Malic acid

Endpoint summary

Additional information

The acute toxicity of malic acid to Daphnia magna has been assessed 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.

Read across from fumaric acid to malic acid is considered valid. 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.

Juvenile fish, D. rerio, have been exposed to a single fumaric acid concentration of 100 mg/L in a semi-static acute toxicity test of 96 hours duration. The acidic nature of the tested substance resulted in a marked pH change (pH 4.3 - 5.0) which had, at the concentration tested, no influence on survival of the fish. The 96 -hour LC50 determined was >100 mg/L. The NOEC (no-observed effect concentration) was 100 mg/L.

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).

Two 72 hour algal inhibition experiments have been conducted with fumaric acid. In the first experiment algae were exposed over a 72 hour period to fumaric acid at nominal concentrations of 0, 0.39, 0.78, 1.56, 3.13, 6.25, 12.5, 25, 50 and 100 mg/L. pH ranged from 3.4 in the 100 mg/L treatment to 7.5 in the 0.39 mg/L treatment in a concentration related manner. The 72 -hour E_yC₅₀was determined to be 37.2 mg/L with a corresponding NOEC of with 25 mg/L. The 72-hour E_rC₅₀was determined to be 38.9 mg/L with a corresponding NOEC of with 25 mg/L. In the second experiment algae were exposed over a 72 hour period to fumaric acid at a nominal concentration of 0 and 100 mg/L. The pH of the 100 mg/L medium was adjusted to 7.4 at the start of the exposure period.   The 72-hour E_yC₅₀and E_rC₅₀were determined to be >100 mg/L with corresponding NOECs of 100 mg/L. Based on the fact that the effects seen in the first experiment were influenced by the pH change the most appropriate endpoint to use for the assessment of fumaric toxicity is the 72 hour E_rC₅₀value of >100 mg/L obtained in the study with pH adjustment. 

Activated sludge obtained from a sewage treatment plant was exposed in a 3 -hour respiration inhibition test to fumaric acid.The 3 -hour EC50 based on respiration inhibition was >300 mg fumaric acid/L.

These data support the conclusion that malic acid exhbits low toxicity to aquatic organisms.

In the chemical safety assessment performed according to Article 14(3) in connection with Annex I section 3 (Environmental Hazard Assessment) no hazard was identified. Therefore according to REACH Annex I (5.0) exposure estimation is not necessary. Consequently, in accordance with Column 2 of REACH Annex IX, long-term studies do not need to be conducted as all identified uses of the substance are assessed as safe for the environment.