N-(1,3-Dimethylbutyl)-N

OECD SIDS
N-(1,3-DIMETHYLBUTYL)-N´-PHENYL-1,4-PHENYLENEDIAMINE
of US-EPA from 1975 (Monsanto 1978a). In this study a 48 h NOEC of 0.56 mg/l, 24 h LC 50 of 1.0
mg/l, and a 48 h LC 50 of 0.82 mg/l were obtained (nominal concentrations).
A "degradation toxicity"study with Daphnia magna examined how the toxicity of 6PPD solutions
change concurrently with chemical transformation and the occurance of degradation products
(Monsanto 1984). Freshly prepared 6PPD solution exhibited a nominal 48 h NOEC of 0.25 mg/l
and a 48 h LC 50 of 0.51 mg/l. Stirring for 24 h in an open beaker at room temperature, which equals
at least 2 half-lifes (cf Chapter 2.2.5; Monsanto 1979a), decreased the toxicity of the test solution
(containing 6PPD and degradation products) significantly. The 48 h NOEC of aged 6PPD was
larger than 1 mg/l (highest exposure concentration; Monsanto 1984). This detoxification of 6PPD
solution is presumably due to oxidation and/or hydrolysis. The transformation and degradation
products of 6PPD formed under these conditions are less toxic than 6PPD.
In a study according to the Algal Assay Procedure: Bottle Test of the US EPA from 1971 with the
green alga Selenastrum capricornutum, a 96 h EC 50 of 0.6 mg/l (nominal) was obtained (Monsanto
1978b).
Since there are acute studies from 3 trophic levels, an assessment factor of 1000 is applied to
determine the PNEC aqua . The lowest effect value was measured during an acute toxicity test to fish
(Oryzias latipes) with a 96 h LC 50 of 0.028 mg/l (effective concentration), resulting in a PNEC aqua
of 0.028 µg/l.
Toxicity to Microorganisms
Regarding the toxicity to microorganisms, a 3 h oxygen consumption test was performed in
accordance to ISO 8192 with activated sludge. An EC50 of 420 mg/l (presumably nominal, original
reference not available) was determined (Bayer AG 1984). The results of the toxicity tests are
compiled in Table 7.
UNEP PUBLICATIONS 29