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Ecotoxicological information

Short-term toxicity to fish

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Description of key information

The effects of HMX to fish was assessed under static conditions in two freshwater acute toxicity studies. The 96h LC50 of the test substance to Pimephales promelas is > 15 mg/L (nominal concentration) (U.S. Army Medical Research and Development Command, 1984).The 96h-LC50 of the test substance to Lepomis macrochirus, Salmo gairdneri, Ictalurus punctatus and Pimephales promelas was greater than 32 mg/L (nominal concentration) (EG & G Bionomics, 1978).

Key value for chemical safety assessment

LC50 for freshwater fish:
15 mg/L

Additional information

The LC50 values are based on nominal concentrations. In the study by the U.S. Army Medical Research and Development Command, (1984), undissolved chemical was present on the bottom of the test vessels. These studies were performed at the limit of solubility of HMX (4.46 mg/L at 25C in pure water). A study was conducted using vertebrate reconstituted water at concentrations of 10.0, 5.0 and 2.5 rng/L of HMX. No solvents were utilised. Solutions were analysed immediately, after 24 hours, 48 hours and 1 week of continuous stirring at 25C. These results indicated that the HMX was most completely solubilised between 48 hours and 1 week of mixing and that the expected concentration at saturation should be ca. 2.8 mg/L (see Table 1).

Table 1: Solubility of Test substance in Vertebrate Dilution Water

Sample Concentration

Analytical Results (mg/L)

Remarks

0 hoursa

24 hoursa

48 hoursa

1 weeka

2.5 mg/L vert.

0.09

0.11

0.12

mean=0.11

0.58

0.59

0.57

mean=0.57

1.3

1.3

mean=1.3

2.5

2.5

mean=2.5

@ 48h, tepm. 27° also remained warm

5.0 mg/L vert.

0.16

0.14

0.20

mean=0.17

2.8

2.7

2.8

mean=2.8

4.0

4.1

mean=4.0

4.2

4.2

mean=4.2

@ 48h, tepm. 25.5°

10 mg/L vert.

0.23

0.24

0.23

mean=0.23

1.1

1.2

1.2

mean=1.2

1.8

1.8

mean=1.8

2.9

2.9

mean=2.9

@ 48h, tepm. 26°

aRepresents amount of time mixed prior to analysis.