N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine

Short-term toxicity to aquatic invertebrates

Description of key information

The acute toxicity of p-hydroquinone, the most sensitive hydrolysis product of 77PD, to Daphnia magna was investigated in a static test according to ISO 6341 part 15. After 48 hours of exposure an EC50 of 0.13 mg/L (nominal) was determined.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

0.13 mg/L

Additional information

Short-term tests with daphnids

have been performed with 77PD as well as with other similar PPDs yielding EC50-values in the range of 0.2 to 1.7 mg/L. The result of a study performed with 4-HDPA (0.69 mg/L) is within this range.

77PD is hydrolytically unstable at pH 7 and

p-hydroquinone CAS 123 -31 -9 was identified as the most sensitive (secondary) hydrolysis product.

The lowest effect value in acute tests was found for p-hydroquinone (0.13 mg/L) which is close to the values for the PPDs (0.2 to 1.9 mg/L) and 4-HDPA (0.69 mg/L).Although p-hydroquinone is a secondary hydrolysis product of 77PD, it was chosen as a source of key value as it shows the lowest effect concentrations of all PPDs and their degradation products and therefore represents the worst case.

For 4-HDPA and 1,4 -dimethylpentylamino-p-phenol calculated values are available. These calculated values should only be used only for a rough estimation due to the high uncertainty of the method. However they show a trend: The effect values of these intermediate compounds to daphnids are at a higher level and there is no sign for a higher toxicity than found for the PPDs or any of their degradation products. Note: 4 -HDPA is not a hydrolysis product of 77PD but was used for assessment as it is considered to be similar to

1,4 -dimethylpentylamino-p-phenol.

Short-term tests with daphnids to tyre wear particles (TWP)

TWPs are produced containing antioxidants like 77PD in a concentration of about 1%.

The acute toxicities of TWP eluates and sediment elutriates to D. magna were determined in 48-h static testing according to OECD Test No. 202. In this study was evaluated the toxicity of such particles using sediment, the likely reservoir of tire wear particles assessed in Daphnia magna using a sediment elutriate (100, 500, 1000 or 10000 mg/l TWP) in comparison to a standard eluate. Under standard test temperature conditions, no concentration response was observed and EC 50 values were greater than 10,000 mg/L. Additional tests using D. magna were performed both with eluate and with sediment elutriates collected under heated conditions designed to promote the release of chemicals from the rubber matrix to understand what environmental factors may influence the toxicity of TWP. Toxicity was only observed for elutriates generated from TWP leached under high-temperature conditions and the lowest EC 50 value was 5,000 mg/L.