Reaction mass of divinylbenzene and ethylstyrene

PBT assessment

PBT assessment: overall result

PBT status:

the substance is not PBT / vPvB

Justification:

Persistence assessment:

The components of DVB/EVB reaction mass substances are not susceptible to hydrolysis, and other modes of degradation such as direct photolytic degradation are also unimportant. Biodegradation would be expected to be the dominant process affecting fate and lifetime of the substances in the environment. However,little or no biodegradation of the substances, tested as their reaction mass mixtures, has been observed in the OECD screening tests of ready biodegradability. Other alkyl- and alkene-substituted benzenes have been shown to be ultimately biodegradable, and their catabolic pathways have been elucidated.  Therefore, the components of the DVB/EVB reaction mass are not expected to persist indefinitely in the environment. A simulation test in water/sediment concluded that primary degradation of radiolabelled 1,3 EVB and 1,4 DVB to more polar 14C degradation products occurred in the surface water and surface water/sediment mixtures with half-lives ranging from 3.8 to 31.4 days over the test concentration range of 50 to 1500 µg/L. These half-life values are well below the persistence criteria of 40 days and greater for a P/vP classification. Therefore, the DVB/EVB reaction mass substances are not regarded as “P/vP”.

Bioaccumulation assessment:

The log octanol-water partition coefficient (log Kow) of the main constituents of the DVB/EBV reaction mass substances are well below 4.5, and measured fish BCF values for a representative reaction mass substance (57.0% of DVB; 37% EVB) were <453 L/kg wet wt. The bioconcentration potential (bioconcentration factor, BCF) of the four major constituents in divinylbenzene (DVB-55) have been assessed using a quantitative structure-activity relationship (QSAR) model (BCF baseline model v.02.06) as described by Dimitrov et al (2005) and implemented in OASIS CATALOGIC v 5.11.12. Constituents of DVB-55 are not bioaccumulative with high confidence, as BCF values range from 219 and 302 L/kg. Based on this evidence, the DVB/EVB reaction mass can be reliably regarded as having low potential to bioaccumulate.

Toxicity assessment:

Acute toxicity tests for fish, daphnids, and aquatic algae were conducted for various representative reaction mass mixtures of DVB/EVB. An assessment of the inherent toxicity of the compound was based on the selected key studies for fish, daphnids, and algae; where the lowest selected acute E/LC50 values for fish, invertebrates, and algae are 1.28, 1.14, and 1.73 mg/L, respectively. The available chronic aquatic toxicity tests indicated NOEC values of 0.353 and 0.81 mg/L for invertebrate reproduction and algal biomass production, respectively.  The freshwater invertebrate, Daphnia magna, was apparently the most sensitive species tested for acute effects, and chronic effects for this same species have been evaluated as well. Therefore, a robust assessment of aquatic toxicity potential is available for the DVB/EVB reaction mass substances. 

The DVB/EVB reaction mass substances are classified as Reproductive Toxin GHS Category 2, based on the findings in the OECD 422 study of Shibuya et al. (1998). On this sole basis, the DVB/EVB reaction mass substances must be regarded as “T” within the context of PBT assessment for REACH.

Likely routes of exposure:

The available evidence on degradation, bioaccumulation potential, and toxicity for the DVB/EVB reaction mass substances indicate that the screening criteria for persistence (P) are not met, and the screening and definitive criteria for B/vB are not met. While neither the screening nor definitive criteria for aquatic toxicity are met, the Annex XIII criteria for mammalian toxicity (T) are met. Based on the information described below for the relevant endpoints, the components of the DVB/EVB reaction mass are considered as not PBT and not vPvB.

Summary conclusion on PBT or vPvB properties

Constituent	P/vP	B/vB	T
Divinylbenzene (o-, m-, and p- isomers) EC no.: 215-325-5 The concentration of these isomeric components in the various DVB/EVB reaction mass products can range from approximately > 55.0 to < 81.0 % wt.	Primary degradation of [14C]1,3 EVB and [14C]1,4 DVB to more polar [14C]degradation products occurred in surface water and surface water/sediment mixtures with half-lives ranging from 3.8 to 31.4 days over the test concentration range of 50 to 1500 µg/L. (Wildlife, 2013). Conclusion:The criteria for P/vP are not met based on Annex XIII.	Measured log Kow (HPLC method) for the DVB-HP and DVB-55 products indicate a log Kow of approximately 3.8 for all components. Supporting studies for m- and p- isomers of DVB indicate log Kow of 4.15 and 4.18, respectively. Screening criterial for B/vB are not met.  Measured fish BCF for the DVB-55 reaction product ranged from 206 – 453 L/kg wet wt. Therefore, the definitive criteria for B/vB under REACh Annex XIII are also not met.    Conclusion: not B, not vB based on screening and Annex XIII criteria.	Acute aquatic texting of DVB/EVB reaction products indicate E/LC50 values well above the screening criterion of 0.1 mg/L.  Available chronic aquatic toxicity tests indicate NOEC values well above the Annex XIII criterion of 0.01 mg/L. The DVB-HP, - 63, and -55 products are classified as toxic for reproduction, Cat. 3 (R63) underDirective 67/548/EEC. Therefore, the DVB/EVB reaction mass meets Annex XIII criteria for “T”.   Conclusion: T, based on Annex XIII criteria.
Ethylstyrene (o-, m-, and p- isomers) EC no.: 248-846-1 The concentration of these isomeric components in the various DVB/EVB reaction mass products can range from approximately > 19.0 to < 45.0 % wt.	Primary degradation of [14C]1,3 EVB and [14C]1,4 DVB to more polar [14C]degradation products occurred in surface water and surface water/sediment mixtures with half-lives ranging from 3.8 to 31.4 days over the test concentration range of 50 to 1500 µg/L. (Wildlife, 2013). Conclusion:The criteria for P/vP are not met based on Annex XIII.	Measured log Kow (HPLC method) for the DVB-HP and DVB-55 products indicate a log Kow of approximately 3.8 for all components. Supporting studies for m- and p- isomers of DVB indicate log Kow of 4.15 and 4.18, respectively. Screening criterial for B/vB are not met.  Measured fish BCF for the DVB-55 reaction product ranged from 206 – 453 L/kg wet wt. Therefore, the definitive criteria for B/vB under REACh Annex XIII are also not met.    Conclusion: not B, not vB based on screening and Annex XIII criteria.	Acute aquatic texting of DVB/EVB reaction products indicate E/LC50 values well above the screening criterion of 0.1 mg/L.  Available chronic aquatic toxicity tests indicate NOEC values well above the Annex XIII criterion of 0.01 mg/L. The DVB-HP, - 63, and -55 products are classified as toxic for reproduction, Cat. 3 (R63) underDirective 67/548/EEC. Therefore, the DVB/EVB reaction mass meets Annex XIII criteria for “T”.   Conclusion: T, based on Annex XIII criteria.