Malic acid

Short-term toxicity to aquatic invertebrates

Description of key information

Acute toxicity to Daphnia magna: LC50 = 240 mg/L

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

240 mg/L

Additional information

The acute toxicity of malic acid to Daphnia magna has been assesed in an acute immobilisation test conducted using methods similar to established test guidelines. The 48 - hour EC₅₀was 240 mg/L, the high mortality rates observed in daphnids exposed at concentrations of 320, 560, and 1,000 mg/L being attributed to the acidic nature of the test medium at these higher concentrations.

In addition, the 48 hour acute toxicity of fumaric acid has been determined in two semi-static tests. In the first experiment daphnids were exposed over a 48 hour period to fumaric acid at nominal concentrations of 0, 6.25, 12.5, 25, 50 and 100 mg/L. pH ranged from 3.7 in the 100 mg/L treatment to 7.4 in the 6.25 mg/L treatment in a dose related manner. The 48 -hour EC₅₀was determined to be 66 mg/L (nominal) with 95% confidence limits of 59 to 73 mg/L. In the second experiment daphnids were exposed over a 48 hour period to fumaric acid at a nominal concentration of 0 and 100 mg/L. The pH of the 100 mg/L was adjusted to 8.3. The 48-hour EC₅₀was determined to be >100 mg/L (nominal).

Read across from fumaric acid to malic acid is considered valid and malic acid is concluded to have low toxicity to aquatic organisms. The rational for read across is that fumaric acid will metabolise in biological systems to malic acid. Fumaric acid is also slightly more fat soluble and is considered more likely to absorb to membranes and increase exposure to aquatic organisms.