2-methyl-p-phenylenediamine sulfate

Endpoint summary

Additional information

Summary:

PTD is an oxidative dye molecule which reacts during product use. This is e.g. the case during hair coloring processes. Furthermore from hair product formulation manufacturing sites PTD is disposed to waste water treatment plants as a results of washing and cleaning processes of batch container and other technical equipment’s. Our knowledge of PTD oxidation suggests that the reaction of PTD does not lead to loss of the material from toxicity test solutions via volatilization, sorption to containers, or biodegradation. We suspect that PTD is transformed to reactants which remain in the toxicity test. Given the need in REACH to include transformation products in safety evaluations and the need to be conservative in the environmental assessment, it is proposed to base the PNEC on toxicity test endpoints derived from nominal concentrations to best reflect the fact that toxicity is being caused by both PTD and PTD transformation products.  

 

Rational:

During environmental aquatic toxicity studies PTD measured concentrations were are typically significantly below the nominal concentrations. E.g. in one of the aquatic semi-static daphnia study PTD measured concentrations were 55-76% of nominal (renewal at 24 hours). Another aquatic acute tox study with algae the PTD measured concentrations were 9-25% of nominal (no renewal over 72 hours).

 

 Toxicity testing of PTD in the presence of a stabilizer – here ascorbic acid - showed that PTD is less toxic than degradation products which where formed during toxicity tests duration. Fish Embryo testing (FET, OECD draft guideline 236) with PTD in the presence of 0.04% ascorbic acid showed that PTD is not toxic at a concentration of up to 2 mg/L. In the absence of the stabilizer ascorbic acid, PTD has an LC50 less than 1 mg/L in the FET test. 

 

 Biodegradation testing demonstrates slow conversion of PTD to CO2 (17% CO2 in 28 days). Thus, we expect that removal during the aerobic sewage treatment simulation test is a result of PTD primary degradation (i.e., oxidative reaction with itself to form dimers and trimers and reaction with other components of the synthetic sewage feed and the activated sludge). 

 

 Based on the above, we can summarize that PTD is an oxidative dye molecule which reacts during product use. This is e.g. the case during hair coloring processes. Furthermore from hair color product formulation manufacturing site PTD is disposed to waste water treatment plants as a results of washing and cleaning processes of batch container and other technical equipment’s. We know that the reaction of PTD does not lead to significant loss of the material from solution via volatilization, sorption to containers, or biodegradation. We suspect that PTD is transformed to reactants which remain in the toxicity test. Given the need in REACH for us to include transformation products in our safety evaluation and the need to be conservative in the environmental assessment, it is proposed to base the PNEC on toxicity test endpoints derived from nominal concentrationsto best reflect the fact that toxicity is being caused by both PTD and PTD transformation products.