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PBT assessment

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PBT assessment: overall result

PBT status:
the substance is not PBT / vPvB
Justification:

Assessment of PBT/vPvB Properties

Persistence Assessment

 

In recent GLP studies with only minor deviations from OECD Guideline 301 D, both a C14 chlorinated paraffin (45% chlorination) and a C14-17 chlorinated paraffin (45.6% chlorination) were rapidly biodegraded (64 and 51% degradation over 28 days, respectively) in closed bottle tests (van Ginkel, 2010a,b). These results are indicative of easy and ultimate degradation and, according to REACH guidance Chapter 11, these C14-17 paraffins with a lower degree of chlorination do not meet the Annex XIII persistence criterion. In another GLP study, also with only minor deviations from OECD Guideline 301 D, a 63.2% chlorinated C14-17 paraffin was not readily biodegradable (5% degradation after 28 days), although slow degradation continued throughout the monitoring period (10% after 60 days) (van Ginkel, 2010c).  Two additional OECD Guideline 301 D studies (van Ginkel 2014a,b) of a C15 chlorinated paraffin (51% chlorination by weigh) found that the test material degraded up to 63% by day 60 in an extended study. The study authors concluded that the test material is inherently biodegradable and not classifiable as persistent.

 

The view that MCCPs with a greater % chlorination are less rapidly biodegraded (i.e. more persistent) is further supported by experimental results from tests not specified in the screening criteria for persistence under the REACH guidelines (see “Summary and discussion of degradation”, section 4.1.3 above). In one study, measuring 25-day biochemical oxygen demand (using non-acclimated microorganisms), the extent of degradation of four C14-17 chlorinated paraffins decreased with increasing chlorination, with 15, 10, 5 and 0% degradation for the 40, 45, 52 and 58% chlorinated materials, respectively (Madeley and Birtley, 1980).

 

In addition, biodegradation was observed for two representative chlorinated paraffins with a low and high level of chlorination, respectively, in a simulation test in water and sediment. The half-life of a 35% chlorinated C16 paraffin in sediment from a freshwater lake (containing oligochaete worms) was 12 days, whereas a 69% chlorinated C16 paraffin had a half-life of 58 days (Fisk et al. 1998). Neither of these values fulfil the persistence criterion according to Annex XIII (i.e. T1/2> 120 days in fresh- or estuarine sediment). 

 

Persistence - Conclusion

It is not possible to develop a single conclusion on persistence for MCCP. Some MCCP products, less than 50% Cl (by wt.) have been determined to be readily biodegradable, and thus not persistence. More chlorinated MCCP test materia do biodegrade but at a slower rate and may be persistent and/or forming persistence metabolites. Identification of specific metabolites has not yet been possible, but they are likely forms of chlorinated fatty acids which ECOSAR predicts are less toxic. Environmental monitoring data do not suggest that levels of MCCP are increasing in the environment and several studies in areas with environmental regulation have shown descreasing levels.

 

Bioaccumulation Assessment

 

There are a hierarchy of bioaccumulation data on MCCP, including octanol-water partition coefficient (KOW), bioconcentration factor (BCF), bioaccumulation factor (BAF), biomagnification factor (BMF), and trophic magnification factor (TMF) metrics. Whilst screening bioaccumulation data on MCCP such as KOWand BCF studies indicate a potential concern for bioaccumulation, higher tier data based on MCCP in the environment such limited potential for MCCP to bioaccumulate. See full review under the bioaccumulation section of the dossier.

A review of bioaccumulation potential by Thompson and Vaughan (2014) cites laboratory-derived BMFs ranging from 0.1 to 0.96 (with a mean of 0.38) for juvenile rainbow trout fed diets containing one of four C14 chlorinated paraffins (ranging from 42 to 55% chlorination) or two C16 chlorinated paraffins (34 and 69% chlorination). No clear relationship between BMF and chain length or chlorination level was seen. These values do not fulfill the bioaccumulation criteria (i.e. BMF > 1). Based on field data, Thompson and Vaughan (2014) concluded that there is no convincing evidence for BMFs of > 1 for C14, C15 and C16 chlorinated paraffins (and the mean of the three) derived between trout and three species of potential prey fish caught in Lake Ontario and Lake Michigan (from North America). These values are lipid-normalised, which is the normalisation generally employed for field data.

A subsequent assessment of the BMF and trophic magnification factor (TMF) data for MCCP was conducted by Arnot (2014). This review included 97 measured data points in the assessment, of which 90 (92.8%) were lower than the threshold criterion of a BMF of 1. The median BMF value (central tendency) is 0.27; well below the biomagnifying criterion. In addition, this assessment of MCCP shows that all of the TMFs for the MCCP constituents are < 1. The SETAC POP/PBT expert workshop experts considered that a TMF >1 represented the most conclusive evidence of the bioaccumulative nature of a chemical (Gobas et al., 2009), as such these data indicate that MCCP is not bioaccumulative.

Bioaccumulation - Conclusion

Overall, the available data on MCCPs are indicative of BCF values below 2000 L/kg and BMF values below 1.0. The only exception is a test with a C14 alkane (45% chlorinated) which suggested a BCF value above the criterion. However, this MCCP component has been shown to be not persistent (see above). More significantly, measured BMF and TMF data, which are more representative than BCF for assessing the bioaccumulation potential of MCCP, indicate thatMCCP constituents are not magnifying in the environment (BMF <1 and TMF < 1).

 

Toxicity assessment

 

Daphnia magna appears to be the most sensitive aquatic species to the toxic effects of MCCPs. In a reliable test, conducted according to OECD Guideline 202, a long-term NOEC of 0.01 mg/L has been reported for a C14-17 chlorinated paraffin (52% chlorinated). This value lies right on the cut-off for, but does not meet, the toxicity criterion (NOECless than0.01 mg/L) under Annex XIII. However, there is also a valid short-term EC50 in Daphnia magna for the same substance of 0.0059 mg/L. Taken together, these results are considered to meet the criterion for toxicity (e.g. EC50 and NOEC < 0.01 mg/L) under Annex XIII.

 

Toxicity - Conclusion

MCCPs fulfill the toxicity criterion.

 

PBT/vPvB criteria and justification

 

MCCPs fulfill the toxicity criterion.

 

Currently available information shows that components constituting a significant fraction of MCCPs are readily biodegradable and are not persistent. There seems to be a relationship between the rate of biodegradation and the level of chlorination of linear alkanes; the components with lower degrees of chlorination are biodegraded more quickly.

 

The available data on MCCPs are indicative of BCF values below 2000 L/kg and BMF values below 1.0. The only exception is a test with a C14 alkane (45% chlorinated) which suggested a BCF value above the criterion. However, this MCCP component has been shown to be not persistent (see above). More significantly, measured BMF and TMF data, which are more representative than BCF for assessing the bioaccumulation potential of MCCP, indicate thatMCCP constituents are not magnifying in the environment (BMF <1 and TMF < 1).Overall, it is concluded that MCCPs do not qualify as bioaccumulating or persistent.

 

Overall, based on available test results, it should be concluded that MCCPs do not fulfill the PBT or the vPvB criteria.