Styrene

Endpoint summary

Additional information

Styrene is considered to exert toxic effects by a non-specific mode of action (non-polar narcosis) in aquatic species. Many studies on the effects of styrene on aquatic organisms have been conducted. However, the value of some of these tests is questionable since they were carried out in open systems without taking the rapid volatilization into account and without measurement of the effective concentration. The following results are taken from the most valid and sensitive studies.

 

Results on acute aquatic toxicity:

 

Fish

• LC50 (96 hours) Pimephales promelas 10 mg/l, measured, freshwater (Springborn, 1995)


• LC50 (96h) Pimephales promelas 4.02 mg/l, measured, freshwater (Geiger et al. 1990)

Invertebrates

• EC50(48 hours) Daphnia magna 4.7 mg/l, measured, freshwater (Springborn, 1995)


• LC50 (96 hours) Hyalella azteca 9.5 mg/l, nominal, freshwater (Springborn, 1995)

Algae

• ErC50 (72 hours) Selenastrum capricornutum 4.9 mg/l, measured, freshwater (Springborn, 1995)

 

In general the available studies show that styrene can be considered acutely toxic to aquatic organisms.

 

Results on chronic toxicity:

 

Invertebrates

• NOEC(21d) Daphnia magna 1.01 mg/L, measured, freshwater (Kurume 1995)

Algae

• EC10(96h) Selenastrum capricornutum, 0.28 mg/L, measured, freshwater (Springborn 1995)

 

It is generally accepted that a 72-hour (or longer) EC50 value may be considered as equivalent to a short-term result and that a 72-hour (or longer) EC10 or NOEC value can be considered as a long-term result.

 

Few studies on possible endocrine effects of styrene in aquatic organisms are available. No such effcts were observed in juvenile fish (Ruiz et al., 2012), mussels (Ruiz et al., 2014) or male frog tadpoles (Ohtani et al., 2001). Overall the studies do not indicate an endocrine activity of styrene in the aquatic species investigated (Gelbke H. P. et al., 2015).

 

PNEC derivation

 

Since two chronic toxicity tests are available for styrene, according to TGD an assessment factor of 50 may be applied for the derivation of PNECaqua. However styrene, based on its structure, is expected to exhibit toxicity through a non-polar narcotic mode of action (Verhaar et al., 1992). This suggests that the toxicity between the three aquatic trophic levels (fish, daphnia and algae) is not expected to vary significantly. Acute toxicity data available available for styrene support indeed this assumption. Similar to the approach used in the evaluation of the closely related structure ethylbenzene (see EU Risk Assessment Report on Ethylbenzene) an assessment factor of 10 can therefore be applied to the lowest NOEC from the two available species. As mentioned in Chapter 10 of the Guidance on Information reqirements and Chemical Safety assessment, this is particular important if a substance, like styrene, does not have a potential to bioaccumulate.

 

Applying an assessment factor of 10 to the lowest chronic value for S. capricornutum leads to:

 

PNECaqua = 0.28 mg/L / 10 = 0.028 mg/L

 

 

STP

The inhibition of oxygen consumption in activated sludge was tested using domestic, non adapted sewage slugde resulting in a EC50 (30 min) of approx. 500 mg/l. Toxicity thresholds derived from short-term test with bacteria and protozoa are also available and suitable to assesss the effects of styrene on sewage treatment organisms. They indicate similar (or lower) sensitivity.

 

According to TGD an assessment factor of 100 may be applied for the derivation of PNECmicroorganims which leads to:

 

PNEC microorganisms = 500 mg/L / 100 = 5 mg/L

 

 

Conclusion on classification

The acute toxicity concentrations in fish, daphnia and algae are between 1 mg/L and 10 mg/L, however styrene is readily biodegradable and therefore no environmental classification for acute effects is required.

Regarding the long-term toxicity styrene has to be classified as aquatic chronic 3 which is triggered by the EC10 = 0.28 mg/L for algae.