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Ecotoxicological information

Endpoint summary

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Description of key information

Acute fish toxicity:
Based on nominal concentrations of the source substance 1,6-hexane diamine (HMD; CAS No. 124-09-4), the LC50 (96 h) for fish (Pimephales promelas) determined in a study equivalent to OECD 203 with adaptation of pH is 1825 mg/L (95% CI: 1237-2461), with no effect observed at 1000 mg/L. Because of the identical molecular weight this directly applies to the target substance MPMD.


Toxicity towards freshwater green algae:
The following results in relation to growth rate were obtained from an algal growth inhibition test (OECD TG 201, GLP) based on analytically confirmed nominal test concentrations:
ErC10 (0 to 72 hour) : 60 mg/L; 95% confidence limits 52 to 70 mg/L
ErC20 (0 to 72 hour) : >100 mg/L
ErC50 (0 to 72 hour) : >100 mg/L
NOEC (growth rate; 0 to 72 hour): 10 mg/L


Chronic toxicity to freshwater invertebrates:
The following results were obtained for the test item MPMD (2-Methylpentane-1,5-diamine) from a Daphnia magna reproduction test (OECD TG 211; GLP) based on geometric mean measured concentrations:
EC5 (reproduction; 21 days) = 1.2 mg/L (95% CI: 0.38 – 3.5);
EC8 (reproduction; 21 days) = 5.0 mg/L (95% CI: 1.1 – 24);
EC10 (reproduction; 21 days) > 9.3 mg/L, extrapolated = 11 mg/L (95% CI: 1.6 – 76);
EC50 (reproduction; 21 days) > 9.3 mg/L;
NOEC (reproduction, parental length, adult mortality; 21 days) >= 9.3 mg/L.


Toxicity towards STP microorganisms
In an activated sludge respiration inhibition test according to OECD 209 (2010) with the source substance 1,6-hexane diamine (HMD; CAS No. 124-09-4), nitrification proved to be the most sensitive endpoint (highest test item concentration: 1000 mg/L):
EC50 (3h; total respiration): 1558 mg/L;
EC50 (3h; heterotrophic respiration): >> 1000 mg/L;
EC50 (3h; nitrification): 291 mg/L.
Because of the identical molecular weight, these results are directly applicable to the target substance MPMD.

Additional information

MPMD is an aliphatic primary diamine, and thus a strong base in aquatic solution. This property requires pH-adjustment for testing under environmentally realistic conditions. The supporting study on acute fish toxicity (NATEC, 1997) as well as the supporting study on STP microorganisms’ toxicity (NATEC, 1997) did not take account of this. At pH values around 10 observed toxicity is due to the caustic conditions, and both studies are therefore not reliable. In all other studies, pH was adjusted to between 7.5 to 8.5.
The freshwater algae study including chemical analysis was performed according to GLP and confirmed the stability of the test substance during aquatic tests. It is considered that the algae study was carried out under more stringent conditions (presence of high light intensity, static conditions over 72 h, at a higher temperature and in the presence of algal cells) and therefore high stability during the key study on acute fish toxicity (lacking analytical confirmation) can be expected.
Chronic toxicity results are available for two trophic levels, algae, and aquatic invertebrates. Acute toxicity data for fish demonstrated that this trophic level is clearly the least sensitive: while no acute toxicity data on Daphnia are available for MPMD, for the read-across source substance (see read-across report, data matrix) a reliable short-term test on Daphnia is available, resulting in an EC50 (48 h) of 19.8 mg/L. Accordingly, fish is acutely less sensitive by a factor of more than 90, giving high confidence that a long-term fish toxicity test would have no impact on aquatic invertebrates being the most sensitive trophic level. Moreover, considering the ready biodegradability of MPMD (including full nitrification), any long-term aquatic exposure is highly improbable. Consequently, in order to reduce needless testing on vertebrate animals, and in accordance with REACH Annex IX column 2 (chemical safety assessment does not indicate the need; chronic studies on algae and Daphnia are available) as well as ECHA Guidance provided in chapters R.7b and R.10, the requirement of a long-term fish toxicity study was waived.