Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

Stability

Phototransformation in air:Half-life for reaction with photochemically-produced hydroxyl radicals: estimated to be between 0.175 and 0.262 days.

Half-life for reaction with photochemically-produced ozone: estimated to be 0.057 days.

 

Hydrolysis

Hydrolysis of a structural analogue of the substance, tetrahydromethylphthalic anhydride (MTHPA), has been investigated. The substance was found to hydrolyse rapidly, resulting in formation of the respective di-acid. The calculated half-lives at 20 degree C are, for all three pH values (4, 7 and 9) below 3.5 minutes (about 0.06 hours).

 

Biodegradation

Biodegradation in water - Screening tests

The ready biodegradability of tetrahydromethylphthalic anhydride (MTHPA), of which 3-MTHPA D4 is an isomer, was studied in a Modified MITI Test according to OECD guideline 301 C test methods. The test item was exposed to activated sludge at 24.0 - 26.0 degrees C for 28 days. The oxygen and test material measurements were performed in triplicate. MTHPA changed to the dissociated substance, which was stable under the chosen conditions. Therefore, the substance is considered to be not ready biodegradable.

Biodegradability of the substance itself, 3-MTHPA D4, was calculated using the software BIOWIN v4.10.The results indicate that the substance is not expected to be readily biodegradable.

 

Biodegradation in water and sediment - Simulation tests

In accordance with REACH Regulation 1907/2006/EC (Annex IX - 9.2.1.2 & 9.2.1.4 - column 2) simulation testing on biodegradation in water and sediment does not need to be conducted as direct or indirect exposure of the aquatic and terrestrial compartments for this substance are unlikely. The substance is hydrolysed rapidly in a few minutes to the corresponding dicarboxylic acid. In addition based on the intended uses, exposure of sediments is not likely. A value has been calculated using a Fugacity model according to Mackay, Level III using EPI Suite (v.4.1), see 'Distribution modelling' analysis

 

Biodegradation in soil

In accordance with REACH Regulation 1907/2006/EC (Annex IX - 9.2.1.3 - column 2), simulation testing on biodegradation in soil does not need to be conducted as direct or indirect exposure of the aquatic and terrestrial compartments for this substance are unlikely. The substance is hydrolysed rapidly (in a few minutes) to the corresponding dicarboxylic acid. In addition based on the intended uses, exposure of soil is not likely. A value has been calculated using a Fugacity model according to Mackay, Level III using EPI Suite (v.4.1).

 

Bioacccumulation

Bioaccumulation - aquatic/sediment

The BCF of the substance, 3-MTHPA D4, has been estimated using the hybrid VEGA BCF model v1.2.8 to give a value of 3 L/kg whole body weight. Using another Q(S)AR software, BCFBAF v.3.01, to estimate BCF and BAF of the substance gave values of 6.63 L/kg ww and 6.56 L/kg ww, respectively.

As the substance is rapidly hydrolysed to the corresponding dicarboxylic acids, a Q(S)AR calculation of the BCF of the hydrolysis product of the different isomeric forms of MTHPA was conducted and gave a value of 3.162.

The BCF of 4-cyclohexene-1,2-dicarboxylic acid (CAS No. 88 -98 -2), the hydrolysis product of a similar substance within the cyclic anhydride category (category approach) was experimentally determined to be: <0.2 (conc. 2 mg/L) and <2 (0.2 mg/L). Similarly, the BCF of 4-methylcyclohexane-1,2-dicarboxylic acid. CAS No.57567-84-7, the hydrolysis product of a similar substance within the cyclic anhydrides category (category approach) was experimentally determined to be: <0.2 (conc 0.5 mg/L and <2.4 (conc 0.05 mg/L).

It is therefore concluded that the potential for bioaccumulation of 1,2,3,6-tetrahydro-3-methylphthalic anhydride (3-MTHPA D4) is low.

 

Bioaccumulation - terrestrial

No information is available.

 

Transport and distribution

The adsorption coefficient (Koc) on soil of the substance was calculated using the computer program KOCWIN (v2.00). It is predicted that the substance has a Koc of 10 L/Kg.According to the McCall classification scheme, a Koc of 10 L/Kg means that 1,2,3,6-tetrahydro-3-methylphthalic anhydride would be regarded as very highly mobile (0<Koc<50) in soil.

The Henry's Law constant value of 2.55 Pa-m3/mole indicates that the substance is moderately volatile from surface water.

 

Distribution in environmental compartments has been calculated using a Fugacity model according to Mackay, Level III. Distribution in various environmental compartments is estimated as: Air - 0.187%; Water - 40.6%; Soil - 59.1% and Sediment - 0.0914%. However, the substance is known to be unstable, rapidly hydrolysing to the corresponding di-carboxylic acid in aqueous media and this process is expected to occur in the environment should release occur. As a result the calculated distribution may not be a reasonable estimate. Similar modelling of the degradation product of the substance,3-methylcyclohex-4-ene-1,2-dicarboxylic acid, estimated distribution in the various environmental compartments as: Air - 0.00026%; Water - 19.9%; Soil - 80% and Sediment - 0.119%. Refinement of the modelling, undertaken as part of the CSA, and taking account of the uses of the substance, does not support these estimates.