Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

Phototransformation in air

The stability of METH in the atmosphere was calculated using the software AOPWIN (v1.92). It is predicted that the substance will be degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals, with a half-life ranged from 4.24 and 6.52 hours.

The overall degradation rate constant with OH radicals is estimated ranged from 5.11E-6 to 7.84E-6 cm3/(molecule-day).

The stability of METHAc in the atmosphere was calculated using the software AOPWIN (v1.92). It is predicted that the substance will be degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals, with a half-life ranged from 4.10 to 6.19 hours.

The overall degradation rate constant with OH radicals is estimated ranged from 5.37E-6 to 8.11E-6 cm3/(molecule-day).

In the presence of moisture, 1,2,3,6-tetrahydromethyl-3,6-methanophthalic anhydride (5-METH, 4-METH) rapidly hydrolyse to methylbicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid (5-METHAc, 4-METHAc) and this entity is therefore more relevant to various environmental compartments than the submission substance.

 

Hydrolysis

The substance was highly unstable in water with a half-life in the order of minutes. Instability increased as temperature and pH increased.

Biodegradation

An experimental ready biodegradation test was conducted according to OECD TG 301C. The substance was exposed to activated sludge at 24.0 - 26.0 degree C for 28 days. No biodegradation occurred within this time period as indicated by both indirect and direct analyses. The substance is considered not to be biodegradable.

However the screening test inherent to the water biodegradability of the degradation product, calculated using the same software BIOWIN v4.10,indicate that the corresponding acids (4 -METHAc, 3 -METHAc) are expected to be readily biodegradable.

 

Bioaccumulation

The BCF was estimated using accepted calculation methods.

EPA BCFBAF v.3.01 gives a value of 3.16 L/Kg ww for the corresponding hydrolysis product,methylbicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid (METHAc).

These are in line with experimental data which resulted in a range 3.9 - 5.5

It is therefore concluded that the potential for bioaccumulation of 1,2,3,6-tetrahydromethyl-3,6-methanophthalic anhydride (METH) is low.

Adsorption / desorption

The adsorption coefficients on soil of the registered substance (Koc,n: METH) and the corresponding acid (Koc,i: METHAc) were calculated according to the EPA model KOCWIN (v2.00).

It was verified, using the Log Kow method, that Koc,i < Koc,n.

According to the McCall classification scheme, both the anhydride and acid forms are very highly mobile (0 < Koc < 50) on soil.

The higher value of the anhydride form, Koc= 25.5 L/Kg, was selected with conservative approach for the environmental assessment.

Henry's Law constant

The Henry's Law constants were estimated using the software HENRYWIN (v3.20).

The HLCs of methylbicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid (METHAc) in its identified isomeric forms, as hydrolysis products of 1,2,3,6-tetrahydromethyl-3,6-methanophthalic anhydride, were considered for the environmental assessment.

The value of 5.6E-07 Pa m³/mol, as a mean of estimated values, indicates that METHAc is essentially non volatile from surface water.

Distribution modelling

Distribution modelling

Distribution in environmental compartments has been calculated using a Fugacity model, under the emission scenario of 1000 kg/h into each of air, water and soil compartments, according to Mackay, Level III.

The distribution of 5-methylbicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid (5-METHAc) was estimated as: Air= 0.0%; Water= 34.6%; Soil= 65.4% and Sediment= 0.06%.

The distribution of 1-methylbicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid (4-METHAc) was estimated as: Air= 0.0%; Water= 34.5%; Soil= 65.5% and Sediment= 0.06%.

The soil, and less water, were then found to be the major target compartments.