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Sediment toxicity

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Reference
Endpoint:
sediment toxicity: long-term
Data waiving:
exposure considerations
Justification for data waiving:
other:
Justification for type of information:
JUSTIFICATION FOR DATA WAIVING
In accordance column 2 of REACH Annex X, long-term testing to sediment organisms (required in section 9.5.1) does not need to be conducted as the hazard assessment performed during the chemical safety assessment concludes that the substance is classified for the highest environmental hazard - for both acute and chronic environmental toxicity (category 1). Hence, the performance of additional environmental toxicity tests will not impact on the hazard classification, or resultant risk management measures (which will already be very stringent), and will therefore not provide any additional benefit regarding the safe use of this chemical.
Indeed, the available data are adequate for classification and labelling purposes and for PBT assessment.
Furthermore, direct exposure of sediment will not occur from the use of MOTE and indirect exposure will be low. The assessment performed in chapter 9 of the CSR confirms this low indirect environmental exposure and an acceptable risk to aquatic organisms is demonstrated with the use of relevant risk mitigation measures. In addition in environmental monitoring data, environmental levels of octyl tins were demonstrated to be extremely low. Therefore in accordance with Annex XI of the Regulation EC 1907/2006 the study is not necessary.

Description of key information

In accordance column 2 of REACH Annex X, long-term testing to sediment organisms (required in section 9.5.1) does not need to be conducted as the hazard assessment performed during the chemical safety assessment concludes that the substance is classified for the highest environmental hazard - for both acute and chronic environmental toxicity (category 1). Hence, the performance of additional environmental toxicity tests will not impact on the hazard classification, or resultant risk management measures (which will already be very stringent), and will therefore not provide any additional benefit regarding the safe use of this chemical.

Indeed, the available data are adequate for classification and labelling purposes and for PBT assessment.

Furthermore, direct exposure of sediment will not occur from the use of MOTE and indirect exposure will be low. The assessment performed in chapter 9 of the CSR confirms this low indirect environmental exposure and an acceptable risk to aquatic organisms is demonstrated with the use of relevant risk mitigation measures. In addition in environmental monitoring data, environmental levels of octyl tins were demonstrated to be extremely low. Therefore in accordance with Annex XI of the Regulation EC 1907/2006 the study is not necessary.

Key value for chemical safety assessment

Additional information

MOT(EHTG) is always manufactured as a mixture with DOT(EHTG). The MOT(EHTG):DOT(EHTG) mixture is added to polyvinyl chloride (PVC) and chlorinated polyvinyl chloride (CPVC) as a heat stabilizer intended to preserve the polymeric structure and properties of the resins during the final stages of fabrication into finished articles. After being blended into the PVC and CPVC resin, the stabilizers remain there throughout the subsequent processing steps.

All systems are designed and maintained to ensure that moisture is kept away from the resin compound, since the presence of water creates significant problems during processing. Therefore, losses to water during blending and melt processing are very low, as these are designed to be “dry” processes. Furthermore, water is not used on a regular basis to clean equipment, wash out vessels, etc., and no wastewater is generated. Compounded PVC and CPVC material is solid and any spillage is cleaned up by vacuum or sweeping. Once the PVC or CPVC is melt processed into a final part, most of the mono-octyltin chemicals are strongly held within the resin and are highly resistant to leaching although some leaching of monooctyltin compounds may occur from some PVC products .

During melt processing of PVC and CPVC, there is the possibility that mono-octyltins (and other ligands unspecified) can be released into the atmosphere. Measurements by Nowak (2003 cited in RPA 2002, updated 2003) of MOT released during a PVC calendering operation show the values to be 0.003% of the MOT processed being released (RPA 2002, updated 2003).

Several studies have been done to examine environmental levels of mono-octyltins and their fate. Regarding environmental fate, most PVC and CPVC articles will either be recycled or landfilled at end of life.

Some research shows that approximately 80% of organotins detected in untreated wastewater are associated with suspended solids and are removed from wastewater primarily by sedimentation and adsorption into sewage sludge (Fent 1996).

Landfill leachate may directly enter the environment. Mersiowsky et al. (2001) and Mersiowsky and Ejlertsson (1999) found that the concentration of organotins in leachate samples from sanitary landfills were found to be in the low micrograms per liter range. In addition, it is expected that most leachate would be treated at on-site water treatment facilities or released into a municipal sewer. If landfill leachate should directly enter the environment, there would be dilution of the leachate resulting in lowered environmental concentrations than were measured in the leachate.

Octyltins were detected in some sediments in rivers in southwest France that were sampled in 2001, but they were seen less frequently and generally at low concentrations (0-5 ng Sn/L). MOT was found in about half of the sediment samples at concentrations of about 1 μg MOT/kg (Bancon-Montigny et al. 2004 as cited in RPA 2005.