Sodium 3-[(1,5-dihydroxy-2-naphthyl)azo]-4-hydroxybenzenesulphonate

PBT assessment

PBT assessment: overall result

PBT status:

the substance is not PBT / vPvB

Justification:

Persistence Assessment

 

Mordant Black 9 is a dyestuff designed to prove light-, sweat- and wetfastness. It is therefore designedly not readily biodegradable. However, the substance showed hydrolysis at environmentally relevant pH’s ( t_½= 316 days at pH 7, and 155 days at pH 9, at 25°C), indicating the potential for significant removal by hydrolysis. The prediction from The BIOWIN v4.10 model in EPISuite for Biowin4 (Primary Biodegradation Timeframe) is Days-Weeks, therefore the test substance is anticipated to be eliminated from the environment via a mixture of slow biotic and abiotic degradation. Studies on direct phototransformation in water are not available but it is assumed on the basis of chemical structure and nature of use that the substance is not degraded by direct photolysis. It is concluded, therefore, that biotic and abiotic processes would contribute both to the depletion of the substance within the environment. 

As such, the substance is considered a “P” and not “vP” based in this data.

 

Bioaccumulation Assessment

 

Mordant Black 9 has a measured log Kow of -1.4. This value indicates that possible bioaccumulation in the food chain is not anticipated. 

Based on its high water solubility and low partition coefficient, it can be concluded that it is unlikely that Mordant Black 9 could potentially be persistent in the soil/sediment compartment. It will most likely distribute into the water compartment. However, due to the low log Kow the bioavailability of the substance is limited and any substance absorbed it most likely rapidly excreted via the kidneys or feces.

Based on the physico-chemical and environmental data for the substance, it is proposed that the substance does not fulfil the requirement of Annex XIII, Para 1.2 based on evaluation of available data, and cannot be considered a “B” or “vB” based on the available data.

 

Toxicity Assessment

 

The substance did not cause any hazardous effects to any of the trophic levels in the aquatic organisms examined in the acute toxicity studies. All tests were limit tests, with no significant effects noted. The substance is not considered as harmful to aquatic organisms, nor did it demonstrate significant toxicity in any of the mammalian studies conducted on the substance. 

As such, the substance does not fulfil the requirements of Annex XIII, Para 1.3 based on evaluation of available data, and cannot be considered as “T” for the purposes of the assessment.

 

Summary and overall Conclusions on PBT or vPvB Properties

 

The substance is therefore considered to fulfil the criteria for Persistence, but cannot be considered to fulfil the criteria for Toxicity or Bioaccumulation, as specified in REACH Annex XIII. As such, the substance cannot be considered a PBT or vPvB substance, based on the available data.

Likely routes of exposure:

Not applicable