Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

Some abiotic degradation of aldehydes in aqueous solution is expected but no hydrolysis study was performed as the substance was found to be readily biodgradable and is rather insoluble (1.6 mg/L in pure water). Photodegradation in water and hydrolysis have both been observed in preparatory work performed prior to undertaking an algae study (see 6.1.5) however half-lives in water cannot be accurately quantified from this data for use in risk assessment. It should be noted that a photolysis study is not a required endpoint under REACH.

Two valid ready biodegradability studies are available on the biodegradability of the substance. One achieved >60% biodegradation but failed the 10 day window, using a modified Sturm test under closed conditions to prevent loss due to volatility. In a second study following OECD Guideline 301F, the test substance was almost completely mineralised (97% ) within 28 days meeting the 10 day window criterion.

Due to the log Kow of 5.3, the substance meets the criterion for potential B however, A BCF test for fish requires stable testing conditions with accurate analytical measurement of test substance concentrations in water and fish tissue over a significant period of time (weeks).This substance has a relatively low water solubility (1.6 mg/L in pure water and is expected to be lower in test medium). At this stage there are still significant technical problems associated with determining the water solubility limit in test media. The test substance is known to photodegrade rapidly and to hydrolyse in water. It is known to biodegrade rapidly and is expected to be metabolised rapidly in fish tissues. Moreover, it is expected to adsorb to the test system. All these elements contribute to the technical unfeasibility of this study following OECD BCF guidelines. Currently, other methods which could be used to determine a Bioconcentration factor for fish do not have regulatory acceptance.

A valid study was performed to estimate the adsorption coefficient (Koc) of the substance by HPLC using method C19 and the OECD Guideline 121. The substance was determined to have a log Koc value of 4.2 (equivalent Koc=15800).

Due to its rather low volatility (0.068 Pa at 20°C) and its rather low water solubility, the substance is expected to partition to the sediment compartment, but due to its ready biodegrability its half-life in sediment is expected to be low.

It should be noted that the substance disappeared fairly rapidly in the sediment compartment (almost complete loss within 28 days) during the sediment toxicity study with removal at lower concentrations faster than those at higher ones. No HCA was observed in the pelagic compartment at all during the sediment study which also confirms the highly adsorptive nature expected in sediment and rapid degradability of the substance in both water and sediment.