Dichloroacetic acid

Long-term toxicity to fish

Description of key information

medaka LC0 (21 days): >= 2000 mg/L

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Effect concentration:

2 000 mg/L

Additional information

In the publication from McHugh Law et al (1998) the effect of DCA on medaka was investigated for a 21 day exposure period using concentrations of 0 (control), 0.5 and 2.0 g/L. The focus of this study was on histopathology. The test design was similar to the design laid out in OECD 204. The test was performed as semi-static test with 20 - 30 % water renewal twice a week. At start of the exposure, the fish had a total length of 7 to 13 mm.

Each test group received 20 fish. The fish were exposed in 40 L aquaria. The test was performed at 27 +/- 1°C. Prior to use, the pH of the stock solution was adjusted to pH 7.0 +/- 0.5. DCA concentrations were verified by measuring absorbance at 250 nm. The fish were fed twice a day.

No mortality was reported for any of the test groups. Based on the table provided, no mortality occurred during the exposure. No remarkable macroscopic abnormalities were found in any of the specimens. Histopathological examination of fish exposed for 21 days to DCA showed that cytoplasmic vacuolation, cell swelling and sinusoidal compression was apparently caused by DCA exposure. This effect was observed at 0.5 and 2.0 g/L. The fish exposed to the lower concentration of DCA had slightly less severe hepatocellular vacuolation and necrosis after 3 weeks of DCA exposure. Fish exposed to DCA for 3 weeks at a concentration of 0.5 g/L had moderate hepatocytomegaly, sinusoidal compression and marked cytoplasmic vacuolation. Vacuoles were demonstrated to contain glycogen by the PAS reaction.

It can be concluded that DCA does not cause mortality of macroscopic changes in juvenile medaka when exposed for 21 days with up to 2 g/L. Histopathological changes in the liver were already observed at the lowest concentration of 0.5 mg/L and effects were seen already after 72 hours of exposure. At 2.0 g/L, the effects were more pronounced than at 0.5 g/L.

Since histopathological investigation is beyond the scope of the test guideline, the evaluation for regular purposes was focused on mortality and macroscopic findings. The LC0 and EC0, i.e., the concentration at which no mortality or macroscopic findings were observed was the highest test concentration investigated, i.e. 2.0 g/L.

Even if the test has not followed the test guideline 204 in all aspects and was not performed under GLP, it is considered that the results of this study can be used for the risk assessment of DCA. The use of smaller size of the fish is expected to be more conservative than using the recommended longer fish. The temperature deviation is considered to have a relevant impact on the outcome of the test.

The 21 day LC0 is 2.0 g/L (=2000 mg/L). No adverse macroscopic effects were observed at any concentration until day 21, the end of the exposure.

Since this test was not performed according to OECD 210, 212 or 215 and no growth parameters were measured or reported. Therefore, this test will not be used for the derivation of the long-term EC10. Nevertheless, this test provides evidence that a concentration of 2000 mg/L will cause no mortality in medaka when exposed for 21 days.