Isoprene

Long-term toxicity to aquatic invertebrates

Description of key information

The 21 day NOEC for isoprene was 0.402 mg/L (measured TWA) in the MOE study. TLM QSAR modelling was used to calculate NOELR value of isoprene towards D. magna. The calculated NOELR value is 6.149 mg/L.

The lowest value was used for chemical safety assessment.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

6.149 mg/L

Additional information

For chronic toxicity to Daphnia, experimental data for isoprene are available from the Japanese government, giving a 21 day NOEC of 0.402 mg/L. The study by the Ministry of Environment (Japan) follows OECD Guideline 211 (Daphnia magna Reproduction Test). The original study has not been reviewed but a summary is available. The validity of the study cannot be confirmed and many of the study details are missing, therefore it cannot be confirmed that the validity criteria were met but as the data are taken from a regulatory source, the study is considered sufficiently reliable for use for this endpoint. As the data are the lowest result available for this endpoint and the other results are taken from QSAR estimates, this study has been used as the key study for this endpoint.

In addition to the measured data, the ECOSAR programme (Nabholz and Mayo-Bean, 2009) is used to estimate a ChV of 1.27 mg/L (when divided by v2 to adjust for ChV being a geometric mean of NOEC and LOEC, these ChV values correspond to equivalent to a NOEC of 0.90 mg/L) for chronic toxicity to Daphnia. The ECOSAR model is a reliable and appropriate QSAR model to apply to isoprene as it is based on a related chemical dataset that calculates the toxicity of neutral organic hydrocarbons whose mode of action is non-polar narcosis. The endpoint calculated here is therefore a reasonable estimate of its baseline toxicity. A QSAR prediction giving a 16 day EC50 of 1.38 mg/L was used as the key endpoint in the OECD SIDS for isoprene (2005).