[4-[α-[4-(dimethylamino)phenyl]benzylidene]cyclohexa-2,5-dien-1-ylidene]dimethylammonium acetate

Short-term toxicity to fish

Description of key information

LC50 for freshwater = 0.0305 mg/L (based on results on Malachite Green Chloride)

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Effect concentration:

0.03 mg/L

Additional information

Malachite Green (MG) was toxic to all species of fish exposed.

Most of studies done on MG were conducted in freshwater

In Bills study (1977) MG LC50 ranged from 0.0305 to 0.383 mg/L in 96 -h exposures in soft water at 12°C. Results showed that centrarchids were 1.5 to 3.5 times more sensitive to the chemical than the ictalurids and 3 to 7 times more sensitive than the salmonids; the bluegill was the most sensitive species (96-h LC50 0.0305 mg/Ll) and the coho salmon the most resistant (0.383 mg/L).

In some studies the influence that some physical-chemical parameters may have on the toxicity of MG has been reported. Some tests carried out at different pH, show a greater sensitivity to the substance at basic pH (pH=9.5) and this is probably due to conversion to cationic form (carbinol) (Bills et al. 1977).

The absence of positive charge may facilitate the absorption, which occurs almost exclusively through the gills (Plakas et al. 1995; see 6.5).

The variation of the toxicity of MG as a function of temperature is minimal. Small differences were found by testing bodies to unnatural temperatures and this probably induces a state of stress that can lead to greater sensitivity (Bills et al. 1993 and Van Heerden et al. 2000).

The toxicity of MG is not affected by variation in water hardness (Bills et al. 1993).

Some studies show that exposure to MG elicited iperactivity characterized by rapid pectoral and opercular movement, erratic swimming and gradual loss of equilibrium associated with breathing difficulties in the fish. The effects on the behaviour was similar to those observed in several teleostean species exposure to various pesticides (Srivastava et al. 1993).

From anatomical observation of the fish was seen that the MG poisoning leads to a greenish scales and an increased production of mucus from the skin. Some results show that MG does not interfere on the nervous system, but also causes damage to the liver and inhibits the process of conjugation (Srivastava et al. 1993). The activity of GPT had a significant increase. After treatment with MG were observed significant modifications also in the activity of LDH's (Lanari et al. 1996; see 6.4). Toxicants which affect the liver tissue also result in reduction of total serum protein in fish and the liver is found to be severely damaged. Hypercholesterolemia was observed too.