Phthalic anhydride

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

GLP compliance:

yes

Test organisms (species):

Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)

Test type:

not specified

Water media type:

freshwater

Total exposure duration:

72 h

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

32 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

68 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Details on results:

as no details on test conditions are given, it is assumed that the results relate to nominal concentartion based on test substance concentrations

No information is given on pH

Executive summary:

Algal toxicity was determined with pseudokirchneriella subcapitata in the presence of phthalic anhydride according to the OECD TG 201. NOEC was determined as 32 mg/l and EC50 as 68 mg/l after 72h (MITI, 2003).

Description of key information

In two limit tests with and without pH adjustment, the toxicity to the fresh water algae Desmodesmus subspicatus of the hydrolysis product phthalic acid was performed according to EU Method C.3 (Algal Inhibition test). The results of both tests clearly indicate that the toxic effects are not due to substance inherent properties but to a function of pH. The test with pH adjustment gave a NOEC of > 100 mg/l (Bayer Industry Services, 2004).

Key value for chemical safety assessment

EC10 or NOEC for freshwater algae:

100 mg/L

Additional information

Concerning the toxicity towards aquatic algae there is only one test with phthalic anhydride available (MITI, 2003), but should not be used for the hazard assessment, due to missing information on pH. As phthalic anhydride hydrolyses within 30.5 sec forming the main hydrolysis product phthalic acid, tests with phthalic acid are used to draw a conclusion on toxicity to aquatic algae. Algal toxicity was determined by a GLP test with Desmodesmus subspicatus in the presence of phthalic acid according to the OECD TG 201 "Algal Growth Inhibition Test". Two limit tests were conducted with each 100 mg/l with and without pH adjustment. The stability of the test substance was experimentally determined via HPLC before and after an exposure of 72 hours. The 72 h-EC0 was >/= 100 mg/l and the recovery rate was > 98 %, therefore the nominal value was reported. The results are related to both endpoints growth rate and biomass. Without pH adjustment at 100 mg/l 100 % inhibition was observed after 72 hours; pH was determined to be in the range of 4.9 to 5.1. This indicates that phthalic acid causes a pH shift in algal medium. It is the resulting pH that determines the impact of phthalic acid on algae as shown with buffered test substance solution. Thus, toxic effects are not due to substance inherent properties but to a function of the pH (Bayer Industry Services, 2004).