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Environmental fate & pathways

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Additional information

Hydrolysis:

With regard to the chemical structure, o-toluidine is not expected to hydrolyse due to the lack of hydrolysable functional groups.

Phototransformation in air:

In the atmosphere, the substance is degraded by photochemically produced OH radicals. The estimated half-life was 2.915 hours, therefore the substance has no potential for long-range transport.

Biodegradation:

The biodegradability of o-toluidine was tested by 6 different laboratories under the conditions described by the OECD TG 301 A and E. Based on DOC measurement the following results were obtained after 28 days: with the method OECD TG 301 E, five laboratories obtained > 90 % biodegradation, the other one reported a 67 % value. The results obtained with the method OECD TG 301 A showed biodegradation between 88 and 90 % after 28 days.

Additionally according to the national Japanese standard method comparable to the OECD TG 301 C guideline an aerobic ready test was performed. After a period of 28 days 65.4 % biodegradation was observed.

Results on the inherent biodegradability of o-toluidine are also available.

The chosen test design was comparable to the Zahn-Wellens-Test (OECD TG 302 B). Based on COD measurement, a removal of 97.7 % within 5 days was obtained.

With adapted activated sludge from an industrial sewage treatment plant a test on inherent biodegradation was conducted. After 11 days (4 days adaptation) 96 % of the initial concentration were removed.

Under anaerobic conditions o-toluidine could not be removed after a period of 10 months in an aquifer slurry. o-Toluidine revealed no biotic transformation, neither under sulfate reducing nor under methanogenic conditions.

In a further test o-toluidine could not be removed after 150 days in a landfill environment under anaerobic conditions. The test was not performed according to current standard methods but indicates that the substance is stable under anaerobic terms.

Bioaccumualtion:

As no data on BCF were available for o-toluidine the structural analogue p-toluidine was considered to assess the potential for bioaccumulation of the substance.

An experimentally determined BCF value for the structural analogue of < 13 indicates a very low bioaccumulation potential.

An experimentally determined logKow of 1.4 for o-toluidine supports this consideration that the substance has a low potential for bioaccumulation. Therefore a potential for secondary poisoning is not expected.

In addition experimental bioconcentration factors (BCF) for o-toluidine indicate no significant potential for bioaccumulation in oysters (Crassostrea gigas) or mussels (Mytilus edulis). The obtained BCF values were 4.2 and 4.6 for mussels and oyster, respectively.

Adsorption /desorption:

The Koc for o-toluidine was predicted using the QSAR calculation of the Estimation Program Interface (EPI) Suite v 4.11. The Koc was estimated to be 47.63 L/kg (logKow method), and 115 L/kg (MCI method).

The coefficient of distribution (Kd) between the sediment extracted from an aquifer was measured. A Kd of 0.013 was observed for o-toluidine, the Koc was calculated to be 87.

These results indicate a low sorption potential of o-toluidine onto the organic phase of soil or sediments according to the criteria of Litz (1990).

However, adsorption of o-toluidine in soil is influenced by ion-ion interactions. The mechanism responsible for adsorption of o-toluidine and other amines was investigated on montmorillonite. The maximum adsorption occurs when the pH is approximately equal to the pKa (4.44 - 4.45) of the protonation reaction.

Volatilisation:

Indicated by a Henry's Law constant of 0.2 Pa m³/mol o-toluidine is slightly volatile from water.