p-xylene

Endpoint summary

Additional information

Complete acute datasets are available for each of the xylene isomers. Based on the very similar physico-chemical properties of the isomers and the similarity of the results from the acute ecotoxicity studies, we believe that it is appropriate to combine the ecotoxicity data from the three isomers.

 

Data from chronic fish studies are available for p-xylene and mixed xylenes. Data from chronic invertebrate and algal studies are available for m- and p-xylene. Again, based on the very similar physico-chemical properties of the isomers and the similarity of the results from the chronic ecotoxicity studies, we believe that it is appropriate to combine all the available data. This results in a chronic dataset of two invertebrate studies, two fish studies, and a single algal study.

 

The screening criteria for toxicity in the PBT assessment is that a substance with an acute L(E)C50 <0.1 mg/L is considered to potentially meet the T criterion and an L(E)C50 <0.01 mg/L indicates a substance is definitely T. Chronic fish studies are available for p-xylene and mixed xylenes and acute and chronic ecotoxicity data are available from studies conducted with m, p and o-xylene. The most conservative results are: 96 hour LC50 for fish is 2.6 mg/L for p-xylene (Galassi et al. 1988), 24 hour EC50 for invertebrates of 1 mg/L for o-xylene (Galassi et al. 1988), 73 hour EC50 for algae of 4.36 mg/L for p-xylene (TNO, 2004), 35 day NOEC for fish of 0.714 mg/L for p-xylene (Noack, 2017), 7 day NOEC for invertebrates of 1.17 mg/L for m-xylene (Niederlehner et al. 1998) and 73 hour NOEC for algae of 0.44 mg/L for p-xylene (TNO 2004). All of the acute toxicity values are greater than the screening criteria and the chronic toxicity values are greater than the criteria in Annex XIII of the REACH regulations. Therefore, the xylene isomers are not considered to be T.