Potassium carbamoylcarbamate

PBT assessment

PBT assessment: overall result

PBT status:

the substance is not PBT / vPvB

Justification:

Sufficient data are available to assess whether potassium allophonate is persistent (P), bioaccumulative (B), or toxic (T) per the criteria established in ECHA (2012).

A closed bottle ready biodegradability test performed according to Organisation for Economic Co-operation and Development (OECD) Testing Guideline 301D and in accordance with Good Laboratory Practice (GLP) requirements is available for potassium allophonate (ABC Laboratories, Inc., 2013). This study showed the allophonate reached > 60% biodegradation (as measured by biochemical oxygen demand [BOD] as a percentage of theoretical oxygen demand [ThOD]), while meeting the 10-day window criterion. The degradation kinetic on days 7, 14, 21, and 28 was 9.5, 46.7, 78.8, and 72.1%, respectively. The threshold freshwater criterion for persistence under REACH is a half life > 40 days; therefore, since 78.8% degradation was achieved by day 21, potassium allophonate is not persistent per the REACH criteria.

Bioaccumulation testing in aquatic/benthic species is not required for substances with a low potential for bioaccumulation. In a partition coefficient study performed according to OECD Testing Guideline 117 and in accordance with GLP requirements, an experimentally determined log octanol-water partition coefficient (log Pow) ≤ -1.08 was reported (ABC Laboratories, Inc., 2012). In addition, given a lack of any lipophilic moieties in the chemical structure, the entire structure of potassium allophonate is hydrophilic and thus it has a low potential to cross biological membranes. A low potential for bioaccumulation is supported using Quantitative Structure Activity Relationship (QSAR) estimates; BCFBAF Program v3.01, found in EPIWIN v4.10, predicts a bioconcentration factor (BCF) of 3.162 L/kg tissue (wet weight), indicating that bioaccumulation is not expected for allophanic acid (non-ionic form of allophonate) (US EPA, 2013). The threshold criterion for bioaccumulation under REACH is a BCF > 2000 L/kg; therefore, potassium allophonate is not bioaccumulative per the REACH criterion.

The toxicity component of the PBT evaluation consists of three individual criteria: 1) chronic no observed effect concentration (NOEC) < 0.01 mg/L for marine or freshwater organisms; or 2) carcinogenic (Category 1 or 2), Mutagenic (Category 1 or 2), or Toxic to Reproduction (Category 1, 2 or 3) (CMR); or 3) displays endocrine disrupting effects.

Chronic ecotoxicological testing data for aquatic species are not available for potassium allophonate, as the substance hydrolysed to urea at environmental pH of 7.3 with an estimated half life of 3 hours (Cheng et al., 2005). Urea is then further hydrolysed to ammonia and carbon dioxide by urease, an extracellular enzyme that originates from microorganisms and plant roots (NLM, 2013; OECD SIDS, 2013; U.S. EPA, 2011). Neither potassium allophonate nor its hydrolysis product, urea have been assigned harmonized classifications (or proposed classifications in this registration dossier) for carcinogenicity (categories 1 or 2), mutagenicity (categories 1 or 2), or toxicity to reproduction (categories 1, 2 or 3). No long-term studies with potassium allophonate are available from which to gather data on possible interaction with the endocrine system. Further, urea is a natural product of endogenous metabolism.

As potassium allophonate does not meet any of the individual criteria for toxicity as specified in ECHA Guidance on information requirements and chemical safety assessment, Chapter R.11: PBT Assessment. Version 1.1, it is not considered toxic per the REACH criteria

The available information indicates that potassium allophonate does not meet any of the individual criteria for persistence, bioaccumulation, or toxicity per the REACH criteria; therefore a very persistent/very bioaccumulative (vP/vB) assessment was not carried out.

References:

ABC Laboratories, Inc. 2012a. Potassium Allophonate: Determination of n-Octanol/Water Partition Coefficient by High Performance Liquid Chromatography (HPLC). Testing laboratory: ABC Laboratories, Inc., 7200 E. ABC Lane, Columbia, MO 65202. Owner company: Kerr Fire Fighting Chemicals, Ashcroft Rd., Knowsley Industrial Park, Kirby, Liverpool L33 7TS, England. Company study no.: 68014. Report date: 2011-05-14.

ABC Laboratories, Inc. 2013. Potassium Allophonate: Determination of the Ready Biodegradability Using the Closed Bottle Test Method. Testing laboratory: ABC Laboratories, Inc., 7200 E. ABC Lane, Columbia, MO 65202. Owner company: Kerr Fire Fighting Chemicals, Ashcroft Rd., Knowsley Industrial Park, Kirby, Liverpool L33 7TS, England. Company study no.: 68015. Report date: 2013-01-09.

Cheng, G., Shapir, N., Sadowsky, M. J. and Wackett, L. P. 2005. Allophonate hydrolase, not urease, functions in bacterial cyanuric acid metabolism. Applied and Environmental Microbiology, 71(8): 4437-45.

European Chemicals Agency (ECHA). 2012. Guidance on information requirements and chemical safety assessment. Chapter R.11: PBT Assessment. Version 1.1. November 2012.

United States Environmental Protection Agency (U.S. EPA). 2013. Estimation Programs Interface Suite™ for Microsoft® Windows, v 4.10. United States Environmental Protection Agency, Washington DC, USA.

Likely routes of exposure:

The likely routes of exposure for both ecological and human receptors to potassium allophonate can be determined from the usage scenario of the product containing this substance and available physicochemical and environmental fate and transport data.

The relevant environmental compartments to consider or exposure of ecological rectors are: air, freshwater, freshwater sediment, marine water, marine sediment and soil. Potassium allophonate is anionic at environmental pH and has a high capacity for hydrogen bonding; therefore, volatilisation from soil and surface water is not expected and exposure of potassium allophonate to air is not anticipated.

Negligible volatility, high water solubility and a logPow of < -1.08 all indicate that potassium allophonate will partition to the aquatic compartment. As demonstrated in Cheng et al. (2005) and discussed in the read-across strategy document attached to this Chemical Safety Report (CSR), allophonate rapidly hydrolyzes to urea at environmentally-relevant pH with a half life of 3 hours. Therefore, aquatic receptors in freshwater and marine water are unlikely to be exposed to potassium allophonate for any meaningful exposure duration.

No experimental data are available for potassium allophonate; however, a Quantitative Structure Activity Relationship (QSAR) was used to estimate organic carbon normalised adsorption coefficient (Koc) of 0.3533 L/kg (US EPA, 2013). This estimate indicates that allophonate has a low potential for adsorption to organic carbon. When also considering that potassium allophonate has an experimentally-determined octanol-water partition coefficient (log Kow) of ca. -1.08 and a readily biodegradable test result in an Organisation for Economic Co-operation and Development (OECD) Test Guideline 301D study, potassium allophonate has a low potential for adsorption. Therefore, exposure of sediment-dwelling freshwater or marine organisms to potassium allophonate is not anticipated.

Exposure of soil-dwelling organisms through oral ingestion of soil and dermal exposure is possible should potassium allophonate be released to this environmental compartment.

Given the usage scenario of potassium allophonate as an ingredient in fire extinguishers, the primary route of exposure for human receptors is the dermal route of exposure. Secondary exposure by ingestion is also possible. Inhalational exposure is also possible, however unlikely, during the time the product is airborne (i.e., after being emitted from the extinguisher but before reaching the intended surface). Allophonate will be contained within foam matrix which further reduced the possibility of inhalational exposure.

References:

Cheng, G., Shapir, N., Sadowsky, M. J. and Wackett, L. P. 2005. Allophonate hydrolase, not urease, functions in bacterial cyanuric acid metabolism. Applied and Environmental Microbiology, 71(8): 4437-45.

United States Environmental Protection Agency (US EPA). 2013. Estimation Programs Interface Suite™ for Microsoft® Windows, v 4.10. United States Environmental Protection Agency, Washington DC, USA.