4-amino-m-cresol

Toxicity to aquatic algae and cyanobacteria

Description of key information

The 72 hour EC50 value of 4-amino-m-cresol to Pseudokirchneriella subcapitata for inhibition of yield, biomass and growth rate were 0.012, 0.011 and 0.035 mg/L, respectively, based on geometric mean measured concentrations. The  72 hour EC10 values for yield, biomass and specific growth rate after 72 hours were 0.0073, 0.0068 and 0.0098 mg/L respectively. The corresponding NOEC values for yield, biomass and specific growth rate after 72 hours were 0.0063 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:

0.035 mg/L

EC10 or NOEC for freshwater algae:

0.01 mg/L

Additional information

The toxicity of 4-Amino-m-cresol to Pseudokirchneriella subcapitata was determined in a 72 hours algae growth inhibition test, under static conditions, following the OECD 201 guideline and the GLP.

Test vessels (250 mL conical flasks) were prepared containing 100 mL of the appropriate test or control medium. Each test vessel was inoculated with 1 x 104 algae cells/mL and incubated at 21 - 24°C (under 4440-8880 Lux light intensity) for 72 hours with cell counts at 24-hour intervals.

The nominal tested concentrations were 0.10, 0.32, 1.0, 3.2 and 10 mg/L. Samples of test media were analysed at 0 (new media) and 24, 48 and 72 hours (expired test media).

Analysis of the samples at 0 hours showed measured concentrations to range from 83% to 96% of nominal with the exception of the 0.10 mg/L test sample which showed a measured concentration of 164% of nominal. Given that this concentration was below the nominal value for the 72-hour No Observed Effect Concentrations (NOECs), it was considered that this high value did not affect the integrity of the test. A gradual decline in measured concentration was observed at 24, 48 and 72 hours. Analysis of the 72 hour samples showed measured concentrations to range from less than the limit of quantification (LOQ) of the analytical method (assessed as 0.002 mg/L) to 0.0133 mg/L. Given the decline in measured concentration observed over the 72-hour test period, it was considered justifiable to base the results on geometric mean measured concentrations. These were calculated to be 0.0036, 0.0063, 0.011, 0.035 and 0.13 mg/L.

All the validity criteria were met except the pH in the controls which increases by more than 1.5. This marked increase of pH is linked to the important algal growth in the controls and the consumption of CO2. So this pH variation decreases with the increase of the concentrations of the tested solutions. For the tested concentration that have an inhitory effect, the pH variation is less than 1.5 compared to the pH measured at T0.  

Based on geometric mean measured concentrations, the 72-hour EC50 for inhibition of yield, biomass and growth rate were calculated to be 0.012, 0.011 and 0.035 mg/L, respectively. The  72 -hour EC10 values for yield, biomass and specific growth rate after 72 hours were 0.0073, 0.0068 and 0.0098 mg/L respectively. The corresponding NOEC values for yield, biomass and specific growth rate after 72 hours were 0.0063 mg/L.