6,6-dimethylbicyclo[3.1.1]hept-2-ene-2-propionaldehyde

Short-term toxicity to fish

Description of key information

For Pino Acetald, the 96h-LC50 in fish (Cyprinus carpio) was determined to be 1.5 mg/L, based on read across from Pinyl isobutyr aldehyde.

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Effect concentration:

1.5 mg/L

Additional information

For Pino Acetald no experimental data on acute fish toxicity is available, this information can be retrieved from Pinyl isobutyr aldehyde using read across. First the experimental information of Pinyl isobutyr aldehyde is presented and thereafter the read across justification to use this information for Pino Acetald.

 

Pinyl isobutyr aldehyde

A study was performed to assess the acute toxicity of the substance to fish (Cyprinus carpio). The study was conducted in accordance with OECD TG 203 and GLP. In a semi-static test set-up in air-tight closed vessels (fill volume: 6.2 L), seven fish per concentration were exposed to 5 concentrations of the substance in test water (10, 18, 32, 56 and 100% of a saturated solution prepared at a loading rate of 100 mg/L) and a control. Throughout the test, test solutions were refreshed in intervals of 24 hours. After 3.5 hours all fish in the two highest treatment groups had died. Hypoactive swimming was observed in the test group at 0.76 mg/L after 24 and 48 hours, whereas no abnormalities were observed after 3.5, 72 and 96 hours. In the test group at 1.3 mg/L, incidences of mortality were observed within 24 hours, as well as loss of equilibrium and/or immobility at all other timepoints. Based on mortality the following effect value was determined: 96 -h LC50 = 1.5 mg/L. All results are expressed in terms of mean measured concentrations. Initial measured concentrations in fresh solutions at test start and at t=72 hours were comparable and decreased in used solutions to 52 -78 % of initial during the first refreshment period of 24 hours, and to 49 -54% of initial during the last refreshment period of 24 hours. Therefore, geometric mean measured concentrations were calculated for the first and last time interval, and these values were used to calculate the 0 -96 h (arithmetic) mean measured concentrations.

Pino Acetald (Cas no.: 33885-51-7) and its fish toxicity using read across from Pinyl Isobutyr aldehyde (CAS no.: 33885-52-8)

Introduction and hypothesis for the analogue approach

Pino Acetald is an alpha-Pinene with a propanal chain attached to the methyl group present at the second position. For this substance, no data on fish 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 fish toxicity of Pino Acetald, the analogue approach is selected because for a related analogue, reliable fish toxicity data are present, which can be used for read-across.

Hypothesis: Pino Acetald has the same fish toxicity as Pinyl Isobutyr aldehyde.

Available experimental information: For Pino Acetald Daphnia and algae toxicity data is available but not for fish. For the structural Pino Isobutyr aldehyde an OECD TG 203 guideline fish study is available rated reliability Klimisch 1, providing a 96h-LC50 of 1.5 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

Pino Acetald is a mono-constituent with a purity of 98.4% and all impurities are < 2%.

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 Pino Acetald the structural close analogue Pinyl Isobutyr aldehyde is selected for read across because for this substance fish toxicity information was available.

Structural similarities and differences: Pino Acetald and Pinyl Isobutyr aldehyde have the same backbone and functional groups. They are both alpha-Pinenes with a propanal chain attached. The difference is the addition of two methyl groups to the propanal chain of Pinyl Isobutyr aldehyde. These two additional -CH3 fragment increases the log Kow with 1.0 using KowWIN for prediction.

Bioavailability: Pino Acetald and Pinyl Isobutyr aldehyde have similar bioavailability based on the similarity in chemical structure and physico-chemical properties as presented in the data matrix and based on measured and calculated data (Table 1).

Table 1: Measured aquatic toxicity data and ECOSAR calculated aquatic effect values using ECOSARs’ predicted log Kow (3.76

	Pino Acetald		Pinyl Isobutyr aldehyde
	Measured	ECOSAR calculated using predicted Log Kow	Measured	ECOSAR calculated using predicted Log Kow
Algae 72h-EC50 (mg/L)	4.2	1.858	>0.66	0.594
Algae 72h-EC10 (mg/L)	1.9	0.989	0.37	0.382
Daphnia 48h-EC50 (mg/L)	0.67	0.817	0.51	0.214
Fish 96h-EC50 (mg/L)		1.219	1.5	0.493

From the ECOSAR data and measured data on Pino Acetald and Pinyl Isobutyr aldehyde it can be seen that Daphnia likely is the most sensitive species and read-across for fish toxicity is justified.

In view of the lower log Kow of 1.1 for Pino Acetald, the aquatic toxicity values for Pino Acetald and Pinyl Isobutyr aldehyde should be converted using molecular weight and log Kow (Table 2).

Table 2: The conversion to Pino Acetald from Pinyl Isobutyr aldehyde would result in the following information:

	Pinyl Isobutyr aldehyde					Pino Acetald
Species	Effect (mg/l)	MW	Effect (mmol/L)	Effect (Log mmol/l)	Log Kow	Log Kow	Effect (Log mmol/l)	Effect (mmol/L)	MW	Effect (mg/l)
Algae EC50	0.66	206	0.003	-2.49	5.4	4.3	-1.99	0.010	179	1.85
Algae EC10	0.37	206	0.002	-2.75	5.4	4.3	-2.19	0.007	179	1.17
Daphnia	0.51	206	0.002	-2.61	5.4	4.3	-2.08	0.008	179	1.50
Fish	1.50	206	0.007	-2.14	5.4	4.3	-1.70	0.020	179	3.55

The measured aquatic toxicity values for Pino Acetald (EC10 algae but especially EC50 Daphna) are quite similar (a little higher) compared to the effect levels of Pinyl Isobutyr aldehyde without conversion for Log Kow and MW. This means that when conversion is applied based on MW and log Kow, the predicted values of Pino Acetald for acute Daphnia is underestimated: 1.5 and 0.67 mg/l, respectively (see Table 2). In view of the potential underestimation of the acute fish toxicity for Pino Acetald when conversion would be applied (as was shown for acute Daphnia toxicity), conversion will not be done despite differences in MW and log Kow for Pinyl Isobutyr aldehyde. In view of the acute Daphnia toxicity value for Pino Acetald being almost the same as for Pinyl Isobutyr aldehyde, the fish toxicity of Pino Acetald is considered the same as for Pinyl Isobutyr aldehyde and therefore results in 1.5 mg/l.

Mode of Action (MoA): Both Pino Acetald and Pinyl Isobutyr aldehyde have an acetal MoA according to ECOSAR and OECD Toolbox.

Uncertainty of the prediction: 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 Pino Acetald no data on fish toxicity is available, but for the structural analogue Pinyl Isobutyr aldehyde 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. Pinyl Isobutyr aldehyde has a LC50 for fish of 1.5 mg/l. Conversion using log Kow and molecular weight was not applied to prevent potential underestimation of the fish toxicity.

Final conclusion on hazard: For Pino Acetald fish toxicity is based on the structural analogue Pinyl Isobutyr aldehyde. This results in a fish 96h-LC50 of 1.5 mg/l.

 Data matrix: Information on Pino Acetald and Pinyl Isobutyr aldehyde for assessment of toxicity to fish.

Common names	Pino Acetald Target	Pinyl Isobutyr aldehyde Source
Chemical structures
Chemical name	6,6-dimethylbicyclo[3.1.1]hept-2-ene-2-propionaldehyde	α,α,6,6-tetramethylbicyclo[3.1.1]hept-2-ene-2-propionaldehyde
CAS no.	33885-51-7	33885-52-8
EC no.	251-717-2	251-718-8
Empirical formula	C12H18O	C14H22O
Molecular weight	178.75	206
Phys-Chem
Physical state	Liquid	Liquid
Water solubility (mg/L)	61 at 24°C (OECD 105)	10.8 at 22°C (OECD 105)
Log Kow	4.3 (OECD TG 117)	5.4 (OECD TG 117)
Aquatic toxicity
Algae (72h-ErC50) (mg/l)	4.2 (OECD 201)	>0.66 (OECD 201)
Algae (72h-ErC10) (mg/l)	1.9 (OECD 201)	0.37 (OECD 201)
Daphnia (48h-EC50) (mg/l)	0.67 (OECD 202)	0.51 (OECD 202)
Fish (96h-LC50) (mg/l)	Read-across	1.5 (OECD 203)