Xylene

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

PNEC aqua (freshwater)

PNEC value:

0.044 mg/L

Assessment factor:

10

Extrapolation method:

assessment factor

PNEC freshwater (intermittent releases):

0.01 mg/L

Marine water

Hazard assessment conclusion:

PNEC aqua (marine water)

PNEC value:

0.004 mg/L

Assessment factor:

100

Extrapolation method:

assessment factor

PNEC marine water (intermittent releases):

0.001 mg/L

STP

Hazard assessment conclusion:

PNEC STP

PNEC value:

1.6 mg/L

Assessment factor:

10

Extrapolation method:

assessment factor

Sediment (freshwater)

Hazard assessment conclusion:

PNEC sediment (freshwater)

PNEC value:

2.52 mg/kg sediment dw

Extrapolation method:

equilibrium partitioning method

Sediment (marine water)

Hazard assessment conclusion:

PNEC sediment (marine water)

PNEC value:

0.252 mg/kg sediment dw

Extrapolation method:

equilibrium partitioning method

Hazard for air

Air

Hazard assessment conclusion:

no hazard identified

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:

PNEC soil

PNEC value:

0.852 mg/kg soil dw

Assessment factor:

50

Extrapolation method:

assessment factor

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

no potential for bioaccumulation

Additional information

PNECs were derived for freshwater, saltwater, sediment, and soil using the experimental data or equilibrium partitioning calculations. The latter where experimental data was lacking.

 

The screening criteria for environmental 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. A chronic fish study is available for 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 0.96 mg/L for Ethylbenzene (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 meet the environmental T criteria.

Conclusion on classification

The lowest 96 hour LC50 for fish is 2.6 mg/L. The lowest 24 hour EC50 for Daphnia magna is 1 mg/L. The lowest 72 or 96 hour ErC50 for algae is 4.36 mg/L. These values would not result in a classification for acute hazard to the environment.

None of the LC or EC50 from the acute ecotoxicity tests conducted with the xylene isomers are less than 1 mg/L and therefore on balance of the data a classification for acute hazard to the environment is not required.

Available data indicate that xylene isomers are readily biodegradable and that they will partition to the air from water, further reducing their potential for exposure. An experimentally determined BCF for mixed xylenes in fish gave a result of 25.9 L/kg, indicating a low potential for bioaccumulation. Taken together with the acute toxicity results, these results would not result in a classification for chronic hazard to the environment.

However, on 10th March 2011, Commission Regulation (EC) No 1272/2008 [CLP Regulations] was amended. The new criteria for environmental classification state that if chronic data are available these results should be used to determine the chronic classification. The xylene isomers have a complete chronic data set, with the lowest chronic effect being a 72 hour NOEC of 0.44 mg/L for algae. This results in a chronic Category 3 classification under the CLP Regulations. This has been added as a self classification to the dossier.