1,4-dioxacyclohexadecane-5,16-dione

Toxicity to soil macroorganisms except arthropods

Description of key information

Zenolide earthworm NOEC is >445 mg/kg soil dw based on read across from Habanolide, which was tested in an OECD TG 222. The values were converted for molecular weight and log Kow

Key value for chemical safety assessment

Long-term EC10, LC10 or NOEC for soil macroorganisms:

445 mg/kg soil dw

Additional information

The read across to Zenolide is presented in the Terrestrial toxicity Overall Endpoint summary. The executive summary of the Habanolide long-earthworm study is presented below.

Habanolide earthworm toxicity

The effect of the test item on mortality, biomass and the reproductive potential of the earthworm species Eisenia fetida (Savigny) were determined according to OECD TG 222 (2004). The study was conducted under static conditions over 8 weeks with five different application rates of 62.5, 125, 250, 500, and 1000 mg test item/kg soil dry weight, which were mixed into artificial soil containing 5% peat. After two days of mixing the test substance with artificial soil and additionally one day of equilibration of treated soil, sexually mature earthworms were inserted into 8 control as well as solvent control replicates and into 4 replicates per test item concentration (10 earthworms per replicate). The earthworms had an individual body weight ranging between 0.30 and 0.53 g at test initiation. The measured concentration of the test item in the pooled soil samples (1000 mg test item/kg soil dry weight) at test start was 54.4 %, indicating a distinct loss of the test item caused by the application procedure. Under the conditions of this study, the test item did not induce mortality nor pathological symptoms of adult earthworms after an exposure of 28 days in all tested concentrations. As there were no statistical differences concerning the reduction of body weight and reproduction rate determined between the control and the solvent control, the controls were pooled for statistical evaluation. Compared to the pooled control, there were no statistically significant differences in earthworm body weights observed. After further four weeks the reproduction rate (average number of Juveniles) was 189 in the pooled control and ranged between 187 and 206 in the treatment rates. Compared to the pooled control, there were no statistically significant differences in the level of earthworm reproduction in all test item concentrations. Overall, the 56d-NOEC of the test item concerning mortality, biomass and reproduction of earthworms was determined to be 544 mg test item/kg soil dry weight. All validity criteria recommended by the test guideline were fulfilled.

Zenolide(CAS #54982-83-1) and its terrestrial toxicity using read across from Habanolide (CAS #111879-80-2)

Introduction and hypothesis for the analogue approach

Zenolide is a cyclic aliphatic double ester. According to ECHA Guidance Chapter R.7c (2017) Table R.7.11-2, substances with a log Kow <5 and being ready biodegradable, but with aquatic EC/LC50 values <1 mg/L are considered to be Hazard Category 2. In that case a short-term soil toxicity test has to be performed. For Zenolide, which is considered to be Hazard Category 2, no experimental terrestrial toxicity information is available. In accordance with Article 13 of REACH,lacking information can be generated by means of applying alternative methods such as QSARs, grouping and read-across. For assessing the terrestrial toxicity of Zenolide, the analogue approach is selected because for one closely related analogue, reliable soil toxicity information is available.

Hypothesis: Zenolide’s terrestrial EC10/NOEC values can be derived from Habanolide after conversion using molecular weight and log Kow.

Available experimental information: For Habanolide, long-term terrestrial toxicity information is available for earthworms (OECD TG 222, GLP), which is considered to be Klimisch 1.

Target chemical and source chemical(s)

The information on Zenolide and Habanolide supporting the read across are presented in the Data matrix.

Purity and impurities

Zenolide is a mono-constituent with a high purity> 95% and therefore the impurities are not expected to influence the results.

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.

Structural similarities and differences: Zenolide and Habanolide are both cyclic aliphatic esters. They have a similar backbone and a similar functional group. The difference between these two structures is that Zenolide has a double ester while Habanolide has a single ester. In addition, the cyclic-alkyl chain of Habanolide has one unsaturated bond which is not present in Zenolide. The structural similarities fatty acid chain combined with an ester indicate a somewhat similar behaviour in sludge and soil of Zenolide and Habanolide.

Bioavailability: The physico-chemical properties of Zenolide of both substances indicate some differences. Zenolide has a lower log Kow and a higher water solubility. The log Koc of the two substances differ less. Zenolide will be somewhat more present in the pore water and Habanolide more in the soil particles. In view of the earthworms exposed to pore water and eating soil particles this difference may not be critical for assessing the soil toxicity for these worms.

Mode of action (MoA): Zenolide and Habanolide have both an ester as functional group and therefore the MoA will be the same. The difference in log Kow values and the anticipated difference in earthworm toxicity between Zenolide and Habanolide: 3.65 and 5.45, respectively. Conversion to Zenolide from Habanolide: The slightly lower toxicity of Zenolide compared to Habanolide based on the lower log Kow are accounted for when deriving the terrestrial toxicity values using the following equation: (Log NOEC/EC10 target (mmol) = Log NOEC/EC10 source (mmol) x log Kow source/Log Kow target).

Uncertainty of the prediction: There are no remaining uncertainties other than those presented above.

Data matrix

The relevant information on physico-chemical properties and toxicological characteristics are presented.

Conclusions for terrestrial toxicity

For Zenolide no terrestrial toxicity information is available, but for the related analogue Habanolide a long-term earthworm study is available and read across can be applied. When using read across information, the result derived should be applicable for risk assessment and it should be presented with adequate and reliable documentation. This documentation is presented here. For Habanolide, the long-term terrestrial toxicity to earthworm NOEC is >544 mg/kg soil dw. For Zenolide these NOEC is converted using molecular weight and log Kow differences.

Final conclusion: Zenolide has a NOEC value of >445 mg/kg dw for earthworms.

 

Data matrix supporting the Zenolide terrestrial toxicity information using read across from Habanolide

Common names	Zenolide	Habanolide
	Target	Source
Chemical structures
CAS no	54982-83-1	111879-80-2 34902-57-3
EC no	259-423-6	422-320-3
Registration information	Yes	Yes
Empirical formula	C14H24O4	C15H26O2
Molecular weight	256	238
Physico-chemical data
Physical state	Liquid	Liquid
Water solubility (mg/l)	75	0.95
Log Kow	3.65	5.45
Fate
Log Koc	3.3	4.65
Terrestrial toxicity
Earthworm (NOEC) mg/kg soil dw	>445 (RA from Habanolide after conversion*)	>544 (OECD TG 222)

*Conversion is necessary in view of the difference in log Kow exceeding 0.5 (3.65 and 5.45, for Zenolide and Habanolide, respectively).