Dibutyl maleate

Endpoint summary

Additional information

For all aquatic endpoints, only data for freshwater species are available. There is no data available for marine species.

For acute toxicity to fish, three static studies with were conducted. The first study conducted according to OECD 203 reported a 96-hr LC50 of 1.2 mg/L based on nominal values, and 0.6 mg/L based on the geometric mean of the test substance concentrations. The two other studies were conducted according to the German DIN 38 412 with an incubation period of only 48 hours using the Golden orfe (Leuciscus idus) as test organism. In the first study an 48-hr LC50 value of 6 mg/L was reported, where the second one reported a 48 -hr LC0 of 12 mg/L. Both endpoints are related to nominal values too. The most reliable study is the one conducted according to OECD as it corresponds to currently valid standard. Furthermore, the lowest LC50 was observed here. It has therefore been selected as the key parameter.

For acute toxicity to invertebrates, also three studies are available, all conducted with the freshwater invertebrate Daphnia magna. One study was conducted according to OECD 202, reporting 48-hr EC50 of 21 mg/L based on nominal values. Two studies were conducted according to the DIN 38412 method and reported 24-hr EC values of 15 and 139 mg/L, respectively. Analytical verification of the test concentrations has only been conducted in the OECD study, confirming a sufficient stability of the test substance over the test period. Also, this study is the only one which was conducted to a currently valid standard, therefore resulting in the most reliable endpoint. For this reason, the EC50 of this study was selected as the key parameter although a lower EC50 was reported in one of the 24-hr studies.

For algae, a 72-hour study conducted according to OECD TG 201 using Scenedesmus subspicatus reported a NOEC of 4.2 mg/l and an EC50 of 6.2 mg/L, which is based on biomass.

For microorganisms, results from two aerobic and two anaerobic studies are available. The first, conducted with activated sludge according to OECD 209 reported an EC50 of 488.6 mg/L and an EC10 of 80.2 mg/l. The second one, conducted according to a modification of OECD 209 using Pseudomonas putida as the only test organism reported an EC10 of 1003 mg/L. In the anaerobic studies, both conducted according to the ETAD fermentation tube test, an 24 -hr EC0 of 63 mg/l and a 24 -hr toxicity threshold (TT) of 40 mg/L. The validity of both test could not be proven, as the respective guideline was not available. Furthermore, degradation processes in a STP are mainly aerobic. Therefore, both anaerobic studies were excluded from PNEC development. The endpoints derived from the unmodified OECD study were chosen as the key parameters, as the lowest values compared to the modified one were obtained here.

From the available data it can be deduced that fish are the most sensitive trophic level and the endpoint derived from this study should be used for deriving the PNEC.