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PBT assessment

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PBT assessment: overall result

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

By screening and definitive REACH PBT criteria, PPVE is very persistent, “vP”.  An evaluation of its physical/chemical properties including Henry’s law constant (HLC), as well as its fate in water or soil concludes that PPVE is rapidly removed to the atmospheric compartment by volatilization, and will not partition into water or soil from the atmosphere. Therefore, this substance is non-persistent in the aquatic and terrestrial environments. It has a long half-life only in the atmosphere and is subject to long-range atmospheric transport but is not subject to deposition in remote or pristine environments.  Due to mixing in the atmosphere and lack of partitioning out of the atmosphere, concentrations in the biosphere will be negligible. Widespread exposure to PPVE will not occur.

Based on the expected partitioning behavior of PPVE, additional laboratory studies on the biodegradation and bioaccumulation in the water, sediment and soil compartments are not relevant for the evaluation of the PBT properties of this substance. The “B” criterion in aquatic organisms is not met based on the screening level criterion log Kow < 4.5, which is further supported by lack of exposure in the aquatic compartment. The calculated log Koa value indicates that PPVE cannot bioaccumulate in air-breathing animals. Collectively, the log Kow, the HLC, and the calculated Koa indicate that PPVE is not expected to bioaccumulate in aquatic, sediment or soil organisms. PPVE does not fulfill the criteria for bioaccumulative (“B”) or very bioaccumulative (“vB”).

Based on available data, PPVE is not classified as carcinogenic, mutagenic, or toxic to reproduction or specific target organ toxic after repeated dose. PPVE does not meet the REACH “T” criteria for mammalian toxicity. This information combined with the lack of acute aquatic toxicity can be used to conclude that PPVE does not fulfill the screening criteria for toxic (“T”).

The only Impurity identified at > 0.1% is C3F7-O-CHF-CF3 (TFEE-1) at 1.0 – 1.3%. Information on PBT properties of TFEE-1 was obtained using QSAR modeling as well as readacross and included a modeled log Kow of 3.44, (KOWWIN v1.68), a modeled Henry’s Law constant of 9.573E5 Pa-m³/mole (HENRYWIN v3.20), and a log Koa of 1.127 from Koa = Kow(RT) / HLC, all determined in accordance with Section 1.4 of Annex XI.

TFEE-1 is not persistent in the aquatic and terrestrial environments.  As an impurity, its release pattern follows that of PPVE: release is solely to the atmospheric compartment during use.  It is not released to water or soil during use and would partition to the atmosphere if it were released to the aquatic or terrestrial compartments.   TFEE-1 is not expected to be readily biodegradable, nor does it undergo rapid hydrolysis or photolysis. The primary fate is degradation in the lower atmosphere by reaction with hydroxyl radicals although the process is projected to be slow (atmospheric lifetime, >67 years.  It is rapidly removed from water and soil by volatilization, and it will not partition into water or soil from the atmosphere due to a high modeled Henry’s Law constant. Because this low volume impurity has a long environmental half-life in the atmosphere, will not partition out of the atmosphere, and will be mixed thoroughly in the atmosphere, concentrations in the biosphere will be negligible and thus widespread exposure to TFEE-1 will not occur.

The modeled log Kow, modeled Henry’s Law constant , and calculated log Koa , coupled with no known mechanisms of non-lipid bioconcentration, show that TFEE-1 does not meet does not meet the criteria for bioaccumulative (“B”) or very bioaccumulative (“vB”). Toxicity was determined using a read across approach from the analogous substance HFE-7200 (C4F9OC2H5).  HFE-7200 and TFEE-1 are of similar size (MW TFEE-1 = 286, MW HFE-7200 = 264) and functionality (both highly fluorinated ethers), with similar hydrophobicity (Log Kow = 3.44 for TFEE-1 and 4.34 for HFE-7200) with similar partitioning behavior. By read across, TFEE-1 is not expected to be toxic to aquatic organisms. Based on available data, TFEE-1 is not classified as CMR, and does not show specific target organ toxicity after repeated dosing. TFEE-1 does not meet the REACH “T” criteria for mammalian toxicity. This information combined with the acute aquatic toxicity data can be used to conclude that TFEE-1 does not fulfill the screening criteria for toxic (“T”).

The ultimate degradation products of PPVE are expected to be hydrofluoric acid (HF), perfluoropropionic acid (PFPA) and carbon dioxide.  HF and CO2 are inorganic substances not needing a PBT assessment.  The stable degradation product PFPA showed no biodegradation (< 3%) but was not inhibitory in the toxicity control.  PFPA is not expected to undergo rapid hydrolysis or photolysis and is thus expected to be persistent/very persistent in water, soil and sediment. The log Kow of PFPA ranged from (–1.31) to (–1.33), as calculated using ACD/Labs v12.00. In a 2002 internal GLP-compliant bioconcentration study with Cyprinus carpio, following Japanese methods, PFPA was found to not bioconcentrate.  The BCF at 0.01 mg/L exposure was calculated to be ≤ 4.8 and the BCF at 1.0 mg/L exposure was calculated to be 1.2.  The study was deemed reliable without restrictions. Based on three toxicokinetic studies with a PFPA salt, the rat serum half-life following oral exposure is less than 24 hours, with the serum half-life following intravenous exposure of slightly longer than 24 hours.  Elimination is faster in females than males.  Based on the half-life data from these studies and its log Kow, PFPA does not fulfill the criteria for bioaccumulative (“B”) or very bioaccumulative (“vB”).

Eight acute aquatic toxicity studies were completed for PFPA.   Two studies were with freshwater fish, one with Daphnia magna and five with various species of algae and duckweed.  The lowest measured ErC50 was 10.4 mg/L with the green algae Pseudokirchneriella subcapitata.  The lowest NOEC was 3.47 for the same species.  This algal species was found to be the most sensitive over all other algal, plant and aquatic organism species evaluated. PFPA administered via inhalation for 2 hours to rats (Klimisch 3) resulted in a 4 hour equivalent LC50 value of greater than 11 mg/L.  Administering PFPA to rats for 28 days via oral gavage resulted in a No Observed Adverse Effect Level (NOAEL) of 320 mg/kg/day (the highest dose tested).  PFPA was negative in an Ames assay and in a chromosome aberration test in the presence and absence of metabolic activation. Based on available data, PFPA is not classified as CMR, and does not show specific target organ toxicity after repeated dosing. PFPA does not meet the REACH “T” criteria for mammalian toxicity. This information combined with the acute aquatic toxicity data can be used to conclude that PFPA does not fulfill the screening criteria for toxic (“T”).

The data show that the properties of the substance PPVE, its sole relevant contaminant TFEE-1, and its degradation product PFPA, do NOT meet the specific criteria in Annex XIII Section 1, or while not allowing a direct comparison with all the criteria, nevertheless indicate that each substance would not have these properties. Substance is NOT PBT or vPvB.