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

Endpoint summary

Additional information

Summary of ecotox data for the PPDs (parent compounds)

An overview over the relevant ecotoxicological key data for the PPDs is given in the following table.

Table: Results of all available ecotoxicity tests, except those with reliability 3 (references are explained in the IUCLID dossier and in the CSR)

 

	6PPD	7PPD	77PD	44PD
short-term toxicity to fish	96h-LC50 0.028 mg/L,                         MITI 1999 96h LC50 0.29 mg/L, (MITI 2001) 96h LC0 5 mg/L (Bayer 1984)	96h LC50=0.3 mg/L, Monsanto 1983 96h LC50=0.42 mg/L, Monsanto 1983 96h LC50=0.4 mg/L, Monsanto 1981	96h-LC50 0.06 mg/L, Monsanto 1981 96h-LC50 0.14 mg/L (Monsanto 1981)	0.24 mg/L (Monsanto 1981)   96h-LC50 0.368 mg/L (MITI 2010)
long-term toxicity to fish	NOEC 0.0037 mg/L, (MITI 2002)
short-term toxicity to aquatic invertebrates	48h-EC50 0.23 mg/L, (MITI 1999) 48h-EC50 0.51 mg/L, (Monsanto 1984) 48h-EC50 0.79 mg/L, (Monsanto 1984) 48h-EC50 0.82 mg/L, (Monsanto 1978)	48h LC50=0.2 mg/L, Monsanto 1983 48h LC50=0.21 mg/L, Monsanto 1981	48h LC50 = 0.37 mg/L Monsanto1979 48h LC50 = 1.7 mg/L Monsanto 1981	EC50 0.54 mg/L (MITI 2010)   EC50 1.4 mg/L (Monsanto 1981)
long-tem toxicity to aquatic invertebrates
toxicity to aquatic algae and cyano bacteria	72h-EC50 4.6 mg/L NOEC 0.5 mg/L (Flexsys 1998) *			EC50 0.939 mg/L, NOEC 0.0958 mg/L (MITI 2010)

* Study performed with 6QDI

Fish

 

Typical LC50 values in acute fish tests are in the range of 0.1 to 5 mg/L. Two results, one from a test with 6PPD and one from 77PD are the most sensitive ones (0.028, 0.06 mg/L). Selecting the results of these 2 tests for read-across represents the worst case and is therefore acceptable. The long-term fish test, performed with 6PPD yields a NOEC of 0.0037 mg/L. Typically, the ratio of the fish short-term and the long-term results (EC50/NOEC) is about 10 (Ahlers, J., 2006). Thus, this low NOEC-value is considered as conservative and read-across to the other PPDs including 77PD is justified.

 

 

Aquatic invertebrates

 

Short-term tests have been performed with each individual PPD yielding EC50-values in the range of 0.2 to 1.7 mg/L.

Indivual values from tests with 77PD (EC50 0.37 and 1.7 mg/L) and from

the study performed with 4-HDPA (EC50 0.69 mg/L) is within this range (Table below). This supports strongly the read-across approach for the long-term test performed with 4-HDPA also for 77PD although 4 -HDPA is not a hydrolysis product of 77PD but a similar substance. The NOEC of 0.028 mg/L is even more conservative considering the ratio of the daphnids short-term and long-term results (EC50/NOEC) of about 7 (Ahlers, J., 2006).

 

 

Aquatic algae and cyano bacteria

 

Studies are available with 44PD and from 6QDI, the oxidized form of 6PPD. The results (EC50 0.9 to 1.5 mg/L) show that algae are the least sensitive trophic level. The effect values of 4-HPDA (Table below) are n the same order of magnitude and thus read-across is justified..

 

 

 

 

Ecotoxicity of Degradation products

 

Due to the rapid hydrolysis, also the degradation products are evaluated concerning their effects in aquatic organisms. An overview over the relevant ecotoxicological key data for the degradation products (from hydrolysis and biodegradation reports) of the PPDs is given in the table below. 4 -HDPA and  N-phenyl-p-benzoquinone monoimine are not hydrolysis products of 77PD but from 6PPD and 7PPD and thus also used for read-across.

Table: Results of ecotoxicity tests (references are explained in the IUCLID dossier and in the CSR); Green fields contain results of experimental tests.

 

	4-HDPA CAS 122-37-2	N-Phenyl-p-benzoquinone monoimine CAS 2406-04-4	N-2-,5-Dimethylpentyl-p-aminophenol	p-Benzo-quinone	p-Hydro-quinone	1,3-Dimethyl-butylamine or 1,4-Dimethyl-pentylamine
short-term toxicity to fish	LC50 12.7 mg/L calc. ECOSAR	LC50 1.78 mg/L calc. ECOSAR	LC50 2.1 mg/L calc. ECOSAR	96h-LC50 0.045 mg/L (DeGraeve 1980)	96h-LC50 0.17 mg/L (OECD 2002) (Wellens 1982)	read-across with sec. Butylamine: LC50 <68 mg/L OECD 2011
						read-across with n-Octylamine: LC50 5.19 mg/L OECD 2011
long-term toxicity to fish
short-term toxicity to aquatic invertebrates	EC50(48h) 0.69 mg/L (Currenta 2010)	3.8 mg/L calc.ECOSAR	1.4 mg/L calc.ECOSAR		48h-EC50 0.134 mg/L (Crisinel 1994)	read-across with sec. Butylamine: EC50 40 mg/L OECD 2011
	48h-EC50 5.3 mg/L calc. ECOSAR					read-across with n-Octylamine: EC50 1.9 mg/L
						OECD 2011
long-tem toxicity to aquatic invertebrates	NOEC (21d) 0.028 mg/L Currenta 2010				NOEC0.0029 mg/L (ECHA dissemin.)
toxicity to aquatic algae and cyano bacteria	EC50 2.6 mg/L NOEC 0.23 mg/L, (Currenta 2010)	51.1 mg/L calc.ECOSAR	5.3 mg/L calc.ECOSAR		3d-EC50 0.335 mg/L (OECD 2002) (Devillers 1990)	read-across with sec. Butylamine: EC50 2.03 mg/L
	96h-EC50 23.4 mg/L calc.ECOSAR					read-across with n-Octylamine: LC50 0.23 mg/L OECD 2011

 

Generally the effect values of the aliphatic amine components are higher and therefore covered by the ecotoxicity of the parent substances and the aromatic degradation products.

 

Fish

 

Obviously, fish is the most sensitive organism for the family of PPDs and their degradation products. The lowest effect value was found for p-hydroquinone (0.044 mg/L) which is rather similar to the values for p-benzoquinone (0.045 mg/L) and for 6PPD (0.028 mg/L).

For 4-HDPA and N-phenylbenzoquinone-imine only calculated values are available. The calculated values should 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 three intermediate compounds to fish are at a higher level and there is no indication for a higher toxicity exceeding those for 6PPD or p-hydroquinone.

 

 

Aquatic invertebrates

 

The lowest effect value in acute tests was found for p-hydroquinone (0.134 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).

For 4-HDPA, N-phenylbenzoquinone-imine and 1,4-dimethylpentyl-p-aminophenol, calculated values are available. For these calculated values, the same goes true as for the calculated values for fish: They 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 three intermediate compounds to daphnids are at a higher level and there is no sign for a higher toxicity than found for the PPDs or their degradation products.

There is an indication of one long-term result (NOEC 0.0029 mg/L; expressed in 77PD equivalents 0.007 mg/L) from p-hydroquinone (ECHA dissemination tool). This effect value is even lower than the chronic value of 4-HDPA (NOEC 0.028 mg/L) and can therefore be considered as most the conservative one which should cover the whole range of PPDs. Using the NOEC value of 0.007 mg/L and the lowest acute value (0.134 mg/L), the ratio of the daphnids short-term to long-term results (EC50/NOEC) of about 19 is more conservative as the value of 7 (Ahlers, J., 2006).

 

 

Aquatic algae and cyano bacteria

 

Studies are available with p-hydroquinone and with 4-HDPA. The results show that algae are the least toxic trophic level.

 

Conclusion on ecotoxicityand selection of key values

 

Experimental and calculated values for the four PPDs and for six ecotxicological relevant degradation products were evaluated and the relevant lowest effect concentrations were taken as key values:

 

Table: Key values of ecotoxicological endpoints:

	Read-across based on	Key values
short-term toxicity to fish	6PPD	LC50              0.028 mg/L
long-term toxicity to fish	6PPD	NOEC            0.0037 mg/L
short-term toxicity to aquatic invertebrates	7PPD	EC50              0.2 mg/L
	p-Hydroquinone	EC50              0.134 mg/L
long-tem toxicity to aquatic invertebrates	p-Hydroquinone	NOEC             0.007 mg/L
toxicity to aquatic algae and cyano bacteria	p-Hydroquinone	EC50              0.335 mg/L
	44PD	NOEC            0.0958 mg/L

Effects of Tyre wear particles (TWP)

Tyres typically contain about 1% of a PPD antioxidant. By abrasion of tyres, emission of TWPs to the environment occurs. Two studies with TWPs are available. One study for acute effects in auqatic organisms and one study for chronic effects in aquatic and benthic organisms have been performed (Marwood 2010, Marwood, 2011). The results are summarised in the following Table:

	Type	Effect values
short-term toxicity to fish	LC50	>10000 mg/LE
long-term toxicity to fish	EC0	>10000 mg/L
short-term toxicity to aquatic invertebrates	EC50	5000 mg/L
long-tem toxicity to aquatic invertebrates	EC10	>10000 mg/L
toxicity to aquatic algae and cyano bacteria	EC50	>10000 mg/L
long-tem toxicity to sediment dwelling organisms (Hyalella Azteca)	EC0	>10000 mg/L
long-tem toxicity to sediment dwelling organisms (Chironomus tentans)	EC10	10000 mg/L

As a conclusion, no effects have been observed in any acute of chronic tests.

In parallel to the acute tests,TWP were incubated with moderately hard water at 44C for 72 h, and the resulting leachate was analyzed for select organic constituents.

(results of relevant materials of the PPD's)

Parameter	Leachate blank [mg/L]	TRWP Leachate [mg/L]
N-(1,3-dimethylbutyl)-N'-phenylbenzene-1,4-diamine (6PPD)	< 1	< 0.3
N-Isopropyl-N-phenyl-p-phenylenediamine (IPPD)	< 1	< 0.3
N,N'-Bis(1,4 -dimethylpentyl)-p-phenylenediamine (77PD)	1.7 - 5*	<38 or (26 mg/L)

*Detected but not quantifiable; range represents range of limit of detection and limit of quantification

Discussion of the leachate analytis:

•           The authors measured the concentration of selected substances, which are typical constituents of TWP, in a leachate resulting of the incubation of TWP in water at 44°C for 72h. This data displays a realistic approach in describing the entry of TWP substances into the environment. Among others the concentration of 6PPD was measured which can be used due to the chemical similarity as read-across for 7PPD. A concentration < 0.3 mg/L for 6PPD was determined. As a conservative approach an actual concentration of 0.15 mg/L (half LOQ) is used for further assessment. A nominal concentration of 10000 mg/L TWP was applied into the study and as a concentration of 1% is assumed for 77PD (see above) the total nominal amount of the substance is 100 mg/L. Considering the measured concentration of the substance in the leachate of 0.15 mg/L in conclusion 0.15% of the substance is released into the environment (equals a factor of 0.0015). Therefore the predicted environmental concentration can be refined with this factor to display realistic environmental concentrations of the substance.

•           The concentration of 77PD in the leachate of TWP was also measured in the study of Marwood (2011) but was not taken into consideration as this value seems not to be plausible. Two different concentration values for 77PD were reported, 26 mg/L and > 38 mg/L, that are contradictory. There is no explanation in the text dealing with this discrepancy. Further 77PD was detected in the leachate blank but could not be quantified. In conclusion the above mentioned discrepancies were the reason for omitting the measured values for 77PD as it is an artefact. This assumption is supported by the outcome of the ecotoxicity where an effect with 77PD would have been expected. It is assumed that the PPDs are used in the same concentration range in TWP and the water solubility of 6PPD and 77PD is very similar. Therefore the measured value for 6PPD, the leading substance for the PPD family, was also used for 77PD and 7PPD as read-across.

Toxicity to microorganisms:

A test with activated sludge with a duration fo 3 hours was performed according to the OECD Guideline 209. For 77PD an EC50 of 57 mg/L was observed (Bayer, 1989).