Terephthalic acid

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

PNEC aqua (freshwater)

PNEC value:

0.38 mg/L

Assessment factor:

50

Extrapolation method:

assessment factor

PNEC freshwater (intermittent releases):

1.9 mg/L

Marine water

Hazard assessment conclusion:

PNEC aqua (marine water)

PNEC value:

0.038 mg/L

Assessment factor:

500

Extrapolation method:

assessment factor

STP

Hazard assessment conclusion:

PNEC STP

PNEC value:

50 mg/L

Assessment factor:

10

Extrapolation method:

assessment factor

Sediment (freshwater)

Hazard assessment conclusion:

PNEC sediment (freshwater)

PNEC value:

0.52 mg/kg sediment dw

Extrapolation method:

equilibrium partitioning method

Sediment (marine water)

Hazard assessment conclusion:

PNEC sediment (marine water)

PNEC value:

0.052 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:

0.71 mg/kg soil dw

Extrapolation method:

equilibrium partitioning method

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

no potential for bioaccumulation

Conclusion on classification

Classification of terephthalic acid for effects in the environment

Three reliable, GLP-compliant short-term toxicity studies are available for terephthalic acid in the free acid form, providing endpoints for three key trophic levels: fish, invertebrates and algae. In all three studies, there were no adverse effects up to and including the exposure limit which was dictated by the limited solubility of TPA in the various aquatic test media. The lowest of three similar endpoints is the algal ErC50: >19.0 mg TPA/L (mean measured). A reliable, GLP-compliant study is also available for the long-term effects of terephthalic acid in the free acid form on aquatic invertebrates (D. magna). There were no adverse effects on adult survival or reproduction up to and including the exposure limit, and the 21 -day NOEC was 19.5 mg TPA/L (mean measured).

In determining the classification appropriate to terephthalic acid, it is necessary to consider all available evidence concerning its persistence, potential to accumulate and predicted or observed environmental fate and behaviour that may present a long-term and/or delayed danger to the structure and/or functioning of aquatic ecosystems. These points are considered below.

Persistence.

Reliable studies are available to demonstrate that terephthalic acid is readily biodegradable. Terephthalic acid may therefore be expected to degrade rapidly, and to be completely mineralised,i.e. converted to CO2 and H2O without forming any recalcitrant metabolites. Terephthalic acid and its degradation intermediates are non-persistent. Terephthalic acid is expected to degrade rapidly under anaerobic as well as aerobic conditions.

Potential to accumulate.

QSAR-predicted and measured log10 Kow values for terephthalic acid are less than 3.0. The potential for terephthalic acid to bioaccumulate in the tissues of organisms that inhabit aquatic or terrestrial matrices contaminated with TPA is therefore negligible. The risk that terephthalic acid may biomagnify through successive trophic levels of aquatic or terrestrial food chains is consequently also negligible. 

Environmental fate and behaviour.

TPA is a dicarboxylic acid. The first step that may be predicted in its environmental fate, prior to biodegradation, is its conversion to terephthalate salts. Three reliable, GLP-compliant short-term studies are available in which TPA was treated with NaOH solution to convert the free acid to its highly soluble sodium terephthalate salt(s) prior to exposure to fish, daphnia and algae. No adverse effects occurred in these studies, up to and including the highest nominal TPA-equivalent concentrations of 1000 mg/L. The lowest endpoint from these three studies (the 72 -h ErC50 for growth inhibition of D. subspicatus) was >668 mg TPA-equiv/L (mean measured). These studies demonstrate the low intrinsic toxicity of terephthalate to aquatic biota, and - taking into account its susceptibility to rapid biodegradation - provide assurance that terephthalic acid does not present a long-term and/or delayed danger to the structure and/or functioning of aquatic ecosystems. 

No classification is triggered based on available data, according to Regulation (EC) No 1272/2008.

Terephthalic acid is readily biodegradable and therefore does not satisfy the criteria for classification as persistent (P). 

The calculated BCF of terephthalic acid is 3.16 L/kg wet weight and below the threshold of 2000. 

Terephthalic acid does not satisfy the criterion for classification as bioaccumulative (B).

The long-term NOECs for freshwater algae and invertebrates are 19.0 and 19.5 mg/L, respectively, for the free acid form of TPA. Both values exceed the trigger value of 0.01 mg/L.

TPA does not satisfy the environmental effects criterion for classification as toxic (T).

Terephthalic acid is therefore not a PBT (or vPvB) substance.