3-(p-methoxyphenyl)-2-methylpropionaldehyde

Endpoint summary

Description of key information

Abiotic degradation:

Air:

No experimental data on the phototransformation of the substance in air are available. Based on estimation with the QSAR model AopWin (v1.92), in air the substance undergoes rapid degradation after reaction with hydroxyl radicals. The DT50-values after reaction with hydroxyl radicals are 7.164 hours. This indicates that the substance is not a long-range transported chemical in air according to the UNECE criteria (http://www.unece.org/fileadmin/DAM/env/documents/2000/ece/eb/ece%20eb%20air.60.e.pdf). This half-live will not be used for the CSA because these are calculated and not experimental values.

Water:

The hydrolysis test for this substance is not needed because of its ready biodegradability. The substance is expected to be hydrolytically stable because it does not contain hydrolysable groups such as ester, carbamates, epoxides, halomethanes, acylhalides (see Hydrowin, EpiSuite for all hydrolysable groups).  The half-life at 25 °C is > 1 year.

Biotic degradation:

The biodegradation potential of the substance in water was determined in a screening study according to OECD TG 301F (Manometric Respirometry) and in compliance with GLP criteria. In this study 30 mg/L test substance was inoculated with activated sludge from a municipal wastewater treatment plant for 30 days under aerobic conditions in the dark. During the incubation period the biological oxygen demand (BOD) was measured and biodegradation expressed as percentage of the theoretical uptake (ThOD). After the 28-day incubation period 81% of the substance was biodegraded. The 10-day window criterion was met. Based on these findings, the test substance is classified as readily biodegradable.

Bioaccumulation:

The BCFs for aquatic and terrestrial organisms were calculated using QSARs of Veith et al. (1979) and Jager (1998), both incorporated in the EUSES model, and yielded values of 18 and 3.23 L/kg ww, respectively.

Transport and distribution:

The adsorption/desorption test does not need to be conducted as based on the physico-chemical properties, the substance can be expected to have a low potential for adsorption (log Kow is 2.3). Therefore, the organic carbon-water partitioning coefficient (Koc) was calculated from the log Kow using the equation from EUSES (non-hydrophobics QSAR, because the log Kow < 3). The calculated Koc value is 164 L/kg (log Koc = 2.21). This Koc-value indicates that the substance has a low potential to adsorb to sediment/soil.

The Henry's law constant is calculated using the equation from EUSES. Using a molecular weight of 178.23 g/mol, and the experimentally determined vapour pressure of 0.30 Pa (at 24 °C) and water solubility of 1085.7 mg/L (at 24 °C) the Henry's law constant at environmental temperature (12 °C) is calculated to be 0.0249 Pa·m³/mol.

Based on Level III environmental distribution modelling using EPISUITE (assuming equal and continuous releases to air, water and soil) using the CAS number 5462-06-6 and the measured physicochemical parameters (water solubility = 1085.7 mg/L, vapour pressure = 0.0024 mg Hg and log Kow = 2.3) as input, it is estimated that the majority of the substance released to the environment will partition mainly into soil (68.1%) and water (31.4%) with minor amounts to air (0.392%) and sediment (0.116%).

The SimpleTreat model, which is incorporated in EUSES, simulates the distribution of the substance in a Sewage Treatment Plant (STP). Model calculations show that 86% of the substance will be degraded and that 12.5%, 1.52% and 0.00992% will partition to water, sewage sludge and air, respectively.