N-1,3-dimethylbutyl-N'-phenyl-p-phenylenediamine

Endpoint summary

Additional information

Studies with PPDs (6PPD, 7PPD, 77PD, 44PD) (Allmendinger 2012)

An overview on the relevant ecotoxicological key data for the PPDs is given in the Table below.

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)	96h-LC50 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 0.23mg/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 LC500.21 mg/L,(Monsanto 1981)	48h LC50 0.37 mg/L (Monsanto1979) 48h LC50 1.7 mg/L (Monsanto 1981)	48h EC50 0.54 mg/L (MITI 2010)   48h EC50 1.4 mg/L (Monsanto 1981)
long-term 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 two tests for read-across represents the worst case and should therefore be acceptable. The long-term fish test, performed with 6PPD, yields a NOEC of 0.0037 mg/L. Typically, the fish short-term and long-term results are in a ratio(EC50/NOEC) of about 10 (Ahlers, J., 2006). Thus, th low NOEC-value of 6PPD is considered as being conservative and thus justifies the read-across to the other PPDs.

 

 

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. The result of the study performed with 4-HDPA (0.69 mg/L) is within this range (cf. Table 6). T

 

 

Aquatic algae and cyano bacteria

 

Studies are available with 44PD and 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. 

 

 

Studies with degradation products

 

Due to the rapid hydrolysis, also the degradation products are subject to evaluation as regards their effects in aquatic organisms. An overview over the relevant ecotoxicological key data of the degradation products (from hydrolysis and biodegradation reports) of the PPDs is given in the Table below.

Table: Results of ecotoxicity tests (references are explained in the IUCLID dossier and in the CSR);Green fields: results of experimental tests, yellow fields; calculated values

	4-HDPA	N-Phenyl-p-benzoquinone monoimine		p-Benzo-quinone	p-Hydro-quinone	1,3-Dimethyl-butylamine e
CAS No.	122-37-2	2406-04-4		106-51-4	123-31-9	54548-48-0
short-term toxicity to fish	LC50 12.7 mg/L calc. ECOSAR	LC50 1.78 mg/L calc. ECOSAR		96h-LC50 0.045 mg/L (DeGraeve 1980)	96h-LC50 0.044 mg/L (DeGraeve 1980)	read-across with sec. Butylamine: LC50 <68 mg/L (OECD 2011)
						read-across withn-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		-	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-term toxicity to aquatic invertebrates	21d-NOEC 0.028 mg/L (Currenta 2010)	-		-	NOEC0.0029 mg/L (ECHA dissemin.)
toxicity to aquatic algae and cyano bacteria	72h-EC50 2.6 mg/L NOEC 0.23 mg/L, (Currenta 2010)	51.1 mg/L calc. ECOSAR		-	3d-EC50 0.335 mg/L (OECD 2002) (Devillers 1990)	read-across with sec. Butylamine: EC50 2.03 mg/L (OECD 2011)
	96h-EC50 23.4 mg/L calc.ECOSAR					read-across with n-Octylamine: LC50 0.23 mg/L (OECD 2011)

In general 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 and N-phenylbenzoquinone-imine, 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 6PPD 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:

 

	Data source 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	6PPD	EC50             0.23 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
	6PPD	NOEC         0.5 mg/L

Summary of toxicity test results with the original substance 6PPD

Valid acute and chronic studies are available for the 3 trophic levels. Fish is the most sensitive organism with an EL50 of 0.028 mg/L and a 30d-NOEC of0.0037 mg/L.

Effects of Tyre wear particles (TWP)

Tyres typically contain up to 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:

Summary of toxicity test results with tyre wear particles

A considerable amount of publications is available for the effects of substance which might be dissolved from rubber into water. As 6PPD has a water solublity of about 1 mg/L, toxicity of tyre wear particles to aquatic organism should be expected if relevant portions of the substance do migrate from tyres to water. Effect values of 6PPD in acute studies are in the range of 0.028 to 0.2 mg/L. The data presented for tyre wear particles are needed in order to evaluate the effectsin the environment of pure 6PPD compared to those of 6PPD used as an additive in tyres.

 

Basic experiments for leaching of rubber ingredients from tyre wear particles were performed[AA3] by Baumann and Ismeyer (1998). They analysed the eluate of 14 different tyres and foundconcentrations[AA4] of 6PPD of less than 10 to 101 µg/l in neutral water and less than 10 to 9660 µg/l in water pH 4. However, these results should be handled with care. They used an elution method (DIN 38414-S4) which is only valid for inorganics and the detection method was not specific enough (only 1 column, FID, no confirmation with MS). Thus, these results should not be taken for assessment of 6PPD in tyre wear particles.

Recent publications on the effects of tyre wear particles to aquatic organisms are described in a weight of evidence approach (Basel convention 1999, Sweet 2008, Marwood 2011). Each of these publications has some deficiencies concerning description of the work or has some methodological deficiencies. Two pf the papers do not clearly describe that 6PPD is contained in the rubber. ( Basel convention 1999), Sweet s 2008). Marwood (2011) analysed for 6PPD but the signal was below the limit of quantitation. All test state that, no effects to daphnia, algae and fish have been observed up to 10000 mg tyre wear particles per litre eluate. However, it is generally known, that all tyres are protected from ageing by antioxidants of the phenylenediamine type and therefore it was decided to use all of these studies in a weight of evidence approach.

As a sum, the weight of evidence approach shows that the effects of tyre wear particles containing phenylenediamines towards aquatic organisms are less sensitive by a factor of 10 to 100 compared to those received with the pure substance.