Cyclohex-1,2-ylenediamine

Endpoint summary

Description of key information

Studies on terrestrial toxicity were performed with source substance HMD (CAS No. 124-09-4) and found to be applicable to the target substance (see read-across report in IUCLID section 13).

With regard to results on earthworms (OECD 222; GLP; RL1; 2017), the most sensitive endpoint was reproduction:

EC10 (56 d, earthworm reproduction) = 176.1 mg test item/kg soil (dw) (95% Confidence limits (CL) = 151.0 – 202.3 mg test item/kg soil (dw).

With regard to nitrogen tranformation by soil organisms (OECD 216; GLP; RL1; 2017), HMD had no adverse effects on N-transformation in lucerne amended soil during 28 days at test item concentrations of up to and including 1000 mg/kg soil dry weight. ICx (28 d; nitrogen transformation) > 1000 mg/kg soil dry weight.

Additional information

The calculated PNEC aquatic for the submission substance DCH is 1.3 mg/L, using an assessment factor of 10 based on the fact that chronic toxicity results are available for two trophic levels, and combined with the fact that acute toxicity data for fish demonstrated that this trophic level is clearly the least sensitive by far more than a factor of 10 in relation to the ErC50 determined from algae (being representative for acute exposure, as no acute toxicity tests on aquatic invertebrates is available for DCH). Due to the short cyclic carbon chain length of DCH, any surface-active properties can safely be excluded, and the octanol-water partition coefficient is very low (below 1). Because there is no potential for bioaccumulation, secondary poisoning needs not to be assessed. Aliphatic amines are readily protonated at environmental pH and due to their positive charge are prone to bind to negatively charged solid matter. According to the available adsorption-desorption study (OECD 106; RL1) on read across source substance 1,6-hexane diamine (HMD), there is relevant binding to soil and sediment. In spite of this adsorptive behaviour, DCH was shown to be readily biodegradable fulfilling the 10-day window requirement with total nitrification within 28 days (measured nitrate concentration approximately equalled the theoretical one). From these properties, rapid degradation in sewage treatment plants or the environment is expected which would lead to overall low environmental concentrations. In addition, due to adsorption on suspended matter or soil, bioavailable concentrations in the aquatic phase are expected to be low. Due to the observed rapid mineralization, accumulation in soil or sediment is not anticipated. This is confirmed by the study on nitrogen-transformation of read-across source substance HMD by soil organisms (OECD 216; RL 1): independently from the substance concentration (between 62.5 and 1000 mg/kg soil dry weight), consistently between 50% and 64% of the substance borne nitrogen was transformed to nitrate within 28 days, in addition to the nitrate stemming from amending soil with Lucerne meal containing nitrogen. As cleavage of the C-N-bonds is a prerequisite for nitrification and will reduce adsorption and increase bioavailability; and considering in addition ready biodegradability; this allows for concluding on rapid mineralization of DCH within natural soil. Regarding the terrestrial compartment, reliable long-term results from read-across source substance HMD on earthworm (OECD 222; RL 1) and soil microorganisms (OECD 216; RL1) are available. A PNEC_soil was derived from these data in parallel to the EPM-method, as required according to ECHA guidance R.7c, sections R.7.11.5.3 and R.7.11.6.3. From these experimental data (two trophic levels, i.e. detrivors and consumers; AF 50 according to ECHA guidance R.10), a terrestrial PNEC of 3.52 mg/kg soil (dw) results. This value is lower compared to the terrestrial PNEC obtained from EPM (44 mg/kg soil dw after application of additional factor of 10) and is therefore used for environmental risk assessment. As there is no indication of risk from these confirmatory long-term soil toxicity results (PEC/PNEC_exp <1), no further toxicity testing for soil organisms is required (ECHA guidance R.7c).

Regarding the sediment compartment, the PNEC was calculated using the Equilibrium Partitioning Method based on the aquatic PNEC and the experimentally determined adsorption data from read-across source substance HMD. For sediment, a lower adsorption was observed as compared to soil, and following ECHA’s criterion of log Koc > 4 it is concluded that DCH is not strongly adsorbing to sediment. Hence, no additional factor is applied for sediment compartments with regard to the RCR based on PNEC_sediment derived via the equilibrium partition method. As there is no indication of risk from this RCR (PEC/PNEC_EPM <1), no further toxicity testing for sediment organisms is required.