N-(1,3-Dimethylbutyl)-N

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OECD SIDS N-(1,3-DIMETHYLBUTYL)-N´-PHENYL-1,4-PHENYLENEDIAMINE Table 5 Input parameters and results of the Mackay Fugacity Model Level I (IUCLID 3.3.2) Input Parameters Value Temperature 25 °C Vapour pressure 6.85 10 -3 Pa Water solubility 1 mg/l log K ow 4.68 Results Compartment Calculated distribution Air 0.8 % Water 2.2 % Soil 94.7 % Sediment 2.1 % Susp. Sediment 0.1 % Fish < 0.1 % Taking into account the water solubility (1 mg/l) and vapour pressure (6.85 x 10 -3 Pa), the Henry´s Law Constant was estimated to be 1.84 Pa m 3 mol -1 at 25 C for 6PPD. This indicates a moderate potential for volatilization from surface waters according to the scheme of Thomas (1990). For 4- hydroxydiphenylamine the same calculation yielded a Henry´s Law Constant of 0.0057 Pa m 3 mol -1 at 25 C (EPA 2004). According to the scheme of Thomas (1990), 4-hydroxydiphenylamine is essentially nonvolatile from water. 2.2.5 Biodegradation 6PPD is not readily biodegradable but it is degraded rapidly in the environment by biotic and abiotic processes: In an OECD TG 301C test on ready biodegradability, based on BOD, only ca. 2 % of 6PPD was biodegraded. Based on HPLC, ca. 92 % of 6PPD was removed within 28 d indicating that 6PPD was transformed. About 2/3 of the theoretical amounts of the transformation products 4- hydroxydiphenylamine, and phenylbenzoquinone imine, and 97 % of the 1,3-dimethylbutylamine were recovered. Although the 2-ring intermediates were degraded further, neither aniline nor p- benzoquinone, were recovered in significant quantities (CERI 1994). This observation is consistent with the results of the Bayer study (Bayer Industry Services 2003) on abiotic degradation of 6PPD and 4-hydroxydiphenylamine (cf Chapter 2.2.3). In another respirometer test according to OECD TG 301C, 13 - 40 % of 6PPD were mineralized within 28 d. The difference between the results of 2 replicates was explained with the poor solubility of 6PPD (Bayer AG 1984). In an insufficiently described shake flask test comparable to an US EPA 40 CFR method, measuring biodegradation from CO 2 release, only part of 6PPD (7 %) was completely degraded after 32 d. However, primary degradation was also checked with aerated water, and a rapid 6PPD decline (60 % primary degradation in 25 h) of a 1 mg/l solution was observed (Monsanto 1979a). It is not excluded that abiotic degradation occurred during these tests. 14 UNEP PUBLICATIONS
OECD SIDS N-(1,3-DIMETHYLBUTYL)-N´-PHENYL-1,4-PHENYLENEDIAMINE The primary biodegradation of 6PPD was studied using Mississippi river water under aerobic conditions (Monsanto 1981). Controls of this biodegradation study were made with sterile and with deionized water. During 2 h, the concentration of 6PPD decreased by 57 % in the active river water, by 30 % in the sterile river water, and by 12 % in the deionized water, indicating that both biotic and abiotic degradation occured. After 22 h, when the experiment was finished, 97 % of 6PPD had disappeared from the active river water, 96 % from the sterile river water, and 88 % from the deionized water. The estimated half-lives due to primary transformation are 2.9 h in biologically active river water, 3.9 h in sterile river water, and 6.8 h in sterile deionized water. Apparently, both biotic and abiotic degradation occured leading to the rapid removal of 6PPD under aerobic conditions (Monsanto 1981). Table 6 Biodegradation of 6PPD (IUCLID 3.5) Inoculum Procedure Result Source Activated sludge, nonadapted non adapted mixed microbial inoculum Activated sludge, adapted Mississippi river water (= biologically active river water) (controls with sterile river water and with deionized water) OECD TG 301C Modified MITI I test according to OECD TG 301C shake flask test comparable to an US EPA 40 CFR River die-away assay Biodegradation within 28 d BOD ca. 2 % 6PPD removal (HPLC) ca. 92 % degradation products identified p-hydroxydiphenylamine, phenylbenzoquinone imine, 1,3- dimethylbutylamine aniline, p- benzoquinone 13 -40 % mineralization within 28 d, 10 d window was not fulfilled CERI 1994 Bayer AG 1984 7 % mineralization Monsanto 1979a During 2 h (22 h), the concentration of 6PPD decreased by 57 % (97 %) in the active river water, by 30 % (96 %) in the sterile river water, and by 12 % (88 %) in the deionized water. The estimated half-lives are 2.9 h in active river water, 3.9 h in sterile river water, and 6.8 h in sterile deionized water. Monsanto 1981 In 2002, about 0.73 kg/a 6PPD entered the biological wastewater treatment plant at the Bayer 6PPD manufacturing site in Brunsbüttel. In the influent, the determination limit was 0.1 mg/l, and the maximum 6PPD concentration was 0.24 mg/l. In its effluent 6PPD was not detectable by 250 measurements with a determination limit of 10 µg/l (Bayer Polymers 2003). It can be concluded from these data that the elimination of the Brunsbüttel industrial wastewater treatment plant exceeds at least 96 %. This removal cannot be transferred to other wastewater treatment plants due to different wastewater composition and adaptation processes. 2.2.6 Bioaccumulation Due to the very low stability of 6PPD in aqueous media, a bioaccumulation and geoaccumulation potential is not expected, although QSAR calculations indicate some accumulation potential. The calculated log K ow value (log K ow = 4.68) and a calculated BCF (BCF = 801, calculated with BCF-Program v2.14), indicate that - if 6PPD was stable - there is a moderate potential for bioaccumulation in aquatic organisms (Bayer AG 2003b). Experimentally determined UNEP PUBLICATIONS 15
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N-(1,3-Dimethylbutyl)-N

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