Toluene

Toxicity to aquatic algae and cyanobacteria

Description of key information

The 3 hour EC50 for reduced photosynthesis rate is 134 mg/L. A separate study reports a 72 hour NOEC of 10 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:

134 mg/L

EC10 or NOEC for freshwater algae:

10 mg/L

Additional information

All of the algal toxicity studies that were identified were based on nominal concentrations. This is not ideal for a volatile test substance such as toluene. However, OECD 201 does not require analytical confirmation of the exposure concentrations and the tests were conducted in closed systems which will have reduced volatilisation. Due to this, tests based on nominal concentrations are considered acceptable.

The study by Hutchinson et al (1980) does not follow a standard method, instead using a very short exposure period and a non standard endpoint (reduction in photosynthetic rate). However, it is well documented study and it was the lowest reported acute effect concentration identified in the EU RAR for toluene (2003) and so is considered suitable for use as a key study.

Heijden et al (1988) was used as the key study in the RAR for chronic effects on algae. However, this is a secondary reference and the original paper from which this data is taken is Dunstan et al (1975). This study investigates the effects of toluene on growth measured by cell numbers and in vivo chlorophyll over 72 hours and is therefore more similar to the standard guidelines. A 72 hour NOEC of 10 mg/L is reported in this study, which is used as the key study in the RAR.