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Hydrolysis

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Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
2003-02-10 to 2003-02-13
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Aquatic ecotoxicology study performed according to current guideline and under GLP.
Qualifier:
according to guideline
Guideline:
other: OECD Guideline 201 (Alga, Growth Inhibition Test)
Deviations:
no
Principles of method if other than guideline:
The primary aim of this study was to determine the effects of terephthalic acid on the growth of unicellular aquatic algae. The test organisms were exposed to TPA in an aqueous medium for 72 hours under static conditions (i.e. without test substance renewal). TPA was analysed by HPLC/UV-VIS detection at the beginning and end of the study to confirm the initial exposure concentration and stability of the test substance during the test. The analytical data provided by this study provide insight into the hydrolysis behaviour of terephthalic acid.
GLP compliance:
yes
Radiolabelling:
no
Analytical monitoring:
yes
Duration:
72 h
Initial conc. measured:
19 mg/L
Transformation products:
no

Table 1:      Measured concentrations of terephthalic acid during a 72 -hour, static growth inhibition test withSelenastrum capricornutum.

Nominal TPA concn (mg/L)

Measured TPA concentration (mg/L)

Mean measured as % of nominal

0 hours

72 hours

mean

control

< 0.5

< 0.5

-

-

solvent control

< 0.5

< 0.5

-

-

18

19.0

19.0

19.0

106

Conclusions:
Terephthalic acid, dosed to aqueous algal growth test medium at a measured initial concentration of 19.0 mg/L, remained intact over the course of 72-h incubation at pH 7.8 +/- 0.3 and 22.3 +/- 0.1 degrees C. These data provide evidence that TPA is not prone to rapid hydrolysis in the aquatic environment.
Executive summary:

Terephthalic acid, dosed to aqueous algal growth test medium at a measured initial concentration of 19.0 mg/L, remained intact over the course of 72-h incubation at pH 7.8 +/- 0.3 and 22.3 +/- 0.1 degrees C. These data (DT50 > 3 days) provide evidence that TPA is not prone to rapid hydrolysis in the aquatic environment.

Other data (see Point 5.2.1) show that terephthalic acid is readily biodegradable, with >60% mineralisation (CO2 production) occuring within 5 days. Biodegradation may therefore be considered a more significant dissipation mechanism than hydrolysis tor TPA in the aquatic environment.

Endpoint:
hydrolysis
Data waiving:
study scientifically not necessary / other information available
Justification for data waiving:
the study does not need to be conducted because the substance is readily biodegradable

Description of key information

In accordance with Column 2 adaptation statement of REACH Annex VIII, hydrolysis as a function of pH, information requirement 9.2.2.1, does not need to be conducted if the test substance is readily biodegradable.  

Key value for chemical safety assessment

Additional information

Since terephthalic acid has been shown to be readily biodegradable (Point 5.2.1), a study of its hydrolysis is not required. Under environmental conditions, hydrolysis is unlikely to make a significant contribution to the dissipation of terephthalic acid (or its salts), compared to the rate of its removal by biodegradation.

A confirmatory indication of this is provided by the analytical data from a study of the effect of terephthalic acid on the growth of the unicellular aquatic alga Pseudokirchneriella subcapitata (Government of Japan, 2003d): the initial measured exposure concentration of 19.0 mg TPA/L remained unchanged over the course of the static, 72 -hour incubation at pH 7.8 +/- 0.3. These data (DT50 > 3 days) provide evidence that TPA is not prone to rapid hydrolysis in the aquatic environment. Ready biodegradability test data, on the other hand, show > 60% mineralisation (CO2 production) within 5 days when TPA was dosed at 10 and 20 mg/L (Lebertz, 1991a).