Maleic anhydride

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

PNEC aqua (freshwater)

PNEC value:

0.075 mg/L

Assessment factor:

1 000

Extrapolation method:

assessment factor

PNEC freshwater (intermittent releases):

0.75 mg/L

Marine water

Hazard assessment conclusion:

PNEC aqua (marine water)

PNEC value:

0.007 mg/L

Assessment factor:

10 000

Extrapolation method:

assessment factor

STP

Hazard assessment conclusion:

PNEC STP

PNEC value:

4.46 mg/L

Assessment factor:

10

Extrapolation method:

assessment factor

Sediment (freshwater)

Hazard assessment conclusion:

PNEC sediment (freshwater)

PNEC value:

0.06 mg/kg sediment dw

Extrapolation method:

equilibrium partitioning method

Sediment (marine water)

Hazard assessment conclusion:

PNEC sediment (marine water)

PNEC value:

0.006 mg/kg sediment dw

Extrapolation method:

equilibrium partitioning method

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:

PNEC soil

PNEC value:

0.01 mg/kg soil dw

Extrapolation method:

equilibrium partitioning method

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

PNEC oral

PNEC value:

6.67 mg/kg food

Assessment factor:

30

Additional information

According to the available toxicity data for aquatic organisms, LC₅₀/ EC₅₀of the short-term toxicity test for fish, Daphnia and Algae are 75mg/l ofOncorhynchus mykissandLepomis macrochirus, 330mg/l of Daphnia magna,150mg/l ofPseudokirchneriella subcapitatarespectively. The lowest shot-term LC₅₀from fresh water is 75mg/l from fish and is considered as the most relevant information for deriving for PNEC_{aqua-freshwater}. Then a PNEC_{aquatic-fresh waetr}of 0.075 mg/l has been derived by dividing the LC₅₀of 75 mg/l for fish acute toxicity test by an assessment factor of 1000.

No measured data are currently available for marine organisms therefore the marine PNEC is derived from data obtained for freshwater species (fish) (LC₅₀= 75 mg/l), applying an assessment factor of 10000 to give PNEC_seawater= 0.0075 mg/l.

The intermittent releases PNEC is derived from data obtained for freshwater species (fish)(LC₅₀= 75 mg/l), applying an assessment factor of 100 to give PNEC_{aqua - intermittent releases}= 0.75 mg/l.

The PNEC for waste-water treatment is 4.46 mg/l based on the IC₅₀of 44.6 mg/l and an assessment factor of 10.

No toxicity data are currently available for sediment-dwelling organisms,therefore it is not possible to determine a PNEC_sedbased on measured data. According to the Technical Guidance Document, PNEC_sedcan be calculated by the equilibrium partitioning method. Hence, PNEC_sed= 0.06mg/kg, whichwill be used for risk characterization.

No toxicity data are currently available for marine sediment-dwelling organisms, therefore it is not possible to determine a PNEC_marine-sedbased on measured data. According to the Technical Guidance Document, PNEC_marine-sedcan be calculated by the equilibrium partitioning method. Hence, PNEC_marine-sed=0.006mg/kg, whichwill be used for risk characterization.

No toxicity data are currently available for soil organisms. According to the Technical Guidance Document, PNEC_soilcan be calculated by the equilibrium partitioning method. Hence, PNEC_soil=0.01 mg/kg will be used for risk characterization.

A Henry’s Law constant of 3.6×10^-3Pa.m³/mol can be calculated from the vapour pressure (0.015 kPa at 20℃)and water solubility(4.07×10⁵mg/L). This indicates a preference for water compared to air, and hence a low rate of volatilization from surface water to air. Maleic anhydride and maleic acid are readily biodegraded in water. And the evaluation on the environmental transport and distribution by Fugacity models indicates the very limited distribution ofmaleic anhydride and maleic acid to the air. So, the possibility ofmaleic anhydride and contributing to atmospheric effects is likely to be very small.

The most relevant data for derivation of the PNEC_oral for secondary poisoning for maleic anhydrideis is from a 24-month study in rat. NOAEL of 10 mg/kg bw/d is available. Using the conversion factors given in the Technical Guidance Document:

NOAEL = 10 mg/kg bw/d

NOEC mammal = NOAEL mammal × CONV mammal = 10 mg/kg bw/d × 20 (animal age >6 weeks) = 200 mg/kg food

According to the Technical Guidance Document an assessment factor of 30 is appropriate for the results of a study of this duration. Therefore, applying this assessment factor:

PNEC _oral = NOEC mammal /AF = 200/30 = 6.67 mg/kg food

Conclusion on classification

Acute aquatic toxicity testing indicates a low order of toxicity when the effect of pH is taken into consideration. The combination of low aquatic toxicity, low logkow and readily biodegradability suggest no significant hazard of long-term effects in the aquatic environment. And maleic anhydride and maleic acid are not persistent in the environment and are not expected to bioaccumulate in food webs.

Therefore, maleic anhydride is expected little hazard to the aquatic and terrestrial compartment. And based on its relative low Henry’s law constant and limited distribution to the air, it is expected little hazard to the atmosphere compartment as well. Therefore,maleic anhydride is not classified for environment of Commission Regulation (EC) No: 790/2009.