presented in Table 1 below.

Table 1: Aquatic effect values for Hydratropic Ald DMA (Target) based on read across from Phenylacetaldehyde Dimethyl Acetal (Source)

	Source					Target
Species	Effect (mg/l)	MW	mmol/L	Log mmol/l	Log Kow	Log Kow	Log mmol/l	Convert to 10^	MW	Effect (mg/l)
Algae EC50	81.3	166	0.490	-0.31	2.23	3	-0.42	0.383	180	68.9
Algae EC10	68.7	166	0.414	-0.38	2.23	3	-0.52	0.305	180	54.9

Uncertainty of the prediction: For support: ECOSAR presents acute Daphnia and algae toxicity in the same order of magnitude for both substances. There are no other uncertainties than those which have been addressed above.

Data matrix

The relevant information on physico-chemical properties and toxicological characteristics are presented in the data matrix below.

Conclusions for aquatic toxicity

For Hydratropic Ald DMA no data on algae toxicity is available, but for the structural analogue Phenylacetaldehyde Dimethyl Acetal such information is present. When using read across the result derived should be applicable for C&L and/or risk assessment and be presented with adequate and reliable documentation. This documentation is presented in the current document. Phenylacetaldehyde Dimethyl Acetal has a 72h-ErC50 and 72h-ErC10 for algae of 81.3 and 68.7 mg/l, respectively. After conversion using log Kow and molecular weight these values for Hydratropic Ald DMA are 68.9 and 54.9 mg/l, respectively.

Final conclusion on hazard: For Hydratropic Ald DMA the algae toxicity is based on the structural analogue Phenylacetaldehyde Dimethyl Acetal. This results in analgae 72h-ErC50 and 72h-ErC10 of 68.9 and 54.9 mg/l, respectively.

Data matrix: Information onHydratropic Ald DMA and Phenylacetaldehyde Dimethyl Acetalfor assessment of toxicity to algae.

Common names	Hydratropic Ald DMA Target	Phenylacetaldehyde Dimethyl Acetal Source
Chemical structures
Chemical name	2-phenylpropionaldehyde-dimethyl acetal	1,1-dimethoxy-2-phenylethane
CAS no.	90-87-9	101-48-4
EC no.	202-022-8	202-945-6
Empirical formula	C11H16O2	C10H14O2
Molecular weight	180.25	166.22
Phys-Chem
Physical state	Liquid	Liquid
Water solubility (mg/L)	3484 at 24°C	3900 at 20°C
Log Kow (measured)	3 (OECD TG 117)	2.23 (OECD TG 117)
Aquatic toxicity
Algae (72h-ErC50) (mg/l)	68.9	81.3 (OECD 201)
Algae (72h-ErC10) (mg/l)	54.9	68.7 (OECD 201)
Daphnia (48h-EC50) (mg/l)	≥100 (OECD 202)	≥100 (OECD 202)

 

Key value for chemical safety assessment

EC50 for freshwater algae:

69 mg/L

EC10 or NOEC for freshwater algae:

55 mg/L